Changing default compiler for Atlas from gcc47 to clang-3.3 on AVX capable machines

[Ryan Schmidt]

On Mar 6, 2013, at 08:24, Vincent Habchi wrote:

> as you may know, I am conducting a major overhaul of the Atlas port. And, as part of the preliminary tests, I am happy to disclose that clang-mp-3.3 (3/2013) compiles Atlas with AVX support and, given the proper optimization flags (e.g. -fvectorize -fslp-vectorize) seems to achieve on par or better performance than the reference GCC implementation. This means that happy owners of AVX machines will be – eventually – able to break from the GCC hegemony and almost double the performance of their x86_64 implementation.
> 
> Since no gcc version on MacOS will ever be able to compile AVX assembly or generate AVX code, I was thinking about:
> 
> - Either warning owners of AVX machines that they should use clang-mp-3.3 to squeeze the most of their CPU;
> - Or making clang-mp-3.3 the default compiler for those computers.
> 
> What is your opinion?

But atlas also uses fortran, right? Is it more important for atlas to have better performance by compiling with clang, or to use fortran by compiling with gcc?