20201109, 00:03  #793  
Jun 2012
Boulder, CO
2^{2}·53 Posts 
Quote:


20201122, 23:49  #794 
Oct 2007
London, UK
3×439 Posts 
If noone has any objection I will run some ECM on the t2200 file at the 35 digit level, B1=1E6. I already ran 128 composites at the beginning of the file and found a few factors, but I've decided to switch to a bottom up approach now.
Sadly, ECMGPU seems restricted to composites less than 2^1018 in size, which limits me to the first sixth or so of the file. The last number I can run is: Code:
33100272759546513743540025392907714658971195397577775668521338093978667943386009924363532641^51 If anyone knows where I might get a more uptodate binary for Windows for ECMGPU I'd appreciate it, pretty sure the version I'm using was compiled before the 20 series cards were even released, so perhaps there's some speedup to be gained. 
20201123, 15:29  #795 
Oct 2007
London, UK
10100100101_{2} Posts 
Follow up question, I just took a 41 digit bite out of this number.
Should I keep going on it and run the rest of my curves? How much is factored enough? At the moment I've set ECM to quit a number and move on if it finds a factor without finishing the block of 1152 stage 1 curves that were done on the GPU, but should I finish them off in case another factor pops out? 
20201124, 13:34  #796  
Apr 2006
5·19 Posts 
mwrb2100 will be updated soon, but I can already tell that the weight of sigma(6115909044841454629^16) drops from 65263134 to 60351951.
Quote:
Quote:
For a lower bound on \(\Omega(N)\), we prefer to get a composite cofactor, since it means more prime factors. And if we are confident that the composite cofactor has only 2 prime factors, than factoring it is not necessary since it wouldn't change the factor count nor the smallest available prime that we branch on. By the way, a run for proving \(\Omega(N)\ge 111\) has recently finished without trouble. So an odd perfect number has at least 111 (not necessarily distinct) prime factors. This improves the bound \(\Omega(N)\ge 101\) from 2012. 

20201124, 15:37  #797 
Jun 2012
Boulder, CO
324_{8} Posts 
I'm still poking at the current mwrb2100 a bit. I guess when new mwrb2100/mwrb2200 are ready, you will make an announcement here?

20201126, 05:19  #798  
Oct 2007
London, UK
3×439 Posts 
Quote:
Despite what I just said, I'm also running a "lowhangingfruit" pass over the remainder of the 58185 of 71669 composites in the t2200 file that are too big for GPU stage 1. Just 8 curves each at the 25 digit level which should only take a couple of days. I don't expect to find much, but the machine was idle so why not. 

20201126, 12:56  #799  
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
11×523 Posts 
Quote:
It will depend on your system, the size of the number and what software you use but 11e6 might not be slower for t40 than 3e6. They run about the same speed in the tests I just ran. I would suggest looking at AVXECM for stage 2(assuming it accepts the curve type that GPUECM uses). 

20201126, 15:29  #800  
Oct 2007
London, UK
3×439 Posts 
Quote:
The way I am running these curves at the moment is I have a RTX 2070 GPU running stage 1 (with a VERY old binary ) and 1152 curves in parallel, then I have a 3900X CPU that very approximately tries to keep pace with the GPU by setting the B2 bound appropriately. I was a bit greedy and set B2=14e9 so the CPU is running somewhat slower than the GPU at the moment, but it should speed up when it gets to the smaller composites. Since the run time of stage 1 on the GPU is essentially linear w.r.t. B1 that essentially means that B1=11M will take 3.67 times as long as B1=3M. A full pass of that would basically take a year to run about a quarter of the required curves to complete that level. Edit: Looks like AVXECM requires AVX512 support, which is only available on a select few Intel platforms thus far. Last fiddled with by lavalamp on 20201126 at 15:35 

20201126, 16:02  #801 
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
11·523 Posts 
I was under the impression that there was codepaths for lesser CPUs.

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