Improve demurrage modifier calculation for redistribution cache, add gas bench for same

python/tests/bench.py

@@ -0,0 +1,72 @@
+# standard imports
+import os
+import unittest
+import json
+import logging
+
+# third-party imports
+import web3
+import eth_tester
+import eth_abi
+
+logging.basicConfig(level=logging.DEBUG)
+logg = logging.getLogger()
+
+logging.getLogger('web3').setLevel(logging.WARNING)
+logging.getLogger('eth.vm').setLevel(logging.WARNING)
+
+testdir = os.path.dirname(__file__)
+
+TAX_LEVEL = 10000 * 2 # 2%
+
+
+class Test(unittest.TestCase):
+
+    contract = None
+
+    def setUp(self):
+        eth_params = eth_tester.backends.pyevm.main.get_default_genesis_params({
+            'gas_limit': 9000000,
+            })
+
+        f = open(os.path.join(testdir, '../../solidity/RedistributedDemurrageToken.bin'), 'r')
+        self.bytecode = f.read()
+        f.close()
+
+        f = open(os.path.join(testdir, '../../solidity/RedistributedDemurrageToken.json'), 'r')
+        self.abi = json.load(f)
+        f.close()
+
+        backend = eth_tester.PyEVMBackend(eth_params)
+        self.eth_tester =  eth_tester.EthereumTester(backend)
+        provider = web3.Web3.EthereumTesterProvider(self.eth_tester)
+        self.w3 = web3.Web3(provider)
+        self.sink_address = self.w3.eth.accounts[9]
+
+    def tearDown(self):
+        pass
+
+
+    def test_gas_changeperiod(self):
+        period = 43200
+        for i in range(5):
+            c = self.w3.eth.contract(abi=self.abi, bytecode=self.bytecode)
+            tx_hash = c.constructor('Foo Token', 'FOO', 6, TAX_LEVEL * (10 ** 32), period, self.sink_address).transact({'from': self.w3.eth.accounts[0]})
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+            contract = self.w3.eth.contract(abi=self.abi, address=r.contractAddress)
+
+            start_block = self.w3.eth.blockNumber
+            b = self.w3.eth.getBlock(start_block)
+            start_time = b['timestamp']
+
+            period_seconds = period * 60
+            self.eth_tester.time_travel(start_time + period_seconds + (60 * (10 ** i)))
+            tx_hash = contract.functions.changePeriod().transact()
+            r = self.w3.eth.getTransactionReceipt(tx_hash)
+
+            print('{} ({}): {}'.format(i, 60 * (10 ** i), r['gasUsed']))
+
+if __name__ == '__main__':
+    unittest.main()
+
+ 

python/tests/test_redistribution.py

@@ -84,14 +84,14 @@ class Test(unittest.TestCase):
         self.eth_tester.time_travel(self.start_time + 61)
 
         redistribution = self.contract.functions.redistributions(0).call();
-        self.assertEqual(redistribution.hex(), '000000000100000000000000000000000000000000001e848000000000000001')
+        self.assertEqual(redistribution.hex(), '000000000000000000000000f42400000000010000000000001e848000000001')
 
         tx_hash = self.contract.functions.mintTo(self.w3.eth.accounts[0], 1000000).transact()
         r = self.w3.eth.getTransactionReceipt(tx_hash)
         self.assertEqual(r.status, 1)
 
         redistribution = self.contract.functions.redistributions(1).call()
-        self.assertEqual(redistribution.hex(), '000000000000000000000000000000000000000000002dc6c000000000000002')
+        self.assertEqual(redistribution.hex(), '000000000000000000000000ef4200000000000000000000002dc6c000000002')
     
 
     def test_redistribution_balance_on_zero_participants(self):

solidity/RedistributedDemurrageToken.sol

@@ -18,8 +18,10 @@ contract RedistributedDemurrageToken {
 	uint256 public immutable taxLevel; // PPM per MINUTE
 	uint256 public demurrageModifier; // PPM uint128(block) | uint128(ppm)
 
-	bytes32[] public redistributions; // uint1(isFractional) | uint1(unused) | uint38(participants) | uint160(value) | uint56(period)
-	mapping (address => bytes32) account; // uint20(unused) | uint56(period) | uint160(value)
+	//bytes32[] public redistributions; // uint1(isFractional) | uint1(unused) | uint38(participants) | uint160(value) | uint56(period)
+	bytes32[] public redistributions; // uint1(isFractional) | uint95(unused) | uint20(demurrageModifier) | uint36(participants) | uint72(value) | uint32(period)
+	//mapping (address => bytes32) account; // uint20(unused) | uint56(period) | uint160(value)
+	mapping (address => bytes32) account; // uint152(unused) | uint32(period) | uint72(value)
 	mapping (address => bool) minter;
 	mapping (address => mapping (address => uint256 ) ) allowance; // holder -> spender -> amount (amount is subject to demurrage)
 
@@ -28,7 +30,7 @@ contract RedistributedDemurrageToken {
 	event Transfer(address indexed _from, address indexed _to, uint256 _value);
 	event Approval(address indexed _owner, address indexed _spender, uint256 _value);
 	event Mint(address indexed _minter, address indexed _beneficiary, uint256 _value);
-	//event Debug(uint256 _foo);
+	event Debug(bytes32 _foo);
 	event Decayed(uint256 indexed _period, uint256 indexed _periodCount, uint256 indexed _oldAmount, uint256 _newAmount);
 	event Redistribution(address indexed _account, uint256 indexed _period, uint256 _value);
 
@@ -44,7 +46,7 @@ contract RedistributedDemurrageToken {
 		demurrageModifier |= (1 << 128);
 		taxLevel = _taxLevelMinute; // 38 decimal places
 		sinkAddress = _defaultSinkAddress;
-		bytes32 initialRedistribution = toRedistribution(0, 0, 1);
+		bytes32 initialRedistribution = toRedistribution(0, 1000000, 0, 1);
 		redistributions.push(initialRedistribution);
 		minimumParticipantSpend = 10 ** uint256(_decimals);
 	}
@@ -70,20 +72,24 @@ contract RedistributedDemurrageToken {
 
 		periodCount = actualPeriod() - toDemurragePeriod(demurrageModifier);
 
-		currentDemurrageAmount = toTaxPeriodAmount(anchorDemurrageAmount, periodCount);
+		currentDemurrageAmount = decayBy(anchorDemurrageAmount, periodCount);
 
 		return (baseBalance * currentDemurrageAmount) / (ppmDivider * 1000000);
 	}
 
 	/// Balance unmodified by demurrage
 	function getBaseBalance(address _account) private view returns (uint256) {
-		return uint256(account[_account]) & 0x00ffffffffffffffffffffffffffffffffffffffff;
+		//return uint256(account[_account]) & 0x00ffffffffffffffffffffffffffffffffffffffff;
+		return uint256(account[_account]) & 0xffffffffffffffffff;
 	}
 
 	/// Increases base balance for a single account
 	function increaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
 		uint256 oldBalance;
 		uint256 newBalance;
+		uint256 workAccount;
+
+		workAccount = uint256(account[_account]); // | (newBalance & 0xffffffffffffffffff);
 	
 		if (_delta == 0) {
 			return false;
@@ -92,8 +98,12 @@ contract RedistributedDemurrageToken {
 		oldBalance = getBaseBalance(_account);
 		newBalance = oldBalance + _delta;
 		require(uint160(newBalance) > uint160(oldBalance), 'ERR_WOULDWRAP'); // revert if increase would result in a wrapped value
-		account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
-		account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
+		//account[_account] &= bytes32(0xfffffffffffffffffffffff0000000000000000000000000000000000000000);
+		//account[_account] = bytes32(uint256(account[_account]) & 0xfffffffffffffffffffffffffffffffffffffffffffff000000000000000000);
+		workAccount &= 0xfffffffffffffffffffffffffffffffffffffffffffff000000000000000000;
+		//account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
+		workAccount |= newBalance & 0xffffffffffffffffff;
+		account[_account] = bytes32(workAccount);
 		return true;
 	}
 
@@ -101,6 +111,9 @@ contract RedistributedDemurrageToken {
 	function decreaseBaseBalance(address _account, uint256 _delta) private returns (bool) {
 		uint256 oldBalance;
 	       	uint256 newBalance;
+		uint256 workAccount;
+
+		workAccount = uint256(account[_account]); // | (newBalance & 0xffffffffffffffffff);
 
 		if (_delta == 0) {
 			return false;
@@ -109,8 +122,11 @@ contract RedistributedDemurrageToken {
 		oldBalance = getBaseBalance(_account);	
 		require(oldBalance >= _delta, 'ERR_OVERSPEND'); // overspend guard
 		newBalance = oldBalance - _delta;
-		account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
-		account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
+		//account[_account] &= bytes32(0xffffffffffffffffffffffff0000000000000000000000000000000000000000);
+		workAccount &= 0xfffffffffffffffffffffffffffffffffffffffffffff000000000000000000;
+		//account[_account] |= bytes32(newBalance & 0x00ffffffffffffffffffffffffffffffffffffffff);
+		workAccount |= newBalance & 0xffffffffffffffffff;
+		account[_account] = bytes32(workAccount);
 		return true;
 	}
 
@@ -121,7 +137,6 @@ contract RedistributedDemurrageToken {
 
 		require(minter[msg.sender]);
 
-		applyDemurrage();
 		changePeriod();
 		baseAmount = _amount;
 		totalSupply += _amount;
@@ -132,28 +147,35 @@ contract RedistributedDemurrageToken {
 	}
 
 	// Deserializes the redistribution word
-	function toRedistribution(uint256 _participants, uint256 _value, uint256 _period) private pure returns(bytes32) {
+	// uint1(isFractional) | uint95(unused) | uint20(demurrageModifier) | uint36(participants) | uint72(value) | uint32(period)
+	function toRedistribution(uint256 _participants, uint256 _demurrageModifierPpm, uint256 _value, uint256 _period) private pure returns(bytes32) {
 		bytes32 redistribution;
 
-		redistribution |= bytes32((_participants & 0x7fffffffff) << 216);
-		redistribution |= bytes32((_value & 0xffffffffffffffffffffffff) << 56);
-		redistribution |= bytes32(_period & 0xffffffffffffff);
+		redistribution |= bytes32((_demurrageModifierPpm & 0x0fffff) << 140);
+		redistribution |= bytes32((_participants & 0x0fffffffff) << 104);
+		redistribution |= bytes32((_value & 0xffffffffffffffffff) << 32);
+		redistribution |= bytes32(_period & 0xffffffff);
 		return redistribution;
 	}
 
 	// Serializes the demurrage period part of the redistribution word
 	function toRedistributionPeriod(bytes32 redistribution) public pure returns (uint256) {
-		return uint256(redistribution & 0x00000000000000000000000000000000000000000000000000ffffffffffffff);
+		return uint256(redistribution) & 0xffffffff;
 	}
 
 	// Serializes the supply part of the redistribution word
 	function toRedistributionSupply(bytes32 redistribution) public pure returns (uint256) {
-		return uint256(redistribution & 0x0000000000ffffffffffffffffffffffffffffffffffffffff00000000000000) >> 56;
+		return uint256(redistribution & 0x00000000000000000000000000000000000000ffffffffffffffffff00000000) >> 32;
 	}
 
 	// Serializes the number of participants part of the redistribution word
 	function toRedistributionParticipants(bytes32 redistribution) public pure returns (uint256) {
-		return uint256(redistribution & 0x7fffffffff000000000000000000000000000000000000000000000000000000) >> 216;
+		return uint256(redistribution & 0x00000000000000000000000000000fffffffff00000000000000000000000000) >> 104;
+	}
+
+	// Serializes the number of participants part of the redistribution word
+	function toRedistributionDemurrageModifier(bytes32 redistribution) public pure returns (uint256) {
+		return uint256(redistribution & 0x000000000000000000000000fffff00000000000000000000000000000000000) >> 140;
 	}
 
 	// Client accessor to the redistributions array length
@@ -163,16 +185,19 @@ contract RedistributedDemurrageToken {
 
 	// Add number of participants for the current redistribution period by one
 	function incrementRedistributionParticipants() private returns (bool) {
-		uint256 currentRedistribution;
+		bytes32 currentRedistribution;
+		uint256 tmpRedistribution;
 		uint256 participants;
 
-		currentRedistribution = uint256(redistributions[redistributions.length-1]);
-		participants = ((currentRedistribution & 0x7fffffffff000000000000000000000000000000000000000000000000000000) >> 216) + 1;
-		currentRedistribution &= 0x8000000000ffffffffffffffffffffffffffffffffffffffffffffffffffffff;
-		currentRedistribution |= participants << 216;
+		currentRedistribution = redistributions[redistributions.length-1];
+		participants = toRedistributionParticipants(currentRedistribution) + 1;
+		tmpRedistribution = uint256(currentRedistribution);
+		tmpRedistribution &= 0xfffffffffffffffffffffffffffff000000000ffffffffffffffffffffffffff;
+		tmpRedistribution |= (participants & 0x0fffffffff) << 104;
 
-		//emit Debug(participants);
-		redistributions[redistributions.length-1] = bytes32(currentRedistribution);
+		redistributions[redistributions.length-1] = bytes32(tmpRedistribution);
+
+		return true;
 	}
 
 	// Save the current total supply amount to the current redistribution period
@@ -180,10 +205,11 @@ contract RedistributedDemurrageToken {
 		uint256 currentRedistribution;
 
 		currentRedistribution = uint256(redistributions[redistributions.length-1]);
-		currentRedistribution &= 0xffffffffff0000000000000000000000000000000000000000ffffffffffffff;
-		currentRedistribution |= totalSupply << 56;
+		currentRedistribution &= 0xffffffffffffffffffffffffffffffffffffff000000000000000000ffffffff;
+		currentRedistribution |= totalSupply << 32;
 
 		redistributions[redistributions.length-1] = bytes32(currentRedistribution);
+		return true;
 	}
 
 	// Get the demurrage period of the current block number
@@ -206,14 +232,17 @@ contract RedistributedDemurrageToken {
 
 	// Deserialize the pemurrage period for the given account is participating in
 	function accountPeriod(address _account) public view returns (uint256) {
-		return (uint256(account[_account]) & 0xffffffffffffffffffffffff0000000000000000000000000000000000000000) >> 160;
+		//return (uint256(account[_account]) & 0xffffffffffffffffffffffff0000000000000000000000000000000000000000) >> 160;
+		return (uint256(account[_account]) & 0x00000000000000000000000000000000000000ffffffff000000000000000000) >> 72;
 	}
 
 	// Save the given demurrage period as the currently participation period for the given address
 	function registerAccountPeriod(address _account, uint256 _period) private returns (bool) {
-		account[_account] &= 0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff;
-		account[_account] |= bytes32(_period << 160);
+		//account[_account] &= 0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff;
+		account[_account] &= 0xffffffffffffffffffffffffffffffffffffff00000000ffffffffffffffffff;
+		account[_account] |= bytes32(_period << 72);
 		incrementRedistributionParticipants();
+		return true;
 	}
 
 	// Determine whether the unit number is rounded down, rounded up or evenly divides.
@@ -248,8 +277,8 @@ contract RedistributedDemurrageToken {
 
 		if (truncatedResult < redistributionSupply) {
 			redistributionPeriod = toRedistributionPeriod(_redistribution); // since we reuse period here, can possibly be optimized by passing period instead
-			redistributions[redistributionPeriod-1] &= 0x0000000000ffffffffffffffffffffffffffffffffffffffffffffffffffffff; // just to be safe, zero out all participant count data, in this case there will be only one
-			redistributions[redistributionPeriod-1] |= 0x8000000001000000000000000000000000000000000000000000000000000000;
+			redistributions[redistributionPeriod-1] &= 0xfffffffffffffffffffffffffffff000000000ffffffffffffffffffffffffff; // just to be safe, zero out all participant count data, in this case there will be only one
+			redistributions[redistributionPeriod-1] |= 0x8000000000000000000000000000000000000100000000000000000000000000;
 		}
 
 		increaseBaseBalance(sinkAddress, unit / ppmDivider); //truncatedResult);
@@ -265,6 +294,7 @@ contract RedistributedDemurrageToken {
 			return false;
 		}
 
+		// is this needed?
 		redistributions[_period-1] |= 0x8000000000000000000000000000000000000000000000000000000000000000;
 
 		periodSupply = toRedistributionSupply(redistributions[_period-1]);
@@ -294,7 +324,7 @@ contract RedistributedDemurrageToken {
 			return false;
 		}
 		lastDemurrageAmount = toDemurrageAmount(demurrageModifier);
-		newDemurrageAmount = toTaxPeriodAmount(lastDemurrageAmount, periodCount);
+		newDemurrageAmount = decayBy(lastDemurrageAmount, periodCount);
 		demurrageModifier = 0;
 		demurrageModifier |= (newDemurrageAmount & 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff);
 		demurrageModifier |= (epochPeriodCount << 128);
@@ -302,23 +332,50 @@ contract RedistributedDemurrageToken {
 		return true;
 	}
 
+	// Return timestamp of start of period threshold
+	function getPeriodTimeDelta(uint256 _periodCount) public view returns (uint256) {
+		return periodStart + (_periodCount * periodDuration);
+	}
+
+	// Amount of demurrage cycles inbetween the current timestamp and the given target time
+	function demurrageCycles(uint256 _target) public view returns (uint256) {
+		return (block.timestamp - _target) / 60;
+	}
+
 	// Recalculate the demurrage modifier for the new period
 	// After this, all REPORTED balances will have been reduced by the corresponding ratio (but the effecive totalsupply stays the same)
 	//function applyTax() public returns (uint256) {
-	function changePeriod() public returns (uint256) {
+	function changePeriod() public returns (bool) {
 		bytes32 currentRedistribution;
 		bytes32 nextRedistribution;
 		uint256 currentPeriod;
 		uint256 currentParticipants;
 		uint256 currentRemainder;
+		uint256 currentDemurrageAmount;
+		uint256 nextRedistributionDemurrage;
+		uint256 demurrageCounts;
+		uint256 periodTimestamp;
 
 		currentRedistribution = checkPeriod();
 		if (currentRedistribution == bytes32(0x00)) {
-			return demurrageModifier;
+			return false;
 		}
-		//demurrageModifier -= (demurrageModifier * taxLevel) / 1000000;
+
 		currentPeriod = toRedistributionPeriod(currentRedistribution);
-		nextRedistribution = toRedistribution(0, totalSupply, currentPeriod + 1);
+		periodTimestamp = getPeriodTimeDelta(currentPeriod);
+
+		applyDemurrage();
+		currentDemurrageAmount = toDemurrageAmount(demurrageModifier);
+
+		demurrageCounts = demurrageCycles(periodTimestamp);
+		if (demurrageCounts > 0) {
+			nextRedistributionDemurrage = growBy(currentDemurrageAmount, demurrageCounts) / ppmDivider;
+		} else {
+			nextRedistributionDemurrage = currentDemurrageAmount / ppmDivider;
+		}
+		
+		nextRedistribution = toRedistribution(0, nextRedistributionDemurrage, totalSupply, currentPeriod + 1);
+		emit Debug(bytes32(currentDemurrageAmount));
 		redistributions.push(nextRedistribution);
 
 		currentParticipants = toRedistributionParticipants(currentRedistribution);
@@ -328,11 +385,26 @@ contract RedistributedDemurrageToken {
 			currentRemainder = remainder(currentParticipants, totalSupply); // we can use totalSupply directly because it will always be the same as the recorded supply on the current redistribution
 			applyRemainderOnPeriod(currentRemainder, currentPeriod);
 		}
-		return demurrageModifier;
+		return true;
+	}
+
+	function growBy(uint256 _value, uint256 _period) public view returns (uint256) {
+		uint256 valueFactor;
+		uint256 truncatedTaxLevel;
+	      
+		// TODO: if can't get to work, reverse the iteration from current period.
+		valueFactor = 1000000;
+		truncatedTaxLevel = taxLevel / ppmDivider;
+
+		for (uint256 i = 0; i < _period; i++) {
+			valueFactor = valueFactor + ((valueFactor * truncatedTaxLevel) / 1000000);
+		}
+		return (valueFactor * _value) / 1000000;
 	}
 
 	// Calculate a value reduced by demurrage by the given period
-	function toTaxPeriodAmount(uint256 _value, uint256 _period) public view returns (uint256) {
+	// TODO: higher precision
+	function decayBy(uint256 _value, uint256 _period) public view returns (uint256) {
 		uint256 valueFactor;
 		uint256 truncatedTaxLevel;
 	      
@@ -368,9 +440,10 @@ contract RedistributedDemurrageToken {
 
 		supply = toRedistributionSupply(periodRedistribution);
 		baseValue = ((supply / participants) * (taxLevel / 1000000)) / ppmDivider;
-		value = toTaxPeriodAmount(baseValue, period - 1);
+		value = decayBy(baseValue, period - 1);
 
-		account[_account] &= bytes32(0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff);
+		//account[_account] &= bytes32(0x000000000000000000000000ffffffffffffffffffffffffffffffffffffffff);
+		account[_account] &= bytes32(0xffffffffffffffffffffffffffffffffffffff00000000ffffffffffffffffff);
 		increaseBaseBalance(_account, value);
 
 		emit Redistribution(_account, period, value);
@@ -386,7 +459,6 @@ contract RedistributedDemurrageToken {
 	function approve(address _spender, uint256 _value) public returns (bool) {
 		uint256 baseValue;
 
-		applyDemurrage();
 		changePeriod();
 		applyRedistributionOnAccount(msg.sender);
 
@@ -401,7 +473,6 @@ contract RedistributedDemurrageToken {
 		uint256 baseValue;
 		bool result;
 
-		applyDemurrage();
 		changePeriod();
 		applyRedistributionOnAccount(msg.sender);
 
@@ -418,7 +489,6 @@ contract RedistributedDemurrageToken {
 		uint256 baseValue;
 		bool result;
 
-		applyDemurrage();
 		changePeriod();
 		applyRedistributionOnAccount(msg.sender);