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Subject: Re: Question for the MTD(f) experts

Author: José Carlos

Date: 03:07:57 04/14/04

Go up one level in this thread

On April 14, 2004 at 05:35:40, Tord Romstad wrote:

>On April 14, 2004 at 04:57:01, Dann Corbit wrote:
>>So my next question is, how do you normally populate a hash table with PV nodes,
>>since we only get edge values during the search?  Do I need to follow the pv
>>from hash to hash with a makemove for each succeeding pv node?
>I am not sure exactly what you mean here.  Are you asking how you build the PV
>beyond the first move?  In pseudo code, I do the following:
>void build_PV() {
>  hashentry_t *h;
>  int i;
>  for(h=get_hash(CurrentHashKey), i=0; h!=NULL && i<MAX_DEPTH && he->move;
>      h=get_hash(CurrentHashKey), i++) {
>    PV[i] = h->move;
>    hash_make_move(h->move);
>  }
>  PV[i] = 0;
>hash_make_move() is a function which is similar to make_move(), except
>that it only updates the hash key.

  I get the last part of my pv from the hash table (I'm PVS, not MTD(f), but
there's sometimes more moves in the hash table than in the pv array), but I need
to make() the move (not only update the hash table) in order to walk through
hash moves. I don't understand how you can make several moves in a row by only
updating the hash key. Can you please explain it?

  José C.

>Note that what you get is not really a PV at all.  It is just a string of
>moves which all caused a beta cutoff somewhere in the search.  It could
>be too short, too long, or contain incorrect moves.  In Gothmog, it even
>happens that it contains illegal moves, because I don't hash en passant

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