optimality of ecm depth

mklasson · 2009-03-08, 15:38

Is the current cutoff for automatic ecm in msieve really optimal? (using the -e arg)

Given a C96 msieve does ecm for factors <= 25 digits, which takes <1 minute on this machine. The QS then takes about 100 minutes.

My uninformed guess would be that a fair bit more ecm is warranted, but I don't know the math...

There's no way to specify exactly how much ecm should be done, is there?

10metreh · 2009-03-08, 16:40

Quote:

Originally Posted by mklasson

Is the current cutoff for automatic ecm in msieve really optimal? (using the -e arg)

Given a C96 msieve does ecm for factors <= 25 digits, which takes <1 minute on this machine. The QS then takes about 100 minutes.

My uninformed guess would be that a fair bit more ecm is warranted, but I don't know the math...

There's no way to specify exactly how much ecm should be done, is there?

Roughly t30 on a C96, that's about 400 curves at 25e4. Maybe a bit less, but I'd do at least half t30.

jasonp · 2009-03-08, 20:18

A full t30 would take 10-30 minutes, which is too long. Doing a fraction of an ECM level is a good idea, though.

2009-03-08, 15:38	#1
mklasson Feb 2004 2·3·43 Posts	optimality of ecm depth Is the current cutoff for automatic ecm in msieve really optimal? (using the -e arg) Given a C96 msieve does ecm for factors <= 25 digits, which takes <1 minute on this machine. The QS then takes about 100 minutes. My uninformed guess would be that a fair bit more ecm is warranted, but I don't know the math... There's no way to specify exactly how much ecm should be done, is there?

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2009-03-08, 20:18	#3
jasonp Tribal Bullet Oct 2004 3,541 Posts	A full t30 would take 10-30 minutes, which is too long. Doing a fraction of an ECM level is a good idea, though.