VectorAffineFunction easy constructor

src/Utilities/functions.jl

@@ -2207,14 +2207,7 @@ 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 =
-        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 MOI.VectorAffineFunction(terms, constant)
+    return MOI.VectorAffineFunction(funcs)
 end
 
 """

src/functions.jl

@@ -578,6 +578,19 @@ function VectorAffineFunction{T}(f::VectorOfVariables) where {T}
     return VectorAffineFunction(terms, constants)
 end
 
+function VectorAffineFunction(
+    rows::AbstractVector{ScalarAffineFunction{T}},
+) where {T}
+    ret = VectorAffineFunction{T}(VectorAffineTerm{T}[], T[])
+    for (row, f) in enumerate(rows)
+        push!(ret.constants, f.constant)
+        for term in f.terms
+            push!(ret.terms, VectorAffineTerm(row, term))
+        end
+    end
+    return ret
+end
+
 """
     VectorQuadraticTerm{T}(
         output_index::Int64,

test/functions.jl

@@ -129,6 +129,20 @@ function test_functions_convert_ScalarQuadraticFunction()
     )
 end
 
+function test_vectoraffinefunction_creation()
+    x = MOI.VariableIndex(1)
+    f = MOI.VectorAffineFunction([1.0 * x + 2.0, 3.0 * x + 4.0])
+    g = MOI.VectorAffineFunction(
+        MOI.VectorAffineTerm{Float64}[
+            MOI.VectorAffineTerm(1, MOI.ScalarAffineTerm(1.0, x)),
+            MOI.VectorAffineTerm(2, MOI.ScalarAffineTerm(3.0, x)),
+        ],
+        [2.0, 4.0],
+    )
+    @test f ≈ g
+    return
+end
+
 function test_isapprox_VectorOfVariables()
     x = MOI.VariableIndex(1)
     y = MOI.VariableIndex(2)