mfaktc: a CUDA program for Mersenne prefactoring - Page 199

TheJudger · 2013-01-24, 19:48

Hi,

OK, unless I've calculated something wrong here are the numbers.
As before the time for a single class for 2⁷⁰ to 2⁷¹ is T and it doubles for each bitlevel (ignoring that different kernels will be used):

2⁷⁰ to 2⁷⁴
StopAfterFactor=0: T_average = 14400 = (1 + 2 + 4 + 8) * 960
StopAfterFactor=2, Stages=0: T_average = ~14003.078
StopAfterFactor=2, Stages=1: T_average = ~13847.314

The difference is not that big but keep in mind that additionally the selected kernel can make a big difference. A really worse case: 2⁷⁸ to 2⁸⁰
With Stages=0 mfaktc will choose to slow 95bit kernel without GPU sieving support.
With Stages=1 mfaktc will choose barrett87 for each bitlevel including GPU sieving support.

Technically GPU sieving is possible for the older kernels... but why should somebody spent time on these old and slow kernels?
Barrett87,88 and 92 can only handle single bitlevels at the time
So usually Stages=1 is what you want!

Oliver

flashjh · 2013-01-24, 20:34

I've set Stages=1 (in light of the info above)

This is typical for my 580s in the 61M range:

Dubslow · 2013-01-24, 21:00

Quote:

Originally Posted by rjbelans

I'm running 0.20, but I did play with some settings in the .ini file and my CPU is at a constant 90% + usage because of the other things running. Once the current units are completed, after I get home from work tonight, I will try running with no other programs and I'll put the settings back to defaults.

CPU shouldn't affect it as much as LaurV says. I ran mfaktc with full CPU usage and no CPU usage, and noticed maybe a 1 Eq. GHz drop, from like 206 to 205. That doesn't explain your half-performance discrepancy.

Quote:

Originally Posted by Andi_HB

The GTX 560 Performance is listed with 205 GHz-days/day but this is only with the default settings.

I have decreased the GPUSieveProcessSize=8
and increased the GPUSieveSieveSize=128

This increased my GhzDays from 205 to 268 on the GTX 560 with mfaktc 0.20

:D

(Win 7, 64bit)

Brilliant! I, of course, had to reduce the sieve size down to its minimum as well, to keep screen lag minimal

(throughput was ~185 Eq. GHz at those settings).

ckdo · 2013-01-24, 21:03

Nice try redacting that exponent out. Too bad k_min and k_max are giving it away.

flashjh · 2013-01-24, 21:27

swl551 · 2013-01-24, 21:34

Is there a reason to keep exponents secret? Have there been attacks or malware built that targets TFers working certain ranges? Am I in danger?

chalsall · 2013-01-24, 21:39

Quote:

Originally Posted by swl551

Is there a reason to keep exponents secret? Have there been attacks or malware built that targets TFers working certain ranges? Am I in danger?

A very few people have found themselves the subject of targeted "poaching". Usually in the LLing domain, however.

Those doing serious TFing probably wouldn't even notice if they were poached. And if they did, probably wouldn't care all that much other than possibly wondering why.

rjbelans · 2013-01-24, 23:58

Quote:

Originally Posted by Dubslow

CPU shouldn't affect it as much as LaurV says. I ran mfaktc with full CPU usage and no CPU usage, and noticed maybe a 1 Eq. GHz drop, from like 206 to 205. That doesn't explain your half-performance discrepancy.

It was the settings in the .ini file. After I put everything back to defaults, each core is getting about 325 for a total of 1300GHz-d/day.

chalsall · 2013-01-25, 00:06

Quote:

Originally Posted by rjbelans

It was the settings in the .ini file. After I put everything back to defaults, each core is getting about 325 for a total of 1300GHz-d/day.

I assume you kept a copy of the .ini file which was causing you trouble?

LaurV · 2013-01-25, 02:25

Quote:

Originally Posted by Dubslow

CPU shouldn't affect it as much as LaurV says. I ran mfaktc with full CPU usage and no CPU usage, and noticed maybe a 1 Eq. GHz drop, from like 206 to 205.

Try decreasing the priority of mfaktc or increasing the priority of p95

till they have both the same chance to grab the CPU ticks. Of course if P95 works in iddle mode, mfaktc does not wait for it...
Edit: Disclaimer: don't do that at home!

rjbelans · 2013-01-25, 04:32

Quote:

Originally Posted by chalsall

I assume you kept a copy of the .ini file which was causing you trouble?

You shouldn't ass.u.me anything!

Essentially, I set the last few settings to their maximum number to see what it would do. I would suggest not doing that.

2013-01-24, 20:34	#2180
flashjh "Jerry" Nov 2011 Vancouver, WA 1,123 Posts	I've set Stages=1 (in light of the info above) This is typical for my 580s in the 61M range: Attached Thumbnails Last fiddled with by flashjh on 2013-01-24 at 20:40

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2013-01-24, 19:48	#2179
TheJudger "Oliver" Mar 2005 Germany 10001010111₂ Posts	Hi, OK, unless I've calculated something wrong here are the numbers. As before the time for a single class for 2⁷⁰ to 2⁷¹ is T and it doubles for each bitlevel (ignoring that different kernels will be used): 2⁷⁰ to 2⁷⁴ StopAfterFactor=0: T_average = 14400 = (1 + 2 + 4 + 8) * 960 StopAfterFactor=2, Stages=0: T_average = ~14003.078 StopAfterFactor=2, Stages=1: T_average = ~13847.314 The difference is not that big but keep in mind that additionally the selected kernel can make a big difference. A really worse case: 2⁷⁸ to 2⁸⁰ With Stages=0 mfaktc will choose to slow 95bit kernel without GPU sieving support. With Stages=1 mfaktc will choose barrett87 for each bitlevel including GPU sieving support. Technically GPU sieving is possible for the older kernels... but why should somebody spent time on these old and slow kernels? Barrett87,88 and 92 can only handle single bitlevels at the time So usually Stages=1 is what you want! Oliver

2013-01-24, 21:03	#2182
ckdo Dec 2007 Cleves, Germany 2×5×53 Posts	Nice try redacting that exponent out. Too bad k_min and k_max are giving it away.

2013-01-24, 21:27	#2183
flashjh "Jerry" Nov 2011 Vancouver, WA 1,123 Posts

2013-01-24, 21:34	#2184
swl551 Aug 2012 New Hampshire 2³·101 Posts	Is there a reason to keep exponents secret? Have there been attacks or malware built that targets TFers working certain ranges? Am I in danger?