Add ConflictCount and conflict_index to ConstraintConflictStatus

docs/src/reference/models.md

@@ -160,6 +160,7 @@ COMPUTE_CONFLICT_NOT_CALLED
 NO_CONFLICT_EXISTS
 NO_CONFLICT_FOUND
 CONFLICT_FOUND
+ConflictCount
 ConstraintConflictStatus
 ConflictParticipationStatusCode
 NOT_IN_CONFLICT

src/Utilities/mockoptimizer.jl

@@ -65,9 +65,10 @@ mutable struct MockOptimizer{MT<:MOI.ModelLike,T} <: MOI.AbstractOptimizer
     # Constraint conflicts
     compute_conflict_called::Bool
     conflict_status::MOI.ConflictStatusCode
+    conflict_count::Int
     constraint_conflict_status::Dict{
         MOI.ConstraintIndex,
-        MOI.ConflictParticipationStatusCode,
+        Dict{Int,MOI.ConflictParticipationStatusCode},
     }
     # Basis status
     constraint_basis_status::Dict{
@@ -124,7 +125,11 @@ function MockOptimizer(
         #
         false,
         MOI.COMPUTE_CONFLICT_NOT_CALLED,
-        Dict{MOI.ConstraintIndex,MOI.ConflictParticipationStatusCode}(),
+        0,
+        Dict{
+            MOI.ConstraintIndex,
+            Dict{Int,MOI.ConflictParticipationStatusCode},
+        }(),
         # Basis status
         Dict{MOI.ConstraintIndex,Dict{Int,MOI.BasisStatusCode}}(),
         Dict{MOI.VariableIndex,Dict{Int,MOI.BasisStatusCode}}(),
@@ -302,6 +307,13 @@ function MOI.set(
     return
 end
 
+MOI.get(mock::MockOptimizer, ::MOI.ConflictCount) = mock.conflict_count
+
+function MOI.set(mock::MockOptimizer, ::MOI.ConflictCount, x)
+    mock.conflict_count = x
+    return
+end
+
 function MOI.set(
     mock::MockOptimizer,
     ::MOI.ConflictStatus,
@@ -449,11 +461,11 @@ end
 
 function MOI.set(
     mock::MockOptimizer,
-    ::MOI.ConstraintConflictStatus,
+    attr::MOI.ConstraintConflictStatus,
     idx::MOI.ConstraintIndex,
     value,
 )
-    mock.constraint_conflict_status[xor_index(idx)] = value
+    _safe_set_result(mock.constraint_conflict_status, attr, idx, value)
     return
 end
 
@@ -723,11 +735,17 @@ end
 
 function MOI.get(
     mock::MockOptimizer,
-    ::MOI.ConstraintConflictStatus,
+    attr::MOI.ConstraintConflictStatus,
     idx::MOI.ConstraintIndex,
 )
+    MOI.check_conflict_index_bounds(mock, attr)
     MOI.throw_if_not_valid(mock, idx)
-    return mock.constraint_conflict_status[xor_index(idx)]
+    return _safe_get_result(
+        mock.constraint_conflict_status,
+        attr,
+        idx,
+        "conflict status",
+    )
 end
 
 function _safe_set_result(
@@ -740,6 +758,9 @@ function _safe_set_result(
     if !haskey(dict, xored)
         dict[xored] = V()
     end
+    if hasproperty(attr, :conflict_index)
+        return dict[xored][attr.conflict_index] = value
+    end
     return dict[xored][attr.result_index] = value
 end
 
@@ -754,11 +775,16 @@ function _safe_get_result(
     if result_to_value === nothing
         error("No mock $name is set for ", index_name, " `", index, "`.")
     end
-    value = get(result_to_value, attr.result_index, nothing)
+    data_index = if hasproperty(attr, :conflict_index)
+        attr.conflict_index
+    else
+        attr.result_index
+    end
+    value = get(result_to_value, data_index, nothing)
     if value === nothing
         error(
             "No mock $name is set for $(index_name) `$(index)` at result " *
-            "index `$(attr.result_index)`.",
+            "index `$(data_index)`.",
         )
     end
     return value
@@ -996,10 +1022,10 @@ end
             <:Vector,
         }
         dual_status::MOI.ResultStatusCode,
-        constraint_duals::Pair{Tuple{DataTypeDataType},<:Vector}...;
-        constraint_basis_status = Pair{Tuple{DataTypeDataType},<:Vector}[],
+        constraint_duals::Pair{Tuple{DataType,DataType},<:Vector}...;
+        constraint_basis_status = Pair{Tuple{DataType,DataType},<:Vector}[],
         variable_basis_status = MOI.BasisStatusCode[],
-        constraint_conflict_status = Pair{Tuple{Type,Type},<:Vector}[],
+        constraint_conflict_status = Pair{Tuple{DataType,DataType},<:Vector}[],
     )
 
 Fake the result of a call to `optimize!` in the mock optimizer by storing the
@@ -1053,28 +1079,19 @@ function mock_optimize!(
     MOI.set(mock, MOI.ResultCount(), 1)
     _set_mock_primal(mock, primal)
     _set_mock_dual(mock, dual_status_constraint_duals...)
-    for con_basis_pair in constraint_basis_status
-        F, S = con_basis_pair.first
+    for ((F, S), result) in constraint_basis_status
         indices = MOI.get(mock, MOI.ListOfConstraintIndices{F,S}())
         for (i, ci) in enumerate(indices)
-            MOI.set(
-                mock,
-                MOI.ConstraintBasisStatus(),
-                ci,
-                con_basis_pair.second[i],
-            )
+            MOI.set(mock, MOI.ConstraintBasisStatus(), ci, result[i])
         end
     end
-    for con_conflict_pair in constraint_conflict_status
-        F, S = con_conflict_pair.first
+    if length(constraint_conflict_status) > 0
+        MOI.set(mock, MOI.ConflictCount(), 1)
+    end
+    for ((F, S), result) in constraint_conflict_status
         indices = MOI.get(mock, MOI.ListOfConstraintIndices{F,S}())
         for (i, ci) in enumerate(indices)
-            MOI.set(
-                mock,
-                MOI.ConstraintConflictStatus(),
-                ci,
-                con_conflict_pair.second[i],
-            )
+            MOI.set(mock, MOI.ConstraintConflictStatus(), ci, result[i])
         end
     end
     if length(variable_basis_status) > 0

src/attributes.jl

@@ -217,6 +217,48 @@ function Base.showerror(io::IO, err::ResultIndexBoundsError)
     )
 end
 
+"""
+    struct ConflictIndexBoundsError{AttrType} <: Exception
+        attr::AttrType
+        conflict_count::Int
+    end
+
+An error indicating that the requested attribute `attr` could not be retrieved,
+because the solver returned too few conflicts compared to what was requested.
+For instance, the user tries to retrieve `ConstraintConflictStatus(2)` when
+only one conflict is available, or when the model is feasible.
+
+See also: [`check_conflict_index_bounds`](@ref).
+"""
+struct ConflictIndexBoundsError{AttrType} <: Exception
+    attr::AttrType
+    conflict_count::Int
+end
+
+"""
+    check_conflict_index_bounds(model::ModelLike, attr)
+
+This function checks whether enough conflicts are available in the `model` for
+the requested `attr`, using its `conflict_index` field. If the model
+does not have sufficient conflicts to answer the query, it throws a
+[`ConflictIndexBoundsError`](@ref).
+"""
+function check_conflict_index_bounds(model::ModelLike, attr)
+    conflict_count = get(model, ConflictCount())
+    if !(1 <= attr.conflict_index <= conflict_count)
+        throw(ConflictIndexBoundsError(attr, conflict_count))
+    end
+    return
+end
+
+function Base.showerror(io::IO, err::ConflictIndexBoundsError)
+    return print(
+        io,
+        "Conflict index of attribute $(err.attr) out of bounds. There are " *
+        "currently $(err.conflict_count) conflict(s) in the model.",
+    )
+end
+
 """
     supports(model::ModelLike, sub::AbstractSubmittable)::Bool
 
@@ -1844,6 +1886,16 @@ struct ConflictStatus <: AbstractModelAttribute end
 
 attribute_value_type(::ConflictStatus) = ConflictStatusCode
 
+"""
+    ConflictCount()
+
+An [`AbstractModelAttribute`](@ref) for the number of conflicts found by the
+solver in the most recent call to [`compute_conflict!`](@ref).
+"""
+struct ConflictCount <: AbstractModelAttribute end
+
+attribute_value_type(::ConflictCount) = Int
+
 """
     ListOfVariableAttributesSet()
 
@@ -2673,12 +2725,34 @@ end
 )
 
 """
-    ConstraintConflictStatus()
+    ConstraintConflictStatus(conflict_index = 1)
 
 A constraint attribute to query the [`ConflictParticipationStatusCode`](@ref)
 indicating whether the constraint participates in the conflict.
+
+## `conflict_index`
+
+The optimizer may return multiple conflicts. See [`ConflictCount`](@ref)
+for querying the number of conflicts found.
+
+If the solver does not have a conflict because the
+`conflict_index` is beyond the available solutions (whose number is indicated by
+the [`ConflictCount`](@ref) attribute), then
+`MOI.check_result_index_bounds(model, ConstraintConflictStatus(conflict_index))`
+will throw a [`ResultIndexBoundsError`](@ref).
+
+## Implementation
+
+Optimizers should implement the following methods:
+```julia
+MOI.get(::Optimizer, ::MOI.ConstraintConflictStatus, ::MOI.ConstraintIndex)::T
+```
+They should not implement [`set`](@ref) or [`supports`](@ref).
 """
-struct ConstraintConflictStatus <: AbstractConstraintAttribute end
+struct ConstraintConflictStatus <: AbstractConstraintAttribute
+    conflict_index::Int
+    ConstraintConflictStatus(conflict_index = 1) = new(conflict_index)
+end
 
 function attribute_value_type(::ConstraintConflictStatus)
     return ConflictParticipationStatusCode
@@ -3233,6 +3307,7 @@ function is_set_by_optimize(
         RawSolver,
         ResultCount,
         ConflictStatus,
+        ConflictCount,
         ConstraintConflictStatus,
         TerminationStatus,
         RawStatusString,

test/General/attributes.jl

@@ -71,6 +71,7 @@ function test_attributes_integration_compute_conflict_1()
     @test MOI.get(optimizer, MOI.ConflictStatus()) ==
           MOI.COMPUTE_CONFLICT_NOT_CALLED
     MOI.set(optimizer, MOI.ConflictStatus(), MOI.CONFLICT_FOUND)
+    MOI.set(optimizer, MOI.ConflictCount(), 1)
     MOI.set(
         optimizer,
         MOI.ConstraintConflictStatus(),
@@ -97,9 +98,23 @@ function test_attributes_integration_compute_conflict_1()
     )
     MOI.compute_conflict!(model)
     @test MOI.get(model, MOI.ConflictStatus()) == MOI.CONFLICT_FOUND
+    @test MOI.get(model, MOI.ConflictCount()) == 1
     @test MOI.get(model, MOI.ConstraintConflictStatus(), c1) ==
           MOI.NOT_IN_CONFLICT
     @test MOI.get(model, MOI.ConstraintConflictStatus(), c2) == MOI.IN_CONFLICT
+    @test MOI.get(model, MOI.ConstraintConflictStatus(1), c1) ==
+          MOI.NOT_IN_CONFLICT
+    @test MOI.get(model, MOI.ConstraintConflictStatus(1), c2) == MOI.IN_CONFLICT
+    @test_throws MOI.ConflictIndexBoundsError MOI.get(
+        model,
+        MOI.ConstraintConflictStatus(2),
+        c1,
+    )
+    @test_throws MOI.ConflictIndexBoundsError MOI.get(
+        model,
+        MOI.ConstraintConflictStatus(2),
+        c2,
+    )
 end
 
 MOI.Utilities.@model(
@@ -127,8 +142,10 @@ function test_attributes_integration_compute_conflict_2()
     @test MOI.get(optimizer, MOI.ConflictStatus()) ==
           MOI.COMPUTE_CONFLICT_NOT_CALLED
     MOI.set(optimizer, MOI.ConflictStatus(), MOI.CONFLICT_FOUND)
+    MOI.set(optimizer, MOI.ConflictCount(), 1)
     MOI.compute_conflict!(model)
     @test MOI.get(model, MOI.ConflictStatus()) == MOI.CONFLICT_FOUND
+    @test MOI.get(model, MOI.ConflictCount()) == 1
     @test_throws ArgumentError MOI.get(model, MOI.ConstraintConflictStatus(), c)
 end
 

test/General/errors.jl

@@ -300,6 +300,16 @@ function test_errors_ResultIndexBoundsError()
           " bounds. There are currently 0 solution(s) in the model."
 end
 
+function test_errors_ConflictIndexBoundsError()
+    @test sprint(
+        showerror,
+        MOI.ConflictIndexBoundsError(MOI.ConstraintConflictStatus(1), 0),
+    ) ==
+          "Conflict index of attribute " *
+          "MathOptInterface.ConstraintConflictStatus(1) out of bounds. " *
+          "There are currently 0 conflict(s) in the model."
+end
+
 function test_errors_InvalidCalbackUsage()
     @test sprint(
         showerror,

test/Utilities/mockoptimizer.jl

@@ -158,8 +158,8 @@ function test_conflict_access()
     c = MOI.add_constraint(mock, 1fx + fy, MOI.LessThan(1))
     MOI.set(mock, MOI.ConstraintConflictStatus(), cx, MOI.NOT_IN_CONFLICT)
     MOI.set(mock, MOI.ConstraintConflictStatus(), c, MOI.IN_CONFLICT)
+    MOI.set(mock, MOI.ConflictCount(), 1)
     MOI.compute_conflict!(mock)
-
     @test MOI.get(mock, MOI.ConstraintConflictStatus(), cx) ==
           MOI.NOT_IN_CONFLICT
     @test MOI.get(mock, MOI.ConstraintConflictStatus(), c) == MOI.IN_CONFLICT