Transposition tables for newbs

[bob]

First, most authors will use the term "draft" here instead of "depth" to avoid confusion. Draft, of course, is the difference between the ply at which an entry is stored and the number of full width plies from where the terminal value was determined.

An intermediate programming step is to not reference the stored score at all, but to simply use the stored move as the first move in the move ordering. When this is working reliably, then further work with scores can be done.

Now I'm a bit confused with the term draft. I always store remaining depth (truncated down as I use fractional depths). I think it's ok. Am I missing something? It has nothing to do with extensions/reductions I suppose?

That is correct. Steven's definition is not quite right, because we don't count plies in the q-search as part of the draft. Had he said "from the frontier node (which is the first q-search ply)" then it would be more accurate. But that is probably what he was thinking, anyway.