Merge pull request #345 from scipopt/od/fix-344

Fix bug when deleting bound constraint of a ZeroOne variable

Author: matbesancon

src/MOI_wrapper/variable.jl

@@ -349,6 +349,18 @@ function reset_bounds(o::Optimizer, v, lb, ub, ::Type{MOI.LessThan{Float64}})
     return
 end
 
+function _update_binbounds(set::MOI.Interval, ::Type{<:MOI.LessThan})
+    return MOI.Interval(-Inf, set.upper)
+end
+
+function _update_binbounds(set::MOI.Interval, ::Type{<:MOI.GreaterThan})
+    return MOI.Interval(set.lower, Inf)
+end
+
+function _update_binbounds(::MOI.Interval, ::Type{<:S}) where {S}
+    return MOI.Interval(-Inf, Inf)
+end
+
 function MOI.delete(
     o::Optimizer,
     ci::MOI.ConstraintIndex{MOI.VariableIndex,S},
@@ -360,12 +372,12 @@ function MOI.delete(
     v = var(o, vi)
     if SCIPvarGetType(v) == SCIP_VARTYPE_BINARY
         reset_bounds(o, v, 0.0, 1.0, S)
+        old_set = o.binbounds[vi]
+        o.binbounds[vi] = _update_binbounds(old_set, S)
     else
         inf = SCIPinfinity(o)
         reset_bounds(o, v, -inf, inf, S)
     end
-    # but do delete the constraint reference
-    delete!(o.binbounds, vi)
     type = o.bound_types[vi]
     if type == _kSCIP_LESS_AND_GREATER_THAN && S <: MOI.LessThan
         o.bound_types[vi] = _kSCIP_GREATER_THAN

test/MOI_tests.jl

@@ -1671,6 +1671,27 @@ function test_get_binary_with_bounds()
     return
 end
 
+function test_fix_binary_variable()
+    for set in (
+        MOI.GreaterThan(0.0),
+        MOI.LessThan(1.0),
+        MOI.Interval(0.0, 1.0),
+        MOI.EqualTo(1.0),
+    )
+        model = SCIP.Optimizer()
+        MOI.set(model, MOI.Silent(), true)
+        x = MOI.add_variable(model)
+        c = MOI.add_constraint(model, x, set)
+        MOI.add_constraint(model, x, MOI.ZeroOne())
+        MOI.delete(model, c)
+        MOI.add_constraint(model, x, MOI.EqualTo(0.0))
+        MOI.optimize!(model)
+        @test MOI.get(model, MOI.TerminationStatus()) == MOI.OPTIMAL
+        @test MOI.get(model, MOI.VariablePrimal(), x) == 0.0
+    end
+    return
+end
+
 end  # module TestMOIWrapper
 
 TestMOIWrapper.runtests()