mersenneforum.org Bizarre problem with gnfs-lasieve4I15e
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 2007-11-27, 13:37 #1 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 143608 Posts Bizarre problem with gnfs-lasieve4I15e I'm trying to work out optimal parameters for a rather large SNFS job, and was led, out of a desire to pull lots of relations out of each special-Q so that I wouldn't have to run special-Q well into the area of diminishing returns, to build gnfs-lasieve4I15e by replacing Code: all : $(BINDIR)/gnfs-lasieve4I12e$(BINDIR)/gnfs-lasieve4I13e \ $(BINDIR)/gnfs-lasieve4I14e with Code: all :$(BINDIR)/gnfs-lasieve4I12e $(BINDIR)/gnfs-lasieve4I13e \$(BINDIR)/gnfs-lasieve4I14e \$(BINDIR)/gnfs-lasieve4I15e in ggnfs/src/lasieve4/Makefile But I found that this gave me fewer relations when I used a small-prime bound of 80 million than when I used one of 70 million. The input file is below; I just ran 'gnfs-lasieve4I15e -a job' Code: n: 27312187167948796049898887842782596405655381943670578373120353781997447000328700858938482409418918448758778194857586271196003004729048486053340769161697167767956404785889687728602979284674332324623675660860406658739006337124213538943374972682241 type: snfs skew: 1 c6: 2 c0: -1 Y1: -1 Y0: 1393796574908163946345982392040522594123776 alim: 70 or 80 million rlim: 70 or 80 million lpba: 30 lpbr: 30 mfba: 62 mfbr: 62 alambda: 2.6 rlambda: 2.6 q0: 100000000 qintsize: 10000 For example, the relation Code: -77588747,213413649:41fe9f3,4eeceeb,642B,9991,1D98D,32E883,90F4A3,1D69,D,89:d809cef,16d10281,4E541,5BFC27,B92861,A7,ACF,5F5E1DF appears in the output from sieving to 70M and not when I sieve to 80M; diffing the output files indicates that going to 80M lost me some relations and gained me none. If I do the same from the output files from running the same input file under gnfs-lasieve4I14e, I find (as expected) that I only gain relations. The algebraic-side factors (spot the special-Q) are Code: [167 1] [2767 1] [320833 1] [6028327 1] [12134497 1] [100000223 1] * [226532591 1] [382796417 1] and the rational-side factors are Code: [13 1] [137 1] [7529 1] [25643 1] [39313 1] [121229 1] [3336323 1] [9499811 1] [69200371 1] [82759403 1] so there are no factors on either side in the 70M .. 80M range!
2007-11-27, 17:12   #2
jasonp
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Oct 2004

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Quote:
 Originally Posted by fivemack But I found that this gave me fewer relations when I used a small-prime bound of 80 million than when I used one of 70 million.
Grepping through the lattice siever source, most of the machine-specific versions of lasieve/*/siever_config.h define L1_BITS to be 14, so I suspect the lattice size cannot exceed this number. Maybe you can increment L1_BITS and recompile?

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