#13295: p_group_cohomology 2.1.3
---------------------------------+------------------------------------------
Reporter: SimonKing | Owner: tbd
Type: defect | Status: new
Priority: major | Milestone: sage-5.3
Component: optional packages | Keywords: group cohomology
Work issues: | Report Upstream: None of the above - read
trac for reasoning.
Reviewers: | Authors: Simon King
Merged in: | Dependencies: database_gap-4.4.12.p1
Stopgaps: |
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There is a new version of the optional p_group_cohomology package.
'''__Installation__'''
First, install Gap's Small Groups library (contained in the database_gap
spkg). Then, do
{{{
sage -i
http://sage.math.washington.edu/home/SimonKing/Cohomology/p_group_cohomology-2.1.3.spkg
}}}
'''__Testing__'''
If the environment variable `SAGE_CHECK` is set to `yes`, then a test
suite is run. This will take a considerable amount of time (the test
coverage is 100%). Parallel testing is possible by setting the environment
variable `SAGE_NUMBER_THREADS` to the number of threads being used.
'''__Documentation__'''
Set the environment variable SAGE_SPKG_INSTALL_DOCS to yes. Then, while
installing the package, the documentation will be put into
`SAGE_ROOT/local/share/doc/p_group_cohomology/html/`. Or see
[http://sage.math.washington.edu/home/SimonKing/Cohomology/ here]
'''__Reasons for upgrading__'''
__Name mangling__
There has been yet another Cython upgrade between sage-5.0 and sage-5.2.
By consequence, Python's infamous name mangling now also applies to Python
classes defined in Cython code:
{{{
sage: cython("""
....: class Foo:
....: def __init__(self):
....: self.__cache = "hi"
....: """)
sage: F = Foo()
sage: F.__cache
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
/home/simon/SAGE/prerelease/sage-5.2.rc0/<ipython console> in <module>()
AttributeError: Foo instance has no attribute '__cache'
sage: F._Foo__cache
'hi'
}}}
In Sage-5.0, the attribute `F.__cache` would be available. Hence, I had to
rename some attributes.
__Storing Gap data__
Some computed data (e.g., ideals in the cohomology ring simultaneously
restricting to zero on a given set of subgroups) are defined in terms of
data in Gap (namely, subgroups). We would like to store such data, since
obviously we don't want to recompute everything from scratch.
Unfortunately, pickling of general Gap objects is not available. The new
spkg version works around, so that pickling works, provided that the Gap
object can be reconstructed from its string representation (which holds,
e.g., for permutation groups).
__Use lower bounds for the depth__
Some completeness criteria benefit from knowing a good estimate for the
depth. In some cases, a good estimate is difficult to obtain. In the new
spkg version, the computation of a good bound can be interrupted by
Ctrl-C, and then an easier (but potentially weaker) bound is used.
__New web repository__
Due to a hardware problem on sage.math, the data in the old web repository
are lost. Meanwhile I reconstructed the data and put them to a new
location (namely my home directory on sage.math) which has a back-up. The
new spkg version knows about the new location of the repository.
__Creating a private data base__
When creating a "private" data base of cohomology rings, symbolic links to
the "public" data base (shipped with the package) are created. The old
spkg version did sometimes fail to create the symbolic links.
__A fix for `MeatAxe` matrices__
In the old spkg version, comparing an MTX matrix with None would have
resulted in a crash.
'''__Information for the reviewer__'''
I successfully installed and tested the package with sage-5.2.rc0 on an
`OpenSuse` laptop and on bsd.math. It would be nice to test it on a
variety of platforms, in particular on machines of different endianness,
or on 32-bit machines.
Apart from that, there is not much new mathematics in the spkg: It is
mainly a bug fix release (coping with the Cython upgrade).
__SPKG__
http://sage.math.washington.edu/home/SimonKing/Cohomology/p_group_cohomology-2.1.3.spkg
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13295>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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