ImportError: undefined symbol: GOMP_critical_end

The following ImportError is seen when I try importing chainer. After some offline discussions with @asi1024 , I understand that this ImportError is probably caused after the changes made to CMakeLists in PR #7474 .

>>> import chainer
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/akshay/chainer/chainer/__init__.py", line 10, in <module>
    from chainer import backends  # NOQA
  File "/home/akshay/chainer/chainer/backends/__init__.py", line 1, in <module>
    from chainer.backends import cuda  # NOQA
  File "/home/akshay/chainer/chainer/backends/cuda.py", line 45, in <module>
    from chainer.backends import _cpu
  File "/home/akshay/chainer/chainer/backends/_cpu.py", line 8, in <module>
    import chainerx
  File "/home/akshay/chainer/chainerx/__init__.py", line 8, in <module>
    from chainerx import _core
ImportError: /usr/local/cuda-9.0/lib64/libcusolver.so.9.0: undefined symbol: GOMP_critical_end

[kmaehashi]

@hvy ref: https://github.com/chainer/chainer/pull/2487

[toslunar]

The following fixed the problem. Could you rewrite it to add the flag only when it’s needed?

diff --git a/chainerx_cc/CMakeLists.txt b/chainerx_cc/CMakeLists.txt
index 82d4b5c..af19fbc 100644
--- a/chainerx_cc/CMakeLists.txt
+++ b/chainerx_cc/CMakeLists.txt
@@ -92,7 +92,7 @@ if("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU|Clang|Intel")
         add_definitions(-D_CRT_SECURE_NO_WARNINGS)
     else()
         set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -pthread")
-        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -Wall -Wextra -fPIC -pthread")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -Wall -Wextra -fPIC -pthread -fopenmp")
     endif()
     set(CMAKE_CXX_FLAGS_RELEASE "-O2 -DNDEBUG")  # cmake -DCMAKE_BUILD_TYPE=Release
     set(CMAKE_CXX_FLAGS_DEBUG "-O0")  # cmake -DCMAKE_BUILD_TYPE=Debug