[Bridges] fix deleting variable in bridged objective (#2147)

Author: odow

src/Bridges/bridge_optimizer.jl

@@ -546,6 +546,15 @@ function _delete_variables_in_variables_constraints(
 end
 
 function MOI.delete(b::AbstractBridgeOptimizer, vis::Vector{MOI.VariableIndex})
+    F = MOI.get(b, MOI.ObjectiveFunctionType())
+    if is_objective_bridged(b) && F == MOI.VectorOfVariables
+        f = MOI.get(b, MOI.ObjectiveFunction{MOI.VectorOfVariables}())
+        discard = Base.Fix2(in, vis)
+        if any(discard, f.variables)
+            g = MOI.VectorOfVariables(filter(!discard, f.variables))
+            MOI.set(b, MOI.ObjectiveFunction{MOI.VectorOfVariables}(), g)
+        end
+    end
     if Constraint.has_bridges(Constraint.bridges(b))
         _delete_variables_in_variables_constraints(b, vis)
     end
@@ -575,6 +584,14 @@ function MOI.delete(b::AbstractBridgeOptimizer, vis::Vector{MOI.VariableIndex})
 end
 
 function MOI.delete(b::AbstractBridgeOptimizer, vi::MOI.VariableIndex)
+    F = MOI.get(b, MOI.ObjectiveFunctionType())
+    if is_objective_bridged(b) && F == MOI.VectorOfVariables
+        f = MOI.get(b, MOI.ObjectiveFunction{MOI.VectorOfVariables}())
+        if any(isequal(vi), f.variables)
+            g = MOI.VectorOfVariables(filter(!isequal(vi), f.variables))
+            MOI.set(b, MOI.ObjectiveFunction{MOI.VectorOfVariables}(), g)
+        end
+    end
     if Constraint.has_bridges(Constraint.bridges(b))
         _delete_variables_in_variables_constraints(b, [vi])
     end
@@ -600,6 +617,7 @@ function MOI.delete(b::AbstractBridgeOptimizer, vi::MOI.VariableIndex)
     else
         MOI.delete(b.model, vi)
     end
+    return
 end
 
 function MOI.delete(b::AbstractBridgeOptimizer, ci::MOI.ConstraintIndex)

test/Bridges/bridge_optimizer.jl

@@ -955,6 +955,30 @@ function test_delete_constraint_vector()
     return
 end
 
+function test_deleting_variable_in_bridged_objective()
+    inner = MOI.Utilities.Model{Float64}()
+    model = MOI.Bridges.Objective.VectorFunctionize{Float64}(inner)
+    x = MOI.add_variables(model, 2)
+    MOI.set(model, MOI.ObjectiveSense(), MOI.MIN_SENSE)
+    attr = MOI.ObjectiveFunction{MOI.VectorOfVariables}()
+    MOI.set(model, attr, MOI.VectorOfVariables(x))
+    MOI.delete(model, x[1])
+    @test MOI.get(model, attr) == MOI.VectorOfVariables([x[2]])
+    return
+end
+
+function test_deleting_variables_in_bridged_objective()
+    inner = MOI.Utilities.Model{Float64}()
+    model = MOI.Bridges.Objective.VectorFunctionize{Float64}(inner)
+    x = MOI.add_variables(model, 2)
+    MOI.set(model, MOI.ObjectiveSense(), MOI.MIN_SENSE)
+    attr = MOI.ObjectiveFunction{MOI.VectorOfVariables}()
+    MOI.set(model, attr, MOI.VectorOfVariables(x))
+    MOI.delete(model, [x[1]])
+    @test MOI.get(model, attr) == MOI.VectorOfVariables([x[2]])
+    return
+end
+
 end  # module
 
 TestBridgeOptimizer.runtests()