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Re: GNU C library's libmvec and the GNU Compiler *Collection*.

On 01/06/2016 07:46 PM, Toon Moene wrote:

[ This is relevant for our code, because just the switch to *actual*
   single precision exp/log/sin/cos implementations in glibc's libm
   resulted in a decrease of the running time of our weather forecasting
   code by 25 % (this was in glibc 2.16, IIRC). ]

The reference for this is (on an Ivy Bridge system):

"I have made a home-build glibc-2.17 (on a core-avx system). It works great - linking against it (instead of using the current Debian-Testing's eglibc-2.13) brought the wall-clock time of my weather forecasting job down from 3:35 hours to 2:45 (mostly due to a more efficient implementation of powf, expf and logf)."

So, in minutes of compute time:

This is (215-165) / 215 = 0.23 (23 %). However, that number included a part that ran for an hour (60 minutes) in double precision.

Excluding that we get (155 - 105) / 155 = 0.32 (32 %) improvement in performance for the single precision part of our weather forecasting code.

Kind regards,

Toon Moene - e-mail: - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
At home:; weather:
Progress of GNU Fortran:

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