Fix performance issue in _canonical_quadratic_reduction (#296)

Project.toml

@@ -6,7 +6,6 @@ version = "0.14.2"
 [deps]
 Libdl = "8f399da3-3557-5675-b5ff-fb832c97cbdb"
 MathOptInterface = "b8f27783-ece8-5eb3-8dc8-9495eed66fee"
-SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 
 [compat]
 Libdl = "<0.0.1, 1.6"
@@ -18,7 +17,8 @@ julia = "1.6"
 
 [extras]
 Printf = "de0858da-6303-5e67-8744-51eddeeeb8d7"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "Printf"]
+test = ["Printf", "SparseArrays", "Test"]

src/KNITRO.jl

@@ -7,7 +7,6 @@ module KNITRO
 
 import Libdl
 import MathOptInterface as MOI
-import SparseArrays
 
 const _DEPS_FILE = joinpath(dirname(@__FILE__), "..", "deps", "deps.jl")
 if isfile(_DEPS_FILE)

src/MOI_wrapper.jl

@@ -18,8 +18,11 @@ const _SETS = Union{
 }
 
 function _canonical_quadratic_reduction(f::MOI.ScalarQuadraticFunction)
-    I = Cint[term.variable_1.value for term in f.quadratic_terms]
-    J = Cint[term.variable_2.value for term in f.quadratic_terms]
+    if !MOI.Utilities.is_canonical(f)
+        f = MOI.Utilities.canonicalize!(copy(f))
+    end
+    I = Cint[_c_column(term.variable_1) for term in f.quadratic_terms]
+    J = Cint[_c_column(term.variable_2) for term in f.quadratic_terms]
     V = Cdouble[term.coefficient for term in f.quadratic_terms]
     for i in 1:length(V)
         if I[i] == J[i]
@@ -28,9 +31,6 @@ function _canonical_quadratic_reduction(f::MOI.ScalarQuadraticFunction)
             I[i], J[i] = J[i], I[i]
         end
     end
-    I, J, V = SparseArrays.findnz(SparseArrays.sparse(I, J, V))
-    I .-= Cint(1)
-    J .-= Cint(1)
     return return length(I), I, J, V
 end