On 10/09/2014 08:43 AM, Gilles wrote:
On Thu, 09 Oct 2014 08:12:06 -0500, Ole Ersoy wrote:
Hello,
Just sharing a few more thoughts on this WRT:
https://issues.apache.org/jira/browse/MATH-1124
(1) The issues currently are:
You have to inject an RNG when using the constructor lengthening
instantiation time and possibly increasing memory usage without
benefit.
(2)
The design of the distribution is heavier than it needs to be. For
example if you subclass AbstractIntegerDistribution the code I pasted
below, which I believe is used only in sampling, is included. As a
result of this anything that uses the distributions become heavier and
more complicated than need be, including:
- test code
- subclasses
- composites
- etc.
SAMPLING ONLY CODE IN AbstractIntegerDistribution
I'm not sure for "AbstractIntegerDistribution", but
"inverseCumulativeProbability"
from "AbstractRealDistribution" is used in some classes in package
"o.a.c.m.stat".
I have not looked at this in detail, but is it possible that "o.a.c.m.stat" could be
served in a more "Lightweight" way if this method were on a separate class in perhaps a
o.a.c.m.montecarlo package?
To me it seems more ideal to have something like
AbstractIntegerDistributionSampler and AbstractRealDistributionSampler that own
all the sampling related code. I also prefer composition over inheritance when
possible, but would have to look closer at how that might work.
[...]
Side Note:
There is a logProbability method that just computes the log of a
probability. If someone needs to do this can't they just do
FastMath.log(probability) directly?
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.
Cheers,
- Ole
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