How much ecm should i do???

[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

[jasonp]

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.

[themaster]

i do the ecm on multiple pcs so that is not possible
i looked at msieves code and found

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

[Andi47]

Originally Posted by themaster

i do the ecm on multiple pcs so that is not possible
i looked at msieves code and found

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.

[themaster]

it probably is just that i am used to doing a lot more

[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.

[themaster]

before this i used 1/3 but it often stretched

[xilman]

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

[themaster]

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

[xilman]

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

[themaster]

thanks
this should speed me up quite a bit so i can find more 100 digit RHPs