[ADMB Users] factln
sibert at hawaii.edu
Tue Aug 27 14:38:02 PDT 2013
Has any one noticed small errors in double factln(double n) for small
values of n?
I'm getting the following for n = 0 ... 5
n factn(n) n!
0 -3.41362e-11 1
1 -7.81881e-11 1
2 0.693147 2
3 1.79176 6
4 3.17805 24
5 4.78749 120
Which seem to be incorrect for n=0 and n=1. The difference between 1e-11
is quite small but it turns out to make a difference after a
sufficiently long computation.
The algorithm depends on a series approximation for the log gamma
function. Perhaps arguments 0 and 1 should be treated a special cases?
Emeritus Researcher, SOEST
University of Hawaii at Manoa
Honolulu HI (GMT-10)
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