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Old 2016-09-04, 18:50   #1
mattmill30
 
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Default correlation between GPU utilisation and TF bit-range

Is anyone able to comprehensively explain to a level from which a calculation can be produced, the correlation between TF exponent size and bit-range (and process/sieve size?) against GPU saturation, in order to determine the performance limit of a GPU based upon it's published specs?

Would the focus be completion of classes at a certain rate for the transition overhead to allow graphical tasks to be undertaken in a timely fashion?

It would be useful to know the impact of different bit-ranges on the responsiveness of the hardware, so distribution of TF work can be intelligently assigned for utilisation of unused GPU power. e.g. Workstations.
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Old 2016-09-05, 06:20   #2
LaurV
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Last versions(s) of mfaktx should occupy the GPU 100% when gpu-sieving is used, regardless of bit level and/or exponent, the only exceptions being the "extreme" cases, but those cases are also avoidable, either using the less-classes (420 classes) versions in one side of the chart, or launching multiple instances of mfaktx in the other side of the chart (or both).

The older versions or "extreme versions" of mfaktc (like TFing very small exponents, or the versions modified to sieve higher than 2p+1) which do CPU sieving only will only occupy as much from the GPU as the CPU is able to sieve. I remember that a 4-core CPU (i7-2600k) was not able to saturate two gtx580 cards more than 70% or so, the bottleneck being the CPU-sieving, when I was trying to TF exponents from 2k to 100k (in the ECM area).

James' tables are quite accurate approximations of the performance, for most cards there (exceptions are few "rare" cards with only few benchmarks).

Last fiddled with by LaurV on 2016-09-05 at 06:26
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Old 2016-09-05, 13:00   #3
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For what it's worth, I've not found any configuration for acceptable desktop performance while using GPU sieving under Linux.
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Old 2016-09-06, 01:36   #4
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Quote:
Originally Posted by Mark Rose View Post
for acceptable desktop performance
What do you mean by that? Is the desktop not enough performant when you use mfaktx, like it is not responsive, it has lag, etc., or you talk about mfaktx performance itself, like the cards are not 100% occupied, and the output of TF is slow?
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Old 2016-09-06, 01:45   #5
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Quote:
Originally Posted by LaurV View Post
What do you mean by that? Is the desktop not enough performant when you use mfaktx, like it is not responsive, it has lag, etc., or you talk about mfaktx performance itself, like the cards are not 100% occupied, and the output of TF is slow?
The desktop becomes very laggy, from moving the mouse to scrolling. mfaktc performance is fine.
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Old 2016-09-06, 05:14   #6
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Oh, I got it, I was reading the OP's post totally wrong. I thought he has problems with the output, like he can't get the mfaktx to occupy the card 100% or the output is low. In fact, the problem is that the computer is not responsive. I can't help that under linux. On windoze, playing with the parameters in the ini file may slow mfaktc up to a level where it is not "sensed" by the normal graphic tasks, like playing a movie, or do some cad modeling. I usually don't play animation-intensive games. There is a discussion/tutorial here around, and even some batch files to launch mfaktc in different "hurry" modes.
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Old 2016-10-02, 17:20   #7
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Quote:
Originally Posted by mattmill30 View Post
Is anyone able to comprehensively explain to a level from which a calculation can be produced, the correlation between TF exponent size and bit-range (and process/sieve size?) against GPU saturation, in order to determine the performance limit of a GPU based upon it's published specs?

Would the focus be completion of classes at a certain rate for the transition overhead to allow graphical tasks to be undertaken in a timely fashion?

It would be useful to know the impact of different bit-ranges on the responsiveness of the hardware, so distribution of TF work can be intelligently assigned for utilisation of unused GPU power. e.g. Workstations.
Whilst this won't amount to my original request for a formula, would it be pseudomathmatically valid to ascertain the limit of efficiency for a particular piece of hardware by plotting a graph for each tf level of an exponent on a single piece of hardware, and concluding the efficiency limit where a spike in bit-level/time curve occurs?

Would it also be necessary to create a number of graphs against exponents of disproportionate sizes?

Last fiddled with by mattmill30 on 2016-10-02 at 17:20
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Old 2016-10-03, 14:05   #8
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Quote:
Originally Posted by mattmill30 View Post
Would it also be necessary to create a number of graphs against exponents of disproportionate sizes?
James H has graphs like that on his website.
Here is a link to one: http://www.mersenne.ca/cudalucas.php?model=490
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