A big one!
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- Andrey Kulsha wrote:
>OK, so reading through this, and then reading a little at the ECMNET
> A big one!
> Best wishes,
page, located at:
Is it better to tackle big numbers like this with Prime95 or ecm-5.0.
And, how does it count as an ecm record? Does Prime95 run ecm curves on
numbers, and if so, how do you know what size factors it is looking
for? Does anyone know which is faster, Prime95 or ecm-5.0 on numbers of
the mersenne form? Just curious because I was thinking of contributing
to one of these projects, but wanted to make sure I was contributing as
much as I can.
- David Cleaver wrote:
> Is it better to tackle big numbers like this with Prime95 or ecm-5.0.I did some quick testing on a P4
For stage 1, Prime95 is MUCH faster than GMP-ECM 5
I tried running a few curves with B1=1e6 on M(971) which has no known
factors (293 digits), and on M(959) which has a few known factors (254
digits, i didn't spent time looking for 1 or a few more known factors which
make it a C213).
M(971) Prime95 ~28.5
GMP-ECM 5 ~102
M(959) Prime95 ~28.3
GMP-ECM 5 ~113
Even though M(959) has known factors, GMP-ECM seems faster running on the
For stage 2 things are a bit different. Prime95 uses a default B2=100*B1
while GMP-ECM uses a much larger B2 (in my case for B1=1M, B2 was ~839M)
M(971) Prime95 ~15.5
GMP-ECM 5 ~16.9
M(959) Prime95 ~15.5
GMP-ECM 5 ~14
With the default B2, GMP-ECM needs 75 resp. 64 seconds for 1 curve but has a
higher chance of finding a factor.
So only when a numbers has known factors, B2 might be faster with GMP-ECM
(it is possible to run B1 with prime95 and B2 with GMP-ECM).
On a P3 or Athlon things might be very different since they don't use the
SSE2 optimizations in Prime95
> And, how does it count as an ecm record? Does Prime95 run ecm curves onYou can set the bounds youreself in Prime95
> numbers, and if so, how do you know what size factors it is looking