[GAP Forum] Changing memory allocation for GAP

[Frank Lübeck]

On Wed, Jan 12, 2011 at 08:29:24PM +0000, Sandeep Murthy wrote:
> Is there a command for starting GAP from the command line to
> open with a higher memory allocation, like 256 MB, than the standard 
> one?
> 
> I use GAP v.4.4.12 on Mac OS Leopard.  At present, when I start GAP
> I see the following:
> 
> --------
> 
> Loading the library. Please be patient, this may take a while.
> GAP4, Version: 4.4.12 of 17-Dec-2008, i686-apple-darwin9.6.0-gcc
> Components:  small 2.1, small2 2.0, small3 2.0, small4 1.0, small5 1.0, 
>              small6 1.0, small7 1.0, small8 1.0, small9 1.0, small10 0.2, 
>              id2 3.0, id3 2.1, id4 1.0, id5 1.0, id6 1.0, id9 1.0, id10 0.1, 
>              trans 1.0, prim 2.1  loaded.
> Packages:    AutPGrp 1.2, CTblLib 1.1.3, TomLib 1.1.4, FactInt 1.5.2, 
>              GAPDoc 1.2  loaded.
> Error, file "-L" must exist and be readable
> Error, file "-m" must exist and be readable
> Error, file "128m" must exist and be readable
> Error, file "-o" must exist and be readable
> Error, file "512m" must exist and be readable
> 


Dear Sandeep Murphy, dear Forum,

To find an  explaination in the GAP documentation type 

?command line options

into your GAP session. If one of the arguments in your call of GAP is
a file name, then all further arguments are also interpreted as file names.

So you should call GAP like:
   gap -m 128m -o 512m [maybe more options here] file1 file2 ...

Using the -m option with a larger amount of memory does usually not give
a big performance advantage. But using a higher value with the -o option
causes that you see a message of form

   exceeded the permitted memory (`-o' command line option) at
[...]
brk> 

later than with the default value. (You can type 'return;' at that
brk-prompt, then GAP doubles the value of the -o option.)
Nevertheless, it does not make sense to specify with -o more memory than
your GAP job has available as physical memory.

With best regards,
  Frank Lübeck

-- 
///  Dr. Frank Lübeck, Lehrstuhl D für Mathematik, Templergraben 64,  ///
\\\                    52062 Aachen, Germany                          \\\
///  E-mail: Frank.Luebeck at Math.RWTH-Aachen.De                        ///
\\\  WWW:    http://www.math.rwth-aachen.de/~Frank.Luebeck/           \\\