[GAP Forum] halfing pool size

[Max Neunhoeffer]

Dear Benjamin,

thanks for your email. What happens is the following: With GAP 4.5 the
memory allocation is done in a different way by default. GAP uses mmap
to allocate 4GB as a "pool" but only uses the beginning of it, such
that the memory is actually not physically used.

The message "halfing pool size" happens, if this allocation does not
work, because then GAP tries to half the pool until the allocation
goes through.

If you get the message once, this means that your OS grants GAP 2GB
but not 4GB. Is it possible that you have set a resource limit on the
main memory usage in your OS?

Try "ulimit -a" and look under "max memory size".

You can use GAP's "-s" option to set the pool size to something
different or use "-s 0" to go the old allocation method.

Cheers,
  Max.

On Fri, Jul 27, 2012 at 12:01:29PM +0200, Benjamin Sambale wrote:
> Dear Max,
> 
> I use GAP 4.5.5 on arch linux 64 bit. For creating the workspace I
> used the following options (together with the script
> CreateWorkspace):
> 
> -m 2048m -T -l "$GAP_DIR" "$@"
> 
> For using the workspace I start GAP with:
> 
> -L /usr/local/gap4r5/bin/wsgap4 -T -l "$GAP_DIR" "$@"
> 
> I'm not sure if it's still necessary to pass the "-T", but this
> should be irrelevant.
> 
> Thanks,
> Benjamin
> 
> Am 27.07.2012 11:42, schrieb Max Neunhoeffer:
> >Dear Benjamin,
> >
> >just a quick question, are you working on Windows or on what operating
> >system?
> >How do you exactly start up GAP? In particular the memory related
> >options are interesting.
> >
> >Best regards,
> >   Max.
> >On Fri, Jul 27, 2012 at 10:22:06AM +0200, Benjamin Sambale wrote:
> >>Dear forum,
> >>
> >>every time I start GAP I get the message: "gap: halfing pool size."
> >>Does it mean I allocate to much memory (actually 2GB out of 4GB)?
> >>Btw, I load a workspace usually, but this message does not depend on
> >>that. I found nothing concerning this topic online. And for some
> >>reasons it never appeared on my office machine.
> >>
> >>Thanks,
> >>Benjamin
> >>
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> 

-- 
Max Neunhoeffer              http://www-groups.mcs.st-and.ac.uk/~neunhoef/
> > > > > > > > > > >  May the Source be with you! < < < < < < < < < < < < 
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