mersenneforum.org How much ecm should i do???
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 2008-02-17, 13:39 #1 themaster     Dec 2007 33 Posts How much ecm should i do??? how much ecm should i do before switching to msieve i keep on finding that i have spent more time on ecm than msieve takes this is with numbers between 85 and 100 digits that i am having this problem i have did 35 digit ecm on a 97 digit number a couple of days ago and that turned out to be way too much could people post what rules they would use for switching to msieve i have searched the forum but found nothing thanks
2008-02-17, 14:04   #2
jasonp
Tribal Bullet

Oct 2004

33·131 Posts

Quote:
 Originally Posted by themaster how much ecm should i do before switching to msieve i keep on finding that i have spent more time on ecm than msieve takes this is with numbers between 85 and 100 digits that i am having this problem i have did 35 digit ecm on a 97 digit number a couple of days ago and that turned out to be way too much could people post what rules they would use for switching to msieve i have searched the forum but found nothing thanks
Let the msieve binary do the ECM for you; it already has tuning that guarantees you won't spend too much time before switching to QS.

 2008-02-17, 15:40 #3 themaster     Dec 2007 33 Posts i do the ecm on multiple pcs so that is not possible i looked at msieves code and found Code: static uint32 choose_max_digits(msieve_obj *obj, uint32 bits) { /* choose the amount of work to do. We want the chosen digit level to be a small fraction of what QS and NFS would need */ uint32 max_digits = 15; if (bits == 0) return 0; if (obj->flags & MSIEVE_FLAG_DEEP_ECM) { if (bits > 220) { if (bits < 280) max_digits = 20; else if (bits < 320) max_digits = 25; else if (bits < 360) max_digits = 30; else if (bits < 400) max_digits = 35; else max_digits = 40; } } return max_digits; } this seems a bit low to me
2008-02-17, 16:07   #4
Andi47

Oct 2004
Austria

2×17×73 Posts

Quote:
 Originally Posted by themaster i do the ecm on multiple pcs so that is not possible i looked at msieves code and found Code: static uint32 choose_max_digits(msieve_obj *obj, uint32 bits) { /* choose the amount of work to do. We want the chosen digit level to be a small fraction of what QS and NFS would need */ uint32 max_digits = 15; if (bits == 0) return 0; if (obj->flags & MSIEVE_FLAG_DEEP_ECM) { if (bits > 220) { if (bits < 280) max_digits = 20; else if (bits < 320) max_digits = 25; else if (bits < 360) max_digits = 30; else if (bits < 400) max_digits = 35; else max_digits = 40; } } return max_digits; } this seems a bit low to me
hmmmm... that's roughly what I am doing manually. (I am ECM'ing on multiple PCs too.)

Additionally I do some p-1 and p+1.

 2008-02-17, 16:28 #5 themaster     Dec 2007 338 Posts it probably is just that i am used to doing a lot more
 2008-02-17, 19:41 #6 jbristow     Aug 2007 3×31 Posts I've heard a 2/7 rule of thumb mentioned before. For a 97-digit number, that would mean stopping ECM at 25 or 30 digits if you're trying to optimize computer time.
 2008-02-17, 20:13 #7 themaster     Dec 2007 33 Posts before this i used 1/3 but it often stretched
2008-02-17, 21:42   #8
xilman
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May 2003
Down not across

23×113 Posts

Quote:
 Originally Posted by jbristow I've heard a 2/7 rule of thumb mentioned before. For a 97-digit number, that would mean stopping ECM at 25 or 30 digits if you're trying to optimize computer time.
AFAIK, the rulle of thumb is 2/9 for SNFS and 1/3 for GNFS. This latter rule is consistent with the 3/2 relative difficulties ROT for NFS.

Within reason, it doesn't much matter. If the factorization is non-trivial other considerations come into play, such as memory usage and communication overheads.

Paul

2008-02-18, 10:09   #9
themaster

Dec 2007

33 Posts

Quote:
 Originally Posted by xilman AFAIK, the rulle of thumb is 2/9 for SNFS and 1/3 for GNFS. This latter rule is consistent with the 3/2 relative difficulties ROT for NFS. Within reason, it doesn't much matter. If the factorization is non-trivial other considerations come into play, such as memory usage and communication overheads. Paul
what would u use for QS

2008-02-18, 12:02   #10
xilman
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May 2003
Down not across

23·113 Posts

Quote:
 Originally Posted by themaster what would u use for QS
As I said, it doesn't much matter. QS is only competitive below 100 digits or thereabouts. I'd probably go to around 30 digits or so.

Paul

 2008-02-18, 12:25 #11 themaster     Dec 2007 1B16 Posts thanks this should speed me up quite a bit so i can find more 100 digit RHPs