Add rmm::exec_policy_nosync

include/rmm/exec_policy.hpp

@@ -25,6 +25,7 @@
 #include <rmm/mr/device/thrust_allocator_adaptor.hpp>
 
 #include <thrust/system/cuda/execution_policy.h>
+#include <thrust/version.h>
 
 namespace rmm {
 
@@ -46,4 +47,32 @@ class exec_policy : public thrust_exec_policy_t {
   }
 };
 
+#if THRUST_VERSION >= 101600
+
+using thrust_exec_policy_nosync_t =
+  thrust::detail::execute_with_allocator<rmm::mr::thrust_allocator<char>,
+                                         thrust::cuda_cub::execute_on_stream_nosync_base>;
+/**
+ * @brief Helper class usable as a Thrust CUDA execution policy
+ * that uses RMM for temporary memory allocation on the specified stream
+ * and which allows the Thrust backend to skip stream synchronizations that
+ * are not required for correctness.
+ */
+class exec_policy_nosync : public thrust_exec_policy_nosync_t {
+ public:
+  explicit exec_policy_nosync(cuda_stream_view stream             = cuda_stream_default,
+                       rmm::mr::device_memory_resource* mr = mr::get_current_device_resource())
+    : thrust_exec_policy_nosync_t(
+        thrust::cuda::par_nosync(rmm::mr::thrust_allocator<char>(stream, mr)).on(stream.value()))
+  {
+  }
+};
+
+#else
+
+using thrust_exec_policy_nosync_t = thrust_exec_policy_t;
+using exec_policy_nosync = exec_policy;
+
+#endif
+
 }  // namespace rmm