Go Back > Factoring Projects > Factoring

Thread Tools
Old 2021-04-30, 04:24   #12
VBCurtis's Avatar
Feb 2005
Riverside, CA

24·13·23 Posts

If my only interest was using those two pieces of hardware to factors numbers as fast as possible, I'd run GNFS and ECM in parallel, with a queue of 2-3 numbers that survived ECM and are ready for GNFS (since a few in a row may succumb to ECM, leaving you starved for CPU work if you don't have a queue).

That would be *far* more than 0.32 depth! Then again, GPU-ECM still needs stage 2 to be done on one CPU core (right? that hasn't changed, has it?), so perhaps I'd let the GPU go idle sometimes.

I'd also run really big curves- if you're on C150s, I'd run about half a T45, then half a T50, then however many T55 curves would definitely finish in less time than the current GNFS job. Maybe half a T55? How far you get depends on how fast your GPU is; a 1060 obv isn't going to fly through as many curves as a 30xx.

The idea is that your GPU can save you a couple of GNFS jobs you would have otherwise done if you'd stopped ECM at e.g. 2t45. In the context of "I am limited by my CPU", those are free factors!
VBCurtis is offline   Reply With Quote
Old 2021-04-30, 04:50   #13
Apr 2021

218 Posts

Lots of great info, thanks!
Unitome is offline   Reply With Quote
Old 2021-04-30, 15:49   #14
chris2be8's Avatar
Sep 2009

111111110102 Posts

Given a GPU that can do stage 1 faster than the CPU can do stage 2 (after splitting the stage 2 runs over however many threads the CPU has) I'd treat stage 1 as nearly free and run ECM until (probable saving from the chance of finding a factor)/(CPU time needed for stage 2) matches CPU time needed to factor it with GNFS. Which probably won't be more than 2-3 digits above the optimum for CPU only since time increases quickly with target level.

In my case with 1 GPU and several CPUs I have to do a bit less than that so the GPU can pre-test numbers fast enough to feed the CPUs.

chris2be8 is offline   Reply With Quote
Old 2021-04-30, 18:03   #15
Apr 2021

17 Posts

Thanks for that. That fits with my "back of the napkin number crunching" since B1 values and curve times seem directly proportional for time taken based on this; so that might mean a few digits higher than 0.32x for GPU ECM even assuming best case scenario of 10x speed (which seems hit or miss itself). Maybe instead of 0.32x with CPU, 0.34x might be reasonable with GPU then.

Last fiddled with by Unitome on 2021-04-30 at 18:14
Unitome is offline   Reply With Quote

Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Factorize a 129-digit number mersenneNoob Homework Help 36 2021-04-24 03:27
Factor a 108-digit number sweety439 Factoring 9 2016-12-21 21:22
10 digit number puzzle MattcAnderson Puzzles 13 2014-11-10 18:03
Factoring a 617-digit number? Shakaru Factoring 2 2005-02-23 19:22
10,000,000 digit number Unregistered Software 3 2004-03-03 19:20

All times are UTC. The time now is 03:48.

Fri May 14 03:48:15 UTC 2021 up 35 days, 22:29, 0 users, load averages: 2.87, 2.84, 2.92

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.