mersenneforum.org segfault with large input on Opteron
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 2005-08-15, 02:14 #1 sean     Aug 2004 New Zealand 2·5·23 Posts segfault with large input on Opteron \$ echo '100000!-1' | ecm 1000 GMP-ECM 6.0.1 [powered by GMP 4.1.4] [ECM] Input number is 100000!-1 (456574 digits) Using B1=1000, B2=44623, polynomial x^1, sigma=1288196876 Step 1 took 3245570ms Segmentation fault I also tried running this with -v -v turned on. This produced a few lines with bignums on it. The last few lines before the segfault are: B2'=65280 k=2 b2=32640 d=510 d2=1 dF=64, i0=1 Expected number of curves to find a factor of n digits: 20 25 30 35 40 45 50 55 60 65 3345 451878 1.1e+08 3.5e+10 inf inf inf inf inf inf Initializing tables of differences for F took 86618ms Computing roots of F took 320977ms Any ideas? The machine is a dual 1.8 GHz Opteron with 16GB of RAM. Last fiddled with by sean on 2005-08-15 at 02:17 Reason: more info
 2005-08-15, 07:55 #2 cjohnsto   Jun 2005 3×5 Posts Is GMP and ECM compiled using the stack or heap for number storage?
 2005-08-15, 09:59 #3 akruppa     "Nancy" Aug 2002 Alexandria 2,467 Posts After "Computing roots of F" it starts to build the polynomial F where arithmetic with large polynomials starts. The Kronecker-Schoenhage multiplication in GMP-ECM 6.0 uses a lot of temp space. As cjohnsto notes, the problem is probably that alloca() is used and it runs out of stack space. Alex

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