Igor Schein on Thu, 14 Mar 2002 17:53:07 -0500 |
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Re: isprime functions |
On Thu, Mar 14, 2002 at 09:57:12PM +0000, Mark Chimley wrote: > I have been trying to do some simple verifications of "primeness" using > the functions long isprime (GEN x) and GEN gisprime (GEN X, long flag) > under PARI 2.1.0. I am having a lot of problems. I started with the > simpler function, isprime, but this regularly reported "division by zero > in dvmdii" for randomly selected integers. With these problems I tried > gisprime (X, 1), which uses the Lucas-Lehmer test instead of M-R. > However, this appeared to cause random problems with gadd (I was adding > two in a loop until a number passed gisprime). The errors with gadd > ranged from segmentation faults to "forbidden *** unknown type n", where > n ranged from 30 to 200 or so. > > Due to the random nature of these errors, it would seem less likely that > the problem is with the code surrounding the loop (i.e. user error with > the PARI stack!), although obviously this cannot be ruled out. It would > also seem unlikely that there is a problem with such fundamental > functions. > > Any help in determining the cause of these problems would be gratefully > appreciated. What version of gp are you using? Can you provide an example of a prime which results in an error? Can you reproduce the error using gp? Igor