From 81fbf0c2e15fa1cd02501d52ed48f52e5c43a18d Mon Sep 17 00:00:00 2001
From: heckflosse <heckflosse67@gmx.de>
Date: Mon, 6 Nov 2017 19:09:50 +0100
Subject: [PATCH] Applied patch from @agriggio to check multithreading in fftw3

---
 CMakeLists.txt | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d99a4feaa..626da7019 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -343,11 +343,30 @@ if(OPTION_OMP)
 endif()
 
 # check for libfftw3f_omp
+include(CheckCSourceCompiles)
 if(OPENMP_FOUND)
-    find_library(fftw3f_omp fftw3f_omp PATHS ${FFTW3F_LIBRARY_DIRS})
-    if(fftw3f_omp)
+    set(CMAKE_REQUIRED_INCLUDES ${FFTW3F_INCLUDE_DIRS})
+    set(CMAKE_REQUIRED_LIBRARIES)
+    foreach(l ${FFTW3F_LIBRARIES})
+        find_library(_f ${l} PATHS ${FFTW3F_LIBRARY_DIRS})
+        set(CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES} ${_f})
+    endforeach()
+    check_c_source_compiles(
+"#include <fftw3.h>
+int main()
+{
+    fftwf_init_threads();
+    fftwf_plan_with_nthreads(1);
+    return 0;
+}" _fftw3f_multithread)
+    if(_fftw3f_multithread)
         add_definitions(-DRT_FFTW3F_OMP)
-        set(FFTW3F_LIBRARIES ${FFTW3F_LIBRARIES} ${fftw3f_omp})
+    else()
+        find_library(fftw3f_omp fftw3f_omp PATHS ${FFTW3F_LIBRARY_DIRS})
+        if(fftw3f_omp)
+            add_definitions(-DRT_FFTW3F_OMP)
+            set(FFTW3F_LIBRARIES ${FFTW3F_LIBRARIES} ${fftw3f_omp})
+        endif()
     endif()
 endif()