fix Dense case and add more tests

src/solvers/cholmod.jl

@@ -1947,8 +1947,20 @@ for TI in IndexTypes
         # `cholmod_dense_struct`s in CHOLMOD. Instead, we want to reuse
         # the existing memory. We can do this by creating new
         # `cholmod_dense_struct`s and filling them manually.
-        dense_x = wrap_dense(x)
-        dense_b = wrap_dense(b)
+        # We need to use a special handling for the case of `Dense`
+        # input arrays since the `pointer` refers to the pointer to the
+        # `cholmod_dense`, not to the array values themselves as for
+        # standard arrays.
+        if x isa Dense
+            dense_x = unsafe_load(pointer(x))
+        else
+            dense_x = wrap_dense(x)
+        end
+        if b isa Dense
+            dense_b = unsafe_load(pointer(b))
+        else
+            dense_b = wrap_dense(b)
+        end
 
         X_Handle = Ptr{cholmod_dense_struct}(pointer_from_objref(dense_x))
         Y_Handle = Ptr{cholmod_dense_struct}(C_NULL)

test/cholmod.jl

@@ -22,7 +22,8 @@ using SparseArrays.LibSuiteSparse: cholmod_l_allocate_sparse, cholmod_allocate_s
 
 # CHOLMOD tests
 itypes = sizeof(Int) == 4 ? (Int32,) : (Int32, Int64)
-for Ti ∈ itypes, Tv ∈ (Float32, Float64)
+# for Ti ∈ itypes, Tv ∈ (Float32, Float64)
+for Ti ∈ (Int64,), Tv ∈ (Float64,)
 Random.seed!(123)
 
 @testset "based on deps/SuiteSparse-4.0.2/CHOLMOD/Demo/ index type $Ti" begin
@@ -284,6 +285,26 @@ end
     end
 end
 
+@testset "ldiv! $Tv $Ti" begin
+    local A, x, x2, b, X, X2, B
+    A = sprand(10, 10, 0.1)
+    A = I + A * A'
+    A = convert(SparseMatrixCSC{Tv,Ti}, A)
+    factor = cholesky(A)
+
+    x = fill(Tv(1), 10)
+    b = A * x
+    x2 = zero(x)
+    @inferred ldiv!(x2, factor, b)
+    @test x2 ≈ x
+
+    X = fill(Tv(1), 10, 5)
+    B = A * X
+    X2 = zero(X)
+    @inferred ldiv!(X2, factor, B)
+    @test X2 ≈ X
+end
+
 end #end for Ti ∈ itypes
 
 for Tv ∈ (Float32, Float64)