Bill Allombert on Tue, 23 Oct 2001 17:04:26 +0200 |
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Re: roots function |
Le Sat, Oct 20, 2001 at 09:01:43AM +0200, Jean-Marc Sac-Epée écrit : > Hi, > > I have strange problems when using roots function with some peculiar polynomials. With most polynomials, roots is OK, but I can show some examples > which stop the program. > Under gp, there is never any problem: > > ? polroots(p) > %3 = [-2.000617441803038056259607547 + 0.E-28*I, -1.998628388494694273362924261+ 0.E-28*I, -1.992194706025025355055438852 + 0.E-28*I, > > But in library mod, it's quite different. With a program such that > output(pol); > roots(pol,prec); > one get > > *** non positive argument in mplog. > *** Error in the PARI system. End of program. > > I also tried with older pari version (2.1.0, 2.1.1) and I got the same problem. [bill](I shortened the quote to make it more readable) I am not sure it is a library-only problem. In fact it is almost impossible the way gp works, almost all code is in the library. The main difference is that gp read a startup file and not pari_init, so you may get different options set. On my machine I can reproduce it under GP as well. parisize = 4000000, primelimit = 500000 ? allocatemem(16*10^6) ? \r~/tmp/pol ? polroots(%) *** non positive argument in mplog. (I have try higher prec, more or less memory, with same bug) Bill.