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Old 2021-11-05, 09:56   #67
xilman's Avatar
May 2003
Down not across

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Originally Posted by charybdis View Post
Is this taking stage 2 into account? Unless you've figured out how to run stage 2 on a GPU, there's still a lot of CPU effort involved in running a t70 or t75.

Also 0.28 is very low. Using a more normal figure of 0.31 would suggest running t77 on a c248. With GPU stage 1 the optimal amount of ECM may be even higher. [this number is likely a close call between GNFS and SNFS but that doesn't affect the amount of ECM it needs]
I always use 1/3 and 1/4 because I calculate the likely effort in my head.

Besides which I tend to be impatient and so start sieving perhaps too early.
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Old 2021-11-05, 17:43   #68
Dec 2016

6716 Posts

Originally Posted by SethTro View Post
I updated my optimizer.
I took a look at the "CPU timing" section of the README, and I think you are underestimating the CPU speed for stage 1 by a factor of 2 because you do not take hyperthreading into consideration. I did some benchmarking and found that hyperthreading almost doubles the throughput. So a physical CPU core is almost twice as fast as you measured. The same might be true for stage 2, but I did not yet run benchmarks on that.

Anyway, I'd be interested to join for the step 2 part if someone does the stage 1. I already did a few thousand curves on M1217 with gmp-ecm, fully on CPU, though.
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Old 2021-11-05, 21:04   #69
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Feb 2005
Riverside, CA

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I, too, am willing to run stage 2 on some big-bound ECM curves for M1277. I have a 128GB machine with ~100GB free currently, so bounds on the order of B1=3e9-6e9 are fine with me.
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Old 2021-11-07, 23:53   #70
Dec 2016

103 Posts

Originally Posted by nordi View Post
The same might be true for stage 2, but I did not yet run benchmarks on that.
I did run benchmarks for that now: Running step 2 on all CPU threads leads to a 13.2% increase in throughput. Of course, this also doubles the RAM needed. At 3.4GB for some of the parameters that Seth suggested before, that would be 108.8 GB, which is roughly the maximum I can commit.

Originally Posted by SethTro View Post
260K curves at B1=1.2e9 B2=22.4e12
GPU 48s / curve, CPU 474s /curve
With this setting, a GPU could saturate 10 CPU cores. Since I already have 16 cores, we would either need more GPUs or we can increase B2 even more.

Last fiddled with by nordi on 2021-11-07 at 23:53
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