Add user_cpu_context and ability to provide host_policy via it

Author: olegkkruglov

cpp/oneapi/dal/compute.hpp

@@ -17,6 +17,7 @@
 #pragma once
 
 #include "oneapi/dal/detail/compute_ops.hpp"
+#include "oneapi/dal/detail/user_policy.hpp"
 #include "oneapi/dal/detail/spmd_policy.hpp"
 #include "oneapi/dal/spmd/communicator.hpp"
 
@@ -28,6 +29,11 @@ auto compute(Args&&... args) {
     return dal::detail::compute_dispatch(std::forward<Args>(args)...);
 }
 
+template <typename... Args>
+auto compute(detail::user_cpu_context uctx, Args&&... args) {
+    return dal::detail::compute_dispatch(uctx.get_host_policy(), std::forward<Args>(args)...);
+}
+
 #ifdef ONEDAL_DATA_PARALLEL
 template <typename... Args>
 auto compute(sycl::queue& queue, Args&&... args) {

cpp/oneapi/dal/detail/policy.hpp

@@ -103,6 +103,7 @@ class ONEDAL_EXPORT host_policy : public base {
     }
     host_policy(const host_policy&) = default;
     host_policy(host_policy&&) = default;
+    host_policy& operator= (const host_policy&) = default;
 
     static host_policy get_default() {
         return host_policy(make_default_impl());

cpp/oneapi/dal/train.hpp

@@ -17,6 +17,7 @@
 #pragma once
 
 #include "oneapi/dal/detail/train_ops.hpp"
+#include "oneapi/dal/detail/user_policy.hpp"
 #include "oneapi/dal/detail/spmd_policy.hpp"
 #include "oneapi/dal/spmd/communicator.hpp"
 
@@ -28,6 +29,11 @@ auto train(Args&&... args) {
     return dal::detail::train_dispatch(std::forward<Args>(args)...);
 }
 
+template <typename... Args>
+auto train(detail::user_cpu_context uctx, Args&&... args) {
+    return dal::detail::train_dispatch(uctx.get_host_policy(), std::forward<Args>(args)...);
+}
+
 #ifdef ONEDAL_DATA_PARALLEL
 template <typename... Args>
 auto train(sycl::queue& queue, Args&&... args) {