[GAP Forum] Diagonalize of symmetric matrix 248x248

[Marek Mitros]

Hi,

What is the quickest way to diagonalize symmetric matrix 248x248 with
integral entries. I run Eigenvectors(Rationals, m) but it run long
time on my PC. The matrix is the Gram matrix of Thompson Smith lattice
in dimension 248. See page:
http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/TH.html

I would like to obtain the lattice generators or alternatively
orthogonal representation of Thompson sporadic group.

Regards,
Marek