20150905, 05:25  #144 
"Matthew Anderson"
Dec 2010
Oregon, USA
1192_{10} Posts 
Hi Math People,
Thanks to Henry for showing me polysieve2. I used it to sieve for some primes of up to 19 digits to the Online Encyclopedia of Integer Sequences. My last entry was http://oeis.org/A257140. The sequence is a 13 tuplet with pattern [0, 2, 8, 14, 18, 20, 24, 30, 32, 38, 42, 44, 48]. Here is the associated .b file with 104 primes. I have been using some Maple code that I wrote also, but it is very slow. It would be great if there was software that could search primes with 20 or more digits of similar forms quickly. Does anyone know of such a software? Regards, Matt 
20150906, 19:44  #145 
Jun 2009
2BC_{16} Posts 
Forget what I wrote here first. I finally understood the core of the problem.
Last fiddled with by PuzzlePeter on 20150906 at 19:47 Reason: Slow brain 
20151014, 04:00  #146 
"Dana Jacobsen"
Feb 2011
Bangkok, TH
2×5×7×13 Posts 
I looks like we have both this thread and this one to discuss constellations. Any others? I don't think that one belongs in the GIMPS math forum, but that seems to be another contentious discussion.
From what I can tell from both the OP and almost all discussion, this thread is about finding record large values (e.g. k*2^n1), so looking for huge quadruplets, rather than what Matt is doing, which is finding comprehensive lists of the first N tuples. That's what the other thread is about. Matt, I updated A257140 tonight with 1036 values, as well as the other 13tuplets earlier this week. I'm working on the 14tuplets now (I already found a missing value in A257167). More discussion of this should be on the other thread or a new one. 
20180926, 14:07  #147 
Jun 2009
2^{2}·5^{2}·7 Posts 
It's me again...
I am using polysieve quite a lot and i recently ventured into the realms of pretty big numbers. It works just fine. I love it. But there is one problem. I would like to use it to sieve quite deeply, but I cannot run my machine for months on end due to power outages, updates etc. So I thought about restarting an existing sieve file. I am a really poor programmer. So my way of tackling this problem was to change as little as possible in the original code. Plus I am willing to accept poor user friendliness. So here's what tried to do: I wouldn't even attempt to parse the header line, so the user (i.e. myself) simply needs to input all the information again and some more. No big deal. So I start with a presieved file with the header line deleted. I can always add it with an editor after sieving . Then I fill the alist array from the file and continue sieving. At least that's what I would like to do After several solvable problems I am now at a loss. Everything seems to work just fine until the program tries to assign an array called invtable. That's where I get a segmentation fault and no further error message. My compiler (gcc 4.4) does not say a thing when compiling. The last screen output I get is "Using M=30, mres=15" and the very next line in the code is the line reading "int **invtable". I put a printf command immediately after this, but it does not get executed so I guess that's where the segmentation fault happens. Could anyone please point me to where this is going wrong? That's a section of the code I didn't even touch so I really don't understand what's happening here. I'll attach what I have so far. It's not pretty and there are a lot of printf statements that are left from hunting previous errors. Plus I realized I have started with the version that does not have the assembler bit for mulmod, but I can always change that once it's running. Any help or hints on how to deal with such an error is greatly appreciated. PS: the filename should end in .c but that's not accepted so I changed it to .txt Thanks! Last fiddled with by PuzzlePeter on 20180926 at 14:12 Reason: Typos. Lots of typos. 
20180926, 19:58  #148 
"Robert Gerbicz"
Oct 2005
Hungary
2×19×43 Posts 

20180928, 03:40  #149 
Jun 2009
2^{2}×5^{2}×7 Posts 
I wasn't looking for someone to do the work. But it's great you want to look at it as your result is guaranteed to be better than what I would have come up with.
Thanks a lot! Last fiddled with by PuzzlePeter on 20180928 at 03:41 
20181010, 13:07  #150 
Jun 2009
700_{10} Posts 
After some more testing I need to correct my statement. The whole invtable thing is being executed. I had compiler optimization active which seems to have rearranged the order of execution. The problem seems to be somewhere else.

20181020, 07:21  #151 
Jun 2009
2^{2}×5^{2}×7 Posts 
Okay, I think I got it.
It's still not very comfortable but for me it's good enough. When I think about time I spent hunting a pretty stupid mistake... well, I did learn quite a bit so that's okay I guess. 
20181219, 18:30  #152 
Jun 2009
2^{2}×5^{2}×7 Posts 
Does anyone know what it would take to make the code run on GPU? Is it even worth trying? I have no idea so if this is a stupid approach please tell me so
I know some sieves have been massively accelerated by using GPU computing, but I don't know if this kind of sieve is even suited for GPUs 
20181220, 08:33  #153 
Just call me Henry
"David"
Sep 2007
Liverpool (GMT/BST)
11·557 Posts 
I think your best idea is to get this sieve integrated into mtsieve in order to make it easier to add gpu support.
There are various things that could potentially speed up the code as is. The code currently makes no use of SIMD. That could potentially speed it up massively for p < 2^53. I am not sure where the slowest points of this sieve are though so I can't make any guarantees. 
20181221, 09:57  #154  
Just call me Henry
"David"
Sep 2007
Liverpool (GMT/BST)
11×557 Posts 
Quote:


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