Operation Megabit Twin

[Oddball]

Originally Posted by amphoria

I did a test using a smaller set of k's last weekend and the change from fastarray mode to array mode appeared to occur between 20T and 25T k's.

I don't think fastarray is any better than array mode for large p's. I tried sieving a big 43.9 million candidate file at p=78T, and NewPGen needed 335Mb of RAM. It used array mode, and sieving progressed quite quickly (87 million p/sec). That 87 million p/sec rate remains the same even if the number of candidates is reduced to less than a thousand.

[axn]

Originally Posted by Oddball

I don't think fastarray is any better than array mode for large p's.

For the present purposes, p=100e9 should not be considered "large".

[amphoria]

Originally Posted by axn

For the present purposes, p=100e9 should not be considered "large".

I can confirm this. 20T-40T gives 48 k's per sec whereas 20T-50T gives 0.4 sec per k.

[amphoria]

Taking 106T-109T.

[Oddball]

104T-106T complete:

http://www.sendspace.com/file/1rgo42

Reserving 109T-111T. I've decided to stop phase 1 of the sieve at 120T. There's no point in going higher than that; even at a high sieve depth, the file will be too large for NewPGen to sieve at once, and any work done from 120T and up will be useless if a megabit twin is found before that point.

Phase 2 will involve sieving 6 files for twins only: 0-20T, 20T-40T, and so on until 100T-120T. It'll start sometime next week. Once those files reach a higher sieve depth, there'll be fewer candidates, and array mode will be about the same speed as fastarray mode. The 6 files will then be merged into one giant 0-120T file, which will be sieved at once.

For those of you who're interested, there's a 40% chance that one of the k's in the 0-120T range will yield a twin.

[amphoria]

Originally Posted by Oddball

I've decided to stop phase 1 of the sieve at 120T. There's no point in going higher than that; even at a high sieve depth, the file will be too large for NewPGen to sieve at once, and any work done from 120T and up will be useless if a megabit twin is found before that point.

Phase 2 will involve sieving 6 files for twins only: 0-20T, 20T-40T, and so on until 100T-120T. It'll start sometime next week. Once those files reach a higher sieve depth, there'll be fewer candidates, and array mode will be about the same speed as fastarray mode. The 6 files will then be merged into one giant 0-120T file, which will be sieved at once.

Oddball,

I have already started sieving 0-20T on one core of a Core i7 @ 3.6 Ghz. This was to determine the sieve depth to leave ~4M k's remaining with a view to combining 5 such files which could still be sieved in fastarray mode. It is currently at 985 billion and removing ~29 k's per sec with 17.23 M k's remaining. I could carry on sieving this range until the removal rate reaches 0.4 k's per sec which would then set the target where fastarray mode and array mode are approx equal on this processor if this would be useful. It is currently removing about 3 M k's per day so will reach the initial target of 4M k's within a week.

Dave

[amphoria]

100T-104T complete.

http://www.sendspace.com/file/yz39ua

[Oddball]

Originally Posted by amphoria

Oddball,

I have already started sieving 0-20T on one core of a Core i7 @ 3.6 Ghz. This was to determine the sieve depth to leave ~4M k's remaining with a view to combining 5 such files which could still be sieved in fastarray mode. It is currently at 985 billion and removing ~29 k's per sec with 17.23 M k's remaining. I could carry on sieving this range until the removal rate reaches 0.4 k's per sec which would then set the target where fastarray mode and array mode are approx equal on this processor if this would be useful. It is currently removing about 3 M k's per day so will reach the initial target of 4M k's within a week.

Sounds good. I'll start sieving the 20T-40T range.

[gribozavr]

amphoria, Oddball: do you have the merged files? Should I upload them?

[Oddball]

Originally Posted by gribozavr

amphoria, Oddball: do you have the merged files? Should I upload them?

Could you upload the files (0-20T, 20T-40T, 40T-60T, 60T-80T, and 80T-100T)? I have most of the files, but some of them are missing.

[amphoria]

106T-109T complete.

http://www.sendspace.com/file/t99pfy

Taking 111T-114T.