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Re: SSE "denormals are zeros"

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On Fri, 17 Jun 2016 18:11:28 +0200, Bonita Montero
<Bonita.Montero@gmail.com> wrote:

>Does anyone know what the "denormals are zeros" flag of the
>x86 MXCSR is good for?
>Or more precisely: I know what it does, but I don't know why
>it should make sense to consider denormal values as zeros.


Mainly performance - denormals tend to be slow (although less so on
recent x86s).  Some codes do things like converge to zero, but end up
passing through the denormal range first - just skipping that can
sometimes be a considerable performance improvement.  There are some
downsize to disabling gradual underflow, but in practice many cases
where you get them you're on your way to zero anyway, and in most
cases the advantages of gradual underflow are very small.

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SSE "denormals are zeros" Bonita Montero <Bonita.Montero@gmail.com> - 2016-06-17 18:11 +0200
  Re: SSE "denormals are zeros" Robert Wessel <robertwessel2@yahoo.com> - 2016-06-17 12:33 -0500
    Re: SSE "denormals are zeros" Robert Wessel <robertwessel2@yahoo.com> - 2016-06-17 12:36 -0500
    Re: SSE "denormals are zeros" Bonita Montero <Bonita.Montero@gmail.com> - 2016-06-17 20:02 +0200
      Re: SSE "denormals are zeros" Terje Mathisen <terje.mathisen@tmsw.no> - 2016-06-18 08:07 +0800

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