PART 1 • It's all in the numbers
When you're reading a numeric evaluation, positive numbers mean an
advantage for White, while negative numbers indicate an advantage for
Black.
So what is Houdini telling us with its evaluation of the position above? It's
looked 21 plies (ten and a half moves ahead) and determined that with
best play for both sides (the moves shown by the variation in the analysis
panel), after Black plays 23...b5 he will be 39/100ths of a pawn ahead.
In chess terms, this is equivalent to having a slight advantage (which is
what Houdini is displaying with the Chess Informant symbol to the left of
“-0.39” in the analysis panel).
While we're on the subject, here's a list of the common
Informant symbols and what they mean:
So what does an advantage of 39/100ths of a pawn really indicate? As
we've seen, Black is slightly ahead. In more concrete terms, a tempo is
estimated at being equivalent to about a third of a pawn. So Black's advantage is about the same as being a tempo ahead. More important (and
less abstract) is that we've learned Black is better off attacking White's
Queen and trading minor pieces before he snaps off the f1-Rook to win
the exchange.
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