Karim BELABAS on Sun, 18 May 2003 18:44:21 +0200 (MEST)

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Re: charpoly using too much stack space !

On Sun, 18 May 2003, Bill Allombert wrote:
> On Sat, May 17, 2003 at 01:21:53PM -0500, Gonzalo Tornaria wrote:
> > When computing the characteristic polynomial of big matrices (not so
> > much, in the example 50x50), PARI uses A LOT of stack space, which I
> > believe is not really necesary. I've written a gp function for
> > computing the characteristic polynomial (matrix_charpoly), using what
> > I believe is the same algorithm of charpoly (computing traces, etc.)
> This also hold for libpari but here there is something wrong.
> Here a patch that should fix the problem

This patch is quite correct. I have committed to CVS a different one, which
fixed a number of minor annoyances [ stack leaks ], and handles stack usage
in a less hackish way than previously.

I have not noticed any efficiency loss.

Karim Belabas                     Tel: (+33) (0)1 69 15 57 48
Dép. de Mathématiques, Bât. 425   Fax: (+33) (0)1 69 15 60 19
Université Paris-Sud              http://www.math.u-psud.fr/~belabas/
F-91405 Orsay (France)            http://www.parigp-home.de/  [PARI/GP]