20031209, 18:22  #1 
Feb 2003
163 Posts 
P1 stage 2 with GMPECM 5 ?
GMPECM 5.x can use the ecm stage1 results of prime95 as described somewhere in the forum.
Is there any way to use the P1 results (mxxxxxxx or lxxxxxxx files) of stage 1 generated by prime95, either for extended stage 1 work and/or maybe more interesting for stage 2 (faster and B2>4290000000) ? 
20031209, 21:31  #2  
"Mike"
Aug 2002
1E1D_{16} Posts 
From undoc.txt
Quote:


20031210, 22:14  #3 
Feb 2003
163 Posts 
Well, I knew that the undoc.txt refers to ecm, but I'm interested in an extended P1 stage. And for ecm GMPECM 5 is much faster in stage 2, so it could do a p1 stage2 probably much faster, too.

20040425, 15:52  #4  
Mar 2003
New Zealand
13×89 Posts 
Quote:
I think the only information needed is the number N being tested, the B1 bound, and the P1 residue X at the end of stage one, which are all in the save file. The program just needs to read the save file, convert the numbers to standard hex/decimal format, and format the results for gmpecm to read. Has anyone tried to do this already, or have any suggestions? 

20040425, 20:30  #5 
"Nancy"
Aug 2002
Alexandria
2^{5}×7×11 Posts 
Sorry for the late reply, I didn't see the thread when it was openend and usually don't read these forums very frequently.
I once started to write a tool to convert Prime95 P1 save files to gmpecm format but never quite finished it. In fact, I think it worked o.k. on x86 but portability was not complete. If only I could find that code now.. Anyhow, the Prime95 P1 save file format changed in the meantime, the changes mostly affecting save files from within stage 2 afaik which is not important to getting stage 1 residues over to gmpecm, but will probably prompt a few changes nonetheless. I'll try to find the old code and see what needs to be done. Teaching gmpecm to directly read Prime95 P1 save files is something I'd like to include in the next release, if the other developers agree to the idea. Alex 
20040426, 19:27  #6 
Mar 2003
New Zealand
13×89 Posts 
I have attached a program pm1dump, I haven't done a lot of testing but it works for the tests I have done. It can be compiled with 'gcc o pm1dump pm1dump.c' and then run as
$ mprime; pm1dump mNNNNNNN  ecm resume  B1 B2 where mNNNNNNN (or lNNNNNNN) is the mprime stage 1 save file and B1, B2 are the new bounds. I have noticed that compared to running stage 1 with gmpecm and using the save option that a different residue X is created, and that there is no entry for the initial point X0. Despite this the stage 2 completes and finds the expected factors for the few exponents I have tested. I will post updates to this thread if I find any bugs. 
20040427, 15:40  #7 
Mar 2003
New Zealand
485_{16} Posts 
pm1dump 0.2
I have attached a new version of pm1dump. It now divides the number being P1 tested by the known factors in lowm.txt or lowp.txt before generating the new save file. It uses libgmp to do the arithmetic, so add 'lgmp' to the compile line.

20040427, 16:06  #8 
Mar 2003
New Zealand
13·89 Posts 
It is possible to do stage one P1 on 2^2N1 with Prime95 then continue with stage two on 2^N1 or 2^N+1 separately with gmpecm by using the splitcf program (see http://www.mersenneforum.org/showpos...7&postcount=13). Here is a (trivial) example of doing P1 on 2^893+1 using this method (some output snipped):
$ $ cat worktodo.ini Pminus1=1786,3000,1,0,0 $ $ cat lowm.txt M( 1786 )C: 3 M( 1786 )C: 283 M( 1786 )C: 1787 M( 1786 )C: 174763 M( 1786 )C: 2351 M( 1786 )C: 4513 M( 1786 )C: 524287 M( 1786 )C: 13264529 M( 1786 )C: 6705767506519 $ $ mprime d Mersenne number primality test program version 23.5 P1 on M1786 with B1=3000, B2=3000 M1786 stage 1 complete. 8682 transforms. Time: 0.032 sec. Stage 1 GCD complete. Time: 0.002 sec. $ $ pm1dump m0001786  splitcf p  ecm resume  3000 16000 GMPECM 5.0.3 [powered by GMP 4.1.2] [ECM] Resuming P1 residue Input number is 249060...665097 (258 digits) Using B1=30003000, B2=16000, polynomial Dickson(4) Step 1 took 0ms Step 2 took 33ms ********** Factor found in step 2: 165768537521 Found probable prime factor of 12 digits: 165768537521 Composite cofactor 150245...858457 has 247 digits This might be useful for doing P1 of the Fermat numbers, stage one could be done just once on F(N)2 with mprime, then using the same save file in each case, do stage two with gmpecm on F(N1), F(N2), F(N3), etc. E.g. if stage one has been done on 2^2621441 to B1 and the save file is called m0262144, then run these commands (with appropriate low[mp].txt in the current directory) to do stage two on 2^131072+1, 2^65536+1, and 2^32768+1. pm1dump m0262144  splitcf p  ecm resume  B1 B2 pm1dump m0262144  splitcf m  splitcf p  ecm resume  B1 B2 pm1dump m0262144  splitcf m  splitcf m  splitcf p  ecm resume  B1 B2 
20040505, 21:31  #9 
Jan 2003
37_{8} Posts 
How much faster GMPECM 5 is in p1 factoring in the stage 2?
I am currently running P1 for: Pminus1=67108864,4000000,5000000,0,0 Can I use GMPECM 5 for runnig stage 2 in my test ? (I have 2 Gbytes of memoy) Nuutti 
20040506, 10:42  #10  
Mar 2003
New Zealand
13×89 Posts 
Quote:
According to http://www.mersenne.org/ecmf.htm, F18, F17, F16, F15 have only been tested to B1=32M, 64M, 250M, 1000M respectively. 

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