Merge pull request #1003 from JuliaOpt/bl/empty_vectorize

Fix vectorize for empty vector

Author: blegat

src/Utilities/functions.jl

@@ -1820,13 +1820,13 @@ Returns the vector of scalar affine functions in the form of a
 `MOI.VectorAffineFunction{T}`.
 """
 function vectorize(funcs::AbstractVector{MOI.ScalarAffineFunction{T}}) where T
-    nterms = sum(func -> number_of_affine_terms(T, func), funcs)
-    out_dim = sum(func -> output_dim(T, func), funcs)
+    nterms = mapreduce(func -> number_of_affine_terms(T, func), +, funcs, init=0)
+    out_dim = mapreduce(func -> output_dim(T, func), +, funcs, init=0)
     terms = Vector{MOI.VectorAffineTerm{T}}(undef, nterms)
     constant = zeros(T, out_dim)
     fill_vector(terms, T, fill_terms, number_of_affine_terms, funcs)
     fill_vector(constant, T, fill_constant, output_dim, funcs)
-    return VAF(terms, constant)
+    return MOI.VectorAffineFunction(terms, constant)
 end
 
 """
@@ -1836,16 +1836,16 @@ Returns the vector of scalar quadratic functions in the form of a
 `MOI.VectorQuadraticFunction{T}`.
 """
 function vectorize(funcs::AbstractVector{MOI.ScalarQuadraticFunction{T}}) where T
-    num_affine_terms = sum(func -> number_of_affine_terms(T, func), funcs)
-    num_quadratic_terms = sum(func -> number_of_quadratic_terms(T, func), funcs)
-    out_dim = sum(func -> output_dim(T, func), funcs)
+    num_affine_terms = mapreduce(func -> number_of_affine_terms(T, func), +, funcs, init=0)
+    num_quadratic_terms = mapreduce(func -> number_of_quadratic_terms(T, func), +, funcs, init=0)
+    out_dim = mapreduce(func -> output_dim(T, func), +, funcs, init=0)
     affine_terms = Vector{MOI.VectorAffineTerm{T}}(undef, num_affine_terms)
     quadratic_terms = Vector{MOI.VectorQuadraticTerm{T}}(undef, num_quadratic_terms)
     constant = zeros(T, out_dim)
     fill_vector(affine_terms, T, fill_terms, number_of_affine_terms, funcs)
     fill_vector(quadratic_terms, T, fill_terms, number_of_quadratic_terms, funcs)
     fill_vector(constant, T, fill_constant, output_dim, funcs)
-    return VQF(affine_terms, quadratic_terms, constant)
+    return MOI.VectorQuadraticFunction(affine_terms, quadratic_terms, constant)
 end
 
 function promote_operation(::typeof(vcat), ::Type{T}, ::Type{T}...) where T

test/Utilities/functions.jl

@@ -21,6 +21,15 @@ fz = MOI.SingleVariable(z)
         g2 = MOI.ScalarAffineFunction(MOI.ScalarAffineTerm{Int}[], 1)
         g3 = MOI.ScalarAffineFunction([MOI.ScalarAffineTerm(5, y)], 4)
         @test g ≈ MOIU.vectorize([g1, g2, g3])
+        vov = MOIU.vectorize(MOI.SingleVariable[])
+        @test MOI.output_dimension(vov) == 0
+        @test vov isa MOI.VectorOfVariables
+        aff = MOIU.vectorize(MOI.ScalarAffineFunction{Int}[])
+        @test MOI.output_dimension(aff) == 0
+        @test aff isa MOI.VectorAffineFunction{Int}
+        quad = MOIU.vectorize(MOI.ScalarQuadraticFunction{Int}[])
+        @test MOI.output_dimension(quad) == 0
+        @test quad isa MOI.VectorQuadraticFunction{Int}
     end
     @testset "operate vcat" begin
         v = MOI.VectorOfVariables([y, w])