David Bruant wrote: > In the gcc manual, p.276 (p.288 of the pdf version), we can read for This is a meaningless number without specifying which version of the documentation you're referring to. (And the PDF is autogenerated from the texinfo anyway, which is where any change would have to be made.) > Finally, I would like to know some reason that could make the code > slower by unrolling loops. Unrolling significantly increases code size, which means less space in the cache for other things. On most modern architectures main memory is at least an order of magnitude slower than core execution speed, which means cache misses result in large stalls. Depending on the degree of unrolling this can completely overshadow any gains from the things you listed. The documentation can't really be any more specific because it depends enormously on the specific circumstances involved: the code being compiled, the compiler options in effect, the target architecture, the specific hardware on which it's executing, etc. Brian
