Use memmap for dag cache (#6193)

* Rebase and fix compilation errors (tests not yet fixed)

* Use `debug_assert` over `assert`

* Fix tests

* Assert safety, clean up

* Fix up stale cache removal, move one assert to debug_assert

* Remove printlns

* Add licenses

* Fix benches

* Inline some no-ops in a hot loop that weren't being inlined

* Add spooky comment to make sure no-one removes the inlining annotations

* Minor cleanup

* Add option to switch between mmap and ram

* Flag ethash to use less memory when running light client

* Fix tests

* Remove todo comment (it's done)

* Replace assertion with error return

* Fix indentation

* Use union instead of `transmute`

* Fix benches

* Extract to constants

* Clean up and fix soundness holes

* Fix formatting

* Ignore missing-file errors

* Make incorrect cache size an error condition instead of a panic, remove dead code

* Fix compilation errors from rebase

* Fix compilation errors in tests

* Fix compilation errors in tests

ethash/Cargo.toml

@@ -11,6 +11,8 @@ hash = { path = "../util/hash" }
 primal = "0.2.3"
 parking_lot = "0.4"
 crunchy = "0.1.0"
+memmap = "0.5.2"
+either = "1.0.0"
 
 [features]
 benches = []

ethash/src/cache.rs

@@ -0,0 +1,352 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use compute::Light;
+use either::Either;
+use keccak::{H256, keccak_512};
+use memmap::{Mmap, Protection};
+use parking_lot::Mutex;
+use seed_compute::SeedHashCompute;
+
+use shared::{ETHASH_CACHE_ROUNDS, NODE_BYTES, NODE_DWORDS, Node, epoch, get_cache_size, to_hex};
+
+use std::borrow::Cow;
+use std::fs;
+use std::io::{self, Read, Write};
+use std::path::{Path, PathBuf};
+use std::slice;
+use std::sync::Arc;
+
+type Cache = Either<Vec<Node>, Mmap>;
+
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
+pub enum OptimizeFor {
+	Cpu,
+	Memory,
+}
+
+impl Default for OptimizeFor {
+	fn default() -> Self {
+		OptimizeFor::Cpu
+	}
+}
+
+fn byte_size(cache: &Cache) -> usize {
+	use self::Either::{Left, Right};
+
+	match *cache {
+		Left(ref vec) => vec.len() * NODE_BYTES,
+		Right(ref mmap) => mmap.len(),
+	}
+}
+
+fn new_buffer(path: &Path, num_nodes: usize, ident: &H256, optimize_for: OptimizeFor) -> Cache {
+	let memmap = match optimize_for {
+		OptimizeFor::Cpu => None,
+		OptimizeFor::Memory => make_memmapped_cache(path, num_nodes, ident).ok(),
+	};
+
+	memmap.map(Either::Right).unwrap_or_else(|| {
+		Either::Left(make_memory_cache(num_nodes, ident))
+	})
+}
+
+#[derive(Clone)]
+pub struct NodeCacheBuilder {
+	// TODO: Remove this locking and just use an `Rc`?
+	seedhash: Arc<Mutex<SeedHashCompute>>,
+	optimize_for: OptimizeFor,
+}
+
+// TODO: Abstract the "optimize for" logic
+pub struct NodeCache {
+	builder: NodeCacheBuilder,
+	cache_dir: Cow<'static, Path>,
+	cache_path: PathBuf,
+	epoch: u64,
+	cache: Cache,
+}
+
+impl NodeCacheBuilder {
+	pub fn light(&self, cache_dir: &Path, block_number: u64) -> Light {
+		Light::new_with_builder(self, cache_dir, block_number)
+	}
+
+	pub fn light_from_file(&self, cache_dir: &Path, block_number: u64) -> io::Result<Light> {
+		Light::from_file_with_builder(self, cache_dir, block_number)
+	}
+
+	pub fn new<T: Into<Option<OptimizeFor>>>(optimize_for: T) -> Self {
+		NodeCacheBuilder {
+			seedhash: Arc::new(Mutex::new(SeedHashCompute::new())),
+			optimize_for: optimize_for.into().unwrap_or_default(),
+		}
+	}
+
+	fn block_number_to_ident(&self, block_number: u64) -> H256 {
+		self.seedhash.lock().hash_block_number(block_number)
+	}
+
+	fn epoch_to_ident(&self, epoch: u64) -> H256 {
+		self.seedhash.lock().hash_epoch(epoch)
+	}
+
+	pub fn from_file<P: Into<Cow<'static, Path>>>(
+		&self,
+		cache_dir: P,
+		block_number: u64,
+	) -> io::Result<NodeCache> {
+		let cache_dir = cache_dir.into();
+		let ident = self.block_number_to_ident(block_number);
+
+		let path = cache_path(cache_dir.as_ref(), &ident);
+
+		let cache = cache_from_path(&path, self.optimize_for)?;
+		let expected_cache_size = get_cache_size(block_number);
+
+		if byte_size(&cache) == expected_cache_size {
+			Ok(NodeCache {
+				builder: self.clone(),
+				epoch: epoch(block_number),
+				cache_dir: cache_dir,
+				cache_path: path,
+				cache: cache,
+			})
+		} else {
+			Err(io::Error::new(
+				io::ErrorKind::InvalidData,
+				"Node cache is of incorrect size",
+			))
+		}
+	}
+
+	pub fn new_cache<P: Into<Cow<'static, Path>>>(
+		&self,
+		cache_dir: P,
+		block_number: u64,
+	) -> NodeCache {
+		let cache_dir = cache_dir.into();
+		let ident = self.block_number_to_ident(block_number);
+
+		let cache_size = get_cache_size(block_number);
+
+		// We use `debug_assert` since it is impossible for `get_cache_size` to return an unaligned
+		// value with the current implementation. If the implementation changes, CI will catch it.
+		debug_assert!(cache_size % NODE_BYTES == 0, "Unaligned cache size");
+		let num_nodes = cache_size / NODE_BYTES;
+
+		let path = cache_path(cache_dir.as_ref(), &ident);
+		let nodes = new_buffer(&path, num_nodes, &ident, self.optimize_for);
+
+		NodeCache {
+			builder: self.clone(),
+			epoch: epoch(block_number),
+			cache_dir: cache_dir.into(),
+			cache_path: path,
+			cache: nodes,
+		}
+	}
+}
+
+impl NodeCache {
+	pub fn cache_path(&self) -> &Path {
+		&self.cache_path
+	}
+
+	pub fn flush(&mut self) -> io::Result<()> {
+		if let Some(last) = self.epoch.checked_sub(2).map(|ep| {
+			cache_path(self.cache_dir.as_ref(), &self.builder.epoch_to_ident(ep))
+		})
+		{
+			fs::remove_file(last).unwrap_or_else(|error| match error.kind() {
+				io::ErrorKind::NotFound => (),
+				_ => warn!("Error removing stale DAG cache: {:?}", error),
+			});
+		}
+
+		consume_cache(&mut self.cache, &self.cache_path)
+	}
+}
+
+fn make_memmapped_cache(path: &Path, num_nodes: usize, ident: &H256) -> io::Result<Mmap> {
+	use std::fs::OpenOptions;
+
+	let file = OpenOptions::new()
+		.read(true)
+		.write(true)
+		.create(true)
+		.open(&path)?;
+	file.set_len((num_nodes * NODE_BYTES) as _)?;
+
+	let mut memmap = Mmap::open(&file, Protection::ReadWrite)?;
+
+	unsafe { initialize_memory(memmap.mut_ptr() as *mut Node, num_nodes, ident) };
+
+	Ok(memmap)
+}
+
+fn make_memory_cache(num_nodes: usize, ident: &H256) -> Vec<Node> {
+	let mut nodes: Vec<Node> = Vec::with_capacity(num_nodes);
+	// Use uninit instead of unnecessarily writing `size_of::<Node>() * num_nodes` 0s
+	unsafe {
+		initialize_memory(nodes.as_mut_ptr(), num_nodes, ident);
+		nodes.set_len(num_nodes);
+	}
+
+	nodes
+}
+
+fn cache_path<'a, P: Into<Cow<'a, Path>>>(path: P, ident: &H256) -> PathBuf {
+	let mut buf = path.into().into_owned();
+	buf.push(to_hex(ident));
+	buf
+}
+
+fn consume_cache(cache: &mut Cache, path: &Path) -> io::Result<()> {
+	use std::fs::OpenOptions;
+
+	match *cache {
+		Either::Left(ref mut vec) => {
+			let mut file = OpenOptions::new()
+				.read(true)
+				.write(true)
+				.create(true)
+				.open(&path)?;
+
+			let buf = unsafe {
+				slice::from_raw_parts_mut(vec.as_mut_ptr() as *mut u8, vec.len() * NODE_BYTES)
+			};
+
+			file.write_all(buf).map(|_| ())
+		}
+		Either::Right(ref mmap) => {
+			mmap.flush()
+		}
+	}
+}
+
+fn cache_from_path(path: &Path, optimize_for: OptimizeFor) -> io::Result<Cache> {
+	let memmap = match optimize_for {
+		OptimizeFor::Cpu => None,
+		OptimizeFor::Memory => Mmap::open_path(path, Protection::ReadWrite).ok(),
+	};
+
+	memmap.map(Either::Right).ok_or(()).or_else(|_| {
+		read_from_path(path).map(Either::Left)
+	})
+}
+
+fn read_from_path(path: &Path) -> io::Result<Vec<Node>> {
+	use std::fs::File;
+	use std::mem;
+
+	let mut file = File::open(path)?;
+
+	let mut nodes: Vec<u8> = Vec::with_capacity(file.metadata().map(|m| m.len() as _).unwrap_or(
+		NODE_BYTES * 1_000_000,
+	));
+	file.read_to_end(&mut nodes)?;
+
+	nodes.shrink_to_fit();
+
+	if nodes.len() % NODE_BYTES != 0 || nodes.capacity() % NODE_BYTES != 0 {
+		return Err(io::Error::new(
+			io::ErrorKind::Other,
+			"Node cache is not a multiple of node size",
+		));
+	}
+
+	let out: Vec<Node> = unsafe {
+		Vec::from_raw_parts(
+			nodes.as_mut_ptr() as *mut _,
+			nodes.len() / NODE_BYTES,
+			nodes.capacity() / NODE_BYTES,
+		)
+	};
+
+	mem::forget(nodes);
+
+	Ok(out)
+}
+
+impl AsRef<[Node]> for NodeCache {
+	fn as_ref(&self) -> &[Node] {
+		match self.cache {
+			Either::Left(ref vec) => vec,
+			Either::Right(ref mmap) => unsafe {
+				let bytes = mmap.ptr();
+				// This isn't a safety issue, so we can keep this a debug lint. We don't care about
+				// people manually messing with the files unless it can cause unsafety, but if we're
+				// generating incorrect files then we want to catch that in CI.
+				debug_assert_eq!(mmap.len() % NODE_BYTES, 0);
+				slice::from_raw_parts(bytes as _, mmap.len() / NODE_BYTES)
+			},
+		}
+	}
+}
+
+// This takes a raw pointer and a counter because `memory` may be uninitialized. `memory` _must_ be
+// a pointer to the beginning of an allocated but possibly-uninitialized block of
+// `num_nodes * NODE_BYTES` bytes
+//
+// We have to use raw pointers to read/write uninit, using "normal" indexing causes LLVM to freak
+// out. It counts as a read and causes all writes afterwards to be elided. Yes, really. I know, I
+// want to refactor this to use less `unsafe` as much as the next rustacean.
+unsafe fn initialize_memory(memory: *mut Node, num_nodes: usize, ident: &H256) {
+	let dst = memory as *mut u8;
+
+	debug_assert_eq!(ident.len(), 32);
+	keccak_512::unchecked(dst, NODE_BYTES, ident.as_ptr(), ident.len());
+
+	for i in 1..num_nodes {
+		// We use raw pointers here, see above
+		let dst = memory.offset(i as _) as *mut u8;
+		let src = memory.offset(i as isize - 1) as *mut u8;
+
+		keccak_512::unchecked(dst, NODE_BYTES, src, NODE_BYTES);
+	}
+
+	// Now this is initialized, we can treat it as a slice.
+	let nodes: &mut [Node] = slice::from_raw_parts_mut(memory, num_nodes);
+
+	// For `unroll!`, see below. If the literal in `unroll!` is not the same as the RHS here then
+	// these have got out of sync! Don't let this happen!
+	debug_assert_eq!(NODE_DWORDS, 8);
+
+	// This _should_ get unrolled by the compiler, since it's not using the loop variable.
+	for _ in 0..ETHASH_CACHE_ROUNDS {
+		for i in 0..num_nodes {
+			let data_idx = (num_nodes - 1 + i) % num_nodes;
+			let idx = nodes.get_unchecked_mut(i).as_words()[0] as usize % num_nodes;
+
+			let data = {
+				let mut data: Node = nodes.get_unchecked(data_idx).clone();
+				let rhs: &Node = nodes.get_unchecked(idx);
+
+				unroll! {
+					for w in 0..8 {
+						*data.as_dwords_mut().get_unchecked_mut(w) ^=
+							*rhs.as_dwords().get_unchecked(w);
+					}
+				}
+
+				data
+			};
+
+			keccak_512::write(&data.bytes, &mut nodes.get_unchecked_mut(i).bytes);
+		}
+	}
+}

ethash/src/compute.rs

@@ -19,30 +19,16 @@
 
 // TODO: fix endianess for big endian
 
-use primal::is_prime;
+use keccak::{keccak_512, keccak_256, H256};
-use std::cell::Cell;
+use cache::{NodeCache, NodeCacheBuilder};
+use seed_compute::SeedHashCompute;
+use shared::*;
+use std::io;
+
 use std::mem;
+use std::path::Path;
 use std::ptr;
-use hash;
-use std::slice;
-use std::path::{Path, PathBuf};
-use std::io::{self, Read, Write};
-use std::fs::{self, File};
 
-use parking_lot::Mutex;
-
-pub const ETHASH_EPOCH_LENGTH: u64 = 30000;
-pub const ETHASH_CACHE_ROUNDS: usize = 3;
-pub const ETHASH_MIX_BYTES: usize = 128;
-pub const ETHASH_ACCESSES: usize = 64;
-pub const ETHASH_DATASET_PARENTS: u32 = 256;
-
-const DATASET_BYTES_INIT: u64 = 1 << 30;
-const DATASET_BYTES_GROWTH: u64 = 1 << 23;
-const CACHE_BYTES_INIT: u64 = 1 << 24;
-const CACHE_BYTES_GROWTH: u64 = 1 << 17;
-const NODE_WORDS: usize = 64 / 4;
-const NODE_BYTES: usize = 64;
 const MIX_WORDS: usize = ETHASH_MIX_BYTES / 4;
 const MIX_NODES: usize = MIX_WORDS / NODE_WORDS;
 const FNV_PRIME: u32 = 0x01000193;
@@ -55,48 +41,24 @@ pub struct ProofOfWork {
 	pub mix_hash: H256,
 }
 
-struct Node {
-	bytes: [u8; NODE_BYTES],
-}
-
-impl Default for Node {
-	fn default() -> Self {
-		Node { bytes: [0u8; NODE_BYTES] }
-	}
-}
-
-impl Clone for Node {
-	fn clone(&self) -> Self {
-		Node { bytes: *&self.bytes }
-	}
-}
-
-impl Node {
-	#[inline]
-	fn as_words(&self) -> &[u32; NODE_WORDS] {
-		unsafe { mem::transmute(&self.bytes) }
-	}
-
-	#[inline]
-	fn as_words_mut(&mut self) -> &mut [u32; NODE_WORDS] {
-		unsafe { mem::transmute(&mut self.bytes) }
-	}
-}
-
-pub type H256 = [u8; 32];
-
 pub struct Light {
-	cache_dir: PathBuf,
 	block_number: u64,
-	cache: Vec<Node>,
+	cache: NodeCache,
-	seed_compute: Mutex<SeedHashCompute>,
 }
 
 /// Light cache structure
 impl Light {
-	/// Create a new light cache for a given block number
+	pub fn new_with_builder(
-	pub fn new<T: AsRef<Path>>(cache_dir: T, block_number: u64) -> Light {
+		builder: &NodeCacheBuilder,
-		light_new(cache_dir, block_number)
+		cache_dir: &Path,
+		block_number: u64,
+	) -> Self {
+		let cache = builder.new_cache(cache_dir.to_path_buf(), block_number);
+
+		Light {
+			block_number: block_number,
+			cache: cache,
+		}
 	}
 
 	/// Calculate the light boundary data
@@ -106,107 +68,25 @@ impl Light {
 		light_compute(self, header_hash, nonce)
 	}
 
-	pub fn file_path<T: AsRef<Path>>(cache_dir: T, seed_hash: H256) -> PathBuf {
+	pub fn from_file_with_builder(
-		let mut cache_dir = cache_dir.as_ref().to_path_buf();
+		builder: &NodeCacheBuilder,
-		cache_dir.push(to_hex(&seed_hash));
+		cache_dir: &Path,
-		cache_dir
+		block_number: u64,
-	}
+	) -> io::Result<Self> {
-
+		let cache = builder.from_file(cache_dir.to_path_buf(), block_number)?;
-	pub fn from_file<T: AsRef<Path>>(cache_dir: T, block_number: u64) -> io::Result<Light> {
-		let seed_compute = SeedHashCompute::new();
-		let path = Light::file_path(&cache_dir, seed_compute.get_seedhash(block_number));
-		let mut file = File::open(path)?;
-
-		let cache_size = get_cache_size(block_number);
-		if file.metadata()?.len() != cache_size as u64 {
-			return Err(io::Error::new(io::ErrorKind::Other, "Cache file size mismatch"));
-		}
-		let num_nodes = cache_size / NODE_BYTES;
-		let mut nodes: Vec<Node> = Vec::with_capacity(num_nodes);
-
-		unsafe { nodes.set_len(num_nodes) };
-
-		let buf = unsafe { slice::from_raw_parts_mut(nodes.as_mut_ptr() as *mut u8, cache_size) };
-		file.read_exact(buf)?;
 		Ok(Light {
-			block_number,
+			block_number: block_number,
-			cache_dir: cache_dir.as_ref().to_path_buf(),
+			cache: cache,
-			cache: nodes,
-			seed_compute: Mutex::new(seed_compute),
 		})
 	}
 
-	pub fn to_file(&self) -> io::Result<PathBuf> {
+	pub fn to_file(&mut self) -> io::Result<&Path> {
-		let seed_compute = self.seed_compute.lock();
+		self.cache.flush()?;
-		let path = Light::file_path(&self.cache_dir, seed_compute.get_seedhash(self.block_number));
+		Ok(self.cache.cache_path())
-
-		if self.block_number >= ETHASH_EPOCH_LENGTH * 2 {
-			let deprecated = Light::file_path(
-				&self.cache_dir,
-				seed_compute.get_seedhash(self.block_number - ETHASH_EPOCH_LENGTH * 2)
-			);
-
-			if deprecated.exists() {
-				debug!(target: "ethash", "removing: {:?}", &deprecated);
-				fs::remove_file(deprecated)?;
-			}
-		}
-
-		fs::create_dir_all(path.parent().unwrap())?;
-		let mut file = File::create(&path)?;
-
-		let cache_size = self.cache.len() * NODE_BYTES;
-		let buf = unsafe { slice::from_raw_parts(self.cache.as_ptr() as *const u8, cache_size) };
-		file.write(buf)?;
-		Ok(path)
 	}
 }
 
-pub struct SeedHashCompute {
+pub fn slow_hash_block_number(block_number: u64) -> H256 {
-	prev_epoch: Cell<u64>,
-	prev_seedhash: Cell<H256>,
-}
-
-impl SeedHashCompute {
-	#[inline]
-	pub fn new() -> SeedHashCompute {
-		SeedHashCompute {
-			prev_epoch: Cell::new(0),
-			prev_seedhash: Cell::new([0u8; 32]),
-		}
-	}
-
-	#[inline]
-	fn reset_cache(&self) {
-		self.prev_epoch.set(0);
-		self.prev_seedhash.set([0u8; 32]);
-	}
-
-	#[inline]
-	pub fn get_seedhash(&self, block_number: u64) -> H256 {
-		let epoch = block_number / ETHASH_EPOCH_LENGTH;
-		if epoch < self.prev_epoch.get() {
-			// can't build on previous hash if requesting an older block
-			self.reset_cache();
-		}
-		if epoch > self.prev_epoch.get() {
-			let seed_hash = SeedHashCompute::resume_compute_seedhash(self.prev_seedhash.get(), self.prev_epoch.get(), epoch);
-			self.prev_seedhash.set(seed_hash);
-			self.prev_epoch.set(epoch);
-		}
-		self.prev_seedhash.get()
-	}
-
-	#[inline]
-	pub fn resume_compute_seedhash(mut hash: H256, start_epoch: u64, end_epoch: u64) -> H256 {
-		for _ in start_epoch..end_epoch {
-			unsafe { hash::keccak_256(hash[..].as_mut_ptr(), 32, hash[..].as_ptr(), 32) };
-		}
-		hash
-	}
-}
-
-pub fn slow_get_seedhash(block_number: u64) -> H256 {
 	SeedHashCompute::resume_compute_seedhash([0u8; 32], 0, block_number / ETHASH_EPOCH_LENGTH)
 }
 
@@ -214,34 +94,6 @@ fn fnv_hash(x: u32, y: u32) -> u32 {
 	return x.wrapping_mul(FNV_PRIME) ^ y;
 }
 
-fn keccak_512(input: &[u8], output: &mut [u8]) {
-	unsafe { hash::keccak_512(output.as_mut_ptr(), output.len(), input.as_ptr(), input.len()) };
-}
-
-fn keccak_512_inplace(input: &mut [u8]) {
-	// This is safe since `keccak_*` uses an internal buffer and copies the result to the output. This
-	// means that we can reuse the input buffer for both input and output.
-	unsafe { hash::keccak_512(input.as_mut_ptr(), input.len(), input.as_ptr(), input.len()) };
-}
-
-fn get_cache_size(block_number: u64) -> usize {
-	let mut sz: u64 = CACHE_BYTES_INIT + CACHE_BYTES_GROWTH * (block_number / ETHASH_EPOCH_LENGTH);
-	sz = sz - NODE_BYTES as u64;
-	while !is_prime(sz / NODE_BYTES as u64) {
-		sz = sz - 2 * NODE_BYTES as u64;
-	}
-	sz as usize
-}
-
-fn get_data_size(block_number: u64) -> usize {
-	let mut sz: u64 = DATASET_BYTES_INIT + DATASET_BYTES_GROWTH * (block_number / ETHASH_EPOCH_LENGTH);
-	sz = sz - ETHASH_MIX_BYTES as u64;
-	while !is_prime(sz / ETHASH_MIX_BYTES as u64) {
-		sz = sz - 2 * ETHASH_MIX_BYTES as u64;
-	}
-	sz as usize
-}
-
 /// Difficulty quick check for POW preverification
 ///
 /// `header_hash`      The hash of the header
@@ -261,12 +113,12 @@ pub fn quick_get_difficulty(header_hash: &H256, nonce: u64, mix_hash: &H256) ->
 		ptr::copy_nonoverlapping(header_hash.as_ptr(), buf.as_mut_ptr(), 32);
 		ptr::copy_nonoverlapping(mem::transmute(&nonce), buf[32..].as_mut_ptr(), 8);
 
-		hash::keccak_512(buf.as_mut_ptr(), 64, buf.as_ptr(), 40);
+		keccak_512::unchecked(buf.as_mut_ptr(), 64, buf.as_ptr(), 40);
 		ptr::copy_nonoverlapping(mix_hash.as_ptr(), buf[64..].as_mut_ptr(), 32);
 
 		// This is initialized in `keccak_256`
 		let mut hash: [u8; 32] = mem::uninitialized();
-		hash::keccak_256(hash.as_mut_ptr(), hash.len(), buf.as_ptr(), buf.len());
+		keccak_256::unchecked(hash.as_mut_ptr(), hash.len(), buf.as_ptr(), buf.len());
 
 		hash
 	}
@@ -324,11 +176,7 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 			// leaving it fully initialized.
 			let mut out: [u8; NODE_BYTES] = mem::uninitialized();
 
-			ptr::copy_nonoverlapping(
+			ptr::copy_nonoverlapping(header_hash.as_ptr(), out.as_mut_ptr(), header_hash.len());
-				header_hash.as_ptr(),
-				out.as_mut_ptr(),
-				header_hash.len(),
-			);
 			ptr::copy_nonoverlapping(
 				mem::transmute(&nonce),
 				out[header_hash.len()..].as_mut_ptr(),
@@ -336,11 +184,11 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 			);
 
 			// compute keccak-512 hash and replicate across mix
-			hash::keccak_512(
+			keccak_512::unchecked(
 				out.as_mut_ptr(),
 				NODE_BYTES,
 				out.as_ptr(),
-				header_hash.len() + mem::size_of::<u64>()
+				header_hash.len() + mem::size_of::<u64>(),
 			);
 
 			Node { bytes: out }
@@ -354,7 +202,7 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 	let page_size = 4 * MIX_WORDS;
 	let num_full_pages = (full_size / page_size) as u32;
 	// deref once for better performance
-	let cache: &[Node] = &light.cache;
+	let cache: &[Node] = light.cache.as_ref();
 	let first_val = buf.half_mix.as_words()[0];
 
 	debug_assert_eq!(MIX_NODES, 2);
@@ -364,14 +212,10 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 		let index = {
 			// This is trivially safe, but does not work on big-endian. The safety of this is
 			// asserted in debug builds (see the definition of `make_const_array!`).
-			let mix_words: &mut [u32; MIX_WORDS] = unsafe {
+			let mix_words: &mut [u32; MIX_WORDS] =
-				make_const_array!(MIX_WORDS, &mut mix)
+				unsafe { make_const_array!(MIX_WORDS, &mut mix) };
-			};
 
-			fnv_hash(
+			fnv_hash(first_val ^ i, mix_words[i as usize % MIX_WORDS]) % num_full_pages
-				first_val ^ i,
-				mix_words[i as usize % MIX_WORDS]
-			) % num_full_pages
 		};
 
 		unroll! {
@@ -403,9 +247,8 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 		// times and set each index, leaving the array fully initialized. THIS ONLY WORKS ON LITTLE-
 		// ENDIAN MACHINES. See a future PR to make this and the rest of the code work correctly on
 		// big-endian arches like mips.
-		let mut compress: &mut [u32; MIX_WORDS / 4] = unsafe {
+		let compress: &mut [u32; MIX_WORDS / 4] =
-			make_const_array!(MIX_WORDS / 4, &mut buf.compress_bytes)
+			unsafe { make_const_array!(MIX_WORDS / 4, &mut buf.compress_bytes) };
-		};
 
 		// Compress mix
 		debug_assert_eq!(MIX_WORDS / 4, 8);
@@ -430,7 +273,7 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 		// We overwrite the second half since `keccak_256` has an internal buffer and so allows
 		// overlapping arrays as input.
 		let write_ptr: *mut u8 = mem::transmute(&mut buf.compress_bytes);
-		hash::keccak_256(
+		keccak_256::unchecked(
 			write_ptr,
 			buf.compress_bytes.len(),
 			read_ptr,
@@ -439,25 +282,21 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
 		buf.compress_bytes
 	};
 
-	ProofOfWork {
+	ProofOfWork { mix_hash: mix_hash, value: value }
-		mix_hash: mix_hash,
-		value: value,
-	}
 }
 
+// TODO: Use the `simd` crate
 fn calculate_dag_item(node_index: u32, cache: &[Node]) -> Node {
 	let num_parent_nodes = cache.len();
 	let mut ret = cache[node_index as usize % num_parent_nodes].clone();
 	ret.as_words_mut()[0] ^= node_index;
 
-	keccak_512_inplace(&mut ret.bytes);
+	keccak_512::inplace(ret.as_bytes_mut());
 
 	debug_assert_eq!(NODE_WORDS, 16);
 	for i in 0..ETHASH_DATASET_PARENTS as u32 {
-		let parent_index = fnv_hash(
+		let parent_index = fnv_hash(node_index ^ i, ret.as_words()[i as usize % NODE_WORDS]) %
-			node_index ^ i,
+			num_parent_nodes as u32;
-			ret.as_words()[i as usize % NODE_WORDS],
-		) % num_parent_nodes as u32;
 		let parent = &cache[parent_index as usize];
 
 		unroll! {
@@ -467,69 +306,18 @@ fn calculate_dag_item(node_index: u32, cache: &[Node]) -> Node {
 		}
 	}
 
-	keccak_512_inplace(&mut ret.bytes);
+	keccak_512::inplace(ret.as_bytes_mut());
 
 	ret
 }
 
-fn light_new<T: AsRef<Path>>(cache_dir: T, block_number: u64) -> Light {
+#[cfg(test)]
-	let seed_compute = SeedHashCompute::new();
+mod test {
-	let seedhash = seed_compute.get_seedhash(block_number);
+	use super::*;
-	let cache_size = get_cache_size(block_number);
+	use std::fs;
 
-	assert!(cache_size % NODE_BYTES == 0, "Unaligned cache size");
+	#[test]
-	let num_nodes = cache_size / NODE_BYTES;
+	fn test_get_cache_size() {
-
-	let mut nodes: Vec<Node> = Vec::with_capacity(num_nodes);
-	unsafe {
-		// Use uninit instead of unnecessarily writing `size_of::<Node>() * num_nodes` 0s
-		nodes.set_len(num_nodes);
-
-		keccak_512(&seedhash[0..32], &mut nodes.get_unchecked_mut(0).bytes);
-		for i in 1..num_nodes {
-			hash::keccak_512(nodes.get_unchecked_mut(i).bytes.as_mut_ptr(), NODE_BYTES, nodes.get_unchecked(i - 1).bytes.as_ptr(), NODE_BYTES);
-		}
-
-		debug_assert_eq!(NODE_WORDS, 16);
-
-		// This _should_ get unrolled by the compiler, since it's not using the loop variable.
-		for _ in 0..ETHASH_CACHE_ROUNDS {
-			for i in 0..num_nodes {
-				let idx = *nodes.get_unchecked_mut(i).as_words().get_unchecked(0) as usize % num_nodes;
-				let mut data = nodes.get_unchecked((num_nodes - 1 + i) % num_nodes).clone();
-
-				unroll! {
-					for w in 0..16 {
-						*data.as_words_mut().get_unchecked_mut(w) ^= *nodes.get_unchecked(idx).as_words().get_unchecked(w);
-					}
-				}
-
-				keccak_512(&data.bytes, &mut nodes.get_unchecked_mut(i).bytes);
-			}
-		}
-	}
-
-	Light {
-		block_number,
-		cache_dir: cache_dir.as_ref().to_path_buf(),
-		cache: nodes,
-		seed_compute: Mutex::new(seed_compute),
-	}
-}
-
-static CHARS: &'static [u8] = b"0123456789abcdef";
-fn to_hex(bytes: &[u8]) -> String {
-	let mut v = Vec::with_capacity(bytes.len() * 2);
-	for &byte in bytes.iter() {
-		v.push(CHARS[(byte >> 4) as usize]);
-		v.push(CHARS[(byte & 0xf) as usize]);
-	}
-
-	unsafe { String::from_utf8_unchecked(v) }
-}
-
-#[test]
-fn test_get_cache_size() {
 		// https://github.com/ethereum/wiki/wiki/Ethash/ef6b93f9596746a088ea95d01ca2778be43ae68f#data-sizes
 		assert_eq!(16776896usize, get_cache_size(0));
 		assert_eq!(16776896usize, get_cache_size(1));
@@ -539,10 +327,10 @@ fn test_get_cache_size() {
 		assert_eq!(284950208usize, get_cache_size(2046 * ETHASH_EPOCH_LENGTH));
 		assert_eq!(285081536usize, get_cache_size(2047 * ETHASH_EPOCH_LENGTH));
 		assert_eq!(285081536usize, get_cache_size(2048 * ETHASH_EPOCH_LENGTH - 1));
-}
+	}
 
-#[test]
+	#[test]
-fn test_get_data_size() {
+	fn test_get_data_size() {
 		// https://github.com/ethereum/wiki/wiki/Ethash/ef6b93f9596746a088ea95d01ca2778be43ae68f#data-sizes
 		assert_eq!(1073739904usize, get_data_size(0));
 		assert_eq!(1073739904usize, get_data_size(1));
@@ -551,75 +339,74 @@ fn test_get_data_size() {
 		assert_eq!(1082130304usize, get_data_size(ETHASH_EPOCH_LENGTH + 1));
 		assert_eq!(18236833408usize, get_data_size(2046 * ETHASH_EPOCH_LENGTH));
 		assert_eq!(18245220736usize, get_data_size(2047 * ETHASH_EPOCH_LENGTH));
-}
+	}
 
-#[test]
+	#[test]
-fn test_difficulty_test() {
+	fn test_difficulty_test() {
-	let hash = [0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe, 0xe4, 0x0a, 0xb3, 0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f, 0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94, 0x05, 0x52, 0x7d, 0x72];
+		let hash = [
-	let mix_hash = [0x1f, 0xff, 0x04, 0xce, 0xc9, 0x41, 0x73, 0xfd, 0x59, 0x1e, 0x3d, 0x89, 0x60, 0xce, 0x6b, 0xdf, 0x8b, 0x19, 0x71, 0x04, 0x8c, 0x71, 0xff, 0x93, 0x7b, 0xb2, 0xd3, 0x2a, 0x64, 0x31, 0xab, 0x6d];
+			0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe, 0xe4, 0x0a, 0xb3,
+			0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f, 0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94,
+			0x05, 0x52, 0x7d, 0x72,
+		];
+		let mix_hash = [
+			0x1f, 0xff, 0x04, 0xce, 0xc9, 0x41, 0x73, 0xfd, 0x59, 0x1e, 0x3d, 0x89, 0x60, 0xce,
+			0x6b, 0xdf, 0x8b, 0x19, 0x71, 0x04, 0x8c, 0x71, 0xff, 0x93, 0x7b, 0xb2, 0xd3, 0x2a,
+			0x64, 0x31, 0xab, 0x6d,
+		];
 		let nonce = 0xd7b3ac70a301a249;
-	let boundary_good = [0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x3e, 0x9b, 0x6c, 0x69, 0xbc, 0x2c, 0xe2, 0xa2, 0x4a, 0x8e, 0x95, 0x69, 0xef, 0xc7, 0xd7, 0x1b, 0x33, 0x35, 0xdf, 0x36, 0x8c, 0x9a, 0xe9, 0x7e, 0x53, 0x84];
+		let boundary_good = [
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x3e, 0x9b, 0x6c, 0x69, 0xbc, 0x2c, 0xe2, 0xa2,
+			0x4a, 0x8e, 0x95, 0x69, 0xef, 0xc7, 0xd7, 0x1b, 0x33, 0x35, 0xdf, 0x36, 0x8c, 0x9a,
+			0xe9, 0x7e, 0x53, 0x84,
+		];
 		assert_eq!(quick_get_difficulty(&hash, nonce, &mix_hash)[..], boundary_good[..]);
-	let boundary_bad = [0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x3a, 0x9b, 0x6c, 0x69, 0xbc, 0x2c, 0xe2, 0xa2, 0x4a, 0x8e, 0x95, 0x69, 0xef, 0xc7, 0xd7, 0x1b, 0x33, 0x35, 0xdf, 0x36, 0x8c, 0x9a, 0xe9, 0x7e, 0x53, 0x84];
+		let boundary_bad = [
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x3a, 0x9b, 0x6c, 0x69, 0xbc, 0x2c, 0xe2, 0xa2,
+			0x4a, 0x8e, 0x95, 0x69, 0xef, 0xc7, 0xd7, 0x1b, 0x33, 0x35, 0xdf, 0x36, 0x8c, 0x9a,
+			0xe9, 0x7e, 0x53, 0x84,
+		];
 		assert!(quick_get_difficulty(&hash, nonce, &mix_hash)[..] != boundary_bad[..]);
-}
+	}
 
-#[test]
+	#[test]
-fn test_light_compute() {
+	fn test_light_compute() {
-	let hash = [0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe, 0xe4, 0x0a, 0xb3, 0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f, 0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94, 0x05, 0x52, 0x7d, 0x72];
+		let hash = [
-	let mix_hash = [0x1f, 0xff, 0x04, 0xce, 0xc9, 0x41, 0x73, 0xfd, 0x59, 0x1e, 0x3d, 0x89, 0x60, 0xce, 0x6b, 0xdf, 0x8b, 0x19, 0x71, 0x04, 0x8c, 0x71, 0xff, 0x93, 0x7b, 0xb2, 0xd3, 0x2a, 0x64, 0x31, 0xab, 0x6d];
+			0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe, 0xe4, 0x0a, 0xb3,
-	let boundary = [0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x3e, 0x9b, 0x6c, 0x69, 0xbc, 0x2c, 0xe2, 0xa2, 0x4a, 0x8e, 0x95, 0x69, 0xef, 0xc7, 0xd7, 0x1b, 0x33, 0x35, 0xdf, 0x36, 0x8c, 0x9a, 0xe9, 0x7e, 0x53, 0x84];
+			0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f, 0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94,
+			0x05, 0x52, 0x7d, 0x72,
+		];
+		let mix_hash = [
+			0x1f, 0xff, 0x04, 0xce, 0xc9, 0x41, 0x73, 0xfd, 0x59, 0x1e, 0x3d, 0x89, 0x60, 0xce,
+			0x6b, 0xdf, 0x8b, 0x19, 0x71, 0x04, 0x8c, 0x71, 0xff, 0x93, 0x7b, 0xb2, 0xd3, 0x2a,
+			0x64, 0x31, 0xab, 0x6d,
+		];
+		let boundary = [
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x3e, 0x9b, 0x6c, 0x69, 0xbc, 0x2c, 0xe2, 0xa2,
+			0x4a, 0x8e, 0x95, 0x69, 0xef, 0xc7, 0xd7, 0x1b, 0x33, 0x35, 0xdf, 0x36, 0x8c, 0x9a,
+			0xe9, 0x7e, 0x53, 0x84,
+		];
 		let nonce = 0xd7b3ac70a301a249;
 		// difficulty = 0x085657254bd9u64;
-	let light = Light::new(&::std::env::temp_dir(), 486382);
+		let light = NodeCacheBuilder::new(None).light(&::std::env::temp_dir(), 486382);
 		let result = light_compute(&light, &hash, nonce);
 		assert_eq!(result.mix_hash[..], mix_hash[..]);
 		assert_eq!(result.value[..], boundary[..]);
-}
+	}
 
-#[test]
+	#[test]
-fn test_seed_compute_once() {
+	fn test_drop_old_data() {
-	let seed_compute = SeedHashCompute::new();
-	let hash = [241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253, 147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162];
-	assert_eq!(seed_compute.get_seedhash(486382), hash);
-}
-
-#[test]
-fn test_seed_compute_zero() {
-	let seed_compute = SeedHashCompute::new();
-	assert_eq!(seed_compute.get_seedhash(0), [0u8; 32]);
-}
-
-#[test]
-fn test_seed_compute_after_older() {
-	let seed_compute = SeedHashCompute::new();
-	// calculating an older value first shouldn't affect the result
-	let _ = seed_compute.get_seedhash(50000);
-	let hash = [241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253, 147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162];
-	assert_eq!(seed_compute.get_seedhash(486382), hash);
-}
-
-#[test]
-fn test_seed_compute_after_newer() {
-	let seed_compute = SeedHashCompute::new();
-	// calculating an newer value first shouldn't affect the result
-	let _ = seed_compute.get_seedhash(972764);
-	let hash = [241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253, 147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162];
-	assert_eq!(seed_compute.get_seedhash(486382), hash);
-}
-
-#[test]
-fn test_drop_old_data() {
 		let path = ::std::env::temp_dir();
-	let first = Light::new(&path, 0).to_file().unwrap();
+		let builder = NodeCacheBuilder::new(None);
+		let first = builder.light(&path, 0).to_file().unwrap().to_owned();
 
-	let second = Light::new(&path, ETHASH_EPOCH_LENGTH).to_file().unwrap();
+		let second = builder.light(&path, ETHASH_EPOCH_LENGTH).to_file().unwrap().to_owned();
 		assert!(fs::metadata(&first).is_ok());
 
-	let _ = Light::new(&path, ETHASH_EPOCH_LENGTH * 2).to_file();
+		let _ = builder.light(&path, ETHASH_EPOCH_LENGTH * 2).to_file();
 		assert!(fs::metadata(&first).is_err());
 		assert!(fs::metadata(&second).is_ok());
 
-	let _ = Light::new(&path, ETHASH_EPOCH_LENGTH * 3).to_file();
+		let _ = builder.light(&path, ETHASH_EPOCH_LENGTH * 3).to_file();
 		assert!(fs::metadata(&second).is_err());
+	}
 }

ethash/src/keccak.rs

@@ -0,0 +1,52 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+extern crate hash;
+
+pub type H256 = [u8; 32];
+
+pub mod keccak_512 {
+	use super::hash;
+
+	pub use self::hash::keccak_512 as unchecked;
+
+	pub fn write(input: &[u8], output: &mut [u8]) {
+		unsafe { hash::keccak_512(output.as_mut_ptr(), output.len(), input.as_ptr(), input.len()) };
+	}
+
+	pub fn inplace(input: &mut [u8]) {
+		// This is safe since `sha3_*` uses an internal buffer and copies the result to the output. This
+		// means that we can reuse the input buffer for both input and output.
+		unsafe { hash::keccak_512(input.as_mut_ptr(), input.len(), input.as_ptr(), input.len()) };
+	}
+}
+
+pub mod keccak_256 {
+	use super::hash;
+
+	pub use self::hash::keccak_256 as unchecked;
+
+	#[allow(dead_code)]
+	pub fn write(input: &[u8], output: &mut [u8]) {
+		unsafe { hash::keccak_256(output.as_mut_ptr(), output.len(), input.as_ptr(), input.len()) };
+	}
+
+	pub fn inplace(input: &mut [u8]) {
+		// This is safe since `sha3_*` uses an internal buffer and copies the result to the output. This
+		// means that we can reuse the input buffer for both input and output.
+		unsafe { hash::keccak_256(input.as_mut_ptr(), input.len(), input.as_ptr(), input.len()) };
+	}
+}

ethash/src/lib.rs

@@ -14,28 +14,35 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-//! Ethash implementation
-//! See https://github.com/ethereum/wiki/wiki/Ethash
-
 #![cfg_attr(feature = "benches", feature(test))]
 
 extern crate primal;
-extern crate hash;
 extern crate parking_lot;
+extern crate either;
+extern crate memmap;
 
 #[macro_use]
 extern crate crunchy;
 #[macro_use]
 extern crate log;
-mod compute;
 
+mod compute;
+mod seed_compute;
+mod cache;
+mod keccak;
+mod shared;
+
+pub use cache::{NodeCacheBuilder, OptimizeFor};
+pub use compute::{ProofOfWork, quick_get_difficulty, slow_hash_block_number};
+use compute::Light;
+use keccak::H256;
+use parking_lot::Mutex;
+pub use seed_compute::SeedHashCompute;
+pub use shared::ETHASH_EPOCH_LENGTH;
 use std::mem;
 use std::path::{Path, PathBuf};
-use compute::Light;
-pub use compute::{ETHASH_EPOCH_LENGTH, H256, ProofOfWork, SeedHashCompute, quick_get_difficulty, slow_get_seedhash};
 
 use std::sync::Arc;
-use parking_lot::Mutex;
 
 struct LightCache {
 	recent_epoch: Option<u64>,
@@ -46,15 +53,17 @@ struct LightCache {
 
 /// Light/Full cache manager.
 pub struct EthashManager {
+	nodecache_builder: NodeCacheBuilder,
 	cache: Mutex<LightCache>,
 	cache_dir: PathBuf,
 }
 
 impl EthashManager {
 	/// Create a new new instance of ethash manager
-	pub fn new<T: AsRef<Path>>(cache_dir: T) -> EthashManager {
+	pub fn new<T: Into<Option<OptimizeFor>>>(cache_dir: &Path, optimize_for: T) -> EthashManager {
 		EthashManager {
-			cache_dir: cache_dir.as_ref().to_path_buf(),
+			cache_dir: cache_dir.to_path_buf(),
+			nodecache_builder: NodeCacheBuilder::new(optimize_for.into().unwrap_or_default()),
 			cache: Mutex::new(LightCache {
 				recent_epoch: None,
 				recent: None,
@@ -96,11 +105,19 @@ impl EthashManager {
 			};
 			match light {
 				None => {
-					let light = match Light::from_file(&self.cache_dir, block_number) {
+					let light = match Light::from_file_with_builder(
+						&self.nodecache_builder,
+						&self.cache_dir,
+						block_number,
+					) {
 						Ok(light) => Arc::new(light),
 						Err(e) => {
 							debug!("Light cache file not found for {}:{}", block_number, e);
-							let light = Light::new(&self.cache_dir, block_number);
+							let mut light = Light::new_with_builder(
+								&self.nodecache_builder,
+								&self.cache_dir,
+								block_number,
+							);
 							if let Err(e) = light.to_file() {
 								warn!("Light cache file write error: {}", e);
 							}
@@ -120,7 +137,7 @@ impl EthashManager {
 
 #[test]
 fn test_lru() {
-	let ethash = EthashManager::new(&::std::env::temp_dir());
+	let ethash = EthashManager::new(&::std::env::temp_dir(), None);
 	let hash = [0u8; 32];
 	ethash.compute_light(1, &hash, 1);
 	ethash.compute_light(50000, &hash, 1);
@@ -138,24 +155,89 @@ fn test_lru() {
 mod benchmarks {
 	extern crate test;
 
-	use compute::{Light, light_compute, SeedHashCompute};
 	use self::test::Bencher;
+	use cache::{NodeCacheBuilder, OptimizeFor};
+	use compute::{Light, light_compute};
+
+	const HASH: [u8; 32] = [0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe,
+	                        0xe4, 0x0a, 0xb3, 0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f,
+	                        0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94, 0x05, 0x52, 0x7d, 0x72];
+	const NONCE: u64 = 0xd7b3ac70a301a249;
 
 	#[bench]
-	fn bench_light_compute(b: &mut Bencher) {
+	fn bench_light_compute_memmap(b: &mut Bencher) {
-		use ::std::env;
+		use std::env;
 
-		let hash = [0xf5, 0x7e, 0x6f, 0x3a, 0xcf, 0xc0, 0xdd, 0x4b, 0x5b, 0xf2, 0xbe, 0xe4, 0x0a, 0xb3, 0x35, 0x8a, 0xa6, 0x87, 0x73, 0xa8, 0xd0, 0x9f, 0x5e, 0x59, 0x5e, 0xab, 0x55, 0x94, 0x05, 0x52, 0x7d, 0x72];
+		let builder = NodeCacheBuilder::new(OptimizeFor::Memory);
-		let nonce = 0xd7b3ac70a301a249;
+		let light = Light::new_with_builder(&builder, &env::temp_dir(), 486382);
-		let light = Light::new(env::temp_dir(), 486382);
 
-		b.iter(|| light_compute(&light, &hash, nonce));
+		b.iter(|| light_compute(&light, &HASH, NONCE));
 	}
 
 	#[bench]
-	fn bench_seedhash(b: &mut Bencher) {
+	fn bench_light_compute_memory(b: &mut Bencher) {
-		let seed_compute = SeedHashCompute::new();
+		use std::env;
 
-		b.iter(|| seed_compute.get_seedhash(486382));
+		let light = Light::new(&env::temp_dir(), 486382);
+
+		b.iter(|| light_compute(&light, &HASH, NONCE));
+	}
+
+	#[bench]
+	#[ignore]
+	fn bench_light_new_round_trip_memmap(b: &mut Bencher) {
+		use std::env;
+
+		b.iter(|| {
+			let builder = NodeCacheBuilder::new(OptimizeFor::Memory);
+			let light = Light::new_with_builder(&builder, &env::temp_dir(), 486382);
+			light_compute(&light, &HASH, NONCE);
+		});
+	}
+
+	#[bench]
+	#[ignore]
+	fn bench_light_new_round_trip_memory(b: &mut Bencher) {
+		use std::env;
+		b.iter(|| {
+			let light = Light::new(&env::temp_dir(), 486382);
+			light_compute(&light, &HASH, NONCE);
+		});
+	}
+
+	#[bench]
+	fn bench_light_from_file_round_trip_memory(b: &mut Bencher) {
+		use std::env;
+
+		let dir = env::temp_dir();
+		let height = 486382;
+		{
+			let mut dummy = Light::new(&dir, height);
+			dummy.to_file().unwrap();
+		}
+
+		b.iter(|| {
+			let light = Light::from_file(&dir, 486382).unwrap();
+			light_compute(&light, &HASH, NONCE);
+		});
+	}
+
+	#[bench]
+	fn bench_light_from_file_round_trip_memmap(b: &mut Bencher) {
+		use std::env;
+
+		let dir = env::temp_dir();
+		let height = 486382;
+		{
+			let builder = NodeCacheBuilder::new(OptimizeFor::Memory);
+			let mut dummy = Light::new_with_builder(&builder, &dir, height);
+			dummy.to_file().unwrap();
+		}
+
+		b.iter(|| {
+			let builder = NodeCacheBuilder::new(OptimizeFor::Memory);
+			let light = Light::from_file_with_builder(&builder, &dir, 486382).unwrap();
+			light_compute(&light, &HASH, NONCE);
+		});
 	}
 }

ethash/src/seed_compute.rs

@@ -0,0 +1,109 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use shared;
+use keccak::{keccak_256, H256};
+
+use std::cell::Cell;
+
+pub struct SeedHashCompute {
+	prev_epoch: Cell<u64>,
+	prev_seedhash: Cell<H256>,
+}
+
+impl SeedHashCompute {
+	#[inline]
+	pub fn new() -> SeedHashCompute {
+		SeedHashCompute {
+			prev_epoch: Cell::new(0),
+			prev_seedhash: Cell::new([0u8; 32]),
+		}
+	}
+
+	#[inline]
+	fn reset_cache(&self) {
+		self.prev_epoch.set(0);
+		self.prev_seedhash.set([0u8; 32]);
+	}
+
+	#[inline]
+	pub fn hash_block_number(&self, block_number: u64) -> H256 {
+		self.hash_epoch(shared::epoch(block_number))
+	}
+
+	#[inline]
+	pub fn hash_epoch(&self, epoch: u64) -> H256 {
+		if epoch < self.prev_epoch.get() {
+			// can't build on previous hash if requesting an older block
+			self.reset_cache();
+		}
+		if epoch > self.prev_epoch.get() {
+			let seed_hash = SeedHashCompute::resume_compute_seedhash(
+				self.prev_seedhash.get(),
+				self.prev_epoch.get(),
+				epoch,
+			);
+			self.prev_seedhash.set(seed_hash);
+			self.prev_epoch.set(epoch);
+		}
+		self.prev_seedhash.get()
+	}
+
+	#[inline]
+	pub fn resume_compute_seedhash(mut hash: H256, start_epoch: u64, end_epoch: u64) -> H256 {
+		for _ in start_epoch..end_epoch {
+			keccak_256::inplace(&mut hash);
+		}
+		hash
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::SeedHashCompute;
+
+	#[test]
+	fn test_seed_compute_once() {
+		let seed_compute = SeedHashCompute::new();
+		let hash = [241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253, 147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162];
+		assert_eq!(seed_compute.hash_block_number(486382), hash);
+	}
+
+	#[test]
+	fn test_seed_compute_zero() {
+		let seed_compute = SeedHashCompute::new();
+		assert_eq!(seed_compute.hash_block_number(0), [0u8; 32]);
+	}
+
+	#[test]
+	fn test_seed_compute_after_older() {
+		let seed_compute = SeedHashCompute::new();
+		// calculating an older value first shouldn't affect the result
+		let _ = seed_compute.hash_block_number(50000);
+		let hash = [241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253, 147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162];
+		assert_eq!(seed_compute.hash_block_number(486382), hash);
+	}
+
+	#[test]
+	fn test_seed_compute_after_newer() {
+		let seed_compute = SeedHashCompute::new();
+		// calculating an newer value first shouldn't affect the result
+		let _ = seed_compute.hash_block_number(972764);
+		let hash = [241, 175, 44, 134, 39, 121, 245, 239, 228, 236, 43, 160, 195, 152, 46, 7, 199, 5, 253, 147, 241, 206, 98, 43, 3, 104, 17, 40, 192, 79, 106, 162];
+		assert_eq!(seed_compute.hash_block_number(486382), hash);
+	}
+
+}

ethash/src/shared.rs

@@ -0,0 +1,149 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+use primal::is_prime;
+
+pub const DATASET_BYTES_INIT: u64 = 1 << 30;
+pub const DATASET_BYTES_GROWTH: u64 = 1 << 23;
+pub const CACHE_BYTES_INIT: u64 = 1 << 24;
+pub const CACHE_BYTES_GROWTH: u64 = 1 << 17;
+
+pub const ETHASH_EPOCH_LENGTH: u64 = 30000;
+pub const ETHASH_CACHE_ROUNDS: usize = 3;
+pub const ETHASH_MIX_BYTES: usize = 128;
+pub const ETHASH_ACCESSES: usize = 64;
+pub const ETHASH_DATASET_PARENTS: u32 = 256;
+pub const NODE_DWORDS: usize = NODE_WORDS / 2;
+pub const NODE_WORDS: usize = NODE_BYTES / 4;
+pub const NODE_BYTES: usize = 64;
+
+pub fn epoch(block_number: u64) -> u64 {
+	block_number / ETHASH_EPOCH_LENGTH
+}
+
+static CHARS: &'static [u8] = b"0123456789abcdef";
+pub fn to_hex(bytes: &[u8]) -> String {
+	let mut v = Vec::with_capacity(bytes.len() * 2);
+	for &byte in bytes.iter() {
+		v.push(CHARS[(byte >> 4) as usize]);
+		v.push(CHARS[(byte & 0xf) as usize]);
+	}
+
+	unsafe { String::from_utf8_unchecked(v) }
+}
+
+pub fn get_cache_size(block_number: u64) -> usize {
+	// TODO: Memoise
+	let mut sz: u64 = CACHE_BYTES_INIT + CACHE_BYTES_GROWTH * (block_number / ETHASH_EPOCH_LENGTH);
+	sz = sz - NODE_BYTES as u64;
+	while !is_prime(sz / NODE_BYTES as u64) {
+		sz = sz - 2 * NODE_BYTES as u64;
+	}
+	sz as usize
+}
+
+pub fn get_data_size(block_number: u64) -> usize {
+	// TODO: Memoise
+	let mut sz: u64 = DATASET_BYTES_INIT + DATASET_BYTES_GROWTH * (block_number / ETHASH_EPOCH_LENGTH);
+	sz = sz - ETHASH_MIX_BYTES as u64;
+	while !is_prime(sz / ETHASH_MIX_BYTES as u64) {
+		sz = sz - 2 * ETHASH_MIX_BYTES as u64;
+	}
+	sz as usize
+}
+
+pub type NodeBytes = [u8; NODE_BYTES];
+pub type NodeWords = [u32; NODE_WORDS];
+pub type NodeDwords = [u64; NODE_DWORDS];
+
+macro_rules! static_assert_size_eq {
+	(@inner $a:ty, $b:ty, $($rest:ty),*) => {
+		fn first() {
+			static_assert_size_eq!($a, $b);
+		}
+
+		fn second() {
+			static_assert_size_eq!($b, $($rest),*);
+		}
+	};
+	(@inner $a:ty, $b:ty) => {
+		unsafe {
+			let val: $b = ::std::mem::uninitialized();
+			let _: $a = ::std::mem::transmute(val);
+		}
+	};
+	($($rest:ty),*) => {
+		static_assert_size_eq!(size_eq: $($rest),*);
+	};
+	($name:ident : $($rest:ty),*) => {
+		#[allow(dead_code)]
+		fn $name() {
+			static_assert_size_eq!(@inner $($rest),*);
+		}
+	};
+}
+
+static_assert_size_eq!(Node, NodeBytes, NodeWords, NodeDwords);
+
+#[repr(C)]
+pub union Node {
+	pub dwords: NodeDwords,
+	pub words: NodeWords,
+	pub bytes: NodeBytes,
+}
+
+impl Clone for Node {
+	fn clone(&self) -> Self {
+		unsafe { Node { bytes: *&self.bytes } }
+	}
+}
+
+// We use `inline(always)` because I was experiencing an 100% slowdown and `perf` showed that these
+// calls were taking up ~30% of the runtime. Adding these annotations fixes the issue. Remove at
+// your peril, if and only if you have benchmarks to prove that this doesn't reintroduce the
+// performance regression. It's not caused by the `debug_assert_eq!` either, your guess is as good
+// as mine.
+impl Node {
+	#[inline(always)]
+	pub fn as_bytes(&self) -> &NodeBytes {
+		unsafe { &self.bytes }
+	}
+
+	#[inline(always)]
+	pub fn as_bytes_mut(&mut self) -> &mut NodeBytes {
+		unsafe { &mut self.bytes }
+	}
+
+	#[inline(always)]
+	pub fn as_words(&self) -> &NodeWords {
+		unsafe { &self.words }
+	}
+
+	#[inline(always)]
+	pub fn as_words_mut(&mut self) -> &mut NodeWords {
+		unsafe { &mut self.words }
+	}
+
+	#[inline(always)]
+	pub fn as_dwords(&self) -> &NodeDwords {
+		unsafe { &self.dwords }
+	}
+
+	#[inline(always)]
+	pub fn as_dwords_mut(&mut self) -> &mut NodeDwords {
+		unsafe { &mut self.dwords }
+	}
+}

ethcore/node_filter/src/lib.rs

@@ -133,7 +133,7 @@ mod test {
 	fn node_filter() {
 		let contract_addr = Address::from_str("0000000000000000000000000000000000000005").unwrap();
 		let data = include_bytes!("../res/node_filter.json");
-		let spec = Spec::load(::std::env::temp_dir(), &data[..]).unwrap();
+		let spec = Spec::load(&::std::env::temp_dir(), &data[..]).unwrap();
 		let client_db = Arc::new(::util::kvdb::in_memory(::ethcore::db::NUM_COLUMNS.unwrap_or(0)));
 
 		let client = Client::new(

ethcore/src/engines/basic_authority.rs

@@ -270,7 +270,7 @@ mod tests {
 	/// Create a new test chain spec with `BasicAuthority` consensus engine.
 	fn new_test_authority() -> Spec {
 		let bytes: &[u8] = include_bytes!("../../res/basic_authority.json");
-		Spec::load(::std::env::temp_dir(), bytes).expect("invalid chain spec")
+		Spec::load(&::std::env::temp_dir(), bytes).expect("invalid chain spec")
 	}
 
 	#[test]

ethcore/src/ethereum/ethash.rs

@@ -19,7 +19,7 @@ use std::cmp;
 use std::collections::{BTreeMap, HashMap};
 use std::sync::{Arc, Weak};
 use hash::{KECCAK_EMPTY_LIST_RLP};
-use ethash::{quick_get_difficulty, slow_get_seedhash, EthashManager};
+use ethash::{quick_get_difficulty, slow_hash_block_number, EthashManager, OptimizeFor};
 use bigint::prelude::U256;
 use bigint::hash::{H256, H64};
 use util::*;
@@ -161,18 +161,19 @@ pub struct Ethash {
 
 impl Ethash {
 	/// Create a new instance of Ethash engine
-	pub fn new<T: AsRef<Path>>(
+	pub fn new<T: Into<Option<OptimizeFor>>>(
-		cache_dir: T,
+		cache_dir: &Path,
 		params: CommonParams,
 		ethash_params: EthashParams,
 		builtins: BTreeMap<Address, Builtin>,
+		optimize_for: T,
 	) -> Arc<Self> {
 		Arc::new(Ethash {
 			tx_filter: TransactionFilter::from_params(&params),
 			params,
 			ethash_params,
 			builtins,
-			pow: EthashManager::new(cache_dir),
+			pow: EthashManager::new(cache_dir.as_ref(), optimize_for.into()),
 		})
 	}
 }
@@ -416,7 +417,7 @@ impl Engine for Arc<Ethash> {
 		let result = self.pow.compute_light(header.number() as u64, &header.bare_hash().0, header.nonce().low_u64());
 		let mix = H256(result.mix_hash);
 		let difficulty = Ethash::boundary_to_difficulty(&H256(result.value));
-		trace!(target: "miner", "num: {}, seed: {}, h: {}, non: {}, mix: {}, res: {}" , header.number() as u64, H256(slow_get_seedhash(header.number() as u64)), header.bare_hash(), header.nonce().low_u64(), H256(result.mix_hash), H256(result.value));
+		trace!(target: "miner", "num: {}, seed: {}, h: {}, non: {}, mix: {}, res: {}" , header.number() as u64, H256(slow_hash_block_number(header.number() as u64)), header.bare_hash(), header.nonce().low_u64(), H256(result.mix_hash), H256(result.value));
 		if mix != header.mix_hash() {
 			return Err(From::from(BlockError::MismatchedH256SealElement(Mismatch { expected: mix, found: header.mix_hash() })));
 		}
@@ -849,7 +850,7 @@ mod tests {
 	fn difficulty_frontier() {
 		let spec = new_homestead_test();
 		let ethparams = get_default_ethash_params();
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 
 		let mut parent_header = Header::default();
 		parent_header.set_number(1000000);
@@ -867,7 +868,7 @@ mod tests {
 	fn difficulty_homestead() {
 		let spec = new_homestead_test();
 		let ethparams = get_default_ethash_params();
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 
 		let mut parent_header = Header::default();
 		parent_header.set_number(1500000);
@@ -920,7 +921,7 @@ mod tests {
 			ecip1010_pause_transition: 3000000,
 			..get_default_ethash_params()
 		};
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 
 		let mut parent_header = Header::default();
 		parent_header.set_number(3500000);
@@ -954,7 +955,7 @@ mod tests {
 			ecip1010_continue_transition: 5000000,
 			..get_default_ethash_params()
 		};
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 
 		let mut parent_header = Header::default();
 		parent_header.set_number(5000102);
@@ -1000,7 +1001,7 @@ mod tests {
 	fn gas_limit_is_multiple_of_determinant() {
 		let spec = new_homestead_test();
 		let ethparams = get_default_ethash_params();
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 		let mut parent = Header::new();
 		let mut header = Header::new();
 		header.set_number(1);
@@ -1044,7 +1045,7 @@ mod tests {
 	fn difficulty_max_timestamp() {
 		let spec = new_homestead_test();
 		let ethparams = get_default_ethash_params();
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 
 		let mut parent_header = Header::default();
 		parent_header.set_number(1000000);
@@ -1072,7 +1073,7 @@ mod tests {
 		header.set_number(parent_header.number() + 1);
 		header.set_gas_limit(100_001.into());
 		header.set_difficulty(ethparams.minimum_difficulty);
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 		assert!(ethash.verify_block_family(&header, &parent_header, None).is_ok());
 
 		parent_header.set_number(9);
@@ -1127,7 +1128,7 @@ mod tests {
 			nonce: U256::zero(),
 		}.sign(keypair.secret(), None).into();
 
-		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new());
+		let ethash = Ethash::new(&::std::env::temp_dir(), spec.params().clone(), ethparams, BTreeMap::new(), None);
 		assert!(ethash.verify_transaction_basic(&tx1, &header).is_ok());
 		assert!(ethash.verify_transaction_basic(&tx2, &header).is_ok());
 

ethcore/src/ethereum/mod.rs

@@ -27,7 +27,6 @@ pub mod denominations;
 pub use self::ethash::{Ethash};
 pub use self::denominations::*;
 
-use std::path::Path;
 use super::spec::*;
 
 /// Most recent fork block that we support on Mainnet.
@@ -39,33 +38,47 @@ pub const FORK_SUPPORTED_ROPSTEN: u64 = 10;
 /// Most recent fork block that we support on Kovan.
 pub const FORK_SUPPORTED_KOVAN: u64 = 0;
 
-fn load<'a, T: 'a + Into<Option<&'a Path>>>(cache_dir: T, b: &[u8]) -> Spec {
+fn load<'a, T: Into<Option<SpecParams<'a>>>>(params: T, b: &[u8]) -> Spec {
-	match cache_dir.into() {
+	match params.into() {
-		Some(path) => Spec::load(path, b),
+		Some(params) => Spec::load(params, b),
 		None => Spec::load(&::std::env::temp_dir(), b)
 	}.expect("chain spec is invalid")
 }
 
 /// Create a new Foundation Olympic chain spec.
-pub fn new_olympic(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/olympic.json")) }
+pub fn new_olympic<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/olympic.json"))
+}
 
 /// Create a new Foundation Mainnet chain spec.
-pub fn new_foundation(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/foundation.json")) }
+pub fn new_foundation<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/foundation.json"))
+}
 
 /// Create a new Classic Mainnet chain spec without the DAO hardfork.
-pub fn new_classic(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/classic.json")) }
+pub fn new_classic<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/classic.json"))
+}
 
 /// Create a new Expanse mainnet chain spec.
-pub fn new_expanse(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/expanse.json")) }
+pub fn new_expanse<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/expanse.json"))
+}
 
 /// Create a new Kovan testnet chain spec.
-pub fn new_kovan(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/kovan.json")) }
+pub fn new_kovan<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/kovan.json"))
+}
 
 /// Create a new Foundation Ropsten chain spec.
-pub fn new_ropsten(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/ropsten.json")) }
+pub fn new_ropsten<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/ropsten.json"))
+}
 
 /// Create a new Morden chain spec.
-pub fn new_morden(cache_dir: &Path) -> Spec { load(cache_dir, include_bytes!("../../res/ethereum/morden.json")) }
+pub fn new_morden<'a, T: Into<SpecParams<'a>>>(params: T) -> Spec {
+	load(params.into(), include_bytes!("../../res/ethereum/morden.json"))
+}
 
 // For tests
 

ethcore/src/json_tests/test_common.rs

@@ -52,7 +52,8 @@ pub fn run_test_file(path: &Path, runner: fn (json_data: &[u8]) -> Vec<String>)
 	let mut file = File::open(&path).expect("Error opening test file");
 	file.read_to_end(&mut data).expect("Error reading test file");
 	let results = runner(&data);
-	assert!(results.is_empty());
+	let empty: [String; 0] = [];
+	assert_eq!(results, empty);
 }
 
 macro_rules! test {

ethcore/src/miner/stratum.rs

@@ -171,7 +171,7 @@ impl StratumJobDispatcher {
 	fn payload(&self, pow_hash: H256, difficulty: U256, number: u64) -> String {
 		// TODO: move this to engine
 		let target = Ethash::difficulty_to_boundary(&difficulty);
-		let seed_hash = &self.seed_compute.lock().get_seedhash(number);
+		let seed_hash = &self.seed_compute.lock().hash_block_number(number);
 		let seed_hash = H256::from_slice(&seed_hash[..]);
 		format!(
 			r#"["0x", "0x{}","0x{}","0x{}","0x{:x}"]"#,

ethcore/src/miner/work_notify.rs

@@ -72,7 +72,7 @@ impl NotifyWork for WorkPoster {
 	fn notify(&self, pow_hash: H256, difficulty: U256, number: u64) {
 		// TODO: move this to engine
 		let target = Ethash::difficulty_to_boundary(&difficulty);
-		let seed_hash = &self.seed_compute.lock().get_seedhash(number);
+		let seed_hash = &self.seed_compute.lock().hash_block_number(number);
 		let seed_hash = H256::from_slice(&seed_hash[..]);
 		let body = format!(
 			r#"{{ "result": ["0x{}","0x{}","0x{}","0x{:x}"] }}"#,

ethcore/src/spec/spec.rs

@@ -16,34 +16,37 @@
 
 //! Parameters for a block chain.
 
-use std::io::Read;
-use std::collections::BTreeMap;
-use std::path::Path;
-use std::sync::Arc;
-use rustc_hex::FromHex;
-use hash::{KECCAK_NULL_RLP, keccak};
 use super::genesis::Genesis;
 use super::seal::Generic as GenericSeal;
+use bigint::hash::{H2048, H256};
+use bigint::prelude::U256;
 
 use builtin::Builtin;
-use engines::{Engine, NullEngine, InstantSeal, BasicAuthority, AuthorityRound, Tendermint, DEFAULT_BLOCKHASH_CONTRACT};
+use bytes::Bytes;
-use vm::{EnvInfo, CallType, ActionValue, ActionParams};
+use engines::{AuthorityRound, BasicAuthority, DEFAULT_BLOCKHASH_CONTRACT, Engine, InstantSeal,
+              NullEngine, Tendermint};
 use error::Error;
+
+pub use ethash::OptimizeFor;
 use ethereum;
 use ethjson;
 use executive::Executive;
 use factory::Factories;
+use hash::{KECCAK_NULL_RLP, keccak};
 use header::{BlockNumber, Header};
+use parking_lot::RwLock;
 use pod_state::*;
 use rlp::{Rlp, RlpStream};
+use rustc_hex::FromHex;
 use state::{Backend, State, Substate};
 use state::backend::Basic as BasicBackend;
+use std::collections::BTreeMap;
+use std::io::Read;
+use std::path::Path;
+use std::sync::Arc;
 use trace::{NoopTracer, NoopVMTracer};
-use bigint::prelude::U256;
-use bigint::hash::{H256, H2048};
-use parking_lot::RwLock;
 use util::*;
-use bytes::Bytes;
+use vm::{ActionParams, ActionValue, CallType, EnvInfo};
 
 /// Parameters common to ethereum-like blockchains.
 /// NOTE: when adding bugfix hard-fork parameters,
@@ -88,7 +91,8 @@ pub struct CommonParams {
 	pub eip210_contract_code: Bytes,
 	/// Gas allocated for EIP-210 blockhash update.
 	pub eip210_contract_gas: U256,
-	/// Number of first block where EIP-211 (Metropolis: RETURNDATASIZE/RETURNDATACOPY) rules begin.
+	/// Number of first block where EIP-211 (Metropolis: RETURNDATASIZE/RETURNDATACOPY) rules
+	/// begin.
 	pub eip211_transition: BlockNumber,
 	/// Number of first block where EIP-214 rules begin.
 	pub eip214_transition: BlockNumber,
@@ -139,14 +143,10 @@ impl CommonParams {
 
 	/// Whether these params contain any bug-fix hard forks.
 	pub fn contains_bugfix_hard_fork(&self) -> bool {
-		self.eip98_transition != 0 &&
+		self.eip98_transition != 0 && self.eip155_transition != 0 &&
-			self.eip155_transition != 0 &&
+			self.validate_receipts_transition != 0 && self.eip86_transition != 0 &&
-			self.validate_receipts_transition != 0 &&
+			self.eip140_transition != 0 && self.eip210_transition != 0 &&
-			self.eip86_transition != 0 &&
+			self.eip211_transition != 0 && self.eip214_transition != 0 &&
-			self.eip140_transition != 0 &&
-			self.eip210_transition != 0 &&
-			self.eip211_transition != 0 &&
-			self.eip214_transition != 0 &&
 			self.dust_protection_transition != 0
 	}
 }
@@ -157,25 +157,59 @@ impl From<ethjson::spec::Params> for CommonParams {
 			account_start_nonce: p.account_start_nonce.map_or_else(U256::zero, Into::into),
 			maximum_extra_data_size: p.maximum_extra_data_size.into(),
 			network_id: p.network_id.into(),
-			chain_id: if let Some(n) = p.chain_id { n.into() } else { p.network_id.into() },
+			chain_id: if let Some(n) = p.chain_id {
+				n.into()
+			} else {
+				p.network_id.into()
+			},
 			subprotocol_name: p.subprotocol_name.unwrap_or_else(|| "eth".to_owned()),
 			min_gas_limit: p.min_gas_limit.into(),
-			fork_block: if let (Some(n), Some(h)) = (p.fork_block, p.fork_hash) { Some((n.into(), h.into())) } else { None },
+			fork_block: if let (Some(n), Some(h)) = (p.fork_block, p.fork_hash) {
+				Some((n.into(), h.into()))
+			} else {
+				None
+			},
 			eip98_transition: p.eip98_transition.map_or(0, Into::into),
 			eip155_transition: p.eip155_transition.map_or(0, Into::into),
 			validate_receipts_transition: p.validate_receipts_transition.map_or(0, Into::into),
-			eip86_transition: p.eip86_transition.map_or(BlockNumber::max_value(), Into::into),
+			eip86_transition: p.eip86_transition.map_or(
-			eip140_transition: p.eip140_transition.map_or(BlockNumber::max_value(), Into::into),
+				BlockNumber::max_value(),
-			eip210_transition: p.eip210_transition.map_or(BlockNumber::max_value(), Into::into),
+				Into::into,
+			),
+			eip140_transition: p.eip140_transition.map_or(
+				BlockNumber::max_value(),
+				Into::into,
+			),
+			eip210_transition: p.eip210_transition.map_or(
+				BlockNumber::max_value(),
+				Into::into,
+			),
 			eip210_contract_address: p.eip210_contract_address.map_or(0xf0.into(), Into::into),
 			eip210_contract_code: p.eip210_contract_code.map_or_else(
-				|| DEFAULT_BLOCKHASH_CONTRACT.from_hex().expect("Default BLOCKHASH contract is valid"),
+				|| {
-				Into::into),
+					DEFAULT_BLOCKHASH_CONTRACT.from_hex().expect(
+						"Default BLOCKHASH contract is valid",
+					)
+				},
+				Into::into,
+			),
 			eip210_contract_gas: p.eip210_contract_gas.map_or(1000000.into(), Into::into),
-			eip211_transition: p.eip211_transition.map_or(BlockNumber::max_value(), Into::into),
+			eip211_transition: p.eip211_transition.map_or(
-			eip214_transition: p.eip214_transition.map_or(BlockNumber::max_value(), Into::into),
+				BlockNumber::max_value(),
-			eip658_transition: p.eip658_transition.map_or(BlockNumber::max_value(), Into::into),
+				Into::into,
-			dust_protection_transition: p.dust_protection_transition.map_or(BlockNumber::max_value(), Into::into),
+			),
+			eip214_transition: p.eip214_transition.map_or(
+				BlockNumber::max_value(),
+				Into::into,
+			),
+			eip658_transition: p.eip658_transition.map_or(
+				BlockNumber::max_value(),
+				Into::into,
+			),
+			dust_protection_transition: p.dust_protection_transition.map_or(
+				BlockNumber::max_value(),
+				Into::into,
+			),
 			nonce_cap_increment: p.nonce_cap_increment.map_or(64, Into::into),
 			remove_dust_contracts: p.remove_dust_contracts.unwrap_or(false),
 			wasm: p.wasm.unwrap_or(false),
@@ -188,6 +222,44 @@ impl From<ethjson::spec::Params> for CommonParams {
 	}
 }
 
+/// Runtime parameters for the spec that are related to how the software should run the chain,
+/// rather than integral properties of the chain itself.
+#[derive(Debug, Clone, Copy)]
+pub struct SpecParams<'a> {
+	/// The path to the folder used to cache nodes. This is typically /tmp/ on Unix-like systems
+	pub cache_dir: &'a Path,
+	/// Whether to run slower at the expense of better memory usage, or run faster while using
+	/// more
+	/// memory. This may get more fine-grained in the future but for now is simply a binary
+	/// option.
+	pub optimization_setting: Option<OptimizeFor>,
+}
+
+impl<'a> SpecParams<'a> {
+	/// Create from a cache path, with null values for the other fields
+	pub fn from_path(path: &'a Path) -> Self {
+		SpecParams {
+			cache_dir: path,
+			optimization_setting: None,
+		}
+	}
+
+	/// Create from a cache path and an optimization setting
+	pub fn new(path: &'a Path, optimization: OptimizeFor) -> Self {
+		SpecParams {
+			cache_dir: path,
+			optimization_setting: Some(optimization),
+		}
+	}
+}
+
+impl<'a, T: AsRef<Path>> From<&'a T> for SpecParams<'a> {
+	fn from(path: &'a T) -> Self {
+		Self::from_path(path.as_ref())
+	}
+}
+
+
 /// Parameters for a block chain; includes both those intrinsic to the design of the
 /// chain and those to be interpreted by the active chain engine.
 pub struct Spec {
@@ -258,15 +330,19 @@ impl Clone for Spec {
 }
 
 /// Load from JSON object.
-pub fn load_from<T: AsRef<Path>>(cache_dir: T, s: ethjson::spec::Spec) -> Result<Spec, Error> {
+fn load_from(spec_params: SpecParams, s: ethjson::spec::Spec) -> Result<Spec, Error> {
-	let builtins = s.accounts.builtins().into_iter().map(|p| (p.0.into(), From::from(p.1))).collect();
+	let builtins = s.accounts
+		.builtins()
+		.into_iter()
+		.map(|p| (p.0.into(), From::from(p.1)))
+		.collect();
 	let g = Genesis::from(s.genesis);
 	let GenericSeal(seal_rlp) = g.seal.into();
 	let params = CommonParams::from(s.params);
 
 	let mut s = Spec {
 		name: s.name.clone().into(),
-		engine: Spec::engine(cache_dir, s.engine, params, builtins),
+		engine: Spec::engine(spec_params, s.engine, params, builtins),
 		data_dir: s.data_dir.unwrap_or(s.name).into(),
 		nodes: s.nodes.unwrap_or_else(Vec::new),
 		parent_hash: g.parent_hash,
@@ -279,7 +355,11 @@ pub fn load_from<T: AsRef<Path>>(cache_dir: T, s: ethjson::spec::Spec) -> Result
 		timestamp: g.timestamp,
 		extra_data: g.extra_data,
 		seal_rlp: seal_rlp,
-		constructors: s.accounts.constructors().into_iter().map(|(a, c)| (a.into(), c.into())).collect(),
+		constructors: s.accounts
+			.constructors()
+			.into_iter()
+			.map(|(a, c)| (a.into(), c.into()))
+			.collect(),
 		state_root_memo: RwLock::new(Default::default()), // will be overwritten right after.
 		genesis_state: s.accounts.into(),
 	};
@@ -287,7 +367,12 @@ pub fn load_from<T: AsRef<Path>>(cache_dir: T, s: ethjson::spec::Spec) -> Result
 	// use memoized state root if provided.
 	match g.state_root {
 		Some(root) => *s.state_root_memo.get_mut() = root,
-		None => { let _ = s.run_constructors(&Default::default(), BasicBackend(MemoryDB::new()))?; },
+		None => {
+			let _ = s.run_constructors(
+				&Default::default(),
+				BasicBackend(MemoryDB::new()),
+			)?;
+		}
 	}
 
 	Ok(s)
@@ -305,8 +390,8 @@ macro_rules! load_bundled {
 impl Spec {
 	/// Convert engine spec into a arc'd Engine of the right underlying type.
 	/// TODO avoid this hard-coded nastiness - use dynamic-linked plugin framework instead.
-	fn engine<T: AsRef<Path>>(
+	fn engine(
-		cache_dir: T,
+		spec_params: SpecParams,
 		engine_spec: ethjson::spec::Engine,
 		params: CommonParams,
 		builtins: BTreeMap<Address, Builtin>,
@@ -314,14 +399,43 @@ impl Spec {
 		match engine_spec {
 			ethjson::spec::Engine::Null => Arc::new(NullEngine::new(params, builtins)),
 			ethjson::spec::Engine::InstantSeal => Arc::new(InstantSeal::new(params, builtins)),
-			ethjson::spec::Engine::Ethash(ethash) => Arc::new(ethereum::Ethash::new(cache_dir, params, From::from(ethash.params), builtins)),
+			ethjson::spec::Engine::Ethash(ethash) => Arc::new(ethereum::Ethash::new(
-			ethjson::spec::Engine::BasicAuthority(basic_authority) => Arc::new(BasicAuthority::new(params, From::from(basic_authority.params), builtins)),
+				spec_params.cache_dir,
-			ethjson::spec::Engine::AuthorityRound(authority_round) => AuthorityRound::new(params, From::from(authority_round.params), builtins).expect("Failed to start AuthorityRound consensus engine."),
+				params,
-			ethjson::spec::Engine::Tendermint(tendermint) => Tendermint::new(params, From::from(tendermint.params), builtins).expect("Failed to start the Tendermint consensus engine."),
+				From::from(ethash.params),
+				builtins,
+				spec_params.optimization_setting,
+			)),
+			ethjson::spec::Engine::BasicAuthority(basic_authority) => Arc::new(
+				BasicAuthority::new(
+					params,
+					From::from(
+						basic_authority.params,
+					),
+					builtins,
+				),
+			),
+			ethjson::spec::Engine::AuthorityRound(authority_round) => AuthorityRound::new(
+				params,
+				From::from(
+					authority_round.params,
+				),
+				builtins,
+			).expect(
+				"Failed to start AuthorityRound consensus engine.",
+			),
+			ethjson::spec::Engine::Tendermint(tendermint) => Tendermint::new(
+				params,
+				From::from(tendermint.params),
+				builtins,
+			).expect(
+				"Failed to start the Tendermint consensus engine.",
+			),
 		}
 	}
 
-	// given a pre-constructor state, run all the given constructors and produce a new state and state root.
+	// given a pre-constructor state, run all the given constructors and produce a new state and
+	// state root.
 	fn run_constructors<T: Backend>(&self, factories: &Factories, mut db: T) -> Result<T, Error> {
 		let mut root = KECCAK_NULL_RLP;
 
@@ -337,20 +451,18 @@ impl Spec {
 		for (address, account) in self.genesis_state.get().iter() {
 			db.note_non_null_account(address);
 			account.insert_additional(
-				&mut *factories.accountdb.create(db.as_hashdb_mut(), keccak(address)),
+				&mut *factories.accountdb.create(
-				&factories.trie
+					db.as_hashdb_mut(),
+					keccak(address),
+				),
+				&factories.trie,
 			);
 		}
 
 		let start_nonce = self.engine.account_start_nonce(0);
 
 		let (root, db) = {
-			let mut state = State::from_existing(
+			let mut state = State::from_existing(db, root, start_nonce, factories.clone())?;
-				db,
-				root,
-				start_nonce,
-				factories.clone(),
-			)?;
 
 			// Execute contract constructors.
 			let env_info = EnvInfo {
@@ -385,7 +497,14 @@ impl Spec {
 
 				{
 					let mut exec = Executive::new(&mut state, &env_info, self.engine.as_ref());
-					if let Err(e) = exec.create(params, &mut substate, &mut None, &mut NoopTracer, &mut NoopVMTracer) {
+					if let Err(e) = exec.create(
+						params,
+						&mut substate,
+						&mut None,
+						&mut NoopTracer,
+						&mut NoopVMTracer,
+					)
+					{
 						warn!(target: "spec", "Genesis constructor execution at {} failed: {}.", address, e);
 					}
 				}
@@ -410,22 +529,34 @@ impl Spec {
 	}
 
 	/// Get common blockchain parameters.
-	pub fn params(&self) -> &CommonParams { &self.engine.params() }
+	pub fn params(&self) -> &CommonParams {
+		&self.engine.params()
+	}
 
 	/// Get the known knodes of the network in enode format.
-	pub fn nodes(&self) -> &[String] { &self.nodes }
+	pub fn nodes(&self) -> &[String] {
+		&self.nodes
+	}
 
 	/// Get the configured Network ID.
-	pub fn network_id(&self) -> u64 { self.params().network_id }
+	pub fn network_id(&self) -> u64 {
+		self.params().network_id
+	}
 
 	/// Get the chain ID used for signing.
-	pub fn chain_id(&self) -> u64 { self.params().chain_id }
+	pub fn chain_id(&self) -> u64 {
+		self.params().chain_id
+	}
 
 	/// Get the configured subprotocol name.
-	pub fn subprotocol_name(&self) -> String { self.params().subprotocol_name.clone() }
+	pub fn subprotocol_name(&self) -> String {
+		self.params().subprotocol_name.clone()
+	}
 
 	/// Get the configured network fork block.
-	pub fn fork_block(&self) -> Option<(BlockNumber, H256)> { self.params().fork_block }
+	pub fn fork_block(&self) -> Option<(BlockNumber, H256)> {
+		self.params().fork_block
+	}
 
 	/// Get the header of the genesis block.
 	pub fn genesis_header(&self) -> Header {
@@ -480,7 +611,10 @@ impl Spec {
 	/// Alter the value of the genesis state.
 	pub fn set_genesis_state(&mut self, s: PodState) -> Result<(), Error> {
 		self.genesis_state = s;
-		let _ = self.run_constructors(&Default::default(), BasicBackend(MemoryDB::new()))?;
+		let _ = self.run_constructors(
+			&Default::default(),
+			BasicBackend(MemoryDB::new()),
+		)?;
 
 		Ok(())
 	}
@@ -496,7 +630,7 @@ impl Spec {
 	/// Ensure that the given state DB has the trie nodes in for the genesis state.
 	pub fn ensure_db_good<T: Backend>(&self, db: T, factories: &Factories) -> Result<T, Error> {
 		if db.as_hashdb().contains(&self.state_root()) {
-			return Ok(db)
+			return Ok(db);
 		}
 
 		// TODO: could optimize so we don't re-run, but `ensure_db_good` is barely ever
@@ -507,13 +641,19 @@ impl Spec {
 
 	/// Loads spec from json file. Provide factories for executing contracts and ensuring
 	/// storage goes to the right place.
-	pub fn load<T: AsRef<Path>, R>(cache_dir: T, reader: R) -> Result<Self, String> where R: Read {
+	pub fn load<'a, T: Into<SpecParams<'a>>, R>(params: T, reader: R) -> Result<Self, String>
+	where
+		R: Read,
+	{
 		fn fmt<F: ::std::fmt::Display>(f: F) -> String {
 			format!("Spec json is invalid: {}", f)
 		}
 
-		ethjson::spec::Spec::load(reader).map_err(fmt)
+		ethjson::spec::Spec::load(reader).map_err(fmt).and_then(
-			.and_then(|x| load_from(cache_dir, x).map_err(fmt))
+			|x| {
+				load_from(params.into(), x).map_err(fmt)
+			},
+		)
 	}
 
 	/// initialize genesis epoch data, using in-memory database for
@@ -543,7 +683,7 @@ impl Spec {
 				difficulty: *genesis.difficulty(),
 				gas_limit: *genesis.gas_limit(),
 				last_hashes: Arc::new(Vec::new()),
-				gas_used: 0.into()
+				gas_used: 0.into(),
 			};
 
 			let from = Address::default();
@@ -566,86 +706,139 @@ impl Spec {
 				true,
 			);
 
-			res.map(|(out, proof)| (out, proof.into_iter().map(|x| x.into_vec()).collect()))
+			res.map(|(out, proof)| {
-				.ok_or_else(|| "Failed to prove call: insufficient state".into())
+				(out, proof.into_iter().map(|x| x.into_vec()).collect())
+			}).ok_or_else(|| "Failed to prove call: insufficient state".into())
 		};
 
 		self.engine.genesis_epoch_data(&genesis, &call)
 	}
 
-	/// Create a new Spec which conforms to the Frontier-era Morden chain except that it's a NullEngine consensus.
+	/// Create a new Spec which conforms to the Frontier-era Morden chain except that it's a
-	pub fn new_test() -> Spec { load_bundled!("null_morden") }
+	/// NullEngine consensus.
+	pub fn new_test() -> Spec {
+		load_bundled!("null_morden")
+	}
 
-	/// Create a new Spec which conforms to the Frontier-era Morden chain except that it's a NullEngine consensus with applying reward on block close.
+	/// Create a new Spec which conforms to the Frontier-era Morden chain except that it's a
-	pub fn new_test_with_reward() -> Spec { load_bundled!("null_morden_with_reward") }
+	/// NullEngine consensus with applying reward on block close.
+	pub fn new_test_with_reward() -> Spec {
+		load_bundled!("null_morden_with_reward")
+	}
 
-	/// Create a new Spec which is a NullEngine consensus with a premine of address whose secret is keccak('').
+	/// Create a new Spec which is a NullEngine consensus with a premine of address whose
-	pub fn new_null() -> Spec { load_bundled!("null") }
+	/// secret is keccak('').
+	pub fn new_null() -> Spec {
+		load_bundled!("null")
+	}
 
 	/// Create a new Spec which constructs a contract at address 5 with storage at 0 equal to 1.
-	pub fn new_test_constructor() -> Spec { load_bundled!("constructor") }
+	pub fn new_test_constructor() -> Spec {
+		load_bundled!("constructor")
+	}
 
-	/// Create a new Spec with InstantSeal consensus which does internal sealing (not requiring work).
+	/// Create a new Spec with InstantSeal consensus which does internal sealing (not requiring
-	pub fn new_instant() -> Spec { load_bundled!("instant_seal") }
+	/// work).
+	pub fn new_instant() -> Spec {
+		load_bundled!("instant_seal")
+	}
 
-	/// Create a new Spec with AuthorityRound consensus which does internal sealing (not requiring work).
+	/// Create a new Spec with AuthorityRound consensus which does internal sealing (not
+	/// requiring work).
 	/// Accounts with secrets keccak("0") and keccak("1") are the validators.
-	pub fn new_test_round() -> Self { load_bundled!("authority_round") }
+	pub fn new_test_round() -> Self {
+		load_bundled!("authority_round")
+	}
 
-	/// Create a new Spec with Tendermint consensus which does internal sealing (not requiring work).
+	/// Create a new Spec with Tendermint consensus which does internal sealing (not requiring
+	/// work).
 	/// Account keccak("0") and keccak("1") are a authorities.
-	pub fn new_test_tendermint() -> Self { load_bundled!("tendermint") }
+	pub fn new_test_tendermint() -> Self {
+		load_bundled!("tendermint")
+	}
 
 	/// TestList.sol used in both specs: https://github.com/paritytech/contracts/pull/30/files
 	/// Accounts with secrets keccak("0") and keccak("1") are initially the validators.
-	/// Create a new Spec with BasicAuthority which uses a contract at address 5 to determine the current validators using `getValidators`.
+	/// Create a new Spec with BasicAuthority which uses a contract at address 5 to determine
-	/// Second validator can be removed with "0xbfc708a000000000000000000000000082a978b3f5962a5b0957d9ee9eef472ee55b42f1" and added back in using "0x4d238c8e00000000000000000000000082a978b3f5962a5b0957d9ee9eef472ee55b42f1".
+	/// the current validators using `getValidators`.
-	pub fn new_validator_safe_contract() -> Self { load_bundled!("validator_safe_contract") }
+	/// Second validator can be removed with
+	/// "0xbfc708a000000000000000000000000082a978b3f5962a5b0957d9ee9eef472ee55b42f1" and added
+	/// back in using
+	/// "0x4d238c8e00000000000000000000000082a978b3f5962a5b0957d9ee9eef472ee55b42f1".
+	pub fn new_validator_safe_contract() -> Self {
+		load_bundled!("validator_safe_contract")
+	}
 
 	/// The same as the `safeContract`, but allows reporting and uses AuthorityRound.
 	/// Account is marked with `reportBenign` it can be checked as disliked with "0xd8f2e0bf".
 	/// Validator can be removed with `reportMalicious`.
-	pub fn new_validator_contract() -> Self { load_bundled!("validator_contract") }
+	pub fn new_validator_contract() -> Self {
+		load_bundled!("validator_contract")
+	}
 
-	/// Create a new Spec with BasicAuthority which uses multiple validator sets changing with height.
+	/// Create a new Spec with BasicAuthority which uses multiple validator sets changing with
-	/// Account with secrets keccak("0") is the validator for block 1 and with keccak("1") onwards.
+	/// height.
-	pub fn new_validator_multi() -> Self { load_bundled!("validator_multi") }
+	/// Account with secrets keccak("0") is the validator for block 1 and with keccak("1")
+	/// onwards.
+	pub fn new_validator_multi() -> Self {
+		load_bundled!("validator_multi")
+	}
 
 	/// Create a new spec for a PoW chain
-	pub fn new_pow_test_spec() -> Self { load_bundled!("ethereum/olympic") }
+	pub fn new_pow_test_spec() -> Self {
+		load_bundled!("ethereum/olympic")
+	}
 }
 
 #[cfg(test)]
 mod tests {
+	use super::*;
+	use state::State;
 	use std::str::FromStr;
+	use tests::helpers::get_temp_state_db;
 	use util::*;
 	use views::*;
-	use tests::helpers::get_temp_state_db;
-	use state::State;
-	use super::*;
 
 	// https://github.com/paritytech/parity/issues/1840
 	#[test]
 	fn test_load_empty() {
-		assert!(Spec::load(::std::env::temp_dir(), &[] as &[u8]).is_err());
+		assert!(Spec::load(&::std::env::temp_dir(), &[] as &[u8]).is_err());
 	}
 
 	#[test]
 	fn test_chain() {
 		let test_spec = Spec::new_test();
 
-		assert_eq!(test_spec.state_root(), H256::from_str("f3f4696bbf3b3b07775128eb7a3763279a394e382130f27c21e70233e04946a9").unwrap());
+		assert_eq!(
+			test_spec.state_root(),
+			H256::from_str(
+				"f3f4696bbf3b3b07775128eb7a3763279a394e382130f27c21e70233e04946a9",
+			).unwrap()
+		);
 		let genesis = test_spec.genesis_block();
-		assert_eq!(BlockView::new(&genesis).header_view().hash(), H256::from_str("0cd786a2425d16f152c658316c423e6ce1181e15c3295826d7c9904cba9ce303").unwrap());
+		assert_eq!(
+			BlockView::new(&genesis).header_view().hash(),
+			H256::from_str(
+				"0cd786a2425d16f152c658316c423e6ce1181e15c3295826d7c9904cba9ce303",
+			).unwrap()
+		);
 	}
 
 	#[test]
 	fn genesis_constructor() {
 		::ethcore_logger::init_log();
 		let spec = Spec::new_test_constructor();
-		let db = spec.ensure_db_good(get_temp_state_db(), &Default::default()).unwrap();
+		let db = spec.ensure_db_good(get_temp_state_db(), &Default::default())
-		let state = State::from_existing(db.boxed_clone(), spec.state_root(), spec.engine.account_start_nonce(0), Default::default()).unwrap();
+			.unwrap();
-		let expected = H256::from_str("0000000000000000000000000000000000000000000000000000000000000001").unwrap();
+		let state = State::from_existing(
+			db.boxed_clone(),
+			spec.state_root(),
+			spec.engine.account_start_nonce(0),
+			Default::default(),
+		).unwrap();
+		let expected = H256::from_str(
+			"0000000000000000000000000000000000000000000000000000000000000001",
+		).unwrap();
 		let address = Address::from_str("0000000000000000000000000000000000000005").unwrap();
 
 		assert_eq!(state.storage_at(&address, &H256::zero()).unwrap(), expected);

ethcore/src/tx_filter.rs

@@ -196,7 +196,7 @@ mod test {
 		}
 		"#;
 
-		let spec = Spec::load(::std::env::temp_dir(), spec_data.as_bytes()).unwrap();
+		let spec = Spec::load(&::std::env::temp_dir(), spec_data.as_bytes()).unwrap();
 		let client_db = Arc::new(::util::kvdb::in_memory(::db::NUM_COLUMNS.unwrap_or(0)));
 
 		let client = Client::new(

evmbin/src/main.rs

@@ -230,7 +230,7 @@ impl Args {
 		Ok(match self.flag_chain {
 			Some(ref filename) =>  {
 				let file = fs::File::open(filename).map_err(|e| format!("{}", e))?;
-				spec::Spec::load(::std::env::temp_dir(), file)?
+				spec::Spec::load(&::std::env::temp_dir(), file)?
 			},
 			None => {
 				ethcore::ethereum::new_foundation(&::std::env::temp_dir())

parity/params.rs

@@ -14,12 +14,12 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::{str, fs, fmt, path};
+use std::{str, fs, fmt};
 use std::time::Duration;
 use bigint::prelude::U256;
 use util::{Address, version_data};
 use util::journaldb::Algorithm;
-use ethcore::spec::Spec;
+use ethcore::spec::{Spec, SpecParams};
 use ethcore::ethereum;
 use ethcore::client::Mode;
 use ethcore::miner::{GasPricer, GasPriceCalibratorOptions};
@@ -81,20 +81,20 @@ impl fmt::Display for SpecType {
 }
 
 impl SpecType {
-	pub fn spec<T: AsRef<path::Path>>(&self, cache_dir: T) -> Result<Spec, String> {
+	pub fn spec<'a, T: Into<SpecParams<'a>>>(&self, params: T) -> Result<Spec, String> {
-		let cache_dir = cache_dir.as_ref();
+		let params = params.into();
 		match *self {
-			SpecType::Foundation => Ok(ethereum::new_foundation(cache_dir)),
+			SpecType::Foundation => Ok(ethereum::new_foundation(params)),
-			SpecType::Morden => Ok(ethereum::new_morden(cache_dir)),
+			SpecType::Morden => Ok(ethereum::new_morden(params)),
-			SpecType::Ropsten => Ok(ethereum::new_ropsten(cache_dir)),
+			SpecType::Ropsten => Ok(ethereum::new_ropsten(params)),
-			SpecType::Olympic => Ok(ethereum::new_olympic(cache_dir)),
+			SpecType::Olympic => Ok(ethereum::new_olympic(params)),
-			SpecType::Classic => Ok(ethereum::new_classic(cache_dir)),
+			SpecType::Classic => Ok(ethereum::new_classic(params)),
-			SpecType::Expanse => Ok(ethereum::new_expanse(cache_dir)),
+			SpecType::Expanse => Ok(ethereum::new_expanse(params)),
-			SpecType::Kovan => Ok(ethereum::new_kovan(cache_dir)),
+			SpecType::Kovan => Ok(ethereum::new_kovan(params)),
 			SpecType::Dev => Ok(Spec::new_instant()),
 			SpecType::Custom(ref filename) => {
 				let file = fs::File::open(filename).map_err(|e| format!("Could not load specification file at {}: {}", filename, e))?;
-				Spec::load(cache_dir, file)
+				Spec::load(params, file)
 			}
 		}
 	}

parity/run.rs

@@ -29,6 +29,7 @@ use ethcore::service::ClientService;
 use ethcore::snapshot;
 use ethcore::verification::queue::VerifierSettings;
 use ethsync::{self, SyncConfig};
+use ethcore::spec::{SpecParams, OptimizeFor};
 use fdlimit::raise_fd_limit;
 use hash_fetch::fetch::{Fetch, Client as FetchClient};
 use informant::{Informant, LightNodeInformantData, FullNodeInformantData};
@@ -175,7 +176,7 @@ fn execute_light(cmd: RunCmd, can_restart: bool, logger: Arc<RotatingLogger>) ->
 	use parking_lot::{Mutex, RwLock};
 
 	// load spec
-	let spec = cmd.spec.spec(&cmd.dirs.cache)?;
+	let spec = cmd.spec.spec(SpecParams::new(cmd.dirs.cache.as_ref(), OptimizeFor::Memory))?;
 
 	// load genesis hash
 	let genesis_hash = spec.genesis_header().hash();

rpc/src/v1/impls/eth.rs

@@ -555,7 +555,7 @@ impl<C, SN: ?Sized, S: ?Sized, M, EM> Eth for EthClient<C, SN, S, M, EM> where
 		self.miner.map_sealing_work(&*self.client, |b| {
 			let pow_hash = b.hash();
 			let target = Ethash::difficulty_to_boundary(b.block().header().difficulty());
-			let seed_hash = self.seed_compute.lock().get_seedhash(b.block().header().number());
+			let seed_hash = self.seed_compute.lock().hash_block_number(b.block().header().number());
 
 			if no_new_work_timeout > 0 && b.block().header().timestamp() + no_new_work_timeout < get_time().sec as u64 {
 				Err(errors::no_new_work())

rustfmt.toml

@@ -1,8 +1,8 @@
 verbose=false
-max_width=1000
+max_width=100
-comment_width=1000
+comment_width=100
 tab_spaces=4
-fn_call_width=1000
+fn_call_width=100
 struct_lit_width=32
 fn_call_style="Visual"
 single_line_if_else_max_width=100
@@ -13,3 +13,4 @@ reorder_imports=true
 format_strings=false
 hard_tabs=true
 wrap_match_arms=false
+error_on_line_overflow=false