try simpler gpu code

Author: ChrisRackauckas

ext/LinearSolveCUDAExt.jl

@@ -6,19 +6,18 @@ using SciMLBase: AbstractSciMLOperator
 function SciMLBase.solve!(cache::LinearSolve.LinearCache, alg::CudaOffloadFactorization;
     kwargs...)
     if cache.isfresh
-        fact = LinearSolve.do_factorization(alg, CUDA.CuArray(cache.A), cache.b, cache.u)
+        fact = lu(CUDA.CuArray(cache.A))
         cache.cacheval = fact
         cache.isfresh = false
     end
-
-    copyto!(cache.u, cache.b)
-    y = Array(ldiv!(cache.cacheval, CUDA.CuArray(cache.u)))
+    y = Array(ldiv!(cache.u, cache.cacheval, CUDA.CuArray(cache.u)))
     SciMLBase.build_linear_solution(alg, y, nothing, cache)
 end
 
-function LinearSolve.do_factorization(alg::CudaOffloadFactorization, A, b, u)
-    fact = lu(CUDA.CuArray(A))
-    return fact
+function init_cacheval(alg::CudaOffloadFactorization, A, b, u, Pl, Pr,
+    maxiters::Int, abstol, reltol, verbose::Bool,
+    assumptions::OperatorAssumptions)
+    ArrayInterface.lu_instance(CUDA.CuArray(A))
 end
 
 end