README.md
1[](https://travis-ci.org/gap-packages/cohomolo)
2[](https://codecov.io/gh/gap-packages/cohomolo)
3
4# The GAP 4 package 'cohomolo'
5
6## Package description
7
8It may be used to perform certain cohomological calculations on a finite
9permutation group G. The following properties of G can be computed:
10
111. The p-part Mul_p of the Schur multiplier Mul of G,
12and a presentation of a covering extension of Mul_p by G, for a specified
13prime p;
14
152. The dimensions of the first and second cohomology groups of G
16acting on a finite dimensional KG-module M, where K is a field of prime
17order; and
18
193. Presentations of split and nonsplit extensions of M by G.
20
21
22## Installation
23
24This package uses external binaries and currently works only under
25UNIX/LINUX systems.
26
27To install the package go to the GAP directory `pkg/cohomolo` (the
28directory containing this README file) and call
29
30 ./configure PATH
31
32where `PATH` is a path to the main GAP root directory; so normally you
33would call
34
35 ./configure ../..
36
37and then call
38
39 make
40
41to compile the binary.
42
43If you installed GAP on several architectures, you must execute this
44configure/make step for the `cohomolo` package on each of the architectures
45immediately after configuring GAP itself on this architecture.
46
47
48## Documentation
49
50Full information and documentation can be found in the manual, available
51as PDF `doc/manual.pdf` or as HTML `htm/chapters.htm`, or on the package
52homepage at
53
54 <https://gap-packages.github.io/cohomolo/>
55
56
57## Bug reports and feature requests
58
59Please submit bug reports and feature requests via our GitHub issue tracker:
60
61 <https://github.com/gap-packages/cohomolo/issues>
62
63
64## License
65
66cohomolo is free software; you can redistribute it and/or modify
67it under the terms of the GNU General Public License as published by
68the Free Software Foundation; either version 2 of the License, or
69(at your option) any later version.
70
71For details see the file LICENSE.
72
73
74## Updating from GAP3
75
76This package has been updated from the original GAP3 package
77with minimal changes, so the user should find the interface unchanged.
78In fact the only real changes are that the function `InfoCohomology` has been
79replaced by the `Info` variable `InfoCohomolo`, and the function
80`SplitExtension` has been renamed `SplitExtensionCHR, to avoid clashing
81with an existing GAP function name. (Of course, it does more or less
82the same thing as the GAP function!)
83
){kind=link}
){kind=link}