View Single Post
Old 2020-03-07, 18:13   #13
EugenioBruno
 
Feb 2020

2310 Posts
Default

First of all, again, thanks for the in-depth replies!

(sorry, I've rearranged your post a bit for ease of replying)
Quote:
Originally Posted by kriesel View Post
First, all, please stop referring to LL as if PRP primality testing doesn't exist. PRP is the preferred primality test for new first-test assignments.
Yep, I think I referred to it as PRP in my first post about this, but I was trying to see if I understood the sentence I was quoting.


Quote:
Originally Posted by kriesel View Post
DC can be either LL or PRP. There is a several year backlog of LL DC and growing. There is a need for more PRP DC on which to base an estimate of PRP in the wild total error rate.
Quote:
Originally Posted by kriesel View Post
If you run about 20% DC, 80% first-test by cpu time, that is equivalent to about a 53M DC and a 103M first test in the same time frame, so is consistent with the current 8 year backlog. I encourage you to contribute more DC than that, to help keep the backlog from growing further. I've suggested that the project as a whole could refrain from issuing first-test assignments for one or two months of the year, to address the growing backlog. (Sort of spring and fall cleaning.) That idea is not very popular, although it doesn't reduce the rate of completed first tests much (8 or 17%), yet increases the rate of completed double checks a lot (60% or more).
I'll switch to 100% DC for now. I like shorter jobs anyway, and the idea of working on this backlog appeals a lot to me. I'll also be able to keep monitoring my hardware this way. If my error rates on DCs are unexpectedly high, I know something's wrong.

Quote:
Originally Posted by kriesel View Post
Before gpu TF, factoring depth was less by default for the same exponent than it is now. One can make a case for additional bit levels of factoring that may eliminate the need for a double check, in those cases.

Before first time primality testing, finding a factor saves the first primality test and the double check primality test (and the occasional third and fourth or more). After first time primality testing, further trial factoring if any is weighed against the double check and occasional third or higher check.

[...]

To put it another way, the ratio of TF to primality or P-1 Ghd/day ratings is typically about 0.7 to 1.4 on cpus. On gpus, it's 10. to 40. or so, with ~16. being pretty common.
So as a result of all that history, a lot of DC candidates are still at the TF level that was determined optimal and applied many years ago, which became suboptimal.
These are being revisited and taken further in TF. See for example this detailed exponent report, on one I have reserved for DC: https://www.mersenne.org/report_expo...exp_hi=&full=1
Ah, that makes a lot of sense. I understand.

Quote:
Originally Posted by kriesel View Post
The RTX20xx and GTX16xx are enough more efficient at TF that they raise the ideal TF bit level one more.
Quote:
Originally Posted by kriesel View Post
Your choice of a GTX1650 is a good one. It's about as good a TF throughput per watt as can be found at reasonable price.
Sigh of relief. I actually chose the 1650 based on a benchmark table for mfaktc but I was afraid I misunderstood it. Looks like I didn't!


Quote:
Originally Posted by kriesel View Post
Be patient with yourself. There's a big learning curve. One step at a time.
Contribute how you can and in the ways you enjoy.
Yep, it's a really fun project to follow and contribute to.

Eventually I'd like to get some math chops so I can also understand the discussions on number theory and software development, but I'm in no hurry.
EugenioBruno is offline   Reply With Quote