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# Check if OpenMP supports 128-bit integers out of the box
# or if we have to link against libatomic.
include(CheckCXXSourceCompiles)
include(CMakePushCheckState)
find_package(OpenMP QUIET)
if(NOT (OpenMP_FOUND OR OpenMP_CXX_FOUND))
message(STATUS "Performing Test OpenMP")
message(STATUS "Performing Test OpenMP - Failed")
endif()
# CMake has found OpenMP, now we need to check
# if OpenMP supports 128-bit integers.
if(OpenMP_FOUND OR OpenMP_CXX_FOUND)
cmake_push_check_state()
if(TARGET OpenMP::OpenMP_CXX)
set(CMAKE_REQUIRED_LIBRARIES "OpenMP::OpenMP_CXX")
else()
set(CMAKE_REQUIRED_FLAGS "${OpenMP_CXX_FLAGS}")
endif()
# Our <int128_t.hpp> requires C++11 or later
if(NOT compiler_supports_cpp11)
if(CMAKE_CXX11_EXTENSION_COMPILE_OPTION)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${CMAKE_CXX11_EXTENSION_COMPILE_OPTION} ${CMAKE_CXX_FLAGS}")
elseif(CMAKE_CXX11_STANDARD_COMPILE_OPTION)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${CMAKE_CXX11_STANDARD_COMPILE_OPTION} ${CMAKE_CXX_FLAGS}")
endif()
endif()
if(DISABLE_INT128)
set(CMAKE_REQUIRED_DEFINITIONS "-D${DISABLE_INT128}")
endif()
set(CMAKE_REQUIRED_INCLUDES "${PROJECT_SOURCE_DIR}/include")
# Check if OpenMP supports 128-bit integers
check_cxx_source_compiles("
#include <int128_t.hpp>
#include <omp.h>
#include <stdint.h>
#include <iostream>
int main(int, char** argv) {
using primecount::maxint_t;
uintptr_t n = (uintptr_t) argv;
maxint_t sum = (maxint_t) n;
int iters = (int) n;
#pragma omp parallel for reduction(+: sum)
for (int i = 0; i < iters; i++)
sum += (i / 3) * omp_get_thread_num();
std::cout << (long) sum;
return 0;
}" OpenMP)
if(NOT OpenMP)
# Try if OpenMP works if we link against libatomic.
# This is sometimes required for LLVM/Clang.
find_library(LIB_ATOMIC NAMES atomic atomic.so.1 libatomic.so.1)
if(NOT LIB_ATOMIC)
# Some package managers like homebrew and macports store the compiler's
# libraries in a subdirectory of the library directory. E.g. GCC
# installed via homebrew stores libatomic at lib/gcc/13/libatomic.dylib
# instead of lib/libatomic.dylib. CMake's find_library() cannot easily
# be used to recursively find libraries. Therefore we use this workaround
# here (try adding -latomic to linker options) for this use case.
set(LIB_ATOMIC "-latomic")
endif()
set(CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES}" "${LIB_ATOMIC}")
# Check if OpenMP compiles with libatomic
check_cxx_source_compiles("
#include <int128_t.hpp>
#include <omp.h>
#include <stdint.h>
#include <iostream>
int main(int, char** argv) {
using primecount::maxint_t;
uintptr_t n = (uintptr_t) argv;
maxint_t sum = (maxint_t) n;
int iters = (int) n;
#pragma omp parallel for reduction(+: sum)
for (int i = 0; i < iters; i++)
sum += (i / 3) * omp_get_thread_num();
std::cout << (long) sum;
return 0;
}" OpenMP_with_libatomic)
if(OpenMP_with_libatomic)
list(APPEND PRIMECOUNT_LINK_LIBRARIES "${LIB_ATOMIC}")
else()
set(LIB_ATOMIC "")
endif()
endif()
cmake_pop_check_state()
# OpenMP has been tested successfully, enable it
if(OpenMP OR OpenMP_with_libatomic)
if(TARGET OpenMP::OpenMP_CXX)
list(APPEND PRIMECOUNT_LINK_LIBRARIES "OpenMP::OpenMP_CXX")
else()
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")
endif()
# Create list of OpenMP libs for pkg-config/pkgconf
foreach(X IN LISTS OpenMP_CXX_LIB_NAMES)
string(APPEND PKGCONFIG_LIBS_OPENMP "-l${X} ")
endforeach()
endif()
endif()
# OpenMP test has failed, print warning message
if(NOT OpenMP AND NOT OpenMP_with_libatomic)
if (CMAKE_CXX_COMPILER_ID MATCHES "Clang|LLVM")
message(WARNING "Install the OpenMP library (libomp) to enable multithreading in primecount!")
elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
message(WARNING "Install the OpenMP library (libgomp) to enable multithreading in primecount!")
else()
message(WARNING "Install the OpenMP library to enable multithreading in primecount!")
endif()
endif()
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