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Support nonlinear constraints with Boolean operators #21

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merged 3 commits into from
Jan 26, 2023
Merged

Support nonlinear constraints with Boolean operators #21

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0645849
Support nonlinear constraints with Boolean operators
odow Jan 26, 2023
e6856aa
Add tests
odow Jan 26, 2023
ca90a3a
Add more tests
odow Jan 26, 2023
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7 changes: 7 additions & 0 deletions src/MiniZinc.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,13 @@ function MOI.supports_constraint(
return true
end

MOI.supports(::Model, ::MOI.NLPBlock) = true

function MOI.set(model::Model, ::MOI.NLPBlock, data::MOI.NLPBlockData)
model.ext[:nlp_block] = data
return
end

include("write.jl")
include("optimize.jl")

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3 changes: 3 additions & 0 deletions src/optimize.jl
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Expand Up @@ -83,10 +83,13 @@ end

# The MOI interface

MOI.get(model::Optimizer, ::MOI.SolverName) = "MiniZinc"

MOI.is_empty(model::Optimizer) = MOI.is_empty(model.inner)

function MOI.empty!(model::Optimizer)
MOI.empty!(model.inner)
empty!(model.inner.ext)
model.has_solution = false
empty!(model.primal_solution)
return
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91 changes: 91 additions & 0 deletions src/write.jl
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Expand Up @@ -460,6 +460,89 @@ function _write_predicates(io, model)
return
end

function _write_constraint(io, model, variables, expr::Expr)
print(io, "constraint ")
if Meta.isexpr(expr, :call, 3)
@assert expr.args[1] in (:(<=), :(>=), :(<), :(>), :(==))
_write_expression(io, model, variables, expr.args[2])
rhs = expr.args[3]
if isone(rhs)
println(io, " $(expr.args[1]) true;")
else
@assert iszero(rhs)
println(io, " $(expr.args[1]) false;")
end
else
@assert Meta.isexpr(expr, :comparison, 5)
error("Two sided not supported")
end
return
end

function _write_logical_expression(io, model, variables, expr)
ops = Dict(:|| => "\\/", :&& => "/\\")
op = get(ops, expr.head, nothing)
@assert op !== nothing
print(io, "(")
_write_expression(io, model, variables, expr.args[1])
for i in 2:length(expr.args)
print(io, " ", op, " ")
_write_expression(io, model, variables, expr.args[i])
end
print(io, ")")
return
end

function _write_call_expression(io, model, variables, expr)
ops = Dict(
:- => "-",
:+ => "+",
:(<) => "<",
:(>) => ">",
:(<=) => "<=",
:(>=) => ">=",
)
op = get(ops, expr.args[1], nothing)
@assert op !== nothing
print(io, "(")
_write_expression(io, model, variables, expr.args[2])
for i in 3:length(expr.args)
print(io, " ", op, " ")
_write_expression(io, model, variables, expr.args[i])
end
print(io, ")")
return
end

function _write_expression(io, model, variables, expr::Expr)
if Meta.isexpr(expr, :ref)
@assert expr.args[1] == :x
_write_expression(io, model, variables, expr.args[2])
return
end
if Meta.isexpr(expr, :||) || Meta.isexpr(expr, :&&)
_write_logical_expression(io, model, variables, expr)
else
@assert Meta.isexpr(expr, :call)
_write_call_expression(io, model, variables, expr)
end
return
end

function _write_expression(io, model, variables, x::MOI.VariableIndex)
print(io, _to_string(variables, x))
return
end

function _write_expression(io, model, variables, x::Real)
if isinteger(x)
print(io, round(Int, x))
else
print(io, x)
end
return
end

function Base.write(io::IO, model::Model{T}) where {T}
MOI.FileFormats.create_unique_variable_names(
model,
Expand All @@ -478,6 +561,14 @@ function Base.write(io::IO, model::Model{T}) where {T}
end
_write_constraint(io, model, variables, F, S)
end
nlp_block = get(model.ext, :nlp_block, nothing)
if nlp_block !== nothing
MOI.initialize(nlp_block.evaluator, [:ExprGraph])
for i in 1:length(nlp_block.constraint_bounds)
expr = MOI.constraint_expr(nlp_block.evaluator, i)
_write_constraint(io, model, variables, expr)
end
end
sense = MOI.get(model, MOI.ObjectiveSense())
if sense == MOI.FEASIBILITY_SENSE
println(io, "solve satisfy;")
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93 changes: 93 additions & 0 deletions test/runtests.jl
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Expand Up @@ -1047,6 +1047,99 @@ function test_model_filename()
return
end

function test_model_nlp_boolean()
model = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Int}())
x = MOI.add_variables(model, 2)
MOI.add_constraint.(model, x, MOI.ZeroOne())
nlp = MOI.Nonlinear.Model()
a, b = x
MOI.Nonlinear.add_constraint(nlp, :(($a || $b)), MOI.EqualTo(1.0))
MOI.Nonlinear.add_constraint(nlp, :(($a && $b)), MOI.EqualTo(0.0))
backend = MOI.Nonlinear.ExprGraphOnly()
evaluator = MOI.Nonlinear.Evaluator(nlp, backend, x)
MOI.set(model, MOI.NLPBlock(), MOI.NLPBlockData(evaluator))
solver = MiniZinc.Optimizer{Int}(MiniZinc.Chuffed())
MOI.set(solver, MOI.RawOptimizerAttribute("model_filename"), "test.mzn")
index_map, _ = MOI.optimize!(solver, model)
@test MOI.get(solver, MOI.TerminationStatus()) === MOI.OPTIMAL
@test MOI.get(solver, MOI.ResultCount()) >= 1
y = [index_map[v] for v in x]
sol = round.(Bool, MOI.get(solver, MOI.VariablePrimal(), y))
@test (sol[1] || sol[2]) == true
@test (sol[1] && sol[2]) == false
@test read("test.mzn", String) ==
"var bool: x1;\nvar bool: x2;\nconstraint (x1 \\/ x2) == true;\nconstraint (x1 /\\ x2) == false;\nsolve satisfy;\n"
rm("test.mzn")
return
end

function test_model_nlp_boolean_nested()
model = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Int}())
x = MOI.add_variables(model, 2)
MOI.add_constraint.(model, x, MOI.ZeroOne())
y = MOI.add_variable(model)
MOI.add_constraint(model, y, MOI.Integer())
MOI.add_constraint(model, y, MOI.Interval(0, 10))
nlp = MOI.Nonlinear.Model()
a, b = x
# a || (b && (y < 5))
MOI.Nonlinear.add_constraint(
nlp,
:(($a || ($b && ($y < 5)))),
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@chriscoey nested expressions like this work, for both binary and integer variables.

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Very nice!! 🤩

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I'll merge so that you can experiment with it more easily. It'll have some rough edges (assertion errors) when things go wrong, but we can fix those in time if there is interest.

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awesome yes i plan to experiment with it in the next few days. thanks @odow!

MOI.EqualTo(1.0),
)
MOI.Nonlinear.add_constraint(nlp, :($a < 1), MOI.EqualTo(1.0))
backend = MOI.Nonlinear.ExprGraphOnly()
evaluator = MOI.Nonlinear.Evaluator(nlp, backend, x)
MOI.set(model, MOI.NLPBlock(), MOI.NLPBlockData(evaluator))
solver = MiniZinc.Optimizer{Int}(MiniZinc.Chuffed())
MOI.set(solver, MOI.RawOptimizerAttribute("model_filename"), "test.mzn")
index_map, _ = MOI.optimize!(solver, model)
@test MOI.get(solver, MOI.TerminationStatus()) === MOI.OPTIMAL
@test MOI.get(solver, MOI.ResultCount()) >= 1
sol_x = [index_map[v] for v in [x; y]]
sol = round.(Int, MOI.get(solver, MOI.VariablePrimal(), sol_x))
@test sol[1] == 0
@test sol[2] == 1
@test sol[3] < 5
@test read("test.mzn", String) ==
"var bool: x1;\nvar bool: x2;\nvar 0 .. 10: x3;\nconstraint (x1 \\/ (x2 /\\ (x3 < 5))) == true;\nconstraint (x1 < 1) == true;\nsolve satisfy;\n"
rm("test.mzn")
return
end

function test_model_nlp_boolean_jump()
model = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Int}())
x = MOI.add_variables(model, 2)
MOI.add_constraint.(model, x, MOI.ZeroOne())
nlp = MOI.Nonlinear.Model()
a, b = x
MOI.Nonlinear.add_constraint(nlp, :(($a || $b) - 1.0), MOI.EqualTo(0.0))
MOI.Nonlinear.add_constraint(nlp, :(($a && $b) - 0.0), MOI.EqualTo(0.0))
backend = MOI.Nonlinear.ExprGraphOnly()
evaluator = MOI.Nonlinear.Evaluator(nlp, backend, x)
MOI.set(model, MOI.NLPBlock(), MOI.NLPBlockData(evaluator))
solver = MiniZinc.Optimizer{Int}(MiniZinc.Chuffed())
MOI.set(solver, MOI.RawOptimizerAttribute("model_filename"), "test.mzn")
index_map, _ = MOI.optimize!(solver, model)
@test MOI.get(solver, MOI.TerminationStatus()) === MOI.OPTIMAL
@test MOI.get(solver, MOI.ResultCount()) >= 1
y = [index_map[v] for v in x]
sol = round.(Bool, MOI.get(solver, MOI.VariablePrimal(), y))
@test (sol[1] || sol[2]) == true
@test (sol[1] && sol[2]) == false
@test read("test.mzn", String) ==
"var bool: x1;\nvar bool: x2;\nconstraint ((x1 \\/ x2) - 1) == false;\nconstraint ((x1 /\\ x2) - 0) == false;\nsolve satisfy;\n"
rm("test.mzn")
return
end

function test_model_solver_name()
solver = MiniZinc.Optimizer{Int}(MiniZinc.Chuffed())
@test MOI.get(solver, MOI.SolverName()) == "MiniZinc"
return
end

end

TestMiniZinc.runtests()