Update GPU syntax to allow for backend choices

Author: ChrisRackauckas

R/diffeqr.R

@@ -126,11 +126,32 @@ jitoptimize_sde <- function (de,prob){
 #' }
 #'
 #' @export
-diffeqgpu_setup <- function (){
+diffeqgpu_setup <- function (backend){
   JuliaCall::julia_install_package_if_needed("DiffEqGPU")
   JuliaCall::julia_library("DiffEqGPU")
   functions <- JuliaCall::julia_eval("filter(isascii, replace.(string.(propertynames(DiffEqGPU)),\"!\"=>\"_bang\"))")
   degpu <- julia_pkg_import("DiffEqGPU",functions)
+
+  if (backend == "CUDA") {
+    JuliaCall::julia_install_package_if_needed("CUDA")
+    JuliaCall::julia_library("CUDA")
+    backend <- julia_pkg_import("CUDA",c("CUDABackend"))
+  } else if (backend == "AMDGPU") {
+    JuliaCall::julia_install_package_if_needed("AMDGPU")
+    JuliaCall::julia_library("AMDGPU")
+    backend <- julia_pkg_import("AMDGPU",c("AMDGPUBackend"))
+  } else if (backend == "Metal") {
+    JuliaCall::julia_install_package_if_needed("Metal")
+    JuliaCall::julia_library("Metal")
+    backend <- julia_pkg_import("Metal",c("MetalBackend"))
+  } else if (backend == "oneAPI") {
+    JuliaCall::julia_install_package_if_needed("oneAPI")
+    JuliaCall::julia_library("oneAPI")
+    backend <- julia_pkg_import("oneAPI",c("oneAPIBackend"))
+  } else {
+    stop(paste("Illegal backend choice found. Allowed choices: CUDA, AMDGPU, Metal, and oneAPI. Chosen backend: ", backend)
+  }
+  list(degpu, backend)
 }
 
 julia_function <- function(func_name, pkg_name = "Main",