[Bridges] fix deleting variable in bridged objective (#2150)

Project.toml

@@ -1,6 +1,6 @@
 name = "MathOptInterface"
 uuid = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
-version = "1.15.0"
+version = "1.15.1"
 
 [deps]
 BenchmarkTools = "6e4b80f9-dd63-53aa-95a3-0cdb28fa8baf"

docs/src/changelog.md

@@ -7,6 +7,12 @@ CurrentModule = MathOptInterface
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## v1.15.1 (April 25, 2023)
+
+### Fixed
+
+  - Fixed deleting a variable in a bridged objective (#2150)
+
 ## v1.15.0 (April 19, 2023)
 
 ### Added
@@ -21,7 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  - Fixed [`modify`](@ref) in [`Bridges.Objective.VectorSlackBridge`](@ref) (#2144)
  - Fixed NAME record with spaces in `FileFormats.MPS` (#2146)
  - Fixed deleting a variable in a bridged objective (#2147)
- 
+
 ### Other
 
  - Add a test for variables in one-sided open [`Interval`](@ref) sets (#2133)

src/Bridges/bridge_optimizer.jl

@@ -545,15 +545,67 @@ function _delete_variables_in_variables_constraints(
     end
 end
 
-function MOI.delete(b::AbstractBridgeOptimizer, vis::Vector{MOI.VariableIndex})
+function _delete_variables_in_bridged_objective(
+    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
+    _delete_variables_in_bridged_objective(b, vis, F)
+    return
+end
+
+function _delete_variables_in_bridged_objective(
+    b::AbstractBridgeOptimizer,
+    vis::Vector{MOI.VariableIndex},
+    ::Type{MOI.VectorOfVariables},
+)
+    obj_f = MOI.get(b, MOI.ObjectiveFunction{MOI.VectorOfVariables}())
+    discard = Base.Fix2(in, vis)
+    if !any(discard, obj_f.variables)
+        # There are no variables in the objective function to delete, so we
+        # don't need to do anything.
+        return
+    end
+    new_obj_f = MOI.VectorOfVariables(filter(!discard, obj_f.variables))
+    if MOI.output_dimension(new_obj_f) == 0
+        # We've deleted all variables in the objective. Zero the objective by
+        # setting FEASIBILITY_SENSE, but restore the sense afterwards.
+        sense = MOI.get(b, MOI.ObjectiveSense())
+        MOI.set(b, MOI.ObjectiveSense(), MOI.FEASIBILITY_SENSE)
+        MOI.set(b, MOI.ObjectiveSense(), sense)
+    else
+        MOI.set(b, MOI.ObjectiveFunction{MOI.VectorOfVariables}(), new_obj_f)
+    end
+    return
+end
+
+function _delete_variables_in_bridged_objective(
+    b::AbstractBridgeOptimizer,
+    vis::Vector{MOI.VariableIndex},
+    ::Type{MOI.VariableIndex},
+)
+    obj_f = MOI.get(b, MOI.ObjectiveFunction{MOI.VariableIndex}())
+    if obj_f in vis
+        sense = MOI.get(b, MOI.ObjectiveSense())
+        MOI.set(b, MOI.ObjectiveSense(), MOI.FEASIBILITY_SENSE)
+        MOI.set(b, MOI.ObjectiveSense(), sense)
+    end
+    return
+end
+
+function _delete_variables_in_bridged_objective(
+    ::AbstractBridgeOptimizer,
+    ::Vector{MOI.VariableIndex},
+    ::Type{F},
+) where {F}
+    # Nothing to do here. The variables can be deleted without changing the type
+    # of the objective, or whether one exists.
+    return
+end
+
+function MOI.delete(b::AbstractBridgeOptimizer, vis::Vector{MOI.VariableIndex})
+    if is_objective_bridged(b)
+        _delete_variables_in_bridged_objective(b, vis)
     end
     if Constraint.has_bridges(Constraint.bridges(b))
         _delete_variables_in_variables_constraints(b, vis)
@@ -584,13 +636,8 @@ 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
+    if is_objective_bridged(b)
+        _delete_variables_in_bridged_objective(b, [vi])
     end
     if Constraint.has_bridges(Constraint.bridges(b))
         _delete_variables_in_variables_constraints(b, [vi])

test/Bridges/bridge_optimizer.jl

@@ -979,6 +979,65 @@ function test_deleting_variables_in_bridged_objective()
     return
 end
 
+function test_deleting_all_variables_in_bridged_objective()
+    # We need to make sure that the bridges have the same functionality as the
+    # base Utilities.Model.
+    model_1 = MOI.Utilities.Model{Float64}()
+    model_2 = MOI.Bridges.Objective.VectorFunctionize{Float64}(
+        MOI.Utilities.Model{Float64}(),
+    )
+    for model in (model_1, model_2)
+        x = MOI.add_variable(model)
+        f = MOI.VectorOfVariables([x])
+        MOI.set(model, MOI.ObjectiveSense(), MOI.MIN_SENSE)
+        MOI.set(model, MOI.ObjectiveFunction{typeof(f)}(), f)
+        MOI.delete(model, x)
+        attrs = MOI.get(model, MOI.ListOfModelAttributesSet())
+        @test length(attrs) == 1
+        @test attrs[1] == MOI.ObjectiveSense()
+    end
+    return
+end
+
+function test_deleting_all_vector_variables_in_bridged_objective()
+    # We need to make sure that the bridges have the same functionality as the
+    # base Utilities.Model.
+    model_1 = MOI.Utilities.Model{Float64}()
+    model_2 = MOI.Bridges.Objective.VectorFunctionize{Float64}(
+        MOI.Utilities.Model{Float64}(),
+    )
+    for model in (model_1, model_2)
+        x = MOI.add_variable(model)
+        f = MOI.VectorOfVariables([x])
+        MOI.set(model, MOI.ObjectiveSense(), MOI.MIN_SENSE)
+        MOI.set(model, MOI.ObjectiveFunction{typeof(f)}(), f)
+        MOI.delete(model, [x])
+        attrs = MOI.get(model, MOI.ListOfModelAttributesSet())
+        @test length(attrs) == 1
+        @test attrs[1] == MOI.ObjectiveSense()
+    end
+    return
+end
+
+function test_deleting_all_variables_in_bridged_functionize_objective()
+    # We need to make sure that the bridges have the same functionality as the
+    # base Utilities.Model.
+    model_1 = MOI.Utilities.Model{Float64}()
+    model_2 = MOI.Bridges.Objective.Functionize{Float64}(
+        MOI.Utilities.Model{Float64}(),
+    )
+    for model in (model_1, model_2)
+        x = MOI.add_variable(model)
+        MOI.set(model, MOI.ObjectiveSense(), MOI.MIN_SENSE)
+        MOI.set(model, MOI.ObjectiveFunction{typeof(x)}(), x)
+        MOI.delete(model, x)
+        attrs = MOI.get(model, MOI.ListOfModelAttributesSet())
+        @test length(attrs) == 1
+        @test MOI.ObjectiveSense() in attrs
+    end
+    return
+end
+
 end  # module
 
 TestBridgeOptimizer.runtests()