SNFS targets which need more ECM

[fivemack]

Input number is 8251773826007569935997508400258020387415704842496291384921804552005221900662216913425918766759959411986740389289775723397876489045257317273581231513418658422520832086671482588420883344056709719929170923380392719222127153334982010212372015900798480010407898902278648943275730607 (277 digits)
Using B1=300000000-300000000, B2=3299108824840, polynomial Dickson(30), sigma=3:3380894970
Step 1 took 0ms
Step 2 took 1030674ms
********** Factor found in step 2: 9686520884177541535661024084340500289983192555244349
Found prime factor of 52 digits: 9686520884177541535661024084340500289983192555244349
Prime cofactor 851882107587920364660641481266438338230403696173481878562521588790426709670625553787663550972720378015286810501557748588179170143272281107487622422170172133317187820399465875718881126383728000476177931894438551879974742116443 has 225 digits

Also found with sigma=3:4245679786

[fivemack]

25600@3e8 stage-1 curves completed on C228_150_142.

Owing to a scheduling problem, I won't start stage-2 until tomorrow, and am not quite sure how long it will take.

Starting 30720@3e8 stage-1 curves on C237_139_126

[fivemack]

Dear XYYXF, can we have some more candidates please?

[fivemack]

Stage 2 now started on C228_150_142; on 12 threads on an i7-5820K it should take about eleven days and be finished in the evening of June 1st.

[fivemack]

Stage 2 completed on 25600 curves on C228_150_142; no factor found.

First 12800 of 30720 curves on C237_139_126 completed both stages; no factor found.

Proceeding.

[fivemack]

30720 curves on C237_139_126 completed, no factors found

[swellman]

Originally Posted by fivemack

Stage 2 completed on 25600 curves on C228_150_142; no factor found.

I started test sieving C228_150_142, just out of idle curiosity. It seems to be a relatively fast sieving 15/33 job, though I'm still gathering data.

How much more ECM is warranted before starting SNFS (assuming that is practical on 15e)?

[fivemack]

Originally Posted by swellman

I started test sieving C228_150_142, just out of idle curiosity. It seems to be a relatively fast sieving 15/33 job, though I'm still gathering data.

How much more ECM is warranted before starting SNFS (assuming that is practical on 15e)?

I think we have done enough ECM and can proceed to SNFS at once; I'll be interested to see your timing information once it's available.

[swellman]

Originally Posted by fivemack

I think we have done enough ECM and can proceed to SNFS at once; I'll be interested to see your timing information once it's available.

Should have results by Friday as I am traveling right now. Yields on 15e were 1.8+ for Q <200M but actual timing data on a modern (though non-bleeding edge) processor using the full range of Q won't be available until I'm home.

[wombatman]

Originally Posted by swellman

I started test sieving C228_150_142, just out of idle curiosity. It seems to be a relatively fast sieving 15/33 job, though I'm still gathering data.

How much more ECM is warranted before starting SNFS (assuming that is practical on 15e)?

Using SNFS-281 (not sure if that's right or not) for difficulty and B1=260e6 with 25600 curves, Bayesian tool says no more ECM.

[swellman]

C228_150_142 using the 15e siever, running one case at a time on a lightly loaded i7-3740QM (2.7 GHz) with 16Gb RAM in Win64 environment. Appears to be feasible for 15/33.

n: 338313268707086634350944196310206935873788335179366657051362293687646025379031678776100858721017586250223875732855601898290781411089750754177921272802024755914362548300092366882262859585028219144728898823695818541135039489183653
# 150^142+142^150, difficulty: 280.89, anorm: 6.00e+037, rnorm: -3.92e+052
# scaled difficulty: 283.36, suggest sieving rational side
# size = 6.177e-014, alpha = 0.000, combined = 1.426e-014, rroots = 0
type: snfs
size: 280
skew: 1.0627
c6: 25
c0: 36
Y1: -38237431646084858983458149164083507643015743502
Y0: 200678255510666758709703572094440460205078125
rlim: 500000000
alim: 500000000
lpbr: 33
lpba: 33
mfbr: 66
mfba: 66
rlambda: 3.0
alambda: 3.0

Test sieving with Q in blocks of 5000

Q= 20M     9464 rels	0.25046 sec/rel
Q=100M     9185 rels	0.27238 sec/rel
Q=200M     8307 rels	0.33120 sec/rel
Q=300M     7999 rels	0.39008 sec/rel
Q=400M     7337 rels	0.39881 sec/rel
Q=500M     6589 rels	0.49123 sec/rel
Q=600M     5966 rels	0.53501 sec/rel
Q=700M     6007 rels	0.56676 sec/rel

Suggesting a range of 20M-650M+ for Q.