Hello Alex.
>>> [...]
>
> OK so this results in:
>
> /**
> * Some summary.
> */
> public interface JumpableUniformRandomProvider extends
> UniformRandomProvider {
> /**
> * Creates a copy of the UniformRandomProvider and advances the
> state of the copy.
> * The state of the current instance is not altered. The state of
> the copy will be
> * advanced an equivalent of {@code n} sequential calls to a method
> that updates the
> * state of the provider.
> *
> * @return the copy with an advanced state
> */
> JumpableUniformRandomProvider jump();
> }
>
+1
[Clean and lean: and no side-effects to explain...]
>
> This can be documented in an implementation as:
>
> public class MyJumpingRNG implements JumpableUniformRandomProvider {
> /**
> * {@inheritDoc}
> *
> * <p>The jump size {@code n} is the equivalent of {@code 2^64}
> calls to
> * {@link UniformRandomProvider#nextLong() nextLong()}.
> */
> @Override
> public JumpableUniformRandomProvider jump() {
> // TODO Auto-generated method stub
> return null;
> }
> }
+1
>
> Do we add a second interface for LongJumpableUniformRandomProvider?
Sure, if the functionality is provided by some of the algorithms implemented
in [RNG].
But let's have the two functionalities in separate commits.
>
> >> So the options are (in all cases returning the copy):
> >>
> >> 1. createAndJumpCopy
> >> 2. copyAndJumpParent
> >> 3. jumpParentAndCopy
> >> 4. jump and copy separately
> >>
> >> 1. Your preferred option. A copy of the state is made. The state is
> >> advanced in the copy and returned. But when called repeatedly it will get
> >> the same generator and code must be organised appropriately.
> > We could provide a convenience method in "RandomSource":
> >
> > public UniformRandomProvider[] jump(int n,
> > JumpableUniformRandomProvider parent) {
> > final UniformRandomProvider[] rngs = new UniformRandomProvider[n];
> > UniformRandomProvider tmp = parent;
> > for (int i = 0; i < n; i++) {
> > rngs[i] = restrict(tmp);
> > tmp = tmp.jump();
> > }
> > return rngs;
> > }
>
> +1. Remove the need for the user to repeat boiler plate code.
>
> Same sort of idea of longJump() too.
+1
> >> It is not actually possible to jump forward a single instance. Only
> >> children are advanced.
> > A feature: There is only one way to alter the state of an instance
> > (i.e. a call to "next()").
> OK.
Great. :-)
Gilles
> >
>>> [...]
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