Author rhettinger mark.dickinson, nirinA, rhettinger, stutzbach, terry.reedy 2008-07-21.22:34:42 0.00318031 No <1216679684.4.0.943072620014.issue3366@psf.upfronthosting.co.za>
Content
```Since we're not in a hurry for Py2.7 and 3.1, I would like to this
kicked around a bit on the newsgroup and in numpy forums (personally, I
would also post a pure python equivalent to the ASPN cookbook for
further commentary).

There are several different approximations to choose from.  Each of
them has their own implications for speed and accuracy.  IIRC, the one
I used in test.test_random.gamma() was accompanied by a proof that its
maximum error never exceeded a certain amount.  I think there were some
formulas that made guarantees only over a certain interval and others
that had nice properties in the first and second derivatives (one that
don't have those properties can throw newtonian solvers wildly off the
mark).

Let's let the community use its collective wisdom to select the best
approach and not immediately commit ourselves to the one in this patch.

At one point, Tim was reluctant to add any of these functions because
it is non-trivial to do well and because it would open a can of worms
about why python gets a different answer (possibly not as close to
true) and some other favorite tool (matlab, excel, numpy, and
engineering calculator, etc).

FWIW, I changed the 2.6 version of test_random.gamma() to take
advantage of msum() to increase its accuracy when some of the summands
have nearly cancelling values.```
History
Date User Action Args
2008-07-21 22:34:44rhettingersetspambayes_score: 0.00318031 -> 0.00318031
recipients: + rhettinger, terry.reedy, mark.dickinson, stutzbach, nirinA
2008-07-21 22:34:44rhettingersetspambayes_score: 0.00318031 -> 0.00318031
messageid: <1216679684.4.0.943072620014.issue3366@psf.upfronthosting.co.za>