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Extend the range of precomputed simple groups from orders up to 10^18 to orders up to about 10^27 #3861

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merged 2 commits into from
Jan 22, 2020

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hulpke
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@hulpke hulpke commented Jan 18, 2020

(based on work of Stefan Kohl)

This is -- as basic first option -- simply extending the precomputed list of simple groups of "small" orders from 10^18 to about 10^27

Text for release notes

The range of SimpleGroupsIterator has been extended by 9 magnitudes

@hulpke hulpke added kind: enhancement Label for issues suggesting enhancements; and for pull requests implementing enhancements kind: new feature release notes: to be added PRs introducing changes that should be (but have not yet been) mentioned in the release notes labels Jan 18, 2020
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coveralls commented Jan 18, 2020

Coverage Status

Coverage increased (+0.03%) to 84.761% when pulling 734b395 on hulpke:additions into d1516f2 on gap-system:master.

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In principle this is fine, but the documentation to SimpleGroupsIterator really should be adjusted to match the code change.

Ideally, a few more changes should be made (see my comment), but that's optional for this PR, and can be done by somebody else (e.g. me) in another PR.

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Also: nice patch, thank you :-)

(based on work of Stefan Kohl)
Changed documentation. Fixed also `One/AllSimpleGroup` (why are
these there?) and introduced REBASE SIMPLE_GROUPS_ITERATOR_RANGE variable
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Nice! Minor (and optional) remarks added.

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pos:=First([1..Length(SIMPLEGPSNONL2)],x->SIMPLEGPSNONL2[x][1]>=start);

if start>=10^18 then LOADSIMPLE2(); fi;
pos:=First([1..Length(SIMPLEGPSNONL2)],x->SIMPLEGPSNONL2[x][1]>=start);
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Optional alternative (should be double checked ;-):

Suggested change
pos:=First([1..Length(SIMPLEGPSNONL2)],x->SIMPLEGPSNONL2[x][1]>=start);
pos:=PositionProperty(SIMPLEGPSNONL2,x->x[1]>=start);

Co-Authored-By: Max Horn <max@quendi.de>
@hulpke hulpke merged commit 92c951d into gap-system:master Jan 22, 2020
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Why 10^27? -- This bound seems a bit arbitrary to me. -- Up to order 10^30, there are 2171 non-PSL2's, up to order 10^40, there are 22709 non-PSL2's, up to order 10^50, there are 298023 non-PSL2's and up to order 10^60, there are 4263813 non-PSL2's. -- Of course listing all the latter in the way you do it now would take hundreds of megabytes of text. -- But that's the reason for the iterator code, instead of using just a list.

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hulpke commented Jan 24, 2020

@Stefan-Kohl Yes, 10^27 is arbitary. I don't claim this is the best and end-of-all. If you want to offer your (better) general iterator code as PR, please do so, and I'd be happy to have my code replaced.

@ThomasBreuer ThomasBreuer self-assigned this Feb 17, 2021
@ThomasBreuer ThomasBreuer added release notes: added PRs introducing changes that have since been mentioned in the release notes and removed release notes: to be added PRs introducing changes that should be (but have not yet been) mentioned in the release notes labels Feb 17, 2021
@ThomasBreuer ThomasBreuer removed their assignment Feb 17, 2021
@fingolfin fingolfin changed the title ENHANCE: Extended range of simple groups Extend the range of precomputed simple groups from orders up to 10^18 to orders up to about 10^27 Aug 17, 2022
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