20210206, 13:36  #1 
Feb 2018
23 Posts 
GMPEcm as Pm1 requires very little RAM
A while back I started working on a way to use The faster Prime95 or mprime P1 first stage and proceed to the 2nd stage using GMPEcm running as P1. Which is at least 20 times faster.
What is most interesting is that you can split the work using B2minB2max. It doesn't require to save a B2 files. If you know the work as been done to a certain point. You can start from there. GP2 was able to make it work as the B1 was saved backward, as shown in this link Here is an exemple of one run. B1 is done on Prime95 using a faster PC using Windows10. The second stage is done on a Linux 32bits with 1G Ram. And I run two instances. B1 is at 10 billion and took over 2 hours. B2 is done in steps of 300 billion and takes about 5 minutes. The factor was found during the first step. GMPECM 7.0.4 [configured with GMP 6.1.2] [P1] Tuned for x86/params.h Running on jocelynDellDV051 Resuming P1 residue saved by jocelyn@jocelynDellDV051 with GMPECM 7.0.4 on Fri Feb 5 22:54:18 2021 Input number is ((2^15711))/1250961804686347854556649368571289367 (437 digits) Using special division for factor of 2^15711 Using lmax = 524288 with NTT which takes about 294MB of memory Using B1=1000000000010000000000, B2=1999999879854020364610926900, polynomial x^1 P = 2251799814330893, l = 241920, s_1 = 1, k = s_2 = 47833428732674048, m_1 = 15488384 Can't compute success probabilities for B1 <> B2min Step 1 took 0ms Computing F from factored S_1 took 56019ms Computing h took 11125ms Computing DCTI of h took 7321ms Multipoint evaluation 1 of 1: Computing g_i took 44471ms Computing g*h took 17020ms Computing gcd of coefficients and N took 11921ms Step 2 took 147985ms Peak memory usage: 306MB Joss 
20210207, 00:24  #2 
Feb 2018
23 Posts 
With more Ram and a better machine
compared to a better machine it is no match.
Windows10 64bits 16Gb Ram cpu I53470 steps of 1,000,000,000,000,000 This is done under 17 minutes and would have taken 277 hours on the other pc. GMPECM 7.0.5dev [configured with GMP 6.1.2, enableasmredc] [P1] Resuming P1 residue saved by jocelyn@jocelynDellDV051 with GMPECM 7.0.4 on Fri Feb 5 22:54:18 2021 Input number is ((2^15711))/1250961804686347854556649368571289367 (437 digits) Using special division for factor of 2^15711 Using lmax = 16777216 with NTT which takes about 9792MB of memory Using B1=1000000000010000000000, B2=9999999135152242206728710203396, polynomial x^1 P = 64579515, l = 16777216, s_1 = 7434240, k = s_2 = 3, m_1 = 7742389 Can't compute success probabilities for B1 <> B2min Step 1 took 0ms Computing F from factored S_1 took 199391ms Computing h took 24828ms Computing DCTI of h took 52891ms Multipoint evaluation 1 of 3: Computing g_i took 97109ms Computing g*h took 106985ms Computing gcd of coefficients and N took 37187ms Multipoint evaluation 2 of 3: Computing g_i took 97891ms Computing g*h took 107078ms Computing gcd of coefficients and N took 37312ms Multipoint evaluation 3 of 3: Computing g_i took 97454ms Computing g*h took 106343ms Computing gcd of coefficients and N took 36453ms Step 2 took 1002672ms Peak memory usage: 9684MB Now we just have to wait and see if it leads to a factor. It always depends on B1 being high enough. 
20210211, 02:59  #3 
Feb 2018
17_{16} Posts 
Completed P1 testing M1571
P1 of M1571 has found no new factors other than the ones previously known.
B1=1e+11 done on mprime B2=1e+17 done on GMPEcm using p1 is there a way to report this on Gimps or mersenne.ca ? 
20210211, 04:19  #4 
Romulan Interpreter
"name field"
Jun 2011
Thailand
23624_{8} Posts 
Send it to GIMPS, or PM the results to George, once registered with PrimeNet, then mersenne.ca will sync the result from there. OTOH, for how much ECM that exponent had, the P1 is a bit futile, unless you really raise those bonds few more orders of magnitude.

20210228, 14:30  #5 
Feb 2018
23 Posts 
To add on to my research. When resuming from Prime95, you cannot do resume save. Otherwise you won't find any subsequent factors.
What you can do is search in steps. [b1] 100000 [b2] 10000002000000 Onece you find a factor and wish to continue with that same B1. You can manually add it to the input file. And as you did the first time you need to change the checksum of the input file that looks like that. METHOD=P1; B1=xxxxx; N=(2^yyyy1); X=0x...(the inputed X0 from Prime95).........; CHECKSUM=.............; PROGRAM+GMPECM ..... 
20210228, 16:12  #6  
Random Account
Aug 2009
Not U. + S.A.
2·3·389 Posts 
Quote:


20210228, 16:37  #7 
Sep 2009
2×3^{2}×7×19 Posts 
Checking for factors smooth below B1 has already been done by prime95. ECM is now checking for factors P where P1 has only one factor larger than B1 and less than B2 (the rest being less than B1).
Note the preceding line says it's using about 9792MB to do it. Which I would not call "very little RAM". Chris 
20210301, 11:58  #8  
Feb 2018
23 Posts 
Quote:


20210302, 00:36  #9  
Random Account
Aug 2009
Not U. + S.A.
2·3·389 Posts 
Quote:
Quote:


20210302, 07:15  #10 
Feb 2018
23 Posts 
The input file m1571.txt looks like that:
Code:
METHOD=P1; B1=200000000000; N=((2^15711)/1250961804686347854556649368571289367); X=0x0067F0913DBC6F1FAF640DAF4F4EA4B66858D1B6753E03ED960F83953C186BB0C5C0F519984706CCD432D54F9925B9A0B9F09D7541FFB62267F75E1A50D1F4C9F8724C79BC6823F041018D3E0561D51AE34062D91AFECA001E23436CA14248FA748C0D070D35773EF5A1248524B76B92A3164A43B6FBF617361A7AFB421254321AE855AB7E26EC4BBC34839F5C53C28CCFEE1697734A5F2BADF8C5FAB633352A73EDC1531B8EE229F8DBE053BB38CB8113B12AE16097213261BC749901C168E362A36A881FE; CHECKSUM=3043118422; PROGRAM=GMPECM 7.0.4; Y=0x0; X0=0x0; Y0=0x0; WHO=me@mypc; TIME=Fri Feb 5 22:54:18 2021; ecm pm1 v maxmem 10000 resume m1571.txt 200000000000 2000000000000000 maxmem is in Mb if you know the work has been done to a certain level from that B1 to say B2 1e+20 you can have a command line that looks like that: ecm pm1 v maxmem 10000 resume m1571.txt 200000000000 100000000000000000000100001000000000000000 of course ecm only goes to a certain level of B2 but when you reach it I would say we have done enough for that B1. Last fiddled with by axn on 20210302 at 09:48 
20210302, 09:12  #11 
"Alexander"
Nov 2008
The Alamo City
839 Posts 
Mods: Please put that in a code block.

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