Origin from here. But fix several problem for it.

• The origin file is not compatible with GCC 4.9+.
  • because header immintrin.h is changed between gcc 4.8 and gcc 4.9
  • In gcc 4.9, AVX2 function will always be defined whenever -mavx2 is set or not. So there are multi-define problems when use gcc 4.9 before.
  • In macos, the clang also use the header like gcc 4.9
  • I just add "avx_" prefix for each function in AVX2 to solve this problem.
• There is a warning in int constant variable define.
  • Just add a cast to fix it.
• AVX2 use intrinsics like '_mm256_and_si256', '_mm256_andnot_si256'
  • Change origin header to fix it. Make it work well in both avx and avx2.

Test programs use cmake. Just do

# Install gtest before, and make sure your computer support avx2/avx.
mkdir build
cmake -D CMAKE_BUILD_TYPE=Release ..
make -j 2
./test_avx2 ; ./test_avx

It will run some unittest.

Just include "avx_mathfun.h" in your project.

The origin file uses zlib license. It is not changed.