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I've had 40% speed-ups on some math-heavy C code simply by switching from gcc to clang.

• deleted 17y ago
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• cperciva 17y ago
  Which version of gcc? I had a 2x speedup a few years ago on math-heavy code (FFTs) by switching from gcc 4.2 to gcc 3.4 -- apparently there was a known issue in gcc's optimizer where it would flag too many values as "keep this in a register" and end up spending lots of time moving data to and from the "register overflow space" on the stack. (I don't know if this has been fixed -- as I said, it was a few years ago that I ran into this issue.)
  • alecco 17y ago
    I second that on gcc version. On many math related code gcc-4.4 is amazing. Specially if vectorization and/or SIMD is possible.
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