Re: Eigenvalues of symmetric matrices

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Fri, Dec 01, 2023 at 02:43:11AM +0000, Gordon Royle wrote:
> Hi
> 
> I am using Pari/GP to compute the eigenvalues of a large number (10s of
> millions) of symmetric 0/1-matrices of order about 24 x 24 to 30 x 30; the
> matrices are adjacency matrices of 3-regular graphs and so have exactly three
> 1s per row and column.
> 
> At the moment, I am just using polrootsreal(charpoly(a)), but I wonder if there is a faster way to do it?

We would need a bit more informations, for example:
Maybe give an example ? 
What are you planning to do with the eigenvalues ?

Cheers,
Bill.