63 lines
3.3 KiB
Python
63 lines
3.3 KiB
Python
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__author__ = "Jeremy Saklad"
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from functools import reduce
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from ortools.sat.python import cp_model
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class BoneMarketModel(cp_model.CpModel):
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"""A CpModel with additional functions for common constraints and enhanced enforcement literal support."""
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__slots__ = ()
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def AddAllowedAssignments(self, variables, tuples_list):
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intermediate_variables, constraints = zip(*(self.NewIntermediateIntVar(variable, f'{repr((variables, tuples_list))}: {variable}') for variable in variables))
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super().AddAllowedAssignments(intermediate_variables, tuples_list)
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return constraints
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def AddApproximateExponentiationEquality(self, target, var, exp, upto):
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"""Add an approximate exponentiation equality using a lookup table.
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Set `upto` to a value that is unlikely to come into play.
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Each parameter is interpreted as a BoundedLinearExpression, and a layer of indirection is applied such that each Constraint in the returned tuple can accept an enforcement literal."""
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return self.AddAllowedAssignments((target, var), ((int(base**exp), base) for base in range(upto + 1)))
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def AddMultiplicationEquality(self, target, variables):
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"""Adds `target == variables[0] * .. * variables[n]`.
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Each parameter is interpreted as a BoundedLinearExpression, and a layer of indirection is applied such that each Constraint in the returned tuple can accept an enforcement literal."""
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superclass = super()
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def Multiply(end, stack):
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intermediate_variable, variable_constraint = self.NewIntermediateIntVar(stack.pop(), f'{repr(end)} == {"*".join((repr(variable) for variable in stack))}: last variable')
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partial_target = self.NewIntVar(f'{repr(end)} == {"*".join((repr(variable) for variable in stack))}: partial target')
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recursive_constraints = self.AddMultiplicationEquality(partial_target, stack) if len(stack) > 1 else (self.Add(partial_target == stack.pop()),)
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intermediate_target, target_constraint = self.NewIntermediateIntVar(end, f'{repr(end)} == {"*".join((repr(variable) for variable in stack))}: target')
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superclass.AddMultiplicationEquality(intermediate_target, (partial_target, intermediate_variable))
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return (variable_constraint, *recursive_constraints, target_constraint)
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# Avoid mutating parameter directly
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return Multiply(target, variables.copy() if isinstance(variables, list) else list(variables))
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def NewIntermediateBoolVar(self, name, linear_exp, domain):
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"""Add a fully-reified implication using an intermediate Boolean variable."""
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intermediate = self.NewBoolVar(name)
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self.AddLinearExpressionInDomain(linear_exp, domain).OnlyEnforceIf(intermediate)
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self.AddLinearExpressionInDomain(linear_exp, domain.Complement()).OnlyEnforceIf(intermediate.Not())
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return intermediate
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def NewIntermediateIntVar(self, linear_exp, name, *, lb = cp_model.INT_MIN//8, ub = cp_model.INT_MAX//8):
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"""Creates an integer variable equivalent to the given expression and returns a tuple consisting of the variable and constraint for use with enforcement literals."""
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intermediate = super().NewIntVar(lb, ub, name)
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return (intermediate, self.Add(intermediate == linear_exp))
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def NewIntVar(self, name, *, lb = cp_model.INT32_MIN, ub = cp_model.INT32_MAX):
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return super().NewIntVar(lb, ub, name)
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