Author: JW de Kort
Date: 06:20:15 07/11/01
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On July 10, 2001 at 07:44:50, Leen Ammeraal wrote: >There was a question about Static Exchange Evaluation >in CCC a short while ago, with reactions from >Bob Hyatt and Bruce Moreland. Strangely enough, >these postings, along with one from myself, seem >to have disappeared, so I send my contribution >once again below. > > >Here is my function for Static Exchange Evaluation. >================================================== >It is based on the value cur of the current piece >on the board that is first to be captured, and >two tables: > >att[nAtt-1], ..., att[0] values of attackers >def[nDef-1], ..., def[0] values of defenders > >Note the order: att[nAtt-1] is the first attack, etc. >Let's rewrite Hyatt's example RxR RxR QxR BxQ >as follows, to distinguish between the three rooks >involved: > >R1xR0 R2xR1 QxR2 BxQ > >Then we have: >cur = R0, nAtt = nDef = 2, >att[1] = R1, att[0] = Q >def[1] = R2, def[0] = B >This function returns the value 0 in this case: > >// Static Exchange Evaluation: >int gain(int cur, int *att, int nAtt, int *def, int nDef) >{ int retval = 0; > if (nAtt) > { int profit = cur - gain(att[nAtt-1], def, nDef, att, nAtt-1); > if (profit > 0) > retval = profit; > } > return retval; // Always >= 0 >} > >Explanation: the profit of capturing a piece is equal >to the value of that piece minus the profit of the >opponent after this capture, except that a profit is >set to zero when this computation gave a negative result. >So far, I did not succeed in replacing this function >with a faster, nonrecursive one. It would be nice if >anyone of this forum did and showed an equivalent >but faster version. > >Leen Ammeraal >http://home.wxs.nl/~ammeraal/ Dear mr Ammeraal, Could you plese give some explaination regarding this sources. e.g how do you fill the att[] en def[] arrays? Bedankt! Jan Willem de Kort
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