avoid using the "-Ofast" compiler flag

[jewettaij]

If you compile "filter_mrc" using the "-Ofast" compiler flag, then the filter_mrc program will be mysteriously "Killed" when run with the -surface argument (usually when or after diagonalizing the Hessian located at every voxel). The problem might be in DiagonalizeHessianImage() (which is located in the lib/visfd/feature.hpp file), but I have not bothered to verify this is exactly where the error is occurring.

In any case, the problem can be avoided by using the clang++ compiler with the "-O3 -ffast-math" compiler flags. (...instead of using "-Ofast". See setup_clang.sh for compilation flags.)

Note also that the clang++ compiler is recommended over g++ (GCC), because even the -O3 flag fails when compiling with an old version of the GCC compiler. (See issue #2)

[jewettaij]

Note also that the clang++ compiler is recommended over g++, because even the -O3 flag fails when compiling with g++. (See issue #2)

As of gcc 9.3, this no longer appears to be the case. (GCC seems to be working now...)