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-   -   BOINC NFS sieving - NFS@Home (https://www.mersenneforum.org/showthread.php?t=12388)

Batalov 2009-09-10 08:08

[quote=debrouxl;189258] I've performed some polynomial selection for C157_105_74 and C152_107_66...[/quote]

Sorry, dude, but what for? They have very simple polynomials.

Both difficulty 197, easily done on a single home computer in a fairly short time. You have to pick up some theory. Not every wall deserves to be knocked down with one's forehead.

frmky 2009-09-10 09:08

Oops! Sorry for stealing your thunder! Over the past year or so, I've been growing more frustrated with the state of NFSNet and had been contemplating trying a BOINC project for a while. Your success with the RSA keys, along with the time afforded by my sabbatical this semester, spurred me to action. The applications that I'm using are based on your code modified to support the other sievers, catch more exit conditions, pass sieve ranges on the command line rather than in the input file, and support 64-bit linux. I started with a ~220 digit SNFS, but that proved too small. The current contributors are doing a ~246 digit SNFS in less than a week, and it's still growing.

I'll be happy to share the modified code with you, and I certainly don't mind you going ahead with your plans. I plan to mostly do Cunningham composites. You could concentrate on others, such as XYYXF, OddPerfect, and ElevenSmooth composites.

R.D. Silverman 2009-09-10 09:44

[QUOTE=frmky;189268]Oops! Sorry for stealing your thunder! Over the past year or so, I've been growing more frustrated with the state of NFSNet and had been contemplating trying a BOINC project for a while. Your success with the RSA keys, along with the time afforded by my sabbatical this semester, spurred me to action. The applications that I'm using are based on your code modified to support the other sievers, catch more exit conditions, pass sieve ranges on the command line rather than in the input file, and support 64-bit linux. I started with a ~220 digit SNFS, but that proved too small. The current contributors are doing a ~246 digit SNFS in less than a week, and it's still growing.

I'll be happy to share the modified code with you, and I certainly don't mind you going ahead with your plans. I plan to mostly do Cunningham composites. You could concentrate on others, such as XYYXF, OddPerfect, and ElevenSmooth composites.[/QUOTE]


The Fibonacci/Lucas numbers have a much longer history and tradition
than these last 3..........

fivemack 2009-09-10 09:48

polynomial selection for XYYX is really easy
 
Hello debrouxl

[code]
n: 17075208162502696769894374083900022560666476082993604775871225203067880924979815162772202343023227879807349366915642555719257659222044063449483070644063
skew: 0.5
c6: 66
c0: 1
Y0: 21048519522998348950643
Y1: 564664961438246926567398233604096
[/code]

is a reasonable polynomial for C152_107_66;

[code]
n: 1958662481641326248094427703301790313367601031324000981342287598641007898602778576888614085103799825026482689632839088276269469580340645292584464747639935853
skew: 0.4
c0: 105
c5: 1
Y1: 1794180426060713946801538628555399757824
Y0: -2078928179411367257720947265625
[/code]

should be OK for C157_105_74.

basically you've got, say, 103^55 + 55^103, and you want to write a small multiple of it as a sum of small multiples of fifth or sixth powers.

so it would be 103*(103^9)^6 + 55*(55^17)^6
which you do as c0 = 103, c6 = 55, and either Y0 = 103^9, Y1=55^17 or the other way round, depending on a convention that I don't quite know: I try both, and for one of them the siever gives an error message. If you're using fifth powers, you also need to fiddle with choice of sign until the siever stops complaining. Scientific method, don't you just love it?

Batalov 2009-09-10 09:51

...And there are some Cullen and Woodall's.
W951 is particularly appealing.

debrouxl 2009-09-10 09:59

Batalov: yeah, I'll easily admit that I haven't picked a lot of theory :redface:
Someone suggested a 149-digit xyyxf number at
[url]http://www.unitedti.org/index.php?showtopic=8888&view=findpost&p=135938[/url] (and later posts), so I just tried several other 150-160 digit numbers from the "wanted" list of that project, and wanted to feed them to the rsals grid so as to prevent starvation (and therefore people detaching, weakening the grid).

fivemack: thanks for the explanation :smile:

frmky: don't worry, I wholeheartedly agree that there's room for multiple BOINC projects, each of them dealing with a kind of number, with collaboration between these similar projects :wink:
You did it completely right to go forward with improving squalyl's and FloppusMaximus' initial work. You seem to have time on your hands, and you're putting it to good use :smile:

everybody: from tonight to next Wednesday or Thursday, it's likely that I'll be without Internet access at all... so don't worry if I don't reply.

fivemack 2009-09-10 10:02

[QUOTE=Batalov;189275]...And there are some Cullen and Woodall's.
W951 is particularly appealing.[/QUOTE]

You spelled 'appalling' wrong :smile:

That one's probably over the 32-33 boundary; I don't know whether the issue with >32-bit large primes in msieve is that they don't fit in 32 bits, in which case a simple encoding like

(p<210)?p:210+48*(p/210)+lut[p%210]

gets you to 34 bits, or something a whole lot more subtle.

I don't need a 4x4 compute cluster with infiniband interconnect
I don't need a 4x4 compute cluster with infiniband interconnect
I don't need a 4x4 compute cluster with infiniband interconnect
A 4x4 compute cluster with infiniband interconnect only uses a kilowatt, and it's probably not very much louder than a quite loud vacuum cleaner running 24/7, and it costs under £3000, and think of the matrices you could do, and now that Lynnfield is out it's a lot faster than the one I specced with Shanghais
I don't need a 4x4 compute cluster with infiniband interconnect
I don't need a 4x4 compute cluster with infiniband interconnect
I don't need a 4x4 compute cluster with infiniband interconnect

jasonp 2009-09-10 12:18

[QUOTE=fivemack;189278]
That one's probably over the 32-33 boundary; I don't know whether the issue with >32-bit large primes in msieve is that they don't fit in 32 bits, in which case a simple encoding like

(p<210)?p:210+48*(p/210)+lut[p%210]

gets you to 34 bits, or something a whole lot more subtle.
[/QUOTE]
It just involves a lot of small changes to the initial filtering and linear algebra stages, modifications of data structures, etc. Actually the big reason I haven't gotten to it is that I wanted to use the changes as an excuse to implement run-length compression of lists of primes or lists of ideals. The hardest part is extending code that finds roots of polynomials mod p to p > 2^32

@debrouxl: welcome to the forum :) As fivemack demonstrated, there are tricks that make NFS dramatically easier when your input is not an RSA key; perhaps you should let us know how you'd like to pitch in to any of the ongoing projects here, once you decide.

R.D. Silverman 2009-09-10 12:53

[QUOTE=jasonp;189291]The hardest part is extending code that finds roots of polynomials mod p to p > 2^32
[/QUOTE]

When do you use this? AFAIK we still are not close to using a factor
base with elements > 2^32.....?

R.D. Silverman 2009-09-10 12:54

[QUOTE=frmky;189268] Over the past year or so, I've been growing more frustrated with the state of NFSNet .[/QUOTE]

Join the club!!!!!

R.D. Silverman 2009-09-10 12:58

[QUOTE=Batalov;189275]...And there are some Cullen and Woodall's.
W951 is particularly appealing.[/QUOTE]

How about doing the first two holes in the base 12 tables?

Among all of the first five holes in all the tables, these have been
there the longest.


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