Steve Phelps created MATH-823:
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Summary: Distribution classes should allow randomData to be
configured via constructor or setter
Key: MATH-823
URL: https://issues.apache.org/jira/browse/MATH-823
Project: Commons Math
Issue Type: Improvement
Affects Versions: 3.0
Reporter: Steve Phelps
Priority: Minor
In my application I would like to represent several different probability
distributions using polymorphism - see example below. At compile-time the
distributions are declared of type RealDistribution. These distributions are
then configured with concrete classes at run-time using, e.g. dependency
injection. However, because there is no way to configure the underlying PRNG
-- ie the randomData field of these distributions, there is a danger of
introducing correlations into the random number streams through poor seed
management. If I have dozens of distributions, each configured automatically
with a new RandomDataImpl() then there is the possibility that some of these
streams will share the same seed value introducing spurious correlations.
One solution to this would be to explicitly manage seed values for every
distribution in my simulation by calling reseedRandomGenerator(). However,
this introduces unnecessary complexity and dependencies throughout my code. A
far simpler solution for my use case would be to configure all the
distributions in my simulation to use the same singleton instance of
RandomDataImpl for their randomData field (eg using dependency injection), thus
ensuring truly independent distributions - however currently the API does not
support this.
Could the Distribution classes be refactored to allow the randomData field to
be configured, eg through setters or via the constructor? This would be
similar to the design of the distribution classes provided by the CERN colt
library, which I believe offers more flexibility in this respect. It would
also be ideal, IMHO, if the Distribution objects were POJOs with zero-arg
constructors, which would then allow them to be configured using a
dependency-injection framework.
public class Simulation {
RealDistribution interArrivalTimeDistribution;
RealDistribution sizeDistribution;
double t;
public void run() {
t = 0;
while (true) {
t += interArrivalTimeDistribution.sample();
double magnitude = sizeDistribution.sample();
System.out.println(t + "\t" + magnitude);
}
}
public RealDistribution getInterArrivalTimeDistribution() {
return interArrivalTimeDistribution;
}
public void setInterArrivalTimeDistribution(RealDistribution
interArrivalTimes) {
this.interArrivalTimeDistribution = interArrivalTimes;
}
public RealDistribution getSizeDistribution() {
return sizeDistribution;
}
public void setSizeDistribution(RealDistribution xsizeDistribution) {
this.sizeDistribution = sizeDistribution;
}
}
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