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Outpost evaluation
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Lucas Braesch



Joined: 31 May 2010
Posts: 1756
PostPost subject: Re: Outpost evaluation    Posted: Sat Apr 14, 2012 2:28 pm Reply to topic Reply with quote
Ferdy wrote:

Try this out for a start, basic knight not attacked by enemy pawn and knight protected by friendly pawn, note this is only for white, you take care for the black Smile .

Code:
case KNIGHT:
               score[LIGHT] += knight_pcsq[i];

               //knight outpost for white
               //consider only if it is located inside rank 4 to 6 and file b to g (std board)
               if(COL(i) >= 1 && COL(i) <= 6 && ROW(i) <= 4 && ROW(i) >= 2){
                  //if square i is not attacked by enemy pawn
                  if(piece[i-9] != PAWN || color[i-9] != DARK){
                     if(piece[i-7] != PAWN || color[i-7] != DARK){

                        //visual debug
                        //print_board();
                        //printf("square %d, is not attacked by enemy pawn\n", i);

                        score[LIGHT] += 4;

                        //add bonus if this knight is protected by friendly pawn
                        //left pawn
                        if(piece[i+7] == PAWN && color[i+7] == LIGHT){
                           score[LIGHT] += 2;
                           //visual debug
                        }
                        //right pawn
                        if(piece[i+9] == PAWN && color[i+9] == LIGHT){
                           score[LIGHT] += 2;
                           //visual debug
                        }
                     }
                  }
               }

               break;

Thank you Fernando. After so many failed attempts, I finally got a significant improvement with an implementation inspired by your code. Here's what I do in case anyone is interested:
1/ if a knight is in the outpost zone (File C->F, Rank 4->6), bonus +2 (centipawns)
2/ if a knight that verifies 1/ is also defended by a friendly pawn then I score an additional +3

And I did the same with bishops with +1 and +2 instead of +2 and +3, and that gave a further (small but significant).

My code is a bit more bitboard oriented and avoids loops:
Code:

   static const uint64_t OutPostZone[NB_COLOR] = {
      0x00003C3C3C000000ULL,   // Rank 4->6, File C->F
      0x0000003C3C3C0000ULL   // Rank 3->5, File C->F
   };
...
      /* Knight outposts */
      fss = B->b[us][Knight] & OutPostZone[us] & ~B->st->attacks[them][Pawn];
      if ((count = count_bit(fss))) {
         e->op[us] += count * 2;
         e->eg[us] += count * 2;
         
         if ((count = count_bit(fss & B->st->attacks[us][Pawn]))) {
            e->op[us] += count * 3;
            e->eg[us] += count * 3;
         }
      }

      /* Bishop outposts */
      fss = B->b[us][Bishop] & OutPostZone[us] & ~B->st->attacks[them][Pawn];
      if ((count = count_bit(fss))) {
         e->op[us] += count;
         e->eg[us] += count;
         
         if ((count = count_bit(fss & B->st->attacks[us][Pawn]))) {
            e->op[us] += count * 2;
            e->eg[us] += count * 2;
         }
      }
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Display posts from previous:   
Subject Author Date/Time
Outpost evaluation Lucas Braesch Sun Mar 18, 2012 10:42 am
      Re: Outpost evaluation Ed Schroder Sun Mar 18, 2012 12:15 pm
            Re: Outpost evaluation Lucas Braesch Sun Mar 18, 2012 1:47 pm
                  Re: Outpost evaluation Matthew R. Brades Sun Mar 18, 2012 4:27 pm
                        Re: Outpost evaluation John Merlino Sun Mar 18, 2012 4:44 pm
                              Re: Outpost evaluation Matthew R. Brades Sun Mar 18, 2012 5:54 pm
                                    Re: Outpost evaluation Charles Roberson Sun Mar 18, 2012 8:07 pm
                  Re: Outpost evaluation Pio Korinth Sun Mar 18, 2012 7:38 pm
                        Re: Outpost evaluation Michael Hoffmann Sun Mar 18, 2012 8:35 pm
                              Re: Outpost evaluation Pio Korinth Sun Mar 18, 2012 9:30 pm
                                    Re: Outpost evaluation Pawel Koziol Sun Mar 18, 2012 10:29 pm
                  Re: Outpost evaluation Ed Schroder Mon Mar 19, 2012 12:20 pm
                        Re: Outpost evaluation Robert Purves Tue Mar 20, 2012 7:14 am
                              Re: Outpost evaluation Gabriel LEPERLIER Fri Apr 13, 2012 8:00 pm
                                    Re: Outpost evaluation Ferdinand Mosca Sat Apr 14, 2012 1:34 am
                                          Re: Outpost evaluation Gabriel LEPERLIER Sat Apr 14, 2012 7:24 am
                                          Re: Outpost evaluation Lucas Braesch Sat Apr 14, 2012 2:28 pm
                                                Re: Outpost evaluation Ferdinand Mosca Sat Apr 14, 2012 4:34 pm
                  Re: Outpost evaluation Robert Hyatt Sat Apr 14, 2012 4:16 am
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