id,summary,reporter,owner,description,type,status,priority,milestone,component,resolution,keywords,cc,merged,author,reviewer,upstream,work_issues,branch,commit,dependencies,stopgaps
9894,"Group cohomology spkg, version 2.1.2",SimonKing,,"Version 2.1.2 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 needs the Small Groups library (available in the gap-packages spkg) and can be installed with {{{sage -i http://sage.math.washington.edu/home/SimonKing/Cohomology/p_group_cohomology-2.1.2.spkg}}}
Most importantly: The version 2.0, that is the current ""official"" version of the optional package, would not work with the current version of Sage. So, there has to be an upgrade of the spkg.
Moreover, it has new features.
'''__New Features__'''
'''1. Improved code quality'''
- IIRC, one of the referee's complaint on earlier versions of the package was that the !__init!__.py file actually contains code, rather than just importing things. So, I made a new module ""factory.py"". Now, the !__init!__.py only contains documentation and import statements.
- Moreover, I split the !__call!__ method of the cohomology ring constructor into smaller units.
- Virtually all computations with this package require creating certain data files on disk. However, the data that are shipped by the package are installed in SAGE_DATA. So, if a user has no write access in that folder, he can read from the database, but can not add further computations to it. In previous versions, it meant that the user had to create his/her own database ''from scratch''. This is solved in version 2.1.1: Still, the user will create his/her own database, but this database can make full use of the stuff that already is in SAGE_DATA.
- 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.
- We finally achieved '''100% doctest coverage!! '''
- 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.
- The parallel testscript uncovered a problem with temporary files associated with Sage's pexpect interfaces -- see #10004. The testscript tests if the problem reported at #10004 is fixed, and will only do parallel testing if it is fixed.
'''2. Extended computational capability'''
- 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.
- 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.
'''3. Portability '''
The package fully 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]
'''__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}}}.
However, problems with parallel testing in Version 2.1 revealed a problem with Sage's {{{pexpect}}} interfaces: ''All'' interfaces (e.g., GAP and Singular) and all parallel branches use a single temporary file for passing long commands. A solution is at #10004. The test script of the cohomology spkg will only do parallel testing if gap and singular use different temporary files.
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 -- ''without'' write permission in SAGE_DATA.
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.
'''optional spkg''': [http://sage.math.washington.edu/home/SimonKing/Cohomology/p_group_cohomology-2.1.2.spkg]",enhancement,closed,major,sage-5.0,packages: optional,fixed,modular group cohomology solaris t2,graham.ellis@… david.green@…,,Simon King,"Karl-Dieter Crisman, John Palmieri",N/A,,,,,