From b02562b8f3e1f12b68febc5c44e2212d25ede032 Mon Sep 17 00:00:00 2001
From: Chris Rackauckas <accounts@chrisrackauckas.com>
Date: Sat, 31 Dec 2022 09:09:13 -0500
Subject: [PATCH] Add missing specialization for CHOLMOD

---
 src/factorization.jl        |  1 +
 src/factorization_sparse.jl |  3 ++-
 test/basictests.jl          | 17 +++++++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/factorization.jl b/src/factorization.jl
index b1dd74570..bcbd276b0 100644
--- a/src/factorization.jl
+++ b/src/factorization.jl
@@ -1,4 +1,5 @@
 _ldiv!(x, A, b) = ldiv!(x, A, b)
+
 function _ldiv!(x::Vector, A::Factorization, b::Vector)
     # workaround https://github.com/JuliaLang/julia/issues/43507
     copyto!(x, b)
diff --git a/src/factorization_sparse.jl b/src/factorization_sparse.jl
index e56b80f17..aea1b8862 100644
--- a/src/factorization_sparse.jl
+++ b/src/factorization_sparse.jl
@@ -2,7 +2,8 @@
 # Missing ldiv! definitions: https://github.com/JuliaSparse/SparseArrays.jl/issues/242
 function _ldiv!(x::Vector,
                 A::Union{SparseArrays.QR, LinearAlgebra.QRCompactWY,
-                         SuiteSparse.SPQR.QRSparse}, b::Vector)
+                         SuiteSparse.SPQR.QRSparse,
+                         SuiteSparse.CHOLMOD.Factor}, b::Vector)
     x .= A \ b
 end
 
diff --git a/test/basictests.jl b/test/basictests.jl
index ca053e46d..f82606476 100644
--- a/test/basictests.jl
+++ b/test/basictests.jl
@@ -210,6 +210,23 @@ end
         end
     end
 
+    @testset "CHOLMOD" begin
+        # Create a posdef symmetric matrix
+        A = sprand(100,100,0.01); A = A + A' + 100*I;
+
+        # rhs
+        b=rand(100);
+
+        # Set the problem
+        prob = LinearProblem(A,b)
+        sol = solve(prob)
+
+        # Enforce symmetry to use Cholesky, since A is symmetric and posdef
+        prob2 = LinearProblem(Symmetric(A),b)
+        sol2 = solve(prob2)
+        @test abs(norm(A * sol2.u .- b) - norm(A * sol.u .- b)) < 1e-12
+    end
+
     @testset "Preconditioners" begin
         @testset "Vector Diagonal Preconditioner" begin
             s = rand(n)