Reserved for MF  Sequence 3366
Welcome,
Aliquot Sequence 3366 has been officially assigned to the forum ("Mersenne Forum") on 7 August, 2013. It currently stands at index 2067 with 2^3 * 3^3 * ... * c135. The status of ECM work on the c135 is unknown. This thread will be the place holder for ECM progress and possibly initiation of some NFS processing. Team sieving will most likely be spun off into a separate thread until it completes. Then progress will return here for status updates. Feel free to contribute curves or other electronic cycles you may want to donate. And by all means  have fun!! mod edit: [url]http://www.factordb.com/sequences.php?se=1&aq=3366&action=last20&fr=0&to=100[/url] 
3366:i2067
After running a few hundred curves @ 43e6 I feel confident the c135 is ready for GNFS. (Not that those few curves make it happen but including the history of this Seq.) I've started it on a Core i5. It should finish in 45 days. I won't feel hurt if someone trumps me with an ECM find. :smile:

c143 @ i2068
pm1 2e9  nothing
800 @ 1e6  nothing Passing through 400 @ 3e6 
2000 @ 3e6  nothing.

I'm well past 4000@11e6...

Poly select commencing. I should have one Monday morning USAPacific time.
Curtis 
At 4745 curves @ 11e6, I switched to 43e6 for a while...

At about 1660 curves @ 43000000:
[code] $ python ecm.py threads 2 c 2000 43000000 <ecmIn > ___________________________________________________________________ >  Running ecm.py, a Python driver for distributing GMPECM work  >  on a single machine. It is Copyright, 2012, David Cleaver and  >  is a conversion of factmsieve.py that is Copyright, 2010, Brian  >  Gladman. Version 0.10 (Python 2.6 or later) 30th Sep 2012.  > _________________________________________________________________ > Number(s) to factor: > 82572604842970740226575313011024210867650562043391903215525706141475272605260959388176023149958914785033958356770086632201183899666330968322243 (143 digits) >============================================================================= > Working on number: 825726048429707402...899666330968322243 (143 digits) > Currently working on: job5530.txt > Starting 2 instances of GMPECM... > ./ecm c 1000 43000000 < job5530.txt > job5530_t00.txt > ./ecm c 1000 43000000 < job5530.txt > job5530_t01.txt GMPECM 6.4.4 [configured with GMP 5.1.2, enableasmredc] [ECM] Using B1=43000000, B2=240490660426, polynomial Dickson(12), 2 threads Done 219/2000; avg s/curve: stg1 199.7s, stg2 57.81s; runtime: 28620s Run 219 out of 2000: Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=2507321602 Step 1 took 200036ms Step 2 took 57956ms ********** Factor found in step 2: 1207628288954874358756230750720893104793451481159 Found probable prime factor of 49 digits: 1207628288954874358756230750720893104793451481159 Probable prime cofactor 68375845115745085102927692017310006270434002895546517987965895954910700224363999707612562247077 has 95 digits [/code]:smile: 
c121 @ i2069
pm1 1e9  nothing
This might be a personal run to finish off the c121. Go for it EdH. Clueless at 2^3 * 3^2 ... c121 
OK,
[code] $ python ecm.py threads 2 c 2000 43000000 <ecmIn ... > Working on number: 859816614827472478...578490215531107749 (121 digits) > Currently working on: job4791.txt > Starting 2 instances of GMPECM... > ./ecm c 1000 43000000 < job4791.txt > job4791_t00.txt > ./ecm c 1000 43000000 < job4791.txt > job4791_t01.txt GMPECM 6.4.4 [configured with GMP 5.1.1, enableasmredc] [ECM] Using B1=43000000, B2=240490660426, polynomial Dickson(12), 2 threads Done 285/2000; avg s/curve: stg1 100.8s, stg2 36.44s; runtime: 19837s Run 285 out of 2000: Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=306416374 Step 1 took 101114ms Step 2 took 36583ms ********** Factor found in step 2: 154499827420010610820657248119651788418298611 Found probable prime factor of 45 digits: 154499827420010610820657248119651788418298611 Probable prime cofactor 55651622994376897358779815364928346078694944874963398571536226939862492842759 has 77 digits [/code]:smile: 
Note that 2000 curves at 43M here would take longer than GNFS by quite a margin, without certainty of producing a factor. In general, ECM for more than 25% of expected NFS factoring time is effort better spent on NFS. The ecm target of 30 to 33% of the digit length of the GNFS candidate came from this heuristic.
In this case, it worked nicely and saved you time! While B1 = 3e6 is the "right" choice for a t40, I find that using 11e6 costs little extra time for the t40 level, while increasing my chances of a factor the size you found (p45) pretty substantially. Even doing 250 43e6 curves is a t40, though a B1 that big would cost a fair amount more time for a t40 than a smaller choice. In fact, I've been meaning to sample a bunch of B1s to see which choice minimizes the time to complete a t45 I've done a few experiments before, and 11e6 is not optimal on my machines with gmpecm 6.4. Edit: or was this just for fun? 
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