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2022-08-09, 17:40   #100
swellman

Jun 2012

23·3·151 Posts

Quote:
 Originally Posted by storm5510 I have tried to use -nc2 as a new job start previously, but it looks for a non-existing polynomial file. I am not sure how far -np goes beyond the polynomial selection. -ncr will resume using a checkpoint file, but what creates it? I specify the GPU with -g 0. I seem to remember reading this is required to use a GPU. If not specified, the default is the CPU. I was not aware multiple switches could be used together. I have used 6 threads without issue running Yafu.
You need one file in you msieve directory to generate a polynomial:

Code:
worktodo.ini
The worktodo.ini file contains only the number being factored in decimal notation.

You can then generate a GNFS polynomial using the -np flag, often in conjunction with other flags (like -g 0) for a more efficient search. But the area of poly search is too complex for a single post. Let’s say you generate a polynomial, or build one for SNFS using some of the classic methods or Yafu. Msieve places this polynomial in a file called

Code:
msieve.fb
Or you can create your SNFS poly in msieve.fb format. Look at past examples.

Now just invoke msieve with the command

Code:
./msieve -v -nc target_density=120 -t 8
Where specifying the target density can help build a tighter matrix which msieve can solve faster than a matrix built with the default of TD of 70 or 90, depending on the vintage of your version of msieve.

This will eventually spit out all factors of your number.

If msieve stops, you can restart it with the -ncr flag.

-nc1 starts filtering phase
-nc2 starts linear algebra phase
-nc3 starts square root phase

So if LA fails, you can restart it with the -ncr and -nc3 flags, thus telling msieve to finish LA and continue through square root and grind out the factors.

Last fiddled with by swellman on 2022-08-09 at 17:41

 2022-08-09, 17:49 #101 EdH     "Ed Hall" Dec 2009 Adirondack Mtns 13·192 Posts There are several steps, all with their own files that need to be done in order to make it through. One of the first steps is to find a "good" polynomial (technically, a pair). This polynomial is necessary for the rest of the steps and is located in a file commonly named msieve.fb. Although Msieve can do sieving, for anything larger than a few digits, an external program is used. This program needs the polynomial and creates a file of relations, commonly named msieve.dat. These relations are then filtered (-nc1) and more files are created. Then the stage where the GPU is used can be run (-nc2) and a checkpoint file is created, which can be used for a restart (-ncr). Depending what files you already have, you can choose where to start/continue. All of this can be found in the Readme.nfs documentation supplied in the same folder as msieve. Note: I see swellman has posted as well, but I'll let this one stand as is. It shouldn't conflict.
2022-08-09, 18:56   #102
storm5510
Random Account

Aug 2009
Not U. + S.A.

2×1,123 Posts

Some were interested in my number. 128 digits, a.k.a. C128.

Code:
99183446604001940389822905615521048138949828629950976062436205758607664727160159612467952971325033872947039325281585706220344353
Code:
./msieve -v -g 0 -np
This produces a lot of lines beginning with "crap." The meaning is obvious. A few others say "coeff" or "save" at the front. This was the area I wanted to be able to resume.

Quote:
 Originally Posted by EdH There are several steps, all with their own files that need to be done in order to make it through. One of the first steps is to find a "good" polynomial (technically, a pair). This polynomial is necessary for the rest of the steps and is located in a file commonly named msieve.fb. Although Msieve can do sieving, for anything larger than a few digits, an external program is used. This program needs the polynomial and creates a file of relations, commonly named msieve.dat. These relations are then filtered (-nc1) and more files are created. Then the stage where the GPU is used can be run (-nc2) and a checkpoint file is created, which can be used for a restart (-ncr). Depending what files you already have, you can choose where to start/continue.
I had a pretty good idea this was done is multiple steps just by looking at the switches.

I paragraphed your text above to make it easier to follow.

BTW, I see mentions of "LA." Beyond the obvious, what is this?

 2022-08-09, 19:17 #103 swellman     Jun 2012 362410 Posts LA = linear algebra TD = target_density

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