Use fork_join_executor by default

thrust/thrust/system/hpx/detail/execution_policy.h

@@ -29,6 +29,7 @@
 #include <thrust/detail/type_traits.h>
 #include <thrust/iterator/detail/any_system_tag.h>
 #include <thrust/system/cpp/detail/execution_policy.h>
+#include <thrust/system/hpx/detail/runtime.h>
 
 #include <hpx/execution.hpp>
 
@@ -235,7 +236,7 @@ auto to_hpx_execution_policy(const execution_policy<Derived>& exec) noexcept
   else
   {
     (void) exec;
-    return ::hpx::execution::par;
+    return ::hpx::execution::par.on(runtime.default_executor);
   }
 }
 

thrust/thrust/system/hpx/detail/runtime.h

@@ -30,6 +30,7 @@
 #  pragma system_header
 #endif // no system header
 
+#include <hpx/executors/fork_join_executor.hpp>
 #include <hpx/manage_runtime.hpp>
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -111,18 +112,24 @@ struct init_runtime
   {
     (void) runtime.stop();
   }
+};
+
+struct manage_runtime
+{
+  init_runtime init;
+  ::hpx::execution::experimental::fork_join_executor default_executor;
 
-  static init_runtime& get()
+  static manage_runtime& get()
   {
     // The HPX runtime implicitly depends on thread-local storage, making this object thread_local ensures the correct
     // sequencing of destructors. Since this function is only called from initialization of a global variable, only one
     // instance of the runtime will be created.
-    static thread_local init_runtime m;
+    static thread_local manage_runtime m;
     return m;
   }
 };
 
-inline init_runtime& runtime = init_runtime::get();
+inline manage_runtime& runtime = manage_runtime::get();
 
 template <typename F>
 inline decltype(auto) run_as_hpx_thread(const F& f)
@@ -132,7 +139,8 @@ inline decltype(auto) run_as_hpx_thread(const F& f)
     return f();
   }
 
-  return ::hpx::run_as_hpx_thread(f);
+  constexpr ::hpx::launch::async_policy policy(::hpx::threads::thread_priority::bound);
+  return ::hpx::run_as_hpx_thread(policy, f);
 }
 
 } // end namespace detail

thrust/thrust/system/hpx/memory_resource.h

@@ -31,6 +31,7 @@
 #endif // no system header
 #include <thrust/mr/fancy_pointer_resource.h>
 #include <thrust/mr/new.h>
+#include <thrust/system/hpx/detail/runtime.h>
 #include <thrust/system/hpx/pointer.h>
 
 #include <hpx/parallel/algorithms/for_loop.hpp>
@@ -54,9 +55,10 @@ class topology_resource final : public mr::memory_resource<>
 
     // touch first byte of every page
     const auto page_size = ::hpx::threads::get_memory_page_size();
-    ::hpx::experimental::for_loop_strided(::hpx::execution::par, ptr, ptr + bytes, page_size, [](std::byte* it) {
-      *it = {};
-    });
+    ::hpx::experimental::for_loop_strided(
+      ::hpx::execution::par.on(runtime.default_executor), ptr, ptr + bytes, page_size, [](std::byte* it) {
+        *it = {};
+      });
 
     return ptr;
   }