Manual de Houdini 3 2012 | 页面 248

248

Houdini Help
http://www.mediafire.com/?5vh54gz9d9cfmh5
and extract the bitbase files on your hard disk. The bitbases are loaded in memory at
startup of the engine.
The location of the Scorpio bitbases is specified in the ScorpioPath option.
Probing Frequency
The frequency of the EGTB probing can be configured with the Hard Probe Depth and
Soft Probe Depth options. A "soft probe" will only use the data available in memory,
whereas a "hard probe" can require a relatively slow disk access. Soft probing are
available only with the Gaviota EGTB.
Houdini will always probe the EGTB for the initial position of the search. If an EGTB
mate position is identified, the full main line will be shown immediately. If the initial
position is an EGTB draw but Houdini has a material advantage, and if Contempt is
active, Houdini will still play for a win - the opponent might be human or an engine
without end game table bases.

Question: I don't understand the concept of setting a depth for EGTB probing.
Why wouldn't all positions that have 3-4-5 pieces probe the table bases to get
the evaluation?
EGTB probes are extremely slow compared to a normal evaluation by the engine.
Suppose you have a K+Q+P against K+N ending. Even without consulting the table
bases Houdini knows that this ending is easily won for the K+Q+P side. Consulting the
EGTB for this position would reduce Houdini's playing strength, as it could easily have
evaluated 1,000 other positions instead of making the rather useless EGTB probe.
Even the in-memory "soft" Gaviota or Scorpio probes are sometimes relatively slow
compared to a native evaluation of the position - especially when multiple threads are
running. If two threads simultaneously perform a soft probe, the second thread has to
wait for the first to finish its probe.
This is aggravated by the fact that Houdini contains a lot of end game knowledge in
its native evaluation function - a lot more than most other chess engines. For
example, even in a non-obvious ending like KBP v KB with bishops of the same color,
Houdini knows quite well which positions are won and which are drawn. This means
that except for difficult-to-evaluate endings like KQP v KQ the 5-men EGTB do not
really increase Houdini's playing strength.
To handle this situation in an intelligent way, Houdini will vary the frequency at which
the EGTB are probed depending on the actual end game that is occurring. In difficultto-evaluate endings Houdini will probe the EGTB files much earlier than in endings that
are easy to evaluate.
The frequency of the probing is further influenced by the following parameters:
· Hard Probe Depth is the earliest search depth at which the EGTB probing will result in
a disk access. You can reduce this value if the table base files are installed on a very
fast disk, or if you are running less than 4 threads.

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