Quelle quotfinder.gi
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#############################################################################
##
## orb package
## quotfinder.gi
## Juergen Mueller
## Max Neunhoeffer
## Felix Noeske
##
## Copyright 2005-2008 by the authors.
## This file is free software, see license information at the end.
##
## Implementation stuff for the quotfinder
##
#############################################################################
InstallGlobalFunction( QuotFinder,
function( gens, chain )
local qf;
qf := rec( origgens := gens, chain := chain, bcgens := gens,
dim := Length(gens[1]), subgrpdepth := 0,
curgens := gens, curchain := chain, curcodim := Length(gens[1]),
basech := OneMutable(gens[1]), basechi := OneMutable(gens[1]),
bcplan := OneMutable(gens[1]), bcplani := OneMutable(gens[1]) );
return qf;
end );
InstallGlobalFunction( QF_Recalccurgens,
function( qf )
# uses bcgens, dim, curcodim, and subgrpdepth
# updates curgens and curchain
local gens,i;
qf.curchain := qf.chain;
gens := qf.bcgens;
for i in [1..qf.subgrpdepth] do
gens := ResultOfStraightLineProgram(qf.curchain!.slp,gens);
qf.curchain := qf.curchain!.r;
od;
if qf.curcodim < qf.dim then
for i in [1..Length(gens)] do
if not(IsZero(ExtractSubMatrix(gens[i],[1..qf.dim-qf.curcodim],
[qf.dim-qf.curcodim+1..qf.dim]))) then
Print("Warning: generator #",i," does not respect subspace!\n");
fi;
od;
qf.curgens := List(gens,x->
ExtractSubMatrix(x,[qf.dim-qf.curcodim+1..qf.dim],
[qf.dim-qf.curcodim+1..qf.dim]));
else
qf.curgens := gens;
fi;
Unbind(qf.m);
Unbind(qf.r);
Unbind(qf.blocksizes);
qf.bcplan := OneMutable(qf.curgens[1]);
qf.bcplani := OneMutable(qf.curgens[1]);
end );
InstallGlobalFunction( QF_Chop,
function( qf )
local codim, i, m, r;
m := Module( ShallowCopy(qf.curgens) );
qf.m := m;
r := Chop( m, rec( compbasis := true ) ); # with base change
qf.r := r;
qf.bcplan := r!.basis;
qf.bcplani := r!.basis^-1;
Print("Codimensions: ");
codim := 0;
for i in [Length(r!.acs),Length(r!.acs)-1..1] do
codim := codim + Dimension(r!.db[r!.acs[i]]);
Print( codim," " );
od;
Print("\n");
end );
InstallGlobalFunction( QF_Semisimple,
function( qf )
local i,d;
if not( IsBound( qf.m ) ) then
Print("Not yet chopped! Use QF_Chop first.\n");
return;
fi;
SemiSimplicityBasis( qf.r, qf.curchain );
qf.bcplan := qf.r!.basis;
qf.bcplani := qf.r!.ibasis;
Print("Block sizes: ");
qf.blocksizes := [];
for i in [1..Length(qf.r!.acs)] do
d := Dimension(qf.r!.db[qf.r!.acs[i]]);
Print(i,":",d," ");
Add( qf.blocksizes, d );
od;
Print("\n");
end );
InstallGlobalFunction( QF_ApplyBaseChange,
function( qf )
local bc,bci;
if qf.curcodim < qf.dim then # we have to expand the basechange
bc := OneMutable( qf.origgens[1] );
CopySubMatrix( qf.bcplan, bc,
[1..qf.curcodim], [qf.dim-qf.curcodim+1..qf.dim],
[1..qf.curcodim], [qf.dim-qf.curcodim+1..qf.dim] );
bci := bc^-1;
else
bc := qf.bcplan;
bci := qf.bcplani;
fi;
qf.curgens := List(qf.curgens,x->qf.bcplan*x*qf.bcplani);
qf.bcgens := List(qf.bcgens,x->bc*x*bci);
qf.basech := bc*qf.basech;
qf.basechi := qf.basechi*bci;
qf.bcplan := OneMutable(qf.origgens[1]);
qf.bcplani := OneMutable(qf.origgens[1]);
end );
InstallGlobalFunction( QF_Show,
function( arg )
local s,qf,what,i;
if Length(arg) = 0 then
Print("Usage: QF_Show( qf [,what] ), where what can be:\n");
Print(" \"orig\" : the original generators\n");
Print(" \"cur\" : the current generators in quotient\n");
Print(" \"bc\" : the current generators in full module\n");
Print(" \"plan\" : the would-be generators according to plan\n");
return;
elif Length(arg) = 1 then
qf := arg[1];
if IsOne( qf.bcplan ) then
what := "cur";
else
what := "plan";
fi;
else
qf := arg[1];
what := arg[2];
fi;
Print("Current subgroup size: ",Size(qf.curchain),"\n");
if what = "cur" then
Print("Current codimension: ",qf.curcodim,
", sum of current generators:\n");
s := Sum(qf.curgens);
elif what = "bc" then
Print("Dimension: ",qf.dim,", Sum of current generators:\n");
s := Sum(qf.bcgens);
elif what = "orig" then
Print("Dimension: ",qf.dim,", Sum of original generators:\n");
s := Sum(qf.origgens);
else # what = "plan"
Print("Current codimension: ",qf.curcodim,
", sum of would-be generators according to plan:\n");
s := qf.bcplan * Sum(qf.curgens) * qf.bcplani;
fi;
if Length(s) < 75 then
Display(s);
else
OverviewMat(s);
fi;
if IsBound( qf.blocksizes ) then
Print("Blocksizes: ");
for i in [1..Length(qf.blocksizes)] do
Print(i,":",qf.blocksizes[i]," ");
od;
Print("\n");
fi;
end );
InstallGlobalFunction( QF_Home,
function( qf )
qf.subgrpdepth := 0;
qf.curcodim := qf.dim;
QF_Recalccurgens(qf);
Print("Back to full dimension ",qf.dim," and full group with size ",
Size(qf.curchain),"\n");
end );
InstallGlobalFunction( QF_GotoSubgroup,
function( qf, n )
qf.subgrpdepth := n-1;
QF_Recalccurgens(qf);
Print("Current subgroup size: ",Size(qf.curchain),"\n");
end );
InstallGlobalFunction( QF_GotoQuotient,
function( qf, codim )
qf.curcodim := codim;
QF_Recalccurgens(qf);
Print("Current quotient dimension: ",codim,"\n");
end );
InstallGlobalFunction( QF_OrbitStatistics,
function( arg )
local qf,seconds;
if Length(arg) = 0 then
Print("Usage: QF_OrbitStatistics( qf [, seconds] )\n");
return;
elif Length(arg) = 1 then
seconds := 10;
else
seconds := arg[2];
fi;
qf := arg[1];
OrbitStatisticOnVectorSpace( qf.curgens,Size(qf.curchain),seconds );
end );
InstallGlobalFunction( QF_OrbitStatisticsLines,
function( arg )
local qf,seconds;
if Length(arg) = 0 then
Print("Usage: QF_OrbitStatisticsLines( qf [, seconds] )\n");
return;
elif Length(arg) = 1 then
seconds := 10;
else
seconds := arg[2];
fi;
qf := arg[1];
OrbitStatisticOnVectorSpaceLines( qf.curgens,Size(qf.curchain),seconds );
end );
InstallGlobalFunction( QF_PermuteBlocks,
function( qf, perm )
local nrblocks,newblocksizes,newblockorder,posold,posnew,oldblockstarts,
o,i,j,bc;
if not( IsBound( qf.blocksizes ) ) then
Print("Do not have blocksizes. Either set or use QF_Chop and ",
"QF_Semisimple first.\n");
return;
fi;
nrblocks := Length(qf.blocksizes);
newblocksizes := Permuted(qf.blocksizes,perm);
newblockorder := Permuted([1..nrblocks],perm);
posold := 1;
oldblockstarts := [];
for i in [1..nrblocks] do
Add(oldblockstarts,posold); posold := posold + qf.blocksizes[i];
od;
bc := ZeroMutable(qf.curgens[1]);
posnew := 1;
o := One(BaseField(bc));
for i in [1..nrblocks] do
# Move an old block into its new i-th position:
posold := oldblockstarts[newblockorder[i]];
for j in [1..newblocksizes[i]] do
bc[posnew][posold] := o;
posnew := posnew + 1;
posold := posold + 1;
od;
od;
qf.bcplan := bc * qf.bcplan;
qf.bcplani := qf.bcplani * bc^-1;
qf.blocksizes := newblocksizes;
end );
InstallGlobalFunction( QF_Flip,
function( qf )
local m;
m := Reversed(OneMutable(qf.bcplan));
qf.bcplan := m * qf.bcplan;
qf.bcplani := qf.bcplani * m;
if IsBound(qf.blocksizes) then
qf.blocksizes := Reversed(qf.blocksize);
fi;
end );
##
## This program is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program. If not, see <https://www.gnu.org/licenses/>.
##
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2026-03-28
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