#9894: Group cohomology spkg, version 2.1
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Reporter: SimonKing | Owner: tbd
Type: enhancement | Status: new
Priority: major | Milestone: sage-4.6
Component: optional packages | Keywords: modular group cohomology
solaris t2
Author: Simon King | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Version 2.1 of the modular group cohomology package is now available.
There is extensive
[http://sage.math.washington.edu/home/SimonKing/Cohomology/index.html
documentation]. The package can be installed with {{{sage -i
http://sage.math.washington.edu/home/SimonKing/Cohomology/p_group_cohomology-2.1.spkg}}}
'''__New Features__'''
1. I tried to improve the code quality. For example:
- Typically one has methods whose result can be cached and needs only be
re-computed if the ring approximation changes; this is now being taken
care of by decorators.
- I tried to reduce compiler warnings.
- Using the package, several bugs in Singular and GAP have been
uncovered. The new Singular version 3-1-1 fixes some bugs, so that in some
cases more efficient methods can be used. The package tests the available
Singular version; it both supports the new features and is able to work
around the old Singular bugs.
2. The completeness criteria are further improved. We use three criteria,
namely the modified Benson criterion (found by David Green and myself),
the Symonds criterion and the Hilbert-Poincaré criterion (suggested by
Peter Symonds and worked out by myself). Due to new methods of
constructing parameters, the Symonds criterion is now often the best
choice - but not always, so that it is good to have three methods to
choose from.
3. New functionality includes the computation of preimages of induced
homomorphisms, essential ideals and depth essential ideals. Using the
package, a new example of a group was found for which the square of the
essential ideal does not vanish (this is only the second known example!).
So far, a conjecture of Jon Carlson on depth essential ideals can be
confirmed.
4. '''It works on t2!! ''' This is a very non-trivial achievement. It
involved:
* Changing the names of several functions from {{{C-MeatAxe}}}, since the
Sun linker seems to confuse them with functions from pari. This is a
problem similar to the one found at #1396.
* t2 is a big-endian machine. GAP's random generator depends on the
endianness (which is a bug). Certain internal data used by the cohomology
computations are obtained by randomised algorithms of GAP. The ring
presentation found for the cohomology ring depends on these internal data.
So, in order to get machine independent computationally well defined
results, special care was needed, as discussed on
[http://groups.google.com/group/sage-
devel/browse_thread/thread/623f7291ab7e782e sage-devel]
5. By oversight, the old test script failed to execute the tests of
special methods (such as {{{__add__}}} or {{{__mul__}}}. The new script
now captures all tests, and complains if a class, method or function does
not appear to be tested. Also, the test script does parallel tests.
6. We finally achieved '''100% doctest coverage!! '''
'''__Testing__'''
As usual, if the environment variable {{{SAGE_CHECK}}} is exported and has
the value {{{yes}}}, the test script is automatically executed and the
result saved in {{{SAGE_ROOT/install.log}}}.
The script tests parallely. By default, the number of threads is one third
of the number of available CPUs. This can be overruled by exporting the
environment variable {{{SAGE_NUMBER_THREADS}}}.
I successfully installed and tested the package on the following machines
and the following versions of Sage and Singular:
* t2.math, Sage 4.5.1, Singular 3-1-1
* bsd.math, Sage 4.5.2, Singular 3-1-0, both in 64 and 32 bit mode
* sage.math, Sage 4.5.1, Singular 3-1-0
* x86_64 GNU/Linux, Intel Core2 CPU 6700 @ 2.66GHz, Sage 4.5.2, Singular
3-1-1
On another GNU Linux machine with AMD processors, it builds and seems to
work even with Sage 4.2.1, but apparently the interface to the @parallel
decorator has changed, so that I was not able to run the test script.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9894>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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