mersenneforum.org P-1 stage 2 with GMP-ECM 5 ?
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 2003-12-09, 18:22 #1 hbock     Feb 2003 163 Posts P-1 stage 2 with GMP-ECM 5 ? GMP-ECM 5.x can use the ecm stage1 results of prime95 as described somewhere in the forum. Is there any way to use the P-1 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) ?
2003-12-09, 21:31   #2
Xyzzy

Aug 2002

5×1,669 Posts

From undoc.txt
Quote:
 Alexander Kruppa wrote some code that allows the output of ECM stage 1 to be passed to Paul Zimmermann's more efficient GMP-ECM stage 2. This program is usually faster in stage 1. You can activate this feature by entering GmpEcmHook=1 in prime.ini. Then select ECM bound #2 between 1 and bound #1. Results.txt will contain data that can be fed to GMP-ECM for stage 2.

 2003-12-10, 22:14 #3 hbock     Feb 2003 A316 Posts Well, I knew that the undoc.txt refers to ecm, but I'm interested in an extended P-1 stage. And for ecm GMP-ECM 5 is much faster in stage 2, so it could do a p-1 stage2 probably much faster, too.
2004-04-25, 15:52   #4
geoff

Mar 2003
New Zealand

13·89 Posts

Quote:
 Originally Posted by hbock Is there any way to use the P-1 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) ?
I want to write a program that takes as input a Prime95 P-1 save file with stage one completed to limit B1, and as output writes a gmp-ecm format save file.

I think the only information needed is the number N being tested, the B1 bound, and the P-1 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 gmp-ecm to read.

Has anyone tried to do this already, or have any suggestions?

 2004-04-25, 20:30 #5 akruppa     "Nancy" Aug 2002 Alexandria 2,467 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 P-1 save files to gmp-ecm 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 P-1 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 gmp-ecm, but will probably prompt a few changes nonetheless. I'll try to find the old code and see what needs to be done. Teaching gmp-ecm to directly read Prime95 P-1 save files is something I'd like to include in the next release, if the other developers agree to the idea. Alex
2004-04-26, 19:27   #6
geoff

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

$mprime; pm1dump mNNNNNNN | ecm -resume - B1 B2 where mNNNNNNN (or lNNNNNNN) is the mprime stage 1 save file and B1, B2 are the new bounds. I have noticed that compared to running stage 1 with gmp-ecm and using the -save option that a different residue X is created, and that there is no entry for the initial point X0. Despite this the stage 2 completes and finds the expected factors for the few exponents I have tested. I will post updates to this thread if I find any bugs. Attached Files  pm1dump-0.1.zip (3.4 KB, 178 views) 2004-04-27, 15:40 #7 geoff Mar 2003 New Zealand 13·89 Posts pm1dump 0.2 I have attached a new version of pm1dump. It now divides the number being P-1 tested by the known factors in lowm.txt or lowp.txt before generating the new save file. It uses libgmp to do the arithmetic, so add '-lgmp' to the compile line. Attached Files  pm1dump-0.2.zip (4.1 KB, 164 views)  2004-04-27, 16:06 #8 geoff Mar 2003 New Zealand 13×89 Posts It is possible to do stage one P-1 on 2^2N-1 with Prime95 then continue with stage two on 2^N-1 or 2^N+1 separately with gmp-ecm by using the splitcf program (see http://www.mersenneforum.org/showpos...7&postcount=13). Here is a (trivial) example of doing P-1 on 2^893+1 using this method (some output snipped):$ $cat worktodo.ini Pminus1=1786,3000,1,0,0$ $cat lowm.txt M( 1786 )C: 3 M( 1786 )C: 283 M( 1786 )C: 1787 M( 1786 )C: 174763 M( 1786 )C: 2351 M( 1786 )C: 4513 M( 1786 )C: 524287 M( 1786 )C: 13264529 M( 1786 )C: 6705767506519$ $mprime -d Mersenne number primality test program version 23.5 P-1 on M1786 with B1=3000, B2=3000 M1786 stage 1 complete. 8682 transforms. Time: 0.032 sec. Stage 1 GCD complete. Time: 0.002 sec.$ \$ pm1dump m0001786 | splitcf -p | ecm -resume - 3000 16000 GMP-ECM 5.0.3 [powered by GMP 4.1.2] [ECM] Resuming P-1 residue Input number is 249060...665097 (258 digits) Using B1=3000-3000, 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 P-1 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 gmp-ecm on F(N-1), F(N-2), F(N-3), etc. E.g. if stage one has been done on 2^262144-1 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
 2004-05-05, 21:31 #9 nuutti   Jan 2003 378 Posts How much faster GMP-ECM 5 is in p-1 factoring in the stage 2? I am currently running P-1 for: Pminus1=67108864,4000000,5000000,0,0 Can I use GMP-ECM 5 for runnig stage 2 in my test ? (I have 2 Gbytes of memoy) Nuutti
2004-05-06, 10:42   #10
geoff

Mar 2003
New Zealand

13×89 Posts

Quote:
 Originally Posted by nuutti How much faster GMP-ECM 5 is in p-1 factoring in the stage 2? I am currently running P-1 for: Pminus1=67108864,4000000,5000000,0,0 Can I use GMP-ECM 5 for runnig stage 2 in my test ? (I have 2 Gbytes of memoy)
For a number this large Prime95 is faster. Gmp-ecm can test to higher bounds than Prime95, for 2^67108864-1 this is probably not a consideration, but I have done some timings on the smaller fermat numbers and I estimate that a P4 2.66GHz could test 2^262144-1 to B1=4290M in about 28 days with Prime95, or 2^524288-1 in about 60 days. From that point the fastest way to either extend stage 1 or start stage 2 is to use gmp-ecm separately on F18, F17, F16, etc.

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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