From b29f35c4b489db280f66778019fb65d03ddf3bf7 Mon Sep 17 00:00:00 2001
From: Timo Koch <timo.koch@iws.uni-stuttgart.de>
Date: Fri, 22 Apr 2022 14:51:58 +0200
Subject: [PATCH] [parallel][cmake] Set/decide multithreading backend in CMake
---
cmake/modules/DumuxMacros.cmake | 46 ++++++++++++++++++++++++++++++++
config.h.cmake | 8 ++++++
dumux/parallel/multithreading.hh | 17 +-----------
3 files changed, 55 insertions(+), 16 deletions(-)
diff --git a/cmake/modules/DumuxMacros.cmake b/cmake/modules/DumuxMacros.cmake
index 33c474648b..21299d9aa5 100644
--- a/cmake/modules/DumuxMacros.cmake
+++ b/cmake/modules/DumuxMacros.cmake
@@ -42,3 +42,49 @@ endif()
find_package(OpenMP QUIET)
include(AddOpenMPFlags)
+
+# test if we can use parallel algorithms
+check_cxx_symbol_exists(
+ "std::execution::par_unseq"
+ "execution"
+ DUMUX_HAVE_CXX_EXECUTION_POLICY
+)
+
+if(DUMUX_HAVE_CXX_EXECUTION_POLICY)
+ set(HAVE_CPP_PARALLEL_ALGORITHMS TRUE)
+endif()
+
+# setup multithreading backend
+if(NOT DUMUX_MULTITHREADING_BACKEND)
+ if(TBB_FOUND)
+ set(DUMUX_MULTITHREADING_BACKEND "TBB" CACHE STRING "The multithreading backend")
+ message(STATUS "Dumux multithreading backed: TBB")
+ elseif(OpenMP_FOUND)
+ set(DUMUX_MULTITHREADING_BACKEND "OpenMP" CACHE STRING "The multithreading backend")
+ message(STATUS "Dumux multithreading backed: OpenMP")
+ elseif(Kokkos_FOUND)
+ set(DUMUX_MULTITHREADING_BACKEND "Kokkos" CACHE STRING "The multithreading backend")
+ message(STATUS "Dumux multithreading backed: Kokkos")
+ elseif(DUMUX_HAVE_CXX_EXECUTION_POLICY)
+ set(DUMUX_MULTITHREADING_BACKEND "Cpp" CACHE STRING "The multithreading backend")
+ message(STATUS "Dumux multithreading backed: Cpp")
+ else()
+ set(DUMUX_MULTITHREADING_BACKEND "Serial" CACHE STRING "The multithreading backend")
+ message(STATUS "Dumux multithreading backed: Serial")
+ endif()
+
+# abort if a multithreading backend has been manually selected
+# but it is not available
+else()
+ if(DUMUX_MULTITHREADING_BACKEND STREQUAL "TBB" AND NOT TBB_FOUND)
+ message(FATAL_ERROR "Selected TBB as Dumux multithreading backed but TBB has not been found")
+ elseif(DUMUX_MULTITHREADING_BACKEND STREQUAL "OpenMP" AND NOT OpenMP_FOUND)
+ message(FATAL_ERROR "Selected OpenMP as Dumux multithreading backed but OpenMP has not been found")
+ elseif(DUMUX_MULTITHREADING_BACKEND STREQUAL "Kokkos" AND NOT Kokkos_FOUND)
+ message(FATAL_ERROR "Selected Kokkos as Dumux multithreading backed but Kokkos has not been found")
+ elseif(DUMUX_MULTITHREADING_BACKEND STREQUAL "Cpp" AND NOT DUMUX_HAVE_CXX_EXECUTION_POLICY)
+ message(FATAL_ERROR "Selected Cpp as Dumux multithreading backed but your compiler does not implement parallel STL")
+ else()
+ message(STATUS "Dumux multithreading backed: ${DUMUX_MULTITHREADING_BACKEND}")
+ endif()
+endif()
diff --git a/config.h.cmake b/config.h.cmake
index d552b8de60..199c9f972d 100644
--- a/config.h.cmake
+++ b/config.h.cmake
@@ -76,6 +76,14 @@
/* Set if OpenMP was found */
#cmakedefine HAVE_OPENMP ENABLE_OPENMP
+/* Set the DUMUX_MULTITHREADING_BACKEND */
+#ifndef DUMUX_MULTITHREADING_BACKEND
+#define DUMUX_MULTITHREADING_BACKEND ${DUMUX_MULTITHREADING_BACKEND}
+#endif
+
+/* Set HAVE_CPP_PARALLEL_ALGORITHMS if available */
+#cmakedefine HAVE_CPP_PARALLEL_ALGORITHMS 1
+
/* end dumux
Everything below here will be overwritten
*/
diff --git a/dumux/parallel/multithreading.hh b/dumux/parallel/multithreading.hh
index 7bea4cdb51..1efc82f8be 100644
--- a/dumux/parallel/multithreading.hh
+++ b/dumux/parallel/multithreading.hh
@@ -25,23 +25,8 @@
#ifndef DUMUX_PARALLEL_MULTITHREADING_HH
#define DUMUX_PARALLEL_MULTITHREADING_HH
-// clang doesn't implement this yet (April 2022) although technically a C++17 feature
-#define HAVE_CPP_PARALLEL_ALGORITHMS __cpp_lib_execution && __cpp_lib_execution >= 201603L && __cpp_lib_parallel_algorithm && __cpp_lib_parallel_algorithm >= 201603L
-
-// This variable can be set by the user
-// If not we select a default depending on what's available
#ifndef DUMUX_MULTITHREADING_BACKEND
- #if HAVE_TBB
- #define DUMUX_MULTITHREADING_BACKEND TBB
- #elif HAVE_OPENMP
- #define DUMUX_MULTITHREADING_BACKEND OpenMP
- #elif HAVE_KOKKOS
- #define DUMUX_MULTITHREADING_BACKEND Kokkos
- #elif HAVE_CPP_PARALLEL_ALGORITHMS
- #define DUMUX_MULTITHREADING_BACKEND Cpp
- #else
- #define DUMUX_MULTITHREADING_BACKEND Serial
- #endif
+#define DUMUX_MULTITHREADING_BACKEND Serial
#endif
namespace Dumux::Detail::Multithreading {
--
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