mersenneforum.org Factoring a 172-digit number.
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 2019-02-13, 19:51 #12 VBCurtis     "Curtis" Feb 2005 Riverside, CA 4,211 Posts Linux is easier to code multithreaded support, for one; it also has a compiler built-in, while trying to compile software in Windows can be a pain (to say the least). Alternatives have been provided in this thread already; learn to use one of the software packages (CADO-NFS or factmsieve.py/msieve/GGNFS or YAFU). For windows, YAFU is likely the shortest learning curve, as it was written to automate the use of factmsieve.py/msieve/GGNFS; it's really just a wrapper that organizes the use of the other tools for you. Factor some small numbers to see how everything works, and to reduce the chance you make a mistake that adds 50% to factoring time. It shouldn't take more than 10-15 hours to learn how to use the tools, including a few hours reading forum posts around here to learn which settings do what. You can peruse the queue management thread in NFS@home subforum to see what parameters were chosen for previous C172 or C173 jobs, and just copy those; I'm not sure YAFU has parameters pre-configured above C160s, but it might; if it does you don't need to choose your own. After that, two months of 24/7 running on a desktop (or AWS, if you can figure out how to configure an instance/etc) and you're good!
2019-02-13, 20:15   #13
GP2

Sep 2003

257810 Posts

Quote:
 Originally Posted by CRGreathouse There's a Factoring as a Service project which might help, but I don't know how practical it is at the moment. (I'd love to hear.)
This was last updated three and a half years ago, so I wonder if it isn't outdated.

For instance, maybe you might want to use AWS Batch instead of Slurm or whatever.

What's the crossover point where people give up on ECM and try NFS?

2019-02-13, 20:16   #14
CRGreathouse

Aug 2006

2·3·977 Posts

Quote:
 Originally Posted by VBCurtis Factor some small numbers to see how everything works, and to reduce the chance you make a mistake that adds 50% to factoring time.
I definitely second this. You want to factor a 100-digit number first, then a 105-digit number, then a 110-digit number, just to get a feel for how things work. There is a learning curve.

2019-02-13, 20:17   #15
GP2

Sep 2003

2·1,289 Posts

Quote:
 Originally Posted by Titteris I tried doing the factoring as a service thingy but it turns out Windows isn't supported. Are there any alternatives for this? Why is linux better in this case?
Linux is much cheaper on the cloud. If you want to run Windows instances, you have to pay the Microsoft tax.

If you do run it, make sure you use spot instances in the us-east-2 (Ohio) region, not us-east-1 or any others, which are more expensive.

2019-02-13, 20:20   #16
CRGreathouse

Aug 2006

16E616 Posts

Quote:
 Originally Posted by GP2 What's the crossover point where people give up on ECM and try NFS?
Somewhere around 30 digits you go to QS or MPSQ.

Somewhere around 40 or 45 digits you go to SIQS.

The SIQS-to-GNFS crossover point is around 95 digits. I've heard but never observed as low as 90 digits, and some people say as high as 105 digits (but I think that's outdated). Probably 95-100 digits is safe.

At all sizes except tiny you want to start with some ECM to strip out small factors unless you know the number to have none (e.g., a cryptocraphic semiprime).

 2019-02-13, 21:38 #17 danaj   "Dana Jacobsen" Feb 2011 Bangkok, TH 2·11·41 Posts I'd recommend How to get started with factoring on this forum. Lots of questions answered, lots of links.
2019-02-13, 22:27   #18
xilman
Bamboozled!

May 2003
Down not across

235328 Posts

Quote:
 Originally Posted by Titteris Is there any chance you know of somebody that would be able to provide such services? I’m talking about the 300 CPU cores and doing it on a linux boxes. I appreciate your help, thanks a lot.
How much would you pay me to do it for you?

It's a serious question and there are folks around here who can vouch for my > 25 years experience of factoring hard integers.

 2019-02-13, 22:44 #19 Titteris   Feb 2019 23 Posts Haha man, no clue. I'm pretty low-budget. I would say up to 100$but that means nothing considering that I have no clue how much these things cost in the first place. How much would you want? Keep in mind you're doing it for a good cause ^^ Last fiddled with by Titteris on 2019-02-13 at 22:48 2019-02-13, 22:53 #20 chalsall If I May "Chris Halsall" Sep 2002 Barbados 22×5×11×41 Posts Quote:  Originally Posted by Titteris Keep in mind you're doing it for a good cause. The "good cause" has not yet been defined. Is it you completing a paper due shortly, or unlocking a ransom-ware attack? 2019-02-13, 22:57 #21 Titteris Feb 2019 23 Posts Quote:  Originally Posted by chalsall The "good cause" has not yet been defined. Is it you completing a paper due shortly, or unlocking a ransom-ware attack? Neither this nor that. I was given it as a challenge and if I do it I can skip a long assigment ^^. The thing is, with the skills that we have it is veeeeery hard to do it, less than 4 people out of a thousand do it every year. And it was stated that we can use any method we like. Trust me, I tried the virtual box stuff and factorizing as a service, but I think I'm way above my head. The only good takeaway is that I learned a lot of stuff.  2019-02-13, 23:02 #22 Batalov "Serge" Mar 2008 Phi(3,3^1118781+1)/3 905510 Posts A number like this is more expensive - even without labor costs. A good estimate that you can get workable spot instances at AWS for ~$0.01 per virtual-core-hour. That's ~$0.02 per real core. 300 cores is already$6/hr, $144/day but you will need to fund quite a few days of that activity. So you can see that you are off by an order of magnitude at least already. Babysitting spot instances will requite some labor, and$50/hr for a junior professional is a steal (I'd bet most people are more expensive). Instead you can get normal instances at ~\$0.05/core-hr.

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