Here is a [url=http://www.mersenneforum.org/showpost.php?p=453643&postcount=952]nice post by Fivemack with a worked example[/url] which I bookmarked a while back for future reference. Might be helpful.

[QUOTE=swellman;455654]Here is a [url=http://www.mersenneforum.org/showpost.php?p=453643&postcount=952]nice post by Fivemack with a worked example[/url] which I bookmarked a while back for future reference. Might be helpful.[/QUOTE]

Also very helpful. Thanks!

Two more from the Most Wanted Road Blocks file. These are essentially the same size as the previous p^59-1. On the last number I did trial sieving and modified the lambda to 2.7 and 2.8. It produced the exact same yield (at the low end Q) but the time per rel slightly increased. I’m not sure when it is beneficial to adjust lambda values.

[CODE]n: 847723934416465493580272554892025373599007092570627195956498222363745656989708622154204752294161815812225418255421119129594611560479912098356746948456292420295531238045291708101479001652143055178245176897285838111612431466354707316652219
# 12161^59-1, difficulty: 245.10, skewness: 6.56, alpha: 0.00
# cost: 5.69852e+18, est. time: 2713.58 GHz days (not accurate yet!)
skew: 6.561
c5: 1
c0: -12161
Y1: -1
Y0: 10462403413179934189087975464111709024319498795521
m: 10462403413179934189087975464111709024319498795521
rlim: 134000000
alim: 134000000
lpbr: 31
lpba: 31
mfbr: 62
mfba: 62
rlambda: 2.6
alambda: 2.6[/CODE]

[CODE]n: 1646567655210039000288095767644921118295743082919258060516520401092306844415757601694422313656162831139089237128683705211190457179971017452768733076015656496624625029005054302685465734055828748899565753384816826747043000743982635149655359
# 12301^59-1, difficulty: 245.40, skewness: 6.58, alpha: 0.00
# cost: 5.83134e+18, est. time: 2776.83 GHz days (not accurate yet!)
skew: 6.576
c5: 1
c0: -12301
Y1: -1
Y0: 12002867777697010537813175139358373530690225287601
m: 12002867777697010537813175139358373530690225287601
rlim: 134000000
alim: 134000000
lpbr: 31
lpba: 31
mfbr: 62
mfba: 62
rlambda: 2.6
alambda: 2.6[/CODE]

Lambda determines which entries in the sieve array get looked at; I think alambda=2.5 means 'look at anything where the estimate for the part on the algebraic side remaining after small factors are removed is alim^2.5 or less'. So increasing lambda will slow down the sieving slightly, and it's interesting that it didn't reveal a single extra factor.

If you have done trial sieving and got some yield measurements, please put them at the bottom of the post, otherwise I end up repeating the trial sieving to get the estimate for the initial range to submit.

C237_12161_19 and C238_12301_19 jobs queued to 14e

It looks as if we can sit back for a few days, the queues are reasonably full.

For the C207 blocking progress on HP2(4496) I'd try something like [code]
lpbr: 32
lpba: 33
mfbr: 64
mfba: 66
rlambda: 2.7
alambda: 2.7
[/code]
since the algebraic norms for a GNFS job are much larger than the rational norms. It should need about 3/4 as many relations as 33/33 to build a matrix. So if it doesn't reduce yield too much you should save more time on LA than it will add to sieving.

Or even: [code]
lpbr: 32
lpba: 33
mfbr: 64
mfba: 96
rlambda: 2.7
alambda: 3.7
[/code]
But I've never done a job this large so let test sieving guide you.

Chris

[QUOTE=chris2be8;455737]For the C207 blocking progress on HP2(4496) I'd try something like [code]
lpbr: 32
lpba: 33
mfbr: 64
mfba: 66
rlambda: 2.7
alambda: 2.7
[/code]
since the algebraic norms for a GNFS job are much larger than the rational norms. It should need about 3/4 as many relations as 33/33 to build a matrix. So if it doesn't reduce yield too much you should save more time on LA than it will add to sieving.

Or even: [code]
lpbr: 32
lpba: 33
mfbr: 64
mfba: 96
rlambda: 2.7
alambda: 3.7
[/code]
But I've never done a job this large so let test sieving guide you.

Chris[/QUOTE]

Duly noted. Once I get all the candidate polynomials from the request thread in, I'm going to use YAFU to narrow down the best one and then try all these suggested tweaks to maximize output. Again, I really appreciate all of you providing these tips. :smile:

Another 14e candidate
 

Another 14e candidate with good yield. It has survived t55 by yoyo@Home. plus another 2000 curves @B1=3e8 by me.

C207_128_91

[code]
n: 802320890217478042163831208585260808818112468994562646062921218163624296944397084983306680966607349361160236150639896586413248097648688106047528225560026228558455487639033157834143057744927653178053197649963
# 128^91+91^128, difficulty: 251.06, anorm: 2.57e+38, rnorm: -2.76e+47
# scaled difficulty: 252.56, suggest sieving rational side
# size = 1.360e-12, alpha = 0.179, combined = 1.511e-13, rroots = 0
type: snfs
size: 251
skew: 4.0072
c6: 2
c0: 8281
Y1: -137996870875659993023030601717979081222891
Y0: 81129638414606681695789005144064
rlim: 240000000
alim: 240000000
lpbr: 32
lpba: 32
mfbr: 64
mfba: 64
rlambda: 2.8
alambda: 2.8
[/code]

Anybody got more candidates for 14e? That queue has almost run dry.

I should have another one to propose tomorrow.

Queued C207_128_91

(if you've done the trial sieving, please post something like

[code]
total yield: 1830, q=240001001 (0.30546 sec/rel)
[/code]

or suggest an initial Q-range, otherwise I'll do the trial sieving again to get the initial Q-range)

Ok, I always do trial sieving to verify that the performance of a poly is appropriate for 14e (or 15e). Always just assumed the gatekeepers did some kind of prep behind the curtain but I'll be happy to post test sieving results and suggested sieving range from now on if it helps.

I learned from this forum that for an individual effort, the best starting Q is half of r/alim for SNFS, a third if GNFS. But this rule of thumb does not seem to be best practice for BOINC.

What value of Q0 is preferred? I'll be sure the test 2-3 Q values for estimating the sieving range.

And thank you for enqueining C207_128_91.

[QUOTE=swellman;456227]I learned from this forum that for an individual effort, the best starting Q is half of r/alim for SNFS, a third if GNFS. But this rule of thumb does not seem to be best practice for BOINC.
[/QUOTE]

I use alim/4 for GNFS and alim/6 for SNFS, subject to a minimum starting value of 5M and maximum starting value of 25M. For small (say, a core-week or less) projects, I use alim/3 for GNFS and alim/4 for SNFS.

BOINC seems to start at 20M pretty regularly, and I don't think it matters a whole lot whether one chooses 15M or 20M or 25M to start when alim/rlim are 100M+, so 20M has become a sort of de facto standard for all but the largest projects.

In the past, it was believed that the faster sec/rel times at small Q were illusions because of higher duplicate rates, but I think that has been debunked in the alim/5 to alim/2 region.