Re: Prime[x] crashes kernel for large x

*To*: mathgroup at smc.vnet.net*Subject*: [mg7817] Re: [mg7762] Prime[x] crashes kernel for large x*From*: Richard Finley <trfin at fiona.umsmed.edu>*Date*: Sat, 12 Jul 1997 02:45:56 -0400*Sender*: owner-wri-mathgroup at wolfram.com

I get the same problem with Mma 3.0 (on a Pentium Pro 200 Win95 system) .. I have to restart the kernel before proceeding. One other curiosity, I was trying to find out approximately what size number would cause it to crash and I noted that 2^26 was OK but 2^27 consistently crashes. I started walking up from 2^26 + 40000000 and found that if I go from that to 2^26+50000000 it crashes, but if I perform consecutive trials from 40000000 in steps of 1000000 I can continue to at least 150000000 (which is greater than 2^27) without crashing (that's where I ran out of patience...I don't know how far it would have continued.) Why computing Prime[n+k] should depend on whether you computed Prime[n] in the previous calculation is beyond my understanding of Mma but it is certainly true. For example, if I compute Prime[2^26 + 40000000]//Timing , it takes 8.47 sec the first time you do it, but if you compute it again it gives 0. sec. It appears it "remembers" previous calculations and I presume it somehow uses the results in computations of larger primes...so Prime[2^26 + 50000000] crashes only if you didn't perform Prime[2^26 + 49000000] etc..first. Do others get the same result on other platforms? Any ideas from anyone ? -- Wolfram ? RF At 02:36 PM 7/8/97 -0400, you wrote: > >When I try to find a large prime, for example: > >Prime[2^32 - 1] > >The math kernel crashes with a divide error, and I can't restart it >without quitting mathematica (3.0) and restarting. Am I doing something >wrong, or is this a bug? > >Thanks, > >Michael >michael at qni.com > > > > > >