Karim BELABAS on Thu, 29 May 2003 23:11:02 +0200 (MEST) |
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Re: matsnf segfaults |
On Thu, 29 May 2003, Alexander Shumakovitch wrote: > On Thu, May 29, 2003 at 08:53:31PM +0200, Karim BELABAS wrote: >> P.S: Note that the algorithm used is spectacularly inefficient in medium to >> large dimensions (it was written to be used for 10 x 10 matrices...), so I >> doubt the computation will ever finish. > That's weird! In fact, this matrix was produced by mathnf to speed up > the calculations. It was always the case for me that matsnf performs > faster on matrices prepared by mathnf first. Shouldn't be the case if you add up the HNF precomputation time to the matsnf timings: the first (non-trivial) instruction in matsnf is to replace the matrix by its HNF... [ that is, unless you know a good multiple of the determinant to speed up the modular hnf computation ] > Now in this case, it takes less than a second to get the SNF of the > original matrix directly. But way too much after HNF (it complained about > low memory after a couple of minutes). Is it expected? Well, my followup patch fixed that :-) Karim. -- 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]