Alex Herbert created RNG-180:
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Summary: New SplittableUniformRandomProvider interface
Key: RNG-180
URL: https://issues.apache.org/jira/browse/RNG-180
Project: Commons RNG
Issue Type: New Feature
Components: client-api, core
Affects Versions: 1.5
Reporter: Alex Herbert
Assignee: Alex Herbert
Fix For: 1.5
The minimum java version for RNG is now 1.8. Stream support has been added for
the UniformRandomProvider and Sampler interfaces. These all operate using a
sequential stream. To use a parallel stream requires the concept of splitting
the source of randomness.
I propose to add a Splittable interface. This can be modelled on the interface
in the JDK 17 random package [SplittableGenerator
(javadoc)|https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/random/RandomGenerator.SplittableGenerator.html]:
{code:java}
public interface SplittableUniformRandomProvider
extends UniformRandomProvider {
SplittableUniformRandomProvider split();
SplittableUniformRandomProvider split(SplittableUniformRandomProvider
source);
Stream<SplittableUniformRandomProvider> splits();
Stream<SplittableUniformRandomProvider>
splits(SplittableUniformRandomProvider source);
Stream<SplittableUniformRandomProvider> splits(long streamSize);
Stream<SplittableUniformRandomProvider> splits(long streamSize,
SplittableUniformRandomProvider source);
{code}
The JDK interface has both a split and split(source) method, and similar for
the stream created by repeat splitting. The source is to provide the random
bits to initialise the new instances. In most cases this will just be the
current instance. However it provides a means to provide a small state
splittable generator for the random source of bits and use a larger state
generator to provide new instances from those bits, or vice versa. This allows
more flexibility to control the source of random bits, and the instance type of
the new split generators.
Note: It is possible to implement the entire interface using default methods
except:
{code:java}
SplittableUniformRandomProvider split(SplittableUniformRandomProvider
source);
{code}
The stream can be created by recursively splitting the current instance via a
custom Spliterator<SplittableUniformRandomProvider>.
Also note that the stream methods in UniformRandomProvider can be overridden to
support parallel streams. This requires for example a custom Spliterator.OfInt
to split the generator for parallel generation.
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