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drummers-lowrise
1) Message boards : News : Change in Prime Reporting Procedure (Message 147087)
Posted 270 days ago by Profile GrebulonerProject donor
Are these new prime finding users generally running older and/or slower machines that wouldn't have otherwise been likely to be first? Asking more out of curiosity than anything.

With LLR2, who does PG consider the double checker? (or am I misreading that part and they all get reported as anonymous if there is no response?)
2) Message boards : 321 Prime Search : Multi-threading: Max # of threads for each task Setting? (Message 147016)
Posted 273 days ago by Profile GrebulonerProject donor
Hmm according to task manager my system has the following available:

L1 2.2MB
L2 9MB
L3 90MB


Might you be running a two socket system? 36 cores total across 2 CPUs? (your computers are hidden)

You can fit 6 tasks in L3 with room to spare, so I'd suggest 3 threads/task.

Not fully comparable, of course, but I found much better throughput doing 321 with 6x3t instead of 3x6t on my 18c 10980XE.
3) Message boards : 321 Prime Search : Multi-threading: Max # of threads for each task Setting? (Message 146971)
Posted 274 days ago by Profile GrebulonerProject donor
For the i5-3470 I would run 1 task on 4 cores and for the 3900XT I would run 4 tasks on 3 cores each. These tasks are presently using about 7MB of CPU cache each, so the 3470 will be a bit slow, but the 3900XT should run them pretty quick with that setting.

You will want to make sure that the tasks are run on the same CCX (a CCX is a set of 3 adjacent cores for the 3900XT) for the Ryzen CPU though to maximize efficiency. You can use Process Lasso (free, here https://bitsum.com/) or, if you hop on the Discord server, someone may have a link to another program that the same person who made the LLR2 software wrote. Ryzen 3rd gen CPUs are much more productive and efficient if you can keep a task on the same CCX.

As far as optimal configurations go, that is a function of FFT length and cache size. If you look at the output of a task after you run it (by clicking on the task on your tasks summary page) you can see the FFT size. Multiply that by 8 and you get MB of CPU cache used during the test. For 321 right now the FFT size is 864K, so each task uses about 7MB cache. The i5-3470 has 6MB and each CCX of the 3900XT has 16MB.

Some examples: Looking at PPSE tasks, with an FFT length of 120K (~1MB cache usage), the most efficient configuration would be to run 1 task on each core (4 tasks total for the 3470 and 12 tasks total for the 3900XT). For PPS-Mega the FFT size right now is 256K, or about 2MB per task. You would probably want to run 2 tasks with 2 threads each on the 3470 and 12 tasks with 1 thread each for the 3900XT for optimal throughput, to stay within the cache limits for each CPU.

Hope this helps, and good luck!


Hi, are you talking L2 or L3 CPU cache? I ask because my CPU has only 2MB of L2 but 45MB L3. Should I be calculating for L2 or L3?


Generally speaking, it's L3, but there is an "it depends" based on cache inclusiveness. AMD and consumer Intel chips store a copy of L2 in L3, so only L3 matters (and in Ryzen 3k/5k, it's L3 per CCX). Skylake-X/SP and up (HEDT/server) have a mostly non-inclusive hierarchy, so it's a little less than L2+L3.

What CPU are you using that mixes itsy bitsy L2 with massive L3?
4) Message boards : Number crunching : Have I found a prime or not? I'm confused... (Message 146825)
Posted 278 days ago by Profile GrebulonerProject donor
The "firsts" are counts of tasks that you returned before the double checking user in the last 24 hours. They aren't a count of primes.

Primes you find will show up on a line called "discoveries" and if you are the initial finder, you'll get a notification by a message in your account and email (if you set it up).
5) Message boards : Number crunching : Badges III (Message 146695)
Posted 281 days ago by Profile GrebulonerProject donor


And now that they've slowed down coming:

6) Message boards : Number crunching : Start discussing new goals for 2021 (Message 146565)
Posted 285 days ago by Profile GrebulonerProject donor
I was searching for mfsieve, didn't know it was part of mtsieve, thanks.

The prime limit of 2^52 is probably the reason why sieving came to an end.

Sorry for OT...


It shouldn't be too hard to support up to 2^62, although AVX code cannot be used between 2^52 and 2^62.


This has me quite curious.

Please, explain more!
7) Message boards : Number crunching : Badges III (Message 146464)
Posted 287 days ago by Profile GrebulonerProject donor


Whew! Now to turn my last GPU to WW.
8) Message boards : Wieferich and Wall-Sun-Sun Prime Search : WW project is live (Message 145775)
Posted 298 days ago by Profile GrebulonerProject donor
I wistfully recall running the search on PRPNet...my erroneous Wieferich find is still listed, even!

It's been so long, what was the interval on the old units? 10e9? 10e10?

And in regards to "near finds," it wasn't quite clear to me in the welcome post, but are our near finds are going to be listed on our account pages? If so, will those include previously-found near finds while we re-cover the old PRPNet work even if they aren't listed on the overall PG stats page?

Edit: If you read the WUx2 part, ignore it. I am always mixing up WU vs. task.
9) Message boards : Wieferich and Wall-Sun-Sun Prime Search : Any idea on WU times CPU vs. GPU? (Message 145641)
Posted 301 days ago by Profile GrebulonerProject donor
Is this an INT32 or FP32 project?

How's the credit going to compare to AP27 if the runtime is similar?
10) Message boards : Number crunching : Magellan 500th Anniversary Challenge (Message 145240)
Posted 311 days ago by Profile GrebulonerProject donor
Whoops, my bad. Too many HTML habits and not enough BBCode use.

Second link direct:

https://babel.hathitrust.org/cgi/pt?id=chi.57065015&view=1up&seq=49

Catalog page might offer a way in if that doesn't work?

https://catalog.hathitrust.org/Record/008857619

c.1 ser.2 v.10 1906 is the edition with the solutions.


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