compiled programs significantly slower after upgrading

Dennis Clarke dclarke@blastwave.org
Wed Apr 18 21:45:00 GMT 2018


On 18/04/18 05:28 PM, Jack Stalnaker wrote:
> I upgraded gcc from 4.8.2 to 7.3.0. I also upgraded binutils to 2.30 (from
> the default installed on scientific linux 5).
> 
> Unfortunately, the executable I get is now 5 times slower consistently. I
> have changed nothing about the code itself. I have not changed any
> compilation options either. I'm honestly shocked by such a dramatic
> slowdown. Has something changed significantly between these two versions?
> 
> I realize I haven't given any information about the code itself (it's a mix
> of fortran and c), but the important thing is the significant slowdown when
> only the compilation chain has changed.
> 
> Can anyone give me any insight as to what might be happening or how to
> address it?
> 

With no code at all to consider ?  Not likely.   Take a look at your
optimization options and your settings for "march/mtune" etc in case
you had those.  Look at the actual online manual for 7.3.0 and check
your options as a LOT has changed and a lot deprecated.

Dennis



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