Finding the machine CPU arch

[Vincent Habchi]

Hallo Rainer,

> Couldn't we just select variants like +sse, +sse2, etc. based on the
> current architecture?

I know you are fundamentally against auto-configuration. I see, however, a few reasons why it is a good choice in case of Atlas:

1. From me egoistic and self-centered point of view, I would have to write/maintain a lot of variants with mutual exclusions, etc. which would not simplify the Portfile readability; I am also unsure on how to handle flags variants and universal build (e.g. +avx during a i386 universal build);

2. Most of the users won’t build Atlas as a standalone package but rather as a dependency automatically pulled in by the building process. In that case, there is absolutely no point in using variants (both systems would achieve the same goal, assuming the default variants build for maximum speed);

3. I don’t expect most users of MacPorts, although maybe slightly more technically aware that the standard Mac owner, to know all the arcane about sse/avx. If we except cross-compilation, what would be the point of not compiling for the native arch?

Vincent