[petsc-dev] slow "ar Scq" on cygwin

[Matthew Knepley]

On Thu, Jun 28, 2012 at 3:31 PM, Chetan Jhurani <chetan.jhurani at gmail.com>wrote:

> Thanks Matt, Satish.  A few issues though.****
>
> ** **
>
> Like you said, the latest cygwin has python 2.6.8 which****
>
> does not have argparse.  When I place the following****
>
> in path http://argparse.googlecode.com/svn/trunk/argparse.py****
>
> I can run the python build with 2.6.8.****
>
> ** **
>
> However, the “ar” based build had worked fine and the python****
>
> based build fails for these two files.****
>
> ** **
>
>   src/snes/impls/MULTIB~1/multiblock.c****
>
>   src/snes/impls/vi/rsaug/virsaug.c
>

Yep, it fails, but the build succeeds, so no problem.


> It looks like these two files were NOT compiled in the ar based****
>
> build. The two make.log files are attached.****
>
> ** **
>
> One more question. I tried to run the python based build****
>
> the second time (after it was unsuccessful the first time)****
>
> and then it deleted all the previous .o files it had created in ****
>
> ARCH/lib/libpetsc-obj.  How can that be avoided?
>

It does not do that unless you run 'clean'.

   Matt


> Chetan****
>
> ** **
>
> ** **
>
> *From:* petsc-dev-bounces at mcs.anl.gov [mailto:
> petsc-dev-bounces at mcs.anl.gov] *On Behalf Of *Matthew Knepley
> *Sent:* Thursday, June 28, 2012 1:35 PM
> *To:* For users of the development version of PETSc
> *Subject:* Re: [petsc-dev] slow "ar Scq" on cygwin****
>
> ** **
>
> On Thu, Jun 28, 2012 at 2:23 PM, Chetan Jhurani <chetan.jhurani at gmail.com>
> wrote:****
>
> Hi devs,
>
> Is there a way to avoid running the archiver (ar)
> every time a petsc directory is compiled?
>
> The reason I'm asking this is that when libpetsc.lib
> becomes large enough (say 100MB+, esp. for debug build),
> "ar Sqc" on cygwin takes very long in each directory.
> Depending on OS caching, very long can be 10 seconds per
> PETSc directory just to run ar.
>
> It creates a new temp file from scratch, puts stuff from
> libpetsc.lib and new stuff in it and then renames the
> temp file.  As you can imagine, the compilation process is
> fast in the beginning but crawls by the end.  I've seen
> the same IO sequence on Linux (with Sqc flags to ar), but
> since cygwin IO is slower the effect is more clearly visible.
> Building within a ramdisk leads to 25% faster compilation
> but it was more of a curiosity.****
>
> ** **
>
> Build with Python. It never uses antique things like ar :)****
>
> ** **
>
>   python2.7 ./config/builder2.py build****
>
> ** **
>
>      Matt****
>
>  ****
>
>
> Chetan
>
> ****
>
>
>
> ****
>
> ** **
>
> --
> 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****
>



-- 
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
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