Vector Addition example update

Works with latest DPC++ and SYCL2020 features
README updated to reflect CUDA backend has USM support

Author: Ruyk

examples/vector_addition/README.md

@@ -7,9 +7,6 @@ to highlight how to build an application with SYCL for CUDA using DPC++ support,
 for which an example CMakefile is provided. For detailed documentation on how to
 migrate from CUDA to SYCL, see [SYCL For CUDA Developers](https://developer.codeplay.com/products/computecpp/ce/guides/sycl-for-cuda-developers).
 
-Note currently the CUDA backend does not support the [USM](https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/USM/USM.adoc) extension, so we use
-`sycl::buffer` and `sycl::accessors` instead.
-
 Pre-requisites
 ---------------
 

examples/vector_addition/vector_addition.cpp

@@ -34,10 +34,12 @@ int main(int argc, char *argv[]) {
 
   // Initialize input data
   {
-    const auto dwrite_t = sycl::access::mode::discard_write;
+    const auto dwrite_t = sycl::write_only;
+
+
+    sycl::host_accessor h_a{bufA, sycl::write_only};
+    sycl::host_accessor h_b{bufB, sycl::write_only};
 
-    auto h_a = bufA.get_access<dwrite_t>();
-    auto h_b = bufB.get_access<dwrite_t>();
     for (int i = 0; i < N; i++) {
       h_a[i] = sin(i) * sin(i);
       h_b[i] = cos(i) * cos(i);
@@ -70,8 +72,8 @@ int main(int argc, char *argv[]) {
   myQueue.submit(cg);
 
   {
-    const auto read_t = sycl::access::mode::read;
-    auto h_c = bufC.get_access<read_t>();
+    sycl::host_accessor h_c{bufC, sycl::read_only};
+
     double sum = 0.0f;
     for (int i = 0; i < N; i++) {
       sum += h_c[i];