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# MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
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# Copyright (C) 2020, UChicago Argonne, LLC. All rights reserved.
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# Released under the modified BSD license. See COPYING.md for more details.
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using JuMP
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using MathOptInterface
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const MOI = MathOptInterface
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function varname_split(varname::String)
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m = match(r"([^[]*)\[(.*)\]", varname)
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return m.captures[1], m.captures[2]
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end
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@pydef mutable struct JuMPSolver <: InternalSolver
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function __init__(self; optimizer=CPLEX.Optimizer)
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self.optimizer = optimizer
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end
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function add_constraint(self, constraint)
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@error "JuMPSolver: add_constraint not implemented"
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end
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function set_warm_start(self, solution)
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for (basename, subsolution) in solution
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for (idx, value) in subsolution
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value != nothing || continue
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var = self.basename_idx_to_var[basename, idx]
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JuMP.set_start_value(var, value)
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end
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end
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end
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function clear_warm_start(self)
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@error "JuMPSolver: clear_warm_start not implemented"
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end
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function fix(self, solution)
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for (basename, subsolution) in solution
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for (idx, value) in subsolution
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value != nothing || continue
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var = self.basename_idx_to_var[basename, idx]
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JuMP.fix(var, value, force=true)
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end
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end
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end
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function set_instance(self, instance, model)
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self.instance = instance
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self.model = model
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self.var_to_basename_idx = Dict(var => varname_split(JuMP.name(var))
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for var in JuMP.all_variables(self.model))
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self.basename_idx_to_var = Dict(varname_split(JuMP.name(var)) => var
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for var in JuMP.all_variables(self.model))
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self.bin_vars = [var
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for var in JuMP.all_variables(self.model)
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if JuMP.is_binary(var)]
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JuMP.set_optimizer(self.model, self.optimizer)
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end
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function solve(self; tee=false)
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JuMP.optimize!(self.model)
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self._update_solution()
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primal_bound = JuMP.objective_value(self.model)
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dual_bound = JuMP.objective_bound(self.model)
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if JuMP.objective_sense(self.model) == MOI.MIN_SENSE
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sense = "min"
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lower_bound = dual_bound
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upper_bound = primal_bound
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else
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sense = "max"
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lower_bound = primal_bound
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upper_bound = dual_bound
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end
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@show primal_bound, dual_bound
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return Dict("Lower bound" => lower_bound,
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"Upper bound" => upper_bound,
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"Sense" => sense,
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"Wallclock time" => JuMP.solve_time(self.model),
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"Nodes" => 1,
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"Log" => nothing,
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"Warm start value" => nothing)
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end
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function solve_lp(self; tee=false)
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for var in self.bin_vars
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JuMP.unset_binary(var)
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JuMP.set_upper_bound(var, 1.0)
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JuMP.set_lower_bound(var, 0.0)
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end
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JuMP.optimize!(self.model)
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obj_value = JuMP.objective_value(self.model)
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self._update_solution()
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for var in self.bin_vars
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JuMP.set_binary(var)
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end
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return Dict("Optimal value" => obj_value)
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end
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function get_solution(self)
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return self.solution
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end
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function _update_solution(self)
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solution = Dict()
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for var in JuMP.all_variables(self.model)
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basename, idx = self.var_to_basename_idx[var]
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if !haskey(solution, basename)
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solution[basename] = Dict()
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end
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solution[basename][idx] = JuMP.value(var)
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end
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self.solution = solution
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end
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function set_gap_tolerance(self, gap_tolerance)
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@error "JuMPSolver: set_gap_tolerance not implemented"
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end
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function set_node_limit(self)
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@error "JuMPSolver: set_node_limit not implemented"
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end
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function set_threads(self, threads)
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@error "JuMPSolver: set_threads not implemented"
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end
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function set_time_limit(self, time_limit)
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JuMP.set_time_limit_sec(self.model, time_limit)
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end
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end
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@ -0,0 +1,32 @@
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# MIPLearn: Extensible Framework for Learning-Enhanced Mixed-Integer Optimization
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# Copyright (C) 2020, UChicago Argonne, LLC. All rights reserved.
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# Released under the modified BSD license. See COPYING.md for more details.
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using PyCall
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@pydef mutable struct KnapsackInstance <: Instance
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function __init__(self, weights, prices, capacity)
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self.weights = weights
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self.prices = prices
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self.capacity = capacity
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end
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function to_model(self)
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model = Model()
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n = length(self.weights)
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@variable(model, x[1:n], Bin)
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@objective(model, Max, sum(x[i] * self.prices[i] for i in 1:n))
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@constraint(model, sum(x[i] * self.weights[i] for i in 1:n) <= self.capacity)
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return model
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end
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function get_instance_features(self)
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return [0.]
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end
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function get_variable_features(self, var, index)
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return [0.]
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end
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end
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export KnapsackInstance
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