[petsc-users] Optimized Option

[Barry Smith]

On Jun 3, 2011, at 3:30 PM, Matthew Knepley wrote:

> On Fri, Jun 3, 2011 at 3:28 PM, <zhenglun.wei at gmail.com> wrote:
> Thanks for your reply. 
> So, if I want to use '--with-debugging=0', what is the PETSC_ARCH equal to?
> 
> When you run configure, at the end it prints out a LARGE message that indicates
> 
>   - What PETSC_ARCH it has chosen
> 
>   - Exactly the command line to run when building
> 
> This information is also stored in configure.log

   You should provide a value for the environmental variable PETSC_ARCH before running ./configure 

   For example   PETSC_ARCH=arch-debug    ./configure --with-debugging=1   otherstuff
   then PETSC_ARCH=arch-opt    ./configure --with-debugging=0   otherstuff

    
>  
>     Matt
> 
> I just tried to use PETSC = arch-opt, and a error message comes up: 
> ~/petsc-dev/conf/variables:95: ~/petsc-dev/arch-opt/conf/petscvariables: No such file or directory
> ~l/petsc-dev/conf/rules:1018: ~/petsc-dev/arch-opt/conf/petscrules: No such file or directory
> make: *** No rule to make target `~l/petsc-dev/arch-opt/conf/petscrules'. Stop.
> this really confused me.
> 
> thanks,
> Alan
> 
> On , Barry Smith <bsmith at mcs.anl.gov> wrote:
> > 
> > 
> > On Jun 3, 2011, at 2:57 PM, Alan Wei wrote:
> > 
> > 
> > 
> > > Dear Sir/Madam,
> > 
> > >     Lately, I read there is a optimized version of PETSc by using '--with-debugging=0'. I have two questions here:
> > 
> > > 1, Do I need to use '/config/configure.py ... --with-debugging=0' when I configure the PETSc in order to use the non-debugging version of PETSc? Therefore, if I want to switch PETSc between these two versions, I have to keep configuring.
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> >   ABSOLUTELY NOT.  You use two different values of the environmental variable PETSC_ARCH and switch back and forth by changing the variable. You can even change it on the make command line. For example make mycode PETSC_ARCH=arch-opt
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> >   Note that you can use any name you want for the values of PETSC_ARCH. I often use arch-debug and arch-opt to keep track of them.
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> > > 2, I was using the '--with-debugging=0' to configure the PETSc. However, I tested the computational rate by executing the ex29.c. The non-debugging version does not improve the speed much; in the contrary, it slow down the speed a little bit. The comparison is attached here. Any idea on this.
> > 
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> > 
> >    It depends on the compiler and particular code you are running. We recommend using the option -log_summary to see how much time is spent in each part of the computation and how much it gets better with optimization.
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> >   Barry
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> > > thanks in advance,
> > 
> > > Alan
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> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener