Add functions to check if OpenMP is working (#1000)

* Add check_openmp function

* Fix for non-Apple Clang

* Include omp.h

* Add function checking openmp version

* Use omp_get_num_procs instead

* cmake fixes for openmp

* Link OpenMP with link_libraries

* Return numbers instead of strings

Co-authored-by: Tilman Troester <[email protected]>

CMakeLists.txt

@@ -10,6 +10,9 @@ list(APPEND CMAKE_MODULE_PATH  "${CMAKE_SOURCE_DIR}/cmake/Modules/")
 
 project(ccl VERSION 2.0.0)
 
+# Uncomment to get detailed build outputs
+# set( CMAKE_VERBOSE_MAKEFILE on )
+
 option(FORCE_OPENMP "Forcibly use OpenMP " NO)
 
 # Defines list of CCL src files
@@ -61,25 +64,22 @@ find_package(OpenMP)
 set(CMAKE_C_FLAGS_RELEASE "-O3 -fomit-frame-pointer -fno-common -fPIC -std=gnu99 -DHAVE_ANGPOW")
 set(CMAKE_C_FLAGS_DEBUG   "-O0 -g -fomit-frame-pointer -fno-common -fPIC -std=gnu99 -DHAVE_ANGPOW")
 
-if ("${CMAKE_C_COMPILER_ID}" MATCHES "^(Apple)?Clang$") 
-    if(OpenMP_C_FOUND)
-        # OpenMP flags for macOS clang
-        set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -Xpreprocessor -fopenmp")
-        if(FORCE_OPENMP)
-            set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -Xpreprocessor -fopenmp")
-        endif()
-    endif()
-else()
-    # OpenMP flags for all other compilers clang
-    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -fopenmp")
+if(OpenMP_C_FOUND)
+    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} ${OpenMP_C_FLAGS}")
+    include_directories(${OpenMP_C_INCLUDE_DIR})
+    link_libraries(${OpenMP_libomp_LIBRARY})
     if(FORCE_OPENMP)
-        set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -fopenmp")
+        set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} ${OpenMP_C_FLAGS}")
     endif()
+else()
+    set(openmp_lib "")
 endif()
 
 if(DEFINED ENV{CONDA_PREFIX})
     include_directories("$ENV{CONDA_PREFIX}/include")
     add_link_options("LINKER:-rpath,$ENV{CONDA_PREFIX}/lib")
+    # Use conda libraries if available
+    add_link_options("-L$ENV{CONDA_PREFIX}/lib")
 endif()
 
 # Define include and library directories for external dependencies
@@ -111,7 +111,7 @@ endif()
 # The reason for building ccl as a shared library is that we can link it to
 # class directly, and it's not a dependency anymore
 add_library(ccl SHARED $<TARGET_OBJECTS:objlib>)
-target_link_libraries(ccl ${GSL_LIBRARIES} ${FFTW_LIBRARIES} ${CLASS_LIBRARIES} ${ANGPOW_LIBRARIES} m $<$<BOOL:${OpenMP_C_FOUND}>:OpenMP::OpenMP_C>)
+target_link_libraries(ccl ${GSL_LIBRARIES} ${FFTW_LIBRARIES} ${CLASS_LIBRARIES} ${ANGPOW_LIBRARIES} m)
 
 # Builds the test suite
 add_executable(check_ccl ${TEST_SRC})

include/ccl_utils.h

@@ -63,6 +63,10 @@ void ccl_integ_spline(int ny, int nx,double *x,double **y,
                       double a, double b, double *result,
                       const gsl_interp_type *T, int *status);
 
+int ccl_openmp_version();
+
+int ccl_openmp_threads();
+
 CCL_END_DECLS
 
 #endif

pyccl/pyutils.py

@@ -664,3 +664,19 @@ def _get_spline3d_arrays(gsl_spline, length):
     check(status)
 
     return xarr, yarr, zarr.reshape((length, x_size, y_size))
+
+
+def check_openmp_version():
+    """Return the OpenMP specification release date.
+    Return 0 if OpenMP is not working.
+    """
+
+    return lib.openmp_version()
+
+
+def check_openmp_threads():
+    """Returns the number of processors available to the device.
+    Return 0 if OpenMP is not working.
+    """
+
+    return lib.openmp_threads()

src/ccl_utils.c

@@ -3,6 +3,9 @@
 #include <math.h>
 
 #include <gsl/gsl_errno.h>
+#ifdef _OPENMP
+#include "omp.h"
+#endif
 
 #include "ccl.h"
 
@@ -340,3 +343,21 @@ void ccl_integ_spline(int ny, int nx,double *x,double **y,
     } //end omp parallel
   }
 }
+
+int ccl_openmp_version()
+{
+  #ifdef _OPENMP
+    return _OPENMP;
+  #else
+    return 0;
+  #endif
+}
+
+int ccl_openmp_threads()
+{
+  #ifdef _OPENMP
+    return omp_get_num_procs();
+  #else
+    return 0;
+  #endif
+}