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Message 6298 - Posted: 19 Apr 2020, 17:10:42 UTC

There is now new work from mersenne.org started from 72-73 bit range. All necessarily changes were made.

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Message 6303 - Posted: 19 Apr 2020, 17:50:19 UTC

max GPU WUs in progress are 20 now.

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Message 6328 - Posted: 21 Apr 2020, 5:32:07 UTC

If you have a cc_config and app_config running with the old GPU72 before the name changed pls rename the data to TF to avoid any problems.

[AF>Amis des Lapins] Jean-Luc
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Message 6360 - Posted: 28 Apr 2020, 17:09:43 UTC

For GPU72, it was not recommended to compute two WUs together on two GPUs installed on the same computer.

Is this still the case for TN ?
Or can I run TN calculations on each of my two GPUs on the same computer ?

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Message 6361 - Posted: 28 Apr 2020, 17:17:55 UTC - in response to Message 6360.

For GPU72, it was not recommended to compute two WUs together on two GPUs installed on the same computer.

Is this still the case for TN ?
Or can I run TN calculations on each of my two GPUs on the same computer ?


Its the same, there was only a name change. Maybe in the future after some changes on the program code we could use both.

[AF>Amis des Lapins] Jean-Luc
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Message 6363 - Posted: 28 Apr 2020, 19:12:07 UTC - in response to Message 6361.

OK !
Thank you for your answer.

I'm finishing some WUs from another BOINC project and tomorrow, I start calculations with a RTX 2080 Ti.
I tried to calculate some TN WUs today.
The calculation time of a WU is 22-23 seconds.
That will make a very large number of WUs per day.
I had never seen such a short calculation time for a WU for GPU on BOINC before !

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Message 6364 - Posted: 28 Apr 2020, 19:14:04 UTC - in response to Message 6363.

OK !
Thank you for your answer.

I'm finishing some WUs from another BOINC project and tomorrow, I start calculations with a RTX 2080 Ti.
I tried to calculate some TN WUs today.
The calculation time of a WU is 22-23 seconds.
That will make a very large number of WUs per day.
I had never seen such a short calculation time for a WU for GPU on BOINC before !


will be harder, check FAQ, if we have done this range the next has double runtime but for your 2080 its only a snack :)

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Message 6366 - Posted: 28 Apr 2020, 20:37:34 UTC - in response to Message 6363.

The calculation time of a WU is 22-23 seconds.


You have seen nothing yet :)

What takes you 22-23 seconds now, will take you at n=460M ~11.5 seconds and as we for bit 70 to 71, exhaust the candidates remaining at n~800M, you will litterally see a workunit complete in just 5 seconds.

When we go to bit 71 to 72, your RTX 2080 will start at ~80 sec per candidate and that will then at each doubling of n, cut in half. The reduction in runtime, will smoothly manifest itself, compared to what it were when you started crunching at certain bit level.

Example given for a test at n=125M running 80 seconds for bit 71 to 72, then the testing time will be approximately scaling to the following values:

n=250M testingtime is 40 seconds
n=500M testingtime is 20 seconds
n=1000M testingtime is 10 seconds

If the testingtimes is as follows per 71 to 72 bit, then you will more or less have these runtimes at these levels:

72 to 73 bit (n=250M=80 seconds) (n=500M=40 seconds) (n=1000M=20 seconds)
73 to 74 bit (n=250M=160 seconds) (n=500M=80 seconds) (n=1000M=40 seconds)
74 to 75 bit (n=250M=320 seconds) (n=500M=160 seconds) (n=1000M=80 seconds)
75 to 76 bit (n=250M=640 seconds) (n=500M=320 seconds) (n=1000M=160 seconds)
76 to 77 bit (n=250M=1280 seconds) (n=500M=640 seconds) (n=1000M=320 seconds)
...

It is only possible to scale, once you know the testtime at a given bitlevel, since the higher the bit level, dependant of your hardware, there is a slowdown in productivity :)

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Message 6369 - Posted: 29 Apr 2020, 8:07:24 UTC - in response to Message 6366.

OK, thanks for the detailed explanations !
I'll get right down to the calculations.

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Message 6373 - Posted: 8 May 2020, 17:00:49 UTC

Can we know if we have found prime factors and if so, how many ?

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Message 6374 - Posted: 8 May 2020, 17:21:09 UTC

You can find here number of attempts against successes.

https://www.mersenne.org/report_top_500_tf/

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Message 6375 - Posted: 8 May 2020, 18:05:50 UTC - in response to Message 6374.

All right, thank you !

I assume the number in the "Successes" column is the number of trivial factors found by each person ?

But if we calculate with SRBase on BOINC, can't we see our name separated from all the others, with "Attempts" and "successes" columns ?

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Message 6376 - Posted: 8 May 2020, 18:13:00 UTC - in response to Message 6375.

All right, thank you !

I assume the number in the "Successes" column is the number of trivial factors found by each person ?

But if we calculate with SRBase on BOINC, can't we see our name separated from all the others, with "Attempts" and "successes" columns ?


No, individually only with Primenet.

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Message 6377 - Posted: 8 May 2020, 20:54:46 UTC - in response to Message 6376.

Thank you for your answer !

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Message 6379 - Posted: 9 May 2020, 8:56:07 UTC - in response to Message 6377.

Thank you for your answer !


Even though it is not possible to tell who found a factor and what factor was found, then to give you an idea how much you have contributed, the equation looks like this:

Percentage of tasks resulting in a factor found result: ~1.436 %

You have currently 9,502 valid tasks. 136 of those, using statistical average, have found a factor. In other words, your contribution has saved on an i5-4670 more than 204 realtime (816 CPU) months of first time primality computation - so keep up the good work, as you can see your work is very valuable :)

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Message 6382 - Posted: 9 May 2020, 13:21:52 UTC - in response to Message 6379.

Thank you very much for these valuable explanations.
My understanding is getting better and better and I will almost be able to answer all the questions about TF for SRBase on the Alliance francophone forum.

I still have one last question, if it's not too complicated to answer here:
I don't understand why the task calculation time is shorter for larger exponents?
For example:
n=250M testingtime is 40 seconds
n=500M testingtime is 20 seconds
n=1000M testingtime is 10 seconds

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Message 6383 - Posted: 9 May 2020, 14:57:37 UTC - in response to Message 6382.
Last modified: 9 May 2020, 15:04:02 UTC

Thank you very much for these valuable explanations.
My understanding is getting better and better and I will almost be able to answer all the questions about TF for SRBase on the Alliance francophone forum.

I still have one last question, if it's not too complicated to answer here:
I don't understand why the task calculation time is shorter for larger exponents?
For example:
n=250M testingtime is 40 seconds
n=500M testingtime is 20 seconds
n=1000M testingtime is 10 seconds


Great question :)

A factor for a Mersenne candidate is always defined this way: 2 x k x prime_exponent_n + 1 (that is important to remember in the explanation below)

Let's answer you question, with 70 bit to 71 bit arithmetics:

at n=250M kmin=2,361,183,241,434 and kmax=4,722,366,482,869 (2,361,183,241,434 k to sieve or test for factor)
at n=500M kmin=1,180,591,620,717 and kmax=2,361,183,241,434 (1,180,591,620,717 k to sieve or test for factor)
at n=1000M kmin=590,295,810,358 and kmax=1,180,591,620,717 (590,295,810,358 k to sieve or test for factor)

So as you can see above, the higher n get's the shorter the range of possible factor candidates for the bit level becomes. Therefor it is almost certain, that the previous candidate you tried to factor, will take longer than the current candidate you try to factor.

One nice feature is that the expectancy level of the amount of candidates being factored, remains the same, despite having fewer pairs to test - so with less work you remove the same percentage of candidates and elimintates them from further testing :)

Hope this helped :)

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Message 6384 - Posted: 9 May 2020, 20:12:21 UTC - in response to Message 6383.

Thank you very much, I understand much better !
Now I can even calculate myself the kmin and kmax depending on the exponent n and the number of bits...
I have no more questions !

For your information: in 8-9 days, my RTX 2080 Ti calculated about 30,000 tasks (so I discovered 430 factors !) and the calculation time of a task went from 23-24 seconds to 20-21 for 70-71 bits !

I hope I will soon be able to do the calculations with both GPUs together !

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Message 6385 - Posted: 10 May 2020, 7:08:06 UTC - in response to Message 6384.

I hope I will soon be able to do the calculations with both GPUs together !


I sure hope so. What comforts me is that great minds are working on this. Yesterday I did my own TF work on a noisy ancient GPU using mfakto. It was sure nice to see that the progress bar worked as supposed to :)

A big thank you to all those of you who have taken up the challenge of modernizing and getting mfakt(o)(c) to work flawlessly on BOINC, both at single aswell (eventually) multi GPU systems.

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Message 6565 - Posted: 7 Jun 2020, 15:51:02 UTC - in response to Message 6384.

For your information: in 8-9 days, my RTX 2080 Ti calculated about 30,000 tasks (so I discovered 430 factors !) and the calculation time of a task went from 23-24 seconds to 20-21 for 70-71 bits !


Where do you find your discovered factors?

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