Dear Members of the GAP Forum

We are pleased to announce the release of a new GAP4 share package:
EDIM, by Frank Luebeck.

The main purpose of the EDIM mini package is to publish an
implementation of an algorithm (found by the package author) for
computing prime parts of the elementary divisors of integer matrices
(i.e., the diagonal entries of the Smith normal form).

The programs are developed and already successfully used for large
matrices (up to rank >5000) with moderate entries and many non-trivial
elementary divisors which are products of some small primes. But they
should be useful for other types of matrices as well.

Among the other functions of the package are: An inversion algorithm
for large rational matrices (using a p-adic method), a program for
finding the largest elementary divisor of an integral matrix
(particularly interesting when this is much smaller than the
determinant) and implementations of some normal form algorithms
described by Havas, Majewski, Matthews, Sterling (using LLL- or
modular techniques).

More information can be found from the GAP4 Share packages page

http://www-gap.dcs.st-and.ac.uk/~gap/Info4/share.html

and the package can be downloaded from

http://www-gap.dcs.st-and.ac.uk/~gap/Share/edim.html

Mike Atkinson