I thought I'd try to speed up numpy on my fedora system by rebuilding the atlas package so it would be tuned for my machine. But when I do: rpmbuild -ba -D 'enable_native_atlas 1' atlas.spec it fails with: res/zgemvN_5000_100 : VARIATION EXCEEDS TOLERENCE, RERUN WITH HIGHER REPS. A bit of googling has not revealed a solution. Any hints?