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Old 2009-09-17, 03:34   #46
geoff's Avatar
Mar 2003
New Zealand

13·89 Posts

Even though k=2131 was the lightest weight sequence (accounting for 30% of terms in the sieve), it contributed 24 (42%) of the 57 subsequences sieved by sr2sieve (i.e. there were 24 different values for n mod 720 for the sequence 2^n+2131).

So removing k=2131 from the sieve would be expected to increase speed by a factor of about sqrt(57/33) or 31% (for the BSGS step only, which normally accounts for the bulk of the total sieve time).

With sr2sieve 1.8.9 on my Core 2 Duo 2.66GHz in 64/32 bit mode I was getting 5.04M/2.79M p/s with the old 3k file, and now 6.85M/3.73M p/s with the new 2k file, so about 36%/33% faster.
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