Re: Seeming Non-determinism in Java Programs

Randall R Schulz wrote:
> The queue is
> implemented using a heap, though alternatives such as Skip-Lists are
> available as options (mostly implemented because of the issue I'm
> writing about here).

You haven't explicitly mentioned it... but are you using java.util.PriorityQueue?

...

> It's worth noting that it's often the case that there is relatively
> little distinction between actual FOM values (they are very frequently
> always small integers). While the priority queue may at any time hold
> several thousand items, there may be only a relative handful of
> distinct FOMs ordering that queue. Note, too, that the heap data
> structure is not stable w.r.t. equal key (FOM) values.

Have you tried (for the purpose of finding out more about the behaviour of your system, rather than for algorithmic correctness) extending your FOM, or FOM Comparator within your heap, to never have any two equal values, but to deterministically pick one as before the other?

Regards,
Stephen Denne.

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