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Old 2009-01-13, 21:48   #12
gd_barnes
 
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Quote:
Originally Posted by Flatlander View Post
In a moment of madness, I sieved 93 ks between 3001 and 3199, n from 400k to 500k. If I actually start testing them I'll let you know. lol

Great. Thanks for letting us know. Feel free to coordinate sieving with various folks here if you think someone might be interested.
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Old 2009-02-07, 23:46   #13
Flatlander
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Quote:
Originally Posted by Flatlander View Post
In a moment of madness, I sieved 93 ks between 3001 and 3199, n from 400k to 500k. If I actually start testing them I'll let you know. lol
I've started.
http://mersenneforum.org/showpost.ph...7&postcount=12
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Old 2009-02-08, 04:19   #14
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I am working on 2931
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Old 2009-02-09, 18:26   #15
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Got a few K's reserved.
2927 through 2953.

What is the fastest way to sieve, i used NewPGen in the past.
going up to 2T would take forever with that program though.
Do we have to sieve to 2T ?
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Old 2009-02-09, 18:31   #16
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Quote:
Originally Posted by PCZ View Post
Got a few K's reserved.
2927 through 2953.

What is the fastest way to sieve, i used NewPGen in the past.
going up to 2T would take forever with that program though.
Do we have to sieve to 2T ?
The fastest program to use would be srsieve up until about p=0.5G, and then sr2sieve from there on up to optimal sieve depth. As for how high you'll have to sieve, that depends on what n-range you're doing.

srsieve and sr2sieve can be downloaded at http://www.geocities.com/g_w_reynolds/. Once you download and extract them you can run them each with the -h option to see the various command line flags.

Feel free to drop me or Gary a line if you need help getting started with srsieve/sr2sieve.

Max

P.S.: If you're doing just one or two k's, then the most efficient way to sieve them is to start with srsieve as before, but then switch to sr1sieve instead of sr2sieve. sr1sieve can only run one k at a time, but is much faster than sr2sieve for one k. Thus, if you're doing <=2 k's, your best bet is to sieve them separately with sr1sieve, but if you're doing more than 2 then you should use sr2sieve.

The process for running sr1sieve is slightly different than that for sr2sieve; again, feel free to drop Gary or me a line if you need any help.

Last fiddled with by mdettweiler on 2009-02-09 at 18:32
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Old 2009-02-09, 20:03   #17
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Brian,

On another related note, starting in ~3 days, I'm going to need some help sieving k=1003-2000 for n=500K-1M; a total of 499 k's. I'll have sieved to P=1T and we need it sieved to P=~30T. If you have a quad or two that could help with that, that would be very helpful.

I may put the sieving up for public reservations but it will be somewhat low priority at this point because we'd like to push the 5th/6th/7th drives higher after the 8th drive has finished to n=500K. The smaller k=400-1001 LLR's faster than k=1400-2000 at the same n-range.

I mention this because we'll be using sr2sieve and there should be a lot of helpful tips in there on running it.


Gary
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Old 2009-02-09, 20:33   #18
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Gary
I should be able to help out with the sieving.

BTW
Sr2sieve isn't exactly user friendly :)
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Old 2009-02-10, 01:38   #19
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Quote:
Originally Posted by PCZ View Post
Gary
I should be able to help out with the sieving.

BTW
Sr2sieve isn't exactly user friendly :)

This is true but it is more user friendly then it used to be.

I have time to provide some instructions for sieving your range now. I'll assume that you want to sieve n=350K-1M.

1. Create a folder and copy the most recent versions of 64-bit srsieve, sr2sieve, and srfile into it.

2. In the folder in #1, create a file that has all of your forms in it. For upcoming instructions, I'll call the file "forms2927-2953.txt". It would just be a notepad/wordpad file with the following lines:
2927*2^n-1
2929*2^n-1
2931*2^n-1
2933*2^n-1
(etc.)

3. Do an initial sieve using srsieve. Go to the command prompt, navigate to your folder, and run srsieve with the following command:
srsieve -a -n 350e3 -N 1e6 -m 1e9 -P 500e6 forms2927-2953.txt
[If running Linux, put a "./" before the program name.]

-a tells it to write to an "ABCD" file (the kind that sr2sieve can read)
-n is the lower n-limit, i.e. n=350K
-N is the upper n-limit, i.e. n=1M
-m tells it to not display factors below 1G (1 billion) on the screen. (the display will slow down the program)
-P is how far you want it to initially sieve using srsieve. Anywhere between P=200e6 and 1e9 is good.

4. #3 will write out a file with some cryptic name. (It will tell you what it is.) Rename that to something meaningful. For reference in the upcoming instructions, I'll call it "sieve2927-2953.txt".

5. Run sr2sieve using sieve2927-2953.txt. At the command prompt, run the following command:
sr2sieve -P 5e12 -i sieve2927-2953.txt

-P is the max sieve depth, i.e. P=5T. (If you wanted to begin sieving at a different limit than what is shown on the 1st line of the file, i.e. if you were sieving on multiple cores, you would need to use the -p along with the -P commands.)
-i tells sr2sieve the input file name.

The sieving in #5 will not remove k/n pairs from the file. It writes out factors to a file called factors.txt instead.

6. Run srfile to remove the factors in #5 and write it to a file that can be understood by LLR. At the command prompt, run the following command:
srfile -G -k factors.txt sieve2927-2953.txt.

-G tells it to write out a file that is readable by LLR in n-value sequence.
-k means that the next file contains "known factors". To understand what these known factors are, take a look in that file. It should be pretty clear what they are.

7. #6 will write out a file with some cryptic name. Once again, it will tell you what it is. Rename it to something more meaningful.

8. (Optional) Change the sieve limit on line #1 in the file from #7 to your true sieve limit (in this case 5T or 5000000000000). Unfortunately neither sr2sieve nor srfile will change it even though you sieved to P=5T. It will still show 500000000 (500M), which was your sieve limit from when you ran srsieve in #3.

#8 is not technically necessary but I do it because you may want to sieve the file more in the future and you will likely find that you will forget where you stopped sieving.


Now...that is the easy instructions. I didn't get into computing optimum sieve depth. P=5T is not likely nearly high enough for a large range of n=350K-1M but is probably enough for n=350K-500K or 350K-600K. Also, I didn't get into splitting up the sr2sieve part amongst several cores, which you'll likely want to do, lest it take you many weeks to sieve. Nor did I get into sieving, breaking off the lower n-range, LLRing, then sieving the higher n-range some more, etc., which you'll want to do if your max n-limit is more than twice your min n-limit.

Once you've done the above a couple of times, it's super simple, I promise. At that point, the trickier part about optimum sieve depth and all that mumbo-jumbo won't seem too bad. I too thought it was hideously difficult and non-user friendly when I first ran sr2sieve, only to find out that it was quite easy once I did it a couple of times.

All of the programs come with a helpful README file. You can also get help on the various switches (commands) by typing srsieve -h (or sr2sieve -h or srfile -h) at the command prompt.

One final thing: Never use NewPGen again! (lol) It is WAY too slow for any kind of sieving job except for exotic forms such as twins, quadruplets, Sophie Germain's, etc. The sr(x)sieve suite of programs are many times faster.

Good luck!


Gary

Last fiddled with by gd_barnes on 2009-02-10 at 01:47
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Old 2009-02-10, 04:15   #20
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Thanks for that it has made things much clearer.

Yes i will want to split the sieving work over multiple cores.
Looks like i can vary the values of n and N in step 3 to split the work up.

srsieve -a -n 20e3 -N 350e3 -m 1e9 -P 500e6 forms2927-2953.txt (Not sure if i'll bother with this, do we need the data ?)
srsieve -a -n 350e3 -N 500e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 500e3 -N 600e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 600e3 -N 700e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 700e3 -N 800e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 800e3 -N 900e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 900e3 -N 1e6 -m 1e9 -P 500e6 forms2927-2953.txt

Does the above look right ?
Those pieces can then be sieved to different depths and LLR'd.

Is there a big speed advantage to 64bit ?
I don't mind going 64bit on the sieving boxes if there is a good speed gain.

Is it worth bothering with older AMD's, i have an X2 4800 doing nothing ?
Guessing the core2s sieve much faster so it wouldn't be any good these days.

Last fiddled with by PCZ on 2009-02-10 at 04:31
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Old 2009-02-10, 04:32   #21
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Quote:
Originally Posted by PCZ View Post
Thanks for that it has made things much clearer.

Yes i will want to split the sieving work over multiple cores.
Looks like i can vary the values of n and N in step 3 to split the work up.

Those pieces can then be sieved to different depths and LLR'd.

Is there a big speed advantage to 64bit ?
I don't mind going 64bit on the sieving boxes if there is a good speed gain.

Is it worth bothering with older AMD's, i have an X2 4800 doing nothing ?
Guessing the core2s sieve much faster so it wouldn't be any good these days.

No, don't split the work up by doing different n-ranges on different cores for the same k-values. That would be very inefficient. Efficiency is gained by sieving the entire k and n-range at once. Instead of splitting up the k or n-values, split up the P-values. For instance:

1. Use one core to sieve the entire k and n-range to P=500M using srsieve. That shouldn't take too long...probably < 1 hour.

2. Use multiple cores to sieve the entire k and n-range by doing P=500M-100G on one core, 100G-200G on core 2, 200G-300G on core 3, etc. using sr2sieve. (You can fine-tune this so that they complete at close to the same time but even if you don't, they'll still likely finish within a few hours to a day of each other. The lower P-ranges go slower because there are more possible prime factors.)

3. Assuming that you are using 4 cores, at this point, remove all of your factors from #2. Then (assuming you've removed all factors to P=400G) use sr2sieve and sieve P=400G-800G on core 1, sieve 800G-1200G (0.8T-1.2T) on core 2, etc.

I recommend this method because you'll get a speed-up in sieving by removing the smaller factors and then starting again with a smaller sieve file across all cores.

You'll get much deeper sieve depths in the same amount of time this way instead of splitting it up by k-value or n-range.

What n-range are you sieving and how many cores will you be using? If I know that, I can recommend (close to) the best sieving method.

Most AMD's sieve well. Go ahead and use your old ones if you want to mess with them. Run a test on the older and newer machines for a few mins. to see how fast they sieve. On your newer machines, make sure you have a 64-bit O.S. You'll get the fastest sieving that way.


Gary

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Old 2009-02-10, 04:42   #22
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Quote:
Originally Posted by PCZ View Post
Thanks for that it has made things much clearer.

Yes i will want to split the sieving work over multiple cores.
Looks like i can vary the values of n and N in step 3 to split the work up.

srsieve -a -n 20e3 -N 350e3 -m 1e9 -P 500e6 forms2927-2953.txt (Not sure if i'll bother with this, do we need the data ?)
srsieve -a -n 350e3 -N 500e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 500e3 -N 600e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 600e3 -N 700e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 700e3 -N 800e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 800e3 -N 900e3 -m 1e9 -P 500e6 forms2927-2953.txt
srsieve -a -n 900e3 -N 1e6 -m 1e9 -P 500e6 forms2927-2953.txt

I see you edited your post. Just a couple of more questions to answer that I didn't answer already:

What you suggested here would be correct if you split them up by n-range but no, I don't recommend doing it that way. See my prior post.

Unlike most projects, NPLB tries to leave no prime behind, not even the small ones. So yes, it is preferrable that you also run n=20K-350K, i.e. non-top-5000 ranges. Of course that is your choice. Karsten will reflect all primes, small and large at www.rieselprime.org.

Now that I know you will be sieving n=20K-1M, shoot me your number of cores, and I can give a more exact recommended sieving method. Since you're doing such a wide n-range, I can point you directly to an answer that I gave to MrOzzy on the CRUS project when he asked about the best way to sieve a different base for n=50K-250K. You'll definitely want to sieve the entire thing to a certain depth, break off the lower n-range, LLR it, sieve the rest to a certain depth, break off and LLR a lower n-range, and then do the same at least 2 more times for the remaining n-ranges.


Gary

Last fiddled with by gd_barnes on 2009-02-10 at 04:44
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