Implement fixed-point arithmetic

pyRCV2/method/STVCCounter.py

@@ -102,14 +102,13 @@ class STVCCounter:
 			
 			__pragma__('opov')
 			surplus = count_card.votes - self.quota
-			transfer_value = surplus / count_card.votes
-			count_card.transfers -= surplus
+			#transfer_value = surplus / count_card.votes # Do not do this yet to avoid rounding errors
 			__pragma__('noopov')
 			
 			# Transfer surplus
 			for ballot, ballot_value in count_card.ballots:
 				__pragma__('opov')
-				new_value = ballot_value * transfer_value
+				new_value = (ballot_value * surplus) / count_card.votes
 				candidate = next((c for c in ballot.preferences if self.candidates[c].state == CandidateState.HOPEFUL), None)
 				
 				if candidate is not None:
@@ -120,6 +119,10 @@ class STVCCounter:
 					self.exhausted.ballots.append((ballot, new_value))
 				__pragma__('noopov')
 			
+			__pragma__('opov')
+			count_card.transfers -= surplus
+			__pragma__('noopov')
+			
 			# Declare any candidates meeting the quota as a result of surpluses
 			self.compute_quota()
 			self.elect_meeting_quota()

pyRCV2/numbers/__init__.py

@@ -22,10 +22,12 @@ __pragma__('noskip')
 
 if is_py:
 	__pragma__('skip')
+	from pyRCV2.numbers.fixed_py import Fixed, set_dps
 	from pyRCV2.numbers.native_py import Native
 	from pyRCV2.numbers.rational_py import Rational
 	__pragma__('noskip')
 else:
+	from pyRCV2.numbers.fixed_js import Fixed, set_dps
 	from pyRCV2.numbers.native_js import Native
 	from pyRCV2.numbers.rational_js import Rational
 

pyRCV2/numbers/fixed_js.py

@@ -0,0 +1,50 @@
+#   pyRCV2: Preferential vote counting
+#   Copyright © 2020  Lee Yingtong Li (RunasSudo)
+#
+#   This program is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU Affero General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   This program 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 Affero General Public License for more details.
+#
+#   You should have received a copy of the GNU Affero General Public License
+#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Big.DP = 6
+
+def set_dps(dps):
+	Big.DP = dps
+
+class Fixed:
+	"""
+	Wrapper for big.js (fixed-point arithmetic)
+	"""
+	
+	def __init__(self, val):
+		self.impl = Big(val)
+	
+	def pp(self, dp):
+		"""Pretty print to specified number of decimal places"""
+		return self.impl.toFixed(dp)
+	
+	def __add__(self, other):
+		return Fixed(self.impl.plus(other.impl))
+	def __sub__(self, other):
+		return Fixed(self.impl.minus(other.impl))
+	def __mul__(self, other):
+		return Fixed(self.impl.times(other.impl))
+	def __div__(self, other):
+		return Fixed(self.impl.div(other.impl))
+	
+	def __gt__(self, other):
+		return self.impl.gt(other.impl)
+	def __ge__(self, other):
+		return self.impl.gte(other.impl)
+	def __lt__(self, other):
+		return self.impl.lt(other.impl)
+	def __le__(self, other):
+		return self.impl.lte(other.impl)

pyRCV2/numbers/fixed_py.py

@@ -0,0 +1,53 @@
+#   pyRCV2: Preferential vote counting
+#   Copyright © 2020  Lee Yingtong Li (RunasSudo)
+#
+#   This program is free software: you can redistribute it and/or modify
+#   it under the terms of the GNU Affero General Public License as published by
+#   the Free Software Foundation, either version 3 of the License, or
+#   (at your option) any later version.
+#
+#   This program 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 Affero General Public License for more details.
+#
+#   You should have received a copy of the GNU Affero General Public License
+#   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+from decimal import Decimal
+
+_quantize_exp = 6
+
+def set_dps(dps):
+	global _quantize_exp
+	_quantize_exp = Decimal('10') ** -dps
+
+class Fixed:
+	"""
+	Wrapper for Python Decimal (for fixed-point arithmetic)
+	"""
+	
+	def __init__(self, val):
+		self.impl = Decimal(val).quantize(_quantize_exp)
+	
+	def pp(self, dp):
+		"""Pretty print to specified number of decimal places"""
+		return format(self.impl, '.{}f'.format(dp))
+	
+	def __add__(self, other):
+		return Fixed((self.impl + other.impl).quantize(_quantize_exp))
+	def __sub__(self, other):
+		return Fixed((self.impl - other.impl).quantize(_quantize_exp))
+	def __mul__(self, other):
+		return Fixed((self.impl * other.impl).quantize(_quantize_exp))
+	def __div__(self, other):
+		return Fixed((self.impl / other.impl).quantize(_quantize_exp))
+	
+	def __gt__(self, other):
+		return self.impl > other.impl
+	def __ge__(self, other):
+		return self.impl >= other.impl
+	def __lt__(self, other):
+		return self.impl < other.impl
+	def __le__(self, other):
+		return self.impl <= other.impl

pyRCV2/numbers/native_js.py

@@ -15,10 +15,15 @@
 #   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 class Native:
+	"""
+	Wrapper for JS numbers (naive floating-point arithmetic)
+	"""
+	
 	def __init__(self, val):
 		self.impl = parseFloat(val)
 	
 	def pp(self, dp):
+		"""Pretty print to specified number of decimal places"""
 		return self.impl.toFixed(dp)
 	
 	def __add__(self, other):

pyRCV2/numbers/native_py.py

@@ -15,6 +15,10 @@
 #   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 class Native:
+	"""
+	Wrapper for Python float (naive floating-point arithmetic)
+	"""
+	
 	def __init__(self, val):
 		self.impl = float(val)
 	

pyRCV2/numbers/rational_js.py

@@ -15,10 +15,15 @@
 #   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 class Rational:
+	"""
+	Wrapper for BigRational.js (rational arithmetic)
+	"""
+	
 	def __init__(self, val):
 		self.impl = bigRat(val)
 	
 	def pp(self, dp):
+		"""Pretty print to specified number of decimal places"""
 		return self.impl.valueOf().toFixed(dp)
 	
 	def __add__(self, other):

pyRCV2/numbers/rational_py.py

@@ -17,6 +17,10 @@
 from fractions import Fraction
 
 class Rational:
+	"""
+	Wrapper for Python Fraction (rational arithmetic)
+	"""
+	
 	def __init__(self, val):
 		self.impl = Fraction(val)
 	

test.html

@@ -33,11 +33,12 @@
 	<body>
 		<input type="file" id="bltFile">
 		<button onclick="clickBtn();">OK</button>
-		<select id="numbers"><option value="native" selected>Native</option><option value="rational">Rational</option></select>
+		<select id="numbers"><option value="native" selected>Native</option><option value="rational">Rational</option><option value="fixed">Fixed (6 d.p.)</option></select>
 		
 		<table id="result"></table>
 		
 		<script src="http://peterolson.github.com/BigRational.js/BigInt_BigRat.min.js"></script>
+		<script src="https://cdn.jsdelivr.net/npm/big.js@6.0.0/big.min.js"></script>
 		<script src="bundle.js"></script>
 		
 		<script>

worker.js

@@ -1,4 +1,4 @@
-importScripts('http://peterolson.github.com/BigRational.js/BigInt_BigRat.min.js', 'bundle.js');
+importScripts('http://peterolson.github.com/BigRational.js/BigInt_BigRat.min.js', 'https://cdn.jsdelivr.net/npm/big.js@6.0.0/big.min.js', 'bundle.js');
 
 function sleep(ms) {
 	return new Promise(resolve => setTimeout(resolve, ms));
@@ -11,6 +11,9 @@ onmessage = async function(evt) {
 	if (evt.data.numbers == 'rational') {
 		py.pyRCV2.numbers.set_numclass(py.pyRCV2.numbers.Rational);
 	}
+	if (evt.data.numbers == 'fixed') {
+		py.pyRCV2.numbers.set_numclass(py.pyRCV2.numbers.Fixed);
+	}
 	
 	let election = py.pyRCV2.blt.readBLT(evt.data.data);
 	postMessage({'type': 'init', 'election': {