mfaktc: a CUDA program for Mersenne prefactoring - Page 189

Uncwilly · 2013-01-10, 00:58

Quote:

Originally Posted by LaurV

Time to make Uncwilly happy...

I noticed some significant effort mystically showing up on some exponents in the last day or so.

kracker · 2013-01-10, 01:05

Quote:

Originally Posted by Uncwilly

I noticed some significant effort mystically showing up on some exponents in the last day or so.

lycorn · 2013-01-10, 11:10

Quote:

Originally Posted by James Heinrich

GPU sieving is not enabled below 2⁶⁴. Not only that, but it uses older, less-optimized kernels that are inherently slower.

OK, that explains part of the problem (most of it, actually). Also, I was running the 32-bit version, as I was expecting the sieve to be run on the GPU. The SievePrimesMin parameter was at the default 5000.
Running the 64-bit app, and setting the sievePrimes to 2000 provided the same throughput as 0.19, as expected. The GHz-d/d were roughly half of what is obtained when testing mainstream exponents.
That said, I don´t think I´ll be testing small exponents anymore (at least until some new version pops up).

ixfd64 · 2013-01-10, 17:27

I have two more suggestions for the documentation:

1. For people who aren't familiar with console applications, it would be useful for them to know that pressing Ctrl-C terminates the program smoothly.
2. I'm surprised there is no mention of GPU to 72.

chalsall · 2013-01-10, 18:01

Quote:

Originally Posted by ixfd64

2. I'm surprised there is no mention of GPU to 72.

Oliver asked me to provide some language. Unfortunately something came up which took my mind off the deliverable in time. Next release.

swl551 · 2013-01-11, 04:42

GTX 570 and 0.19 I could run 4 instances on one card clock at 1000mv, 900mhz core. Average combined throughput was 480 ghz per day. Never crashed...

020 has forced drop down to 988mv (default) and 845mhz core to stay reliable. Reducing throughput to only 420 ghz per day. Confirmed on 3 different 570s on different PCs. The oddest thing is that after mfaktc crashes the GPU core clock will NOT go over 405mhz regardless of what I do with afterBurner. I have to reboot to allow the card to return to factory clock speed. This is a condition I have never seen before (below factory clocks)

I recognize all the benefits of 0.20 so this is not a 0.20 vs 0.19. The question is specifically why is 0.20 showing instability where 0.19 did not.

thanks

Scott

Dubslow · 2013-01-11, 04:48

Quote:

Originally Posted by swl551

The question is specifically why is 0.20 showing instability where 0.19 did not.

Possibly simply because the GPU is under more stress now. Depending on the CPU behind those 4 instances, that might not have been enough to truly saturate the card, where now 0.20 can do that thanks to the GPU sieving. What's the Eq. GHz with 0.20 at factory clock, vs. the Eq. GHz with 0.19 at factory clock/4 instances?

LaurV · 2013-01-11, 05:32

Plus one for what Dubslow says. Same story as for P95 SSE versus P95 AVX, the older one could stand tremendous overclocks (over 4.5G for i7-2600k) but for the last AVX versions, which use the CPU better and squeeze it harder, producing a lot more heat, even with my water cooling racks, I had to reduce the clock to get stable results.

ixfd64 · 2013-01-11, 05:33

As I mentioned earlier, mfaktc 0.20 is about three times as fast as 0.19 on my GTX 555. Jobs that previously took 100 minutes to complete now finish in just a little over half an hour. But even more surprising is that the average rate skyrocketed from 100M/s to around 933M/s.

I know the number of candidates per second doesn't matter, but the figures I'm getting are quite... shocking. Is this normal?

LaurV · 2013-01-11, 05:38

Quote:

Originally Posted by ixfd64

Is this normal?

Definitively yes. But take the enthusiasm with a grain of salt, see my post #2057.

TheJudger · 2013-01-11, 10:29

Hi,

Quote:

Originally Posted by ixfd64

As I mentioned earlier, mfaktc 0.20 is about three times as fast as 0.19 on my GTX 555. Jobs that previously took 100 minutes to complete now finish in just a little over half an hour. But even more surprising is that the average rate skyrocketed from 100M/s to around 933M/s.

I know the number of candidates per second doesn't matter, but the figures I'm getting are quite... shocking. Is this normal?

so you manage the edit the mfaktc.ini but did you read it?

Code:

# Keep in mind that "number of candidates (M/G)" and "rate (M/s)" are NOT
# compareable between CPU- and GPU-sieving. When sieving is done on GPU
# those number count all factor candidates prior to sieving while CPU
# sieving counts the numbers after the sieving process.
#

2013-01-10, 17:27	#2072
ixfd64 Bemusing Prompter "Danny" Dec 2002 California 5·479 Posts	I have two more suggestions for the documentation: 1. For people who aren't familiar with console applications, it would be useful for them to know that pressing Ctrl-C terminates the program smoothly. 2. I'm surprised there is no mention of GPU to 72. Last fiddled with by ixfd64 on 2013-01-10 at 17:27

2013-01-11, 04:42	#2074
swl551 Aug 2012 New Hampshire 2³×101 Posts	0.20 unstable at gpu/OC levels that were fine with 0.19 GTX 570 and 0.19 I could run 4 instances on one card clock at 1000mv, 900mhz core. Average combined throughput was 480 ghz per day. Never crashed... 020 has forced drop down to 988mv (default) and 845mhz core to stay reliable. Reducing throughput to only 420 ghz per day. Confirmed on 3 different 570s on different PCs. The oddest thing is that after mfaktc crashes the GPU core clock will NOT go over 405mhz regardless of what I do with afterBurner. I have to reboot to allow the card to return to factory clock speed. This is a condition I have never seen before (below factory clocks) I recognize all the benefits of 0.20 so this is not a 0.20 vs 0.19. The question is specifically why is 0.20 showing instability where 0.19 did not. thanks Scott

2013-01-11, 05:32	#2076
LaurV Romulan Interpreter Jun 2011 Thailand 7²·197 Posts	Plus one for what Dubslow says. Same story as for P95 SSE versus P95 AVX, the older one could stand tremendous overclocks (over 4.5G for i7-2600k) but for the last AVX versions, which use the CPU better and squeeze it harder, producing a lot more heat, even with my water cooling racks, I had to reduce the clock to get stable results. Last fiddled with by LaurV on 2013-01-11 at 05:35

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2013-01-11, 05:33	#2077
ixfd64 Bemusing Prompter "Danny" Dec 2002 California 5·479 Posts	As I mentioned earlier, mfaktc 0.20 is about three times as fast as 0.19 on my GTX 555. Jobs that previously took 100 minutes to complete now finish in just a little over half an hour. But even more surprising is that the average rate skyrocketed from 100M/s to around 933M/s. I know the number of candidates per second doesn't matter, but the figures I'm getting are quite... shocking. Is this normal?