20220911, 17:52  #100 
Mar 2022
Earth
5×23 Posts 
I'm pretty uninformed when it comes to this but.....
Is there a reason mfaktc can't be used? I know it has a minimum exponent size requirement but can that be changed? Last fiddled with by Magellan3s on 20220911 at 17:52 
20220911, 18:22  #101 
"Ben"
Feb 2007
2^{2}·3·311 Posts 
Mfaktc is great at finding small factors but the miminal possible factor size of M1277 is many many orders of magnitude larger than anything it can find. We know this because of the amount of ECM completed on this number.
Last fiddled with by bsquared on 20220911 at 18:25 Reason: Forgot the M 
20220911, 18:38  #102 
Mar 2022
Earth
5×23 Posts 

20220911, 18:51  #103 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
1CC6_{16} Posts 
Aside from the lowexponent issue, there's a limit in mfaktc at 95 bits, mfakto at 92 bits. M1277 has already been TF to 68 bits, and it took ~47,000 GHD. To go to 69 bits would take another ~47,000 GHD, which is ~3 weeks on an RTX2080 GPU. From 6970 would take twice as long, 7071 four times, etc., growing exponentially. Well before ~2^{27} times 3 weeks, run time gets prohibitively long. And if not for that, from 95 bits to 1277/2 is beyond its current capability, requiring someone to code new kernels. https://www.mersenne.ca/exponent/1277
There's no multiGPU implementation of TF for Mersenne numbers, so running a span of x to x+y bits, only parallelizes to 2 GPUs: x to x+y1 on GPU a, x+y1 to x+y on GPU b, giving about equal run time for same model GPUs. Some other possibilities were mentioned earlier in this thread https://mersenneforum.org/showpost.p...3&postcount=18 and VBCurtis responds that reachable TF is pointless because of the amount of ECM that has been done https://mersenneforum.org/showpost.p...7&postcount=19 My attempted summary of factoring choices & past M1277 effort is https://mersenneforum.org/showpost.p...5&postcount=22 which indicates that almost any factors <166. bits would have already been found by ECM, so there's nothing reachable by TF remaining. 
20220911, 19:09  #104  
Mar 2022
Earth
5·23 Posts 
Quote:


20220912, 09:15  #105 
Romulan Interpreter
"name field"
Jun 2011
Thailand
3×23×149 Posts 
Not my intention to contradict anything you (and other guys) said about the difficulty of such job, just want to point out that the TF can be easily paralelized to 960 GPUs (for the 4620 classes version) just by rewriting the checkpoint file of mfaktc, for example. Of course, writing a "parallel" version (where you can specify the class) is quite easy. However, this is futile, it will just shorter the time from (arbitrary) 900 million years to one million years

20220912, 12:12  #106  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
2·29·127 Posts 
Quote:
Last fiddled with by kriesel on 20220912 at 13:04 Reason: apparently razzes are now required for certain posts. Some mods have no sense of humor, or misperceive that in others, or ? 

20220912, 12:20  #107  
Undefined
"The unspeakable one"
Jun 2006
My evil lair
5·7·191 Posts 
Quote:
Instead we should be TFing RSA1024 (and ECMing also). It's smaller so it should be really easy. I think you missed the trailing razz emoji in your quote. I put another one in here, I hope you don't miss that one also. 

20230102, 21:52  #108 
"Oliver"
Sep 2017
Porta Westfalica, DE
1,327 Posts 
A sincere question would be: How much ECM needs to be done on M1277 right now to reach the ECM target? This is a question that is likely only answerable if e.g. Ryan Propper and Sam Wagstaff state on how much ECM they have spent.
Last fiddled with by kruoli on 20230102 at 21:58 Reason: Grammar. 
20230102, 21:58  #109  
"/X\(‘‘)/X\"
Jan 2013
2·1,549 Posts 
Quote:
The ~4000 core‐years is a little harder to come up with. 

20230108, 16:07  #110 
Dec 2022
2·3·37 Posts 
The difficulty then would be of the same order as the record factorisation of RSA250, now 3 years ago. I would put this number to be somewhat a bigger deal than that. As for the ECM, even our limited Primenet records have it near t70, and I wouldn't doubt the real figure to be near t75  surely this has been a very highly investigated number, perhaps the highest ever in ECM effort.
The job will be done by SNFS  either sooner or later  with very good odds. I imagine we'd prefer it sooner, but it's purely a matter of assembling the needed resources. 
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