Bill Allombert on Fri, 01 Dec 2023 10:05:31 +0100

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Re: Eigenvalues of symmetric matrices

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 ?