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 2006-03-29, 18:24 #34 VJS     Dec 2004 29910 Posts Agreed, I did not mean to imply that increasing b2 bounds by 40% will increase your chances of finding a factor by 40% that's certain. What I did want to say is that "increasing the B2 bounds by 40% will increase the time for that curve by roughly 40%". It just wasn't a fair comparision between the two versions with different bounds. I'm uncertain why the beta client uses larger bounds by default although I'm glad to see it doing so. I've always ran a large B2 since stage2 seems to run significantly faster than the old days of B2=100xB1, especially on dual channel boards with sufficient memory. If both clients are running the same speeds with the same bounds I'm uncertain about the improvments. Not being harsh here or anything I just havn't followed the discussion. Last fiddled with by VJS on 2006-03-29 at 18:25
2006-03-29, 22:00   #35
Mystwalker

Jul 2004
Potsdam, Germany

3·277 Posts

Quote:
 Originally Posted by Phil MjX the --enable-asm-redc works for "smaller" numbers (<180 digits ?? the bigger ones being squarred with another method in gmp-ecm) that's why you won't see no effect with such a "large c205 number", try a bench with the c126 I have provided (currently ggnfs'ing)...
Actually, we don't see no effect - we see worse timings for the P4 once --enable-asm-redc is activated.

But it's true that different composites prefer different gmp-ecm variants. Yesterday, I tested the M1071.C205 with my Pentium-M.

Result:
Stage1: 6.1 --enable-asm-redc was fastest, then 6.0.1, then 6.1 - but they differ by 1.5% from first to last.
Stage2: 6.1 (both) are ~15% faster than 6.0.1

But then I put them on 55459*2^1666+1 (507 digits). Here, gmp-ecm 6.0.1 (with gmp4.2) was fastest for stage2 - by ~20%!

Seems like we either find a good way to determine which variant is the best for certain numbers, or we have to benchmark once we start ECM work on a "new" composite. I'll soon test the gwnum variant. And it really gets interesting once someone plays around with "tune".

2006-03-29, 22:05   #36
Mystwalker

Jul 2004
Potsdam, Germany

3·277 Posts

Quote:
 Originally Posted by Prime95 Have you tried the use gwnum option? GPL compatible libraries are available at ftp://mersenne.org/gimps
I just wanted to try, but sadly, I found no way doing so. gmp-ecm's help didn't give me a hint, neither did the configure's help. Did I miss something?

2006-03-30, 17:30   #37
Phil MjX

Sep 2004

5×37 Posts

Quote:
 Originally Posted by Mystwalker But it's true that different composites prefer different gmp-ecm variants.
Clearly, for smaller numbers (gnfs candidates for example), v6.1.beta2 is a good choice with my pentium-m.
For larger numbers, I do agree with you that the improvement isn't so spectacular (but we have tested only two composites with a single B1=3e6 and I am sure that the developpers have reasons for their choices)!!

Let's wait for the final gmp-ecm 6.1 release .
Philippe.

 2006-03-30, 18:56 #38 Andi47     Oct 2004 Austria 1001101100102 Posts A few curves on M1061 (time in milliseconds) at B1=110M Code:  P95, B2=default | GMP-ECM (4.2/6.0.1), B2=100*B1 Kurve Step 1 Step 2 |Step 1 Step 2 1 1571005 194096 |3223343 98944 2 1570854 194047 |3248428 98974 3 1570851 193983 |3229012 99322 ----------------------------------------- average 1570903 194042 | 3233594 99080 Edit: I will do some curves with B2=4290M with GMP-ECM tomorrow. Last fiddled with by Andi47 on 2006-03-30 at 19:00
2006-03-31, 04:30   #39
akruppa

"Nancy"
Aug 2002
Alexandria

2,467 Posts

Quote:
 Originally Posted by Mystwalker I just wanted to try, but sadly, I found no way doing so. gmp-ecm's help didn't give me a hint, neither did the configure's help. Did I miss something?
Say "--with-gwnum=<directory where GWNUM library is>" at configure time. Please let me know how it works.

Thanks,
Alex

 2006-03-31, 14:46 #40 Andi47     Oct 2004 Austria 2·17·73 Posts Code: GMP-ECM 6.0.1 [powered by GMP 4.2] [ECM] Input number is 2^1061-1 (320 digits) Using B1=110000000, B2=4290000000, polynomial Dickson(6), sigma=4229074309 Step 1 took 3224970ms Step 2 took 48658ms Run 2 out of 25: Using B1=110000000, B2=4290000000, polynomial Dickson(6), sigma=4059283320 Step 1 took 3233083ms Step 2 took 48797ms Run 3 out of 25: Using B1=110000000, B2=4290000000, polynomial Dickson(6), sigma=3225355689 Step 1 took 3256811ms Step 2 took 48855ms I interrupted the run after 10 completed curves.
2006-03-31, 16:08   #41
R.D. Silverman

"Bob Silverman"
Nov 2003
North of Boston

750610 Posts

Quote:
 Originally Posted by Andreas Schinde Code: GMP-ECM 6.0.1 [powered by GMP 4.2] [ECM] Input number is 2^1061-1 (320 digits) Using B1=110000000, B2=4290000000, polynomial Dickson(6), sigma=4229074309 Step 1 took 3224970ms Step 2 took 48658ms Run 2 out of 25: Using B1=110000000, B2=4290000000, polynomial Dickson(6), sigma=4059283320 Step 1 took 3233083ms Step 2 took 48797ms Run 3 out of 25: Using B1=110000000, B2=4290000000, polynomial Dickson(6), sigma=3225355689 Step 1 took 3256811ms Step 2 took 48855ms I interrupted the run after 10 completed curves.

I would suggest using larger step 2 limits. It is optimal to spend the
same amount of time in step 1 and step 2. This is independent of the
speed of the computer.

2006-03-31, 17:07   #42
PBMcL

Jan 2005

2×31 Posts

Quote:
 Originally Posted by R.D. Silverman I would suggest using larger step 2 limits. It is optimal to spend the same amount of time in step 1 and step 2. This is independent of the speed of the computer.
Bob, this may be true on a one processor machine, but the disparity in memory requirements between step 1 and step 2 has led me to a different strategy for multi-processor machines in the case where step 2 is going to use most of the available RAM. Given, say, a four processor box I choose B1 and B2 so that step 2 takes just less than a quarter of the total (step 1 plus step 2) time (which may require some test curves), then I stagger start 4 copies of ECM so that only one copy at a time is in step 2. Otherwise the machine spends huge amounts of time swapping pages to/from the disk.

2006-03-31, 20:51   #43
akruppa

"Nancy"
Aug 2002
Alexandria

46438 Posts

Quote:
 Originally Posted by R.D. Silverman I would suggest using larger step 2 limits. It is optimal to spend the same amount of time in step 1 and step 2. This is independent of the speed of the computer.
Is this correct for FFT stage 2 implementations?

Alex

2006-03-31, 22:10   #44
Andi47

Oct 2004
Austria

9B216 Posts

Quote:
 Originally Posted by R.D. Silverman I would suggest using larger step 2 limits. It is optimal to spend the same amount of time in step 1 and step 2. This is independent of the speed of the computer.
This was just for benchmarking - to compare Prime95 with GMP 4.2/ECM6.0.1 at the same B1 and B2 bounds.

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