OpenACC implementation requires GCC 6 and patch

[jeffhammond]

The OpenACC implementation requires GCC 6+ to compile, but then only with a patch.

Please rename the patch to remove the .txt suffix, which Github forced me to add.
0001-use-restrict-instead-of-restrict-which-is-not-a-.patch.txt

Unfortunately, my version of CUDA only supports GCC 5, so I'm kludging them together like this (the important piece is -ccbin):

cmake \
-DCMAKE_CXX_COMPILER=g++-6.2 \
-DCMAKE_C_COMPILER=gcc-6.2 \
-DCMAKE_CXX_FLAGS="-g -O3 -std=gnu++11 -fopenmp -fopenacc -Wall -Wextra" \
-DCMAKE_C_FLAGS="-g -O3 -std=gnu11 -fopenmp -fopenacc -Wall -Wextra" \
-DCUDA_NVCC_FLAGS="-gencode arch=compute_20,code=sm_20 \
                   -gencode arch=compute_30,code=sm_30 \
                   -gencode arch=compute_35,code=sm_35 \
                   -gencode arch=compute_37,code=sm_37 \
                   -gencode arch=compute_50,code=sm_50 \
                   -gencode arch=compute_52,code=sm_52 \
                   -ccbin gcc-5.4 "  ..

GCC 5.4

jrhammon@klondike:~/Work/GPU/GPU-STREAM/build$ /opt/gcc/5.4.0/bin/g++-5.4   -DACC -I/home/jrhammon/Work/GPU/GPU-STREAM/build  -g -O3 -std=gnu++11 -fopenmp -fopenacc -Wall -Wextra -O3 -DNDEBUG   -std=gnu++11 -o CMakeFiles/gpu-stream-acc.dir/main.cpp.o -c /home/jrhammon/Work/GPU/GPU-STREAM/main.cpp
In file included from /home/jrhammon/Work/GPU/GPU-STREAM/ACCStream.h:15:0,
                 from /home/jrhammon/Work/GPU/GPU-STREAM/main.cpp:32:
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:69:40: error: expected primary-expression before ‘)’ token
 int acc_get_num_devices (acc_device_t) __GOACC_NOTHROW;
                                        ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:70:41: error: expected primary-expression before ‘)’ token
 void acc_set_device_type (acc_device_t) __GOACC_NOTHROW;
                                         ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:71:41: error: expected primary-expression before ‘)’ token
 acc_device_t acc_get_device_type (void) __GOACC_NOTHROW;
                                         ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:72:45: error: expected primary-expression before ‘)’ token
 void acc_set_device_num (int, acc_device_t) __GOACC_NOTHROW;
                                             ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:73:39: error: expected primary-expression before ‘)’ token
 int acc_get_device_num (acc_device_t) __GOACC_NOTHROW;
                                       ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:74:26: error: expected primary-expression before ‘)’ token
 int acc_async_test (int) __GOACC_NOTHROW;
                          ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:75:31: error: expected primary-expression before ‘)’ token
 int acc_async_test_all (void) __GOACC_NOTHROW;
                               ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:76:21: error: expected primary-expression before ‘)’ token
 void acc_wait (int) __GOACC_NOTHROW;
                     ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:77:32: error: expected primary-expression before ‘)’ token
 void acc_wait_async (int, int) __GOACC_NOTHROW;
                                ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:78:26: error: expected primary-expression before ‘)’ token
 void acc_wait_all (void) __GOACC_NOTHROW;
                          ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:79:31: error: expected primary-expression before ‘)’ token
 void acc_wait_all_async (int) __GOACC_NOTHROW;
                               ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:80:30: error: expected primary-expression before ‘)’ token
 void acc_init (acc_device_t) __GOACC_NOTHROW;
                              ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:81:34: error: expected primary-expression before ‘)’ token
 void acc_shutdown (acc_device_t) __GOACC_NOTHROW;
                                  ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:82:34: error: expected primary-expression before ‘)’ token
 int acc_on_device (acc_device_t) __GOACC_NOTHROW;
                                  ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:83:27: error: expected primary-expression before ‘)’ token
 void *acc_malloc (size_t) __GOACC_NOTHROW;
                           ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:84:24: error: expected primary-expression before ‘)’ token
 void acc_free (void *) __GOACC_NOTHROW;
                        ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:87:35: error: expected primary-expression before ‘)’ token
 void *acc_copyin (void *, size_t) __GOACC_NOTHROW;
                                   ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:88:46: error: expected primary-expression before ‘)’ token
 void *acc_present_or_copyin (void *, size_t) __GOACC_NOTHROW;
                                              ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:89:35: error: expected primary-expression before ‘)’ token
 void *acc_create (void *, size_t) __GOACC_NOTHROW;
                                   ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:90:46: error: expected primary-expression before ‘)’ token
 void *acc_present_or_create (void *, size_t) __GOACC_NOTHROW;
                                              ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:91:35: error: expected primary-expression before ‘)’ token
 void acc_copyout (void *, size_t) __GOACC_NOTHROW;
                                   ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:92:34: error: expected primary-expression before ‘)’ token
 void acc_delete (void *, size_t) __GOACC_NOTHROW;
                                  ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:93:41: error: expected primary-expression before ‘)’ token
 void acc_update_device (void *, size_t) __GOACC_NOTHROW;
                                         ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:94:39: error: expected primary-expression before ‘)’ token
 void acc_update_self (void *, size_t) __GOACC_NOTHROW;
                                       ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:95:44: error: expected primary-expression before ‘)’ token
 void acc_map_data (void *, void *, size_t) __GOACC_NOTHROW;
                                            ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:96:30: error: expected primary-expression before ‘)’ token
 void acc_unmap_data (void *) __GOACC_NOTHROW;
                              ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:97:30: error: expected primary-expression before ‘)’ token
 void *acc_deviceptr (void *) __GOACC_NOTHROW;
                              ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:98:28: error: expected primary-expression before ‘)’ token
 void *acc_hostptr (void *) __GOACC_NOTHROW;
                            ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:99:37: error: expected primary-expression before ‘)’ token
 int acc_is_present (void *, size_t) __GOACC_NOTHROW;
                                     ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:100:52: error: expected primary-expression before ‘)’ token
 void acc_memcpy_to_device (void *, void *, size_t) __GOACC_NOTHROW;
                                                    ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:101:54: error: expected primary-expression before ‘)’ token
 void acc_memcpy_from_device (void *, void *, size_t) __GOACC_NOTHROW;
                                                      ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:109:42: error: expected primary-expression before ‘)’ token
 void *acc_get_current_cuda_device (void) __GOACC_NOTHROW;
                                          ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:110:43: error: expected primary-expression before ‘)’ token
 void *acc_get_current_cuda_context (void) __GOACC_NOTHROW;
                                           ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:111:33: error: expected primary-expression before ‘)’ token
 void *acc_get_cuda_stream (int) __GOACC_NOTHROW;
                                 ^
/opt/gcc/5.4.0/lib/gcc/x86_64-unknown-linux-gnu/5.4.0/include/openacc.h:112:39: error: expected primary-expression before ‘)’ token
 int acc_set_cuda_stream (int, void *) __GOACC_NOTHROW;
                                       ^

GCC 6.2

jrhammon@klondike:~/Work/GPU/GPU-STREAM/build$ g++-6.2   -DACC -I/home/jrhammon/Work/GPU/GPU-STREAM/build  -g -O3 -std=gnu++11 -fopenmp -fopenacc -Wall -Wextra -O3 -DNDEBUG   -std=gnu++11 -o CMakeFiles/gpu-stream-acc.dir/main.cpp.o -c /home/jrhammon/Work/GPU/GPU-STREAM/main.cpp

[tomdeakin]

The restrict / __restrict__ issue is a nuicense. For some compilers, we require restrict for correct parallelism, on others we must *not have * restrict for correct parallelism.

I also do not think restrict is standard C++ either.

One option is to define our own RESTRICT and set it to nothing, restrict or __restrict__ based on the compiler. I'm not sure this is satisfactory though.

[jeffhammond]

If restrict is used correctly, any incorrectness you see with it is a compiler bug.

And no, restrict isn't ISO C++. It's just supported by every widely used C++ compiler.

[tomdeakin]

Should be fixed in #202