#9894: Group cohomology spkg, version 2.1.1
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Reporter: SimonKing | Owner: SimonKing
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-4.7.1
Component: optional packages | Keywords: modular group cohomology
solaris t2
Work_issues: fix doc tests | Upstream: N/A
Reviewer: Karl-Dieter Crisman | Author: Simon King
Merged: | Dependencies:
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Changes (by SimonKing):
* status: needs_review => needs_work
* work_issues: => fix doc tests
Comment:
__Speed__
I will use the occasion to slightly modify the `MeatAxe` sources (they
already ''are'' modified compared with release 2.2.4):
`MeatAxe` uses plain loops to initialise memory. Actually, Michael Ringe
did replace memset by such loops, in Revision 2.7. However, he does not
explain why he did so.
Since most compilers should be pretty well in optimising memset (or
calloc), I re-introduce the usage of memset and also of calloc. With that
change, the multiplication time for two 2000x2000 matrices over GF(125)
drops from 15 seconds (which already beats the default `Matrix_modn_dense`
in Sage by a loooooong way!) to less than 12 seconds on my machine.
In other words, the cohomology computations should now generally be a bit
faster.
__`_sig_on/_sig_off`__
Concerning sig_on_count: It is really a nice feature that the balance of
_sig_on/_sig_off is automatically tested since sage-4.7.1! I went through
the sources, and indeed it seems that there can be situations where an
error is raised between _sig_on/_sig_off (which must be avoided).
__The other doctest failures__
- The test `pGroupCohomology.factory.CohomologyRingFactory.get_public_db`
verifies that by default the public cohomology data base is in
`SAGE_DATA`. Apparently that is not the case for John's Sage
installations, and thus I'll remove that test.
- There is one test where non-filter-regular but algebraically independent
parameters are not found in the degrees that are expected according to the
doc tests. That is because algebraically ''dependent'' parameters can be
found with a smaller degree sum. Hence, the completion test of Peter
Symonds is used, and the program does not bother to try and find the
smallest possible independent parameters. So, that test has to change.
I am now preparing an update of the package and test it against
sage-4.7.1.rc2. Until that's done, the ticket should be "needs work".
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9894#comment:39>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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