104 lines
3.4 KiB
Rust
104 lines
3.4 KiB
Rust
// Copyright 2015-2017 Parity Technologies (UK) Ltd.
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// This file is part of Parity.
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// Parity is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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// Parity is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with Parity. If not, see <http://www.gnu.org/licenses/>.
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//! Statistical functions.
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use bigint::prelude::*;
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/// Discretised histogram.
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#[derive(Debug, PartialEq)]
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pub struct Histogram {
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/// Bounds of each bucket.
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pub bucket_bounds: Vec<U256>,
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/// Count within each bucket.
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pub counts: Vec<u64>
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}
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impl Histogram {
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/// Histogram of a sorted corpus if it at least spans the buckets. Bounds are left closed.
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pub fn new(corpus: &[U256], bucket_number: usize) -> Option<Histogram> {
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if corpus.len() < 1 { return None; }
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let corpus_end = corpus.last().expect("there is at least 1 element; qed").clone();
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let corpus_start = corpus.first().expect("there is at least 1 element; qed").clone();
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// Bucket needs to be at least 1 wide.
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let bucket_size = {
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// Round up to get the entire corpus included.
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let raw_bucket_size = (corpus_end - corpus_start + bucket_number.into()) / bucket_number.into();
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if raw_bucket_size == 0.into() { 1.into() } else { raw_bucket_size }
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};
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let mut bucket_end = corpus_start + bucket_size;
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let mut bucket_bounds = vec![corpus_start; bucket_number + 1];
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let mut counts = vec![0; bucket_number];
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let mut corpus_i = 0;
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// Go through the corpus adding to buckets.
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for bucket in 0..bucket_number {
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while corpus.get(corpus_i).map_or(false, |v| v < &bucket_end) {
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// Initialized to size bucket_number above; iterates up to bucket_number; qed
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counts[bucket] += 1;
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corpus_i += 1;
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}
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// Initialized to size bucket_number + 1 above; iterates up to bucket_number; subscript is in range; qed
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bucket_bounds[bucket + 1] = bucket_end;
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bucket_end = bucket_end + bucket_size;
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}
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Some(Histogram { bucket_bounds: bucket_bounds, counts: counts })
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}
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}
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#[cfg(test)]
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mod tests {
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use bigint::prelude::U256;
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use super::Histogram;
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#[test]
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fn check_histogram() {
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let hist = Histogram::new(slice_into![643,689,1408,2000,2296,2512,4250,4320,4842,4958,5804,6065,6098,6354,7002,7145,7845,8589,8593,8895], 5).unwrap();
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let correct_bounds: Vec<U256> = vec_into![643, 2294, 3945, 5596, 7247, 8898];
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assert_eq!(Histogram { bucket_bounds: correct_bounds, counts: vec![4,2,4,6,4] }, hist);
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}
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#[test]
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fn smaller_data_range_than_bucket_range() {
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assert_eq!(
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Histogram::new(slice_into![1, 2, 2], 3),
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Some(Histogram { bucket_bounds: vec_into![1, 2, 3, 4], counts: vec![1, 2, 0] })
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);
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}
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#[test]
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fn data_range_is_not_multiple_of_bucket_range() {
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assert_eq!(
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Histogram::new(slice_into![1, 2, 5], 2),
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Some(Histogram { bucket_bounds: vec_into![1, 4, 7], counts: vec![2, 1] })
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);
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}
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#[test]
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fn data_range_is_multiple_of_bucket_range() {
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assert_eq!(
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Histogram::new(slice_into![1, 2, 6], 2),
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Some(Histogram { bucket_bounds: vec_into![1, 4, 7], counts: vec![2, 1] })
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);
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}
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#[test]
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fn none_when_too_few_data() {
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assert!(Histogram::new(slice_into![], 1).is_none());
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}
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}
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