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Dear GAP-forum,

Sorry, it seems now that my last request to forum wasn't absolutely correct,

but this lead to several useful hints. As you possibly remember, I've asked:

does anybody know what hardware resources are necessary to compute

normalized units group of group algebra of group of order 32 over GF(2),

using the function NormalizedUnitsGroupRing ?

So, I have discovered, that really I have no problems with calculation of

NormalizedUnitsGroupRing(G) even if Size(G)=128.

The actual problem is as follows:

gap> G:=TwoGroup(32,10) Group( a1, a2, a3, a4, a5 ) gap> U:=NormalizedUnitsGroupRing(G); #D use multiplication table Group( g1, g2, g3, g4, g5, g6, g7, g8, g9, g10, g11, g12, g13, g14, g15, g16, g17, g18, g19, g20, g21, g22, g23, g24, g25, g26, g27, g28, g29, g30, g31 ) gap> C:=Centre(U); Subgroup( Group( g1, g2, g3, g4, g5, g6, g7, g8, g9, g10, g11, g12, g13, g14, g15, g16, g17, g18, g19, g20, g21, g22, g23, g24, g25, g26, g27, g28, g29, g30, g31 ), [ g3, g4*g7*g9*g13*g14*g16*g22, g10, g11*g15*g17*g21, g18, g19, g23, g25, g26, g28, g29, g30, g31 ] ) gap> D:=Difference(U,C); gap: sorry, cannot extend the workspace, maybe use option '-a <memory>'?

As I could understand, this function calls to Elements(G), and (thanks to

Dr. Andrew C. Aitchison), now I could realize how expensive is this,

so it will be better to try to improve algorithm of my problems solving.

The next question is very similar to the previous one :-)

does anybody know what hardware resources are necessary to compute

normalized units group of group algebra of group of order ***256*** over

GF(2), using the function NormalizedUnitsGroupRing ?

Here I have the following situation:

gap> G:=TwoGroup(256,10);

Group( a1, a2, a3, a4, a5, a6, a7, a8 )

gap> RequirePackage("sisyphos");

gap> U:=NormalizedUnitsGroupRing(G);

#D use multiplication table

fatal error: memory exhausted

Error, output file was not readable in

NormalizedUnitsGroupRing( G ) called from

main loop

brk>

The reason for such calculation is connected with

the problem of involving of certain wreath products

into the unit group of modular group algebras

Sincerely yours, Alexander B. Konovalov, Algebra and Geometry Chair, Zaporozhye State University, Zaporozhye, Ukraine. -------------------------------------------------------------------------- Phone: office (38-0612) 32 59 36, 64 37 12, home 33 91 85 Fax: (38-0612) 32 59 36 P.O.Box 1317, Central Post Office, Zaporozhye, 330000, Ukraine E-mail: konovalov@member.ams.org

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