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Subnormal floating-point numbers are expensive on Intel processors

69 points · 54 comments · zdw

  1. juancn · · focus · HN ↗
    Apparently it only happens on P-cores, recent E-cores have a fast path for subnormals.
    1. rustybolt · · focus · HN ↗
      That seems weird. They did throw extra hardware at it to speed it up for the efficient cores, but not for the performance cores?
      1. Sesse__ · · focus · HN ↗
        They are designed by different teams and have different ways of doing math. You could just as easily say “why are the efficiency cores wasting an extra cycle for each multiplication doing fixups of an uncommon case”.

        Fabian Giesen explains in more detail here: <a href="https:&#x2F;&#x2F;mastodon.gamedev.place&#x2F;@rygorous&#x2F;117277063419144390" rel="nofollow">https:&#x2F;&#x2F;mastodon.gamedev.place&#x2F;@rygorous&#x2F;117277063419144390

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