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From: =?utf-8?Q?Dominique_d=27Humi=C3=A8res?= <dominiq@lps.ens.fr>
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Subject: Re: [patch, libfortran, RFC] Speed up cshift with array shift
Message-Id: <CAF215C5-17D0-48A4-AD1B-14671F84253A@lps.ens.fr>
Date: Tue, 20 Jun 2017 14:25:00 -0000
Cc: gfortran <fortran@gcc.gnu.org>, gcc-patches <gcc-patches@gcc.gnu.org>
To: Thomas Koenig <tkoenig@netcologne.de>
X-SW-Source: 2017-06/txt/msg01468.txt.bz2

Hi Thomas,

On my machine I get the following timings without the patch

 cpu time cshift dim=1   0.490763009    
 cpu time do loop dim=1    5.57969809E-02
 cpu time cshift dim=2   0.416319966    
 cpu time do loop dim=2   0.187106013    
 cpu time cshift dim=3    1.37362707    
 cpu time do loop dim=3    1.39690399    

and

 cpu time cshift dim=1   0.166012987    
 cpu time do loop dim=1    5.48990071E-02
 cpu time cshift dim=2   0.183587968    
 cpu time do loop dim=2   0.191835046    
 cpu time cshift dim=3    1.35024190    
 cpu time do loop dim=3    1.42215610    

with the patch. Do you understand why cshift is so slow for dim=3?

Thanks for working on this issue.

Dominique

PS See also pr45689.