[GAP Forum] Forum Digest, Vol 119, Issue 2

[Dmitrii Pasechnik]

Dear Mark,

On Tue, Feb 18, 2014 at 05:42:47AM -0600, Mark Sapir wrote:
> I finally got a 128 Gb RAM machine and I am trying to run the
> following program commuting a non-commutative Groebner basis. After a
> a couple of hours GAP says that it is out of RAM. I guess I need to
> change the way I call GAP so that it knows that more memory can be
> used.
There is a useful GAP function: 
7.11-3 GasmanLimits

 GasmanLimits( )	( function )
GasmanLimits returns a record with three components: min is the minimum
workspace size as set by the -m command line option in kilobytes. The
workspace size will never be reduced below this by the garbage
collector. max is the maximum workspace size, as set by the '-o' command
line option, also in kilobytes. If the workspace would need to grow past
this point, GAP will enter a break loop to warn the user. A value of 0
indicates no limit. kill is the absolute maximum, set by the -K command
line option. The workspace will never be allowed to grow past this
limit.

E.g.:
gap> GasmanLimits( );
rec( kill := 0, max := 2097152, min := 24576 )

What matters is that kill=0 (i.e. nothing will happen no matter how
much RAM you get)  max is about 2GB.
So in your case max should be set by -o option to something much bigger

> Also if anybody can tell me about a different, stand alone,
> programs that compute non-commutative Groebner bases, I would
> appreciate it.

Singular can apparently compute non-commutatibe GBs:
http://www.singular.uni-kl.de/Manual/latest/sing_539.htm#SEC590

HTH,
Dima
> 
> 
> LoadPackage("GBNP", "0", false);
> SetInfoLevel(InfoGBNP,1);
> SetInfoLevel(InfoGBNPTime,1);
> K:=GaloisField(2);
> A:=FreeAssociativeAlgebra(K,"
> a","b","c","d");
> a:=A.a;;b:=A.b;;c:=A.c;;d:=A.d;;
> Irels:=[
> a-a*a*c-d*a*b,
> b-a*b*c-d*b*b,
> c-a*c*c-d*c*b,
> d-a*d*c-d*d*b,
> 
> a*b*c-a*c*b-b*c*a+b*a*c,
> 
> ];
> 
> GBR:=SGrobner(GP2NPList(Irels));;PrintNPList(GBR);
> 
> Best regards,
> 
> Mark Sapir
> 
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