mersenneforum.org Gratuitous factors thread
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 2018-08-17, 13:19 #452 Nooks   Jul 2018 19 Posts ECM on a C213, the last divisor of (34*10^229-61)/9 with sigma=1:3941682105: Using B1=2900000000, B2=82640965106716, polynomial Dickson(30), sigma=1:3941682105 [...] ********** Factor found in step 2: 35020442769329876367522852735060830348867981850170604303099578467 Found prime factor of 65 digits: 35020442769329876367522852735060830348867981850170604303099578467 Prime cofactor 6463948784722816185901384621852688761921664616020783901443547268726228461664676485561963639543974467240297445194995726733180417921657435498535243769 has 148 digits The factor was found on the 25th curve; taking into account all the other cores running curves this was the 2400th curve of only 9600 I planned to run before handing the problem to CADO-NFS, so I'm counting myself quite lucky!
2018-08-17, 13:49   #453
ET_
Banned

"Luigi"
Aug 2002
Team Italia

112448 Posts

Quote:
 Originally Posted by Nooks ECM on a C213, the last divisor of (34*10^229-61)/9 with sigma=1:3941682105: Using B1=2900000000, B2=82640965106716, polynomial Dickson(30), sigma=1:3941682105 [...] ********** Factor found in step 2: 35020442769329876367522852735060830348867981850170604303099578467 Found prime factor of 65 digits: 35020442769329876367522852735060830348867981850170604303099578467 Prime cofactor 6463948784722816185901384621852688761921664616020783901443547268726228461664676485561963639543974467240297445194995726733180417921657435498535243769 has 148 digits The factor was found on the 25th curve; taking into account all the other cores running curves this was the 2400th curve of only 9600 I planned to run before handing the problem to CADO-NFS, so I'm counting myself quite lucky!

 2018-08-18, 19:49 #454 wpolly     Sep 2002 Vienna, Austria 3·73 Posts Code: Input number is (109^123-1)/(109^41-1)/95898591887152691733740679 (142 digits) Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=1:3742107819 Step 1 took 66545ms Step 2 took 23004ms ********** Factor found in step 2: 113910660004153337924628664386678247208828533 Found prime factor of 45 digits: 113910660004153337924628664386678247208828533 Prime cofactor ((109^123-1)/(109^41-1)/95898591887152691733740679)/113910660004153337924628664386678247208828533 has 98 digits This factor appeared on curve 92 out of a planned 4000.
 2018-09-16, 17:54 #455 BudgieJane     "Jane Sullivan" Jan 2011 Beckenham, UK 3×79 Posts C135 from 1208^47+1: Code: prp43 = 7872050983542095687417246190511880248639711 prp92 = 16940363046999582482928413622346911064605327855533940683539949731286830685125532654826597073 C125 from 1259^47+1 Code: prp38 = 98345853344307565253324824092518095601 prp87 = 929528781257601652853545435226628885326214271769204819819291780270828421426874911996487
 2018-12-10, 13:54 #456 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 23×797 Posts L3780 factored 199-digit GNFS, done entirely locally Code: N 1253697014483921701519774710080293856978446067093422585355224278757029355514329819946916985971979863264272814638205843444068083099253312799641803553719988196912895006268194994880801257942554688556001 SKEW 127028183.52 A0 -595638964036345481237071140491743854143245809544 A1 29926818433789606747718647951662435504208 A2 307924512754708078991927303315680 A3 -4781679268252586458599169 A4 -22400530233973836 A5 102927636 R0 -104023657306189391164144906961130612015 R1 651664577069232468431 Sieved Q=30M .. 285M and 330M..335M with gnfs-lasieve4I16e; 12 Aug - 10 Nov on 64 cores E5-2650 and some other resources; linear algebra was 27 days on 14 cores i9-7940X Code: lpbr: 33 lpba: 33 mfbr: 66 mfba: 96 alambda: 3.5 rlambda: 2.4 alim: 268000000 rlim: 268000000 Code: Tue Nov 13 07:30:38 2018 matrix is 48788680 x 48788857 (23378.5 MB) with weight 7047295017 (144.44/col) Tue Nov 13 07:30:38 2018 sparse part has weight 5543070617 (113.61/col) Tue Nov 13 07:40:47 2018 filtering completed in 2 passes Tue Nov 13 07:40:57 2018 matrix is 48786801 x 48786976 (23378.4 MB) with weight 7047214552 (144.45/col) Tue Nov 13 07:40:57 2018 sparse part has weight 5543053801 (113.62/col) Tue Nov 13 07:43:08 2018 matrix starts at (0, 0) Tue Nov 13 07:43:15 2018 matrix is 48786801 x 48786976 (23378.4 MB) with weight 7047214552 (144.45/col) Tue Nov 13 07:43:15 2018 sparse part has weight 5543053801 (113.62/col) Tue Nov 13 07:43:15 2018 saving the first 240 matrix rows for later Tue Nov 13 07:43:27 2018 matrix includes 256 packed rows Tue Nov 13 07:43:42 2018 matrix is 48786561 x 48786976 (21440.4 MB) with weight 5118664178 (104.92/col) Tue Nov 13 07:43:42 2018 sparse part has weight 4839889639 (99.20/col) Tue Nov 13 07:43:42 2018 using block size 8192 and superblock size 473088 for processor cache size 19712 kB Tue Nov 13 07:45:56 2018 commencing Lanczos iteration (14 threads) Tue Nov 13 07:45:56 2018 memory use: 29766.8 MB Tue Nov 13 07:47:23 2018 linear algebra at 0.0%, ETA 637h43m Tue Nov 13 07:47:47 2018 checkpointing every 80000 dimensions Mon Dec 10 04:01:57 2018 lanczos halted after 191142 iterations (dim = 48786558) Mon Dec 10 04:05:48 2018 recovered 29 nontrivial dependencies Mon Dec 10 04:06:03 2018 BLanczosTime: 2324842 Mon Dec 10 04:06:03 2018 elapsed time 645:47:23 Code: Mon Dec 10 12:47:23 2018 p82 factor: 9214409416745614101198894993721726856303159042273240016125104117470329343249250561 Mon Dec 10 12:47:23 2018 p117 factor: 136058314513954814229280792975681347764936790375643059794253062274788902853667069820292458749493930656793985621603041 Last fiddled with by fivemack on 2018-12-10 at 14:15
 2019-01-02, 17:36 #457 unconnected     May 2009 Russia, Moscow 251010 Posts 59-digit factor of near-repdigit (691*10300-7)/9 was found by ECM Code: Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=3032066922 Step 1 took 382110ms Step 2 took 101223ms ********** Factor found in step 2: 21601138366813705693033870951386003818115059066377541324921 Found probable prime factor of 59 digits: 21601138366813705693033870951386003818115059066377541324921 Composite cofactor 1416732463683710775182530542771135815901595515342842856966117614129678227859411077172659990398292541537568243400899333336769174248499204974915626874899 has 151 digits Happy New Year everyone!
2019-01-02, 18:10   #458
bsquared

"Ben"
Feb 2007

23×419 Posts

Quote:
 Originally Posted by unconnected 59-digit factor of near-repdigit (691*10300-7)/9 was found by ECM Code: Using B1=43000000, B2=240490660426, polynomial Dickson(12), sigma=3032066922 Step 1 took 382110ms Step 2 took 101223ms ********** Factor found in step 2: 21601138366813705693033870951386003818115059066377541324921 Found probable prime factor of 59 digits: 21601138366813705693033870951386003818115059066377541324921 Composite cofactor 1416732463683710775182530542771135815901595515342842856966117614129678227859411077172659990398292541537568243400899333336769174248499204974915626874899 has 151 digits Happy New Year everyone!
Possibly the largest of the year so far :)

 2019-01-07, 07:18 #459 VictordeHolland     "Victor de Hollander" Aug 2011 the Netherlands 23×3×72 Posts Code: P-1 found a factor in stage #2, B1=2000000, B2=40000000, E=6. M55715311 has a factor: 7239753241433926010086285741758451306831 (P-1, B1=2000000, B2=40000000, E=6) 40 digit factor, not composite :).
 2019-01-11, 22:48 #460 petrw1 1976 Toyota Corona years forever!     "Wayne" Nov 2006 Saskatchewan, Canada 32×7×71 Posts Factored twin primes
 2019-01-12, 05:28 #461 LaurV Romulan Interpreter     Jun 2011 Thailand 214038 Posts not really twins (difference of 10), and generally, you can't factor a prime...
 2019-01-12, 07:05 #462 nomead     "Sam Laur" Dec 2018 Turku, Finland 23·41 Posts Heh. Which sort of reminds me, I kinda shot myself in the foot a week ago. I was LL double checking a few exponents and decided to run TF a bit further just for the heck of it ...and found a factor on one of them. Some CPU time wasted, but more saved, as it wasn't even halfway through at that point. M51202189 It even had some (old? low bounds?) P-1 work done on it, but then again, mersenne.ca says that min. B1 is 20,857 and min. B2 10,925,329,931 so maybe it was just one of those hard to find factors.

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