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Old 2012-08-21, 04:48   #1
Walter Nissen
 
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Nov 2006
Terra

4E16 Posts
Question B1 and # curves for ECM

In the table in the readme , we find :
Code:
digits  optimal B1   expected curves
                       N(B1,B2,D)
                      default poly
   20     11e3        74
   25      5e4       214
   30     25e4       430
   35      1e6       904
   40      3e6      2350
   45     11e6      4480
   50     43e6      7553
   55     11e7     17769
   60     26e7     42017
   65     85e7     69408

Table 1: optimal B1 and expected number of curves to find a
factor of D digits with GMP-ECM.
Why do the second derivatives change sign ?
Does this come from the mathematics or is it from the details of
the computer technology used to compute the estimates , such as
available RAM , cache sizes at various levels , disk access times ,
etc. ?
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