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Subject: Re: How can I escape from check in Qsearch?

Author: Daniel Mehrmannn

Date: 06:00:12 05/04/05

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On May 04, 2005 at 01:37:06, Volker Böhm wrote:

>On May 03, 2005 at 17:08:58, Daniel Mehrmannn wrote:
>
>>On May 03, 2005 at 13:51:35, Kevin K wrote:
>>
>>>    quiesce(int alpha, int beta) {
>>>        int score = eval();
>>>        if (score >= beta) return score;
>>>        for (each capturing move m) {
>>>            make move m;
>>>            score = -quiesce(-beta,-alpha);
>>>            unmake move m;
>>>            if (score >= alpha) {
>>>                alpha = score;
>>>                if (score >= beta) break;
>>>            }
>>>        }
>>>        return score;
>>>    }
>>>I found this from http://www.ics.uci.edu/~eppstein/180a/990204.html
>>>But there is no code which takes care of escaping from check.
>>>Where do I have to put code which handles escaping from check in Qsearch?
>>
>>light version:
>>
>>    quiesce(int alpha, int beta) {
>>
>>        SideInCheck = in_check();
>>        if (SideInCheck) {
>>            genAllMoves();
>>        } else {
>>            /* StandPat CutOff */
>>            int score = eval();
>>            if (score >= beta) return score;
>>            genCaptures();
>>        }
>>
>>        for (each capturing move m) {
>>            make move m;
>>            score = -quiesce(-beta,-alpha);
>>            unmake move m;
>>            if (score >= alpha) {
>>                alpha = score;
>>                if (score >= beta) break;
>>                                   ^^^^^^ ?????
>>
>
>                                   must be return beta;
>>
>
>
>No it must not be return beta. The break leads to an exit of the for loop and
>thus to a return score. Returning the value >= beta is "fail soft", returning
>the value == beta is fail hard.
>
>Greetings Volker

Of course you're right, but its definely wrong for a beginner !
daniel



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