[Q-e-developers] Wondering if build-time optimization OK

[Chang, Christopher]

Hi Paolo,

   Fair enough, thanks. Will give build a try without it.

Cheers,

Chris

-----Original Message-----
From: Paolo Giannozzi [mailto:p.giannozzi at gmail.com] 
Sent: Thursday, June 30, 2016 2:53 PM
To: General discussion list for Quantum ESPRESSO developers
Cc: Chang, Christopher
Subject: Re: [Q-e-developers] Wondering if build-time optimization OK

On Thu, Jun 30, 2016 at 9:34 PM, Chang, Christopher <Christopher.Chang at nrel.gov> wrote:

> Is it a good idea to turn -O2 off generally for --enable-debug, and -CB off generally for production builds?

in  my opinion you should never use --enable-debug,unless you have a good reason to.

Paolo

>
> ——
>
>
>
> Hi,
>
>
>
>    I was recently building QE 5.4.0. FWIW,
>
>
>
> [cchang at n1011 ~]$ uname -a
>
> Linux n1011 2.6.32-504.8.1.el6.x86_64 #1 SMP Wed Jan 28 21:11:36 UTC 
> 2015
> x86_64 x86_64 x86_64 GNU/Linux
>
> [cchang at n1011 ~]$ cat /etc/redhat-release
>
> CentOS release 6.6 (Final)
>
> [cchang at n1011 ~]$ mpif90 -v
>
> mpif90 for the Intel(R) MPI Library 5.1.3 for Linux*
>
> Copyright(C) 2003-2015, Intel Corporation.  All rights reserved.
>
> ifort version 16.0.2
>
> [cchang at n1011 ~]$ mpif77 -v
>
> mpif77 for the Intel(R) MPI Library 5.1.3 for Linux*
>
> Copyright(C) 2003-2015, Intel Corporation.  All rights reserved.
>
> Using built-in specs.
>
> COLLECT_GCC=gfortran
>
> COLLECT_LTO_WRAPPER=/nopt/nrel/apps/gcc/5.2.0/libexec/gcc/x86_64-unkno
> wn-linux-gnu/5.2.0/lto-wrapper
>
> Target: x86_64-unknown-linux-gnu
>
> Configured with: ./configure --prefix=/nopt/nrel/apps/gcc/5.2.0
> --enable-bootstrap --disable-multilib
>
> Thread model: posix
>
> gcc version 5.2.0 (GCC)
>
>
>
> Configuration was with
>
>
>
> configure --prefix=/scratch/cchang/qespresso --enable-openmp 
> --enable-parallel --enable-debug --enable-signals 
> --with-scalapack=intel LDFLAGS="-mkl"
>
>
>
> Anyway, I noticed that the space_group.f90 build step seemed to hang, 
> although CPU usage was pegged at 100%.
>
>    After some diagnostic work, I nailed the long build time down to 
> the array bounds checking. If -CB is left off, the file builds in 
> about 2 minutes. I didn’t wait long enough to see how long the 
> standard build would take, but it was more than 11 minutes, possibly much more.
>
>    The reason I write, is that the Intel ifort man page points out 
> that array bounds checking won’t work as expected anyway, if 
> optimizations are turned on. Specifically,
>
>
>
> “
>
> It  is  recommended  that you do bounds checking on unoptimized code. 
> If you use option check bounds on optimized code, it may produce 
> misleading mes-
>
>               sages because registers (not memory locations) are used 
> for bounds values.
>
> “
>
>
>
> ·         Is this a reasonable thing to do for this file?
>
> ·         Is it a good idea to turn it off generally for --enable-debug?
>
>
>
> Thanks for any pointers you can provide,
>
>
>
> Chris
>
>
>
> --
>
> Christopher H. Chang, Ph.D.
>
>    Computational Chemist | NREL Computational Science Center
>
>    Research Associate | University of Colorado/RASEI
>
> 15013 Denver West Parkway, MS ESIF301 | Golden, CO 80401
>
>
>
>
>
>
> _______________________________________________
> Q-e-developers mailing list
> Q-e-developers at qe-forge.org
> http://qe-forge.org/mailman/listinfo/q-e-developers
>



--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222