On Thu, Oct 9, 2014 at 6:03 PM, Ole Ersoy <ole.er...@gmail.com> wrote:
> I think that, for some distribution, the computation of log(p) is more
>>>> accurate. This was a feature request from not long ago.
>>>>
>>>>
>>> Just pasting the method below:
>>>
>>> public double logProbability(int x) {
>>> return FastMath.log(probability(x));
>>> }
>>>
>>> So it retrieves the probability of the index and uses FastMath to compute
>>> the log. We could do:
>>>
>>> FastMath(distribution.probability(x));
>>>
>>> It just seems a bit over engineered to have something this trivial in the
>>> API, unless I'm missing something.
>>>
>>>
>> This is the default implementation. For some distributions there is a more
>> efficient way to compute the logProbability directly, and for these
>> distributions the method is overridden (e.g. GeometricDistribution,
>> BinomialDistribution, ...).
>> Otherwise one would have to call probability(x) first, which in many cases
>> involves calling exp(...) and then compute the log of it, which is just a
>> waste of cpu.
>>
>
> So I guess my question is "Why is there value in having this as part of
> the public API of AbstractIntegerDistribution?". Not really a big deal,
> but it just seems like it's an implementation detail.
>
We could not yet add it to the interface due to binary / source
compatibility rules, but it will be done for 4.0, see the ticket:
https://issues.apache.org/jira/browse/MATH-1039
Thomas
