Add final_touch for bridges

Author: blegat

src/Bridges/Constraint/Constraint.jl

@@ -8,7 +8,7 @@ module Constraint
 
 import LinearAlgebra
 import MathOptInterface
-import OrderedCollections: OrderedDict
+import OrderedCollections: OrderedDict, OrderedSet
 import SparseArrays
 
 const MOI = MathOptInterface

src/Bridges/Constraint/map.jl

@@ -20,12 +20,14 @@ struct Map <: AbstractDict{MOI.ConstraintIndex,AbstractBridge}
     # of creation so we need `OrderedDict` and not `Dict`.
     # For `VariableIndex` constraints: (variable, set type) -> bridge
     single_variable_constraints::OrderedDict{Tuple{Int64,Type},AbstractBridge}
+    needs_final_touch::OrderedDict{Type,OrderedSet}
 
     function Map()
         return new(
             Union{Nothing,AbstractBridge}[],
             Tuple{Type,Type}[],
             OrderedDict{Tuple{Int64,Type},AbstractBridge}(),
+            OrderedDict{Type,OrderedSet}(),
         )
     end
 end
@@ -48,6 +50,7 @@ function Base.empty!(map::Map)
     empty!(map.bridges)
     empty!(map.constraint_types)
     empty!(map.single_variable_constraints)
+    empty!(map.needs_final_touch)
     return map
 end
 
@@ -83,6 +86,7 @@ function Base.getindex(
 end
 
 function Base.delete!(map::Map, ci::MOI.ConstraintIndex)
+    _unregister_for_final_touch(map, map.bridges[_index(ci)])
     map.bridges[_index(ci)] = nothing
     return map
 end
@@ -91,6 +95,8 @@ function Base.delete!(
     map::Map,
     ci::MOI.ConstraintIndex{MOI.VariableIndex,S},
 ) where {S}
+    bridge = map.single_variable_constraints[(ci.value, S)]
+    _unregister_for_final_touch(map, bridge)
     delete!(map.single_variable_constraints, (ci.value, S))
     return map
 end
@@ -278,6 +284,7 @@ function add_key_for_bridge(
     ::F,
     ::S,
 ) where {F<:MOI.AbstractFunction,S<:MOI.AbstractSet}
+    _register_for_final_touch(map, bridge)
     push!(map.bridges, bridge)
     push!(map.constraint_types, (F, S))
     return _index(length(map.bridges), F, S)
@@ -289,10 +296,40 @@ function add_key_for_bridge(
     func::MOI.VariableIndex,
     ::S,
 ) where {S<:MOI.AbstractScalarSet}
+    _register_for_final_touch(map, bridge)
     map.single_variable_constraints[(func.value, S)] = bridge
     return MOI.ConstraintIndex{MOI.VariableIndex,S}(func.value)
 end
 
+function _register_for_final_touch(map::Map, bridge)
+    if MOI.Bridges.needs_final_touch(bridge)
+        if !haskey(map.needs_final_touch, typeof(bridge))
+            map.needs_final_touch[typeof(bridge)] = OrderedSet{typeof(bridge)}()
+        end
+        push!(map.needs_final_touch[typeof(bridge)], bridge)
+    end
+    return
+end
+function _unregister_for_final_touch(b::Map, bridge)
+    if MOI.Bridges.needs_final_touch(bridge)
+        delete!(b.needs_final_touch[typeof(bridge)], bridge)
+    end
+    return
+end
+
+# function barrier to iterate over bridges of the same type in an efficient way
+function _final_touch(bridges)
+    for bridge in bridges
+        MOI.Utilities.final_touch(bridge)
+    end
+end
+
+function MOI.Utilities.final_touch(map::Map)
+    for bridges in values(map.needs_final_touch)
+        _final_touch(bridges)
+    end
+end
+
 """
     EmptyMap <: AbstractDict{MOI.ConstraintIndex, AbstractBridge}
 
@@ -315,3 +352,5 @@ Base.values(::EmptyMap) = MOI.Utilities.EmptyVector{AbstractBridge}()
 has_bridges(::EmptyMap) = false
 
 number_of_type(::EmptyMap, ::Type{<:MOI.ConstraintIndex}) = 0
+
+MOI.Utilities.final_touch(::EmptyMap) = nothing

src/Bridges/bridge.jl

@@ -253,3 +253,14 @@ MathOptInterface.ScalarAffineFunction{Float64}
 ```
 """
 function set_objective_function_type end
+
+"""
+    needs_final_touch(bridge::AbstractBridge)
+
+Return whether [`Utilities.final_touch`](@ref) needs to be called on `bridge`.
+For instance, if the correctness of `bridge` depends on bounds of variable
+or the fact that variables are integer, then the bridging is only valid
+if these do not change. In that case, the bridge can check in `final_touch`
+that they did not change and change the bridging in case it did.
+"""
+needs_final_touch(::AbstractBridge) = false

src/Bridges/bridge_optimizer.jl

@@ -374,7 +374,11 @@ end
 # Implementation of the MOI interface for AbstractBridgeOptimizer
 
 # By convention, the model should be stored in a `model` field
-MOI.optimize!(b::AbstractBridgeOptimizer) = MOI.optimize!(b.model)
+function MOI.optimize!(b::AbstractBridgeOptimizer)
+    MOI.Utilities.final_touch(Constraint.bridges(b))
+    MOI.optimize!(b.model)
+    return
+end
 
 function MOI.is_empty(b::AbstractBridgeOptimizer)
     return isempty(Variable.bridges(b)) &&
@@ -454,6 +458,7 @@ function MOI.supports_incremental_interface(b::AbstractBridgeOptimizer)
     return MOI.supports_incremental_interface(b.model)
 end
 function MOI.Utilities.final_touch(uf::AbstractBridgeOptimizer, index_map)
+    MOI.Utilities.final_touch(Constraint.bridges(b))
     return MOI.Utilities.final_touch(uf.model, index_map)
 end