Add a soft timer to avoid spending much more than 5 seconds on a move

[vchess.git] / public / javascripts / base_rules.js

diff --git a/public/javascripts/base_rules.js b/public/javascripts/base_rules.js
index d4315c7..26c7447 100644 (file)
--- a/public/javascripts/base_rules.js
+++ b/public/javascripts/base_rules.js
@@ -800,9 +800,14 @@ class ChessRules
                return VariantRules.INFINITY;
        }
 
+       static get SEARCH_DEPTH() {
+               return 3; //2 for high branching factor, 4 for small (Loser chess)
+       }
+
        // Assumption: at least one legal move
        getComputerMove(moves1) //moves1 might be precomputed (Magnetic chess)
        {
+               this.shouldReturn = false;
                const maxeval = VariantRules.INFINITY;
                const color = this.turn;
                if (!moves1)
@@ -834,21 +839,32 @@ class ChessRules
                }
                moves1.sort( (a,b) => { return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
 
+               let candidates = [0]; //indices of candidates moves
+               for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
+                       candidates.push(j);
+               let currentBest = moves1[_.sample(candidates, 1)];
+
                // Skip depth 3 if we found a checkmate (or if we are checkmated in 1...)
-               if (Math.abs(moves1[0].eval) < VariantRules.THRESHOLD_MATE)
+               if (VariantRules.SEARCH_DEPTH >= 3
+                       && Math.abs(moves1[0].eval) < VariantRules.THRESHOLD_MATE)
                {
                        // TODO: show current analyzed move for depth 3, allow stopping eval (return moves1[0])
                        for (let i=0; i<moves1.length; i++)
                        {
+                               if (this.shouldReturn)
+                                       return currentBest; //depth-2, minimum
                                this.play(moves1[i]);
                                // 0.1 * oldEval : heuristic to avoid some bad moves (not all...)
-                               moves1[i].eval = 0.1*moves1[i].eval + this.alphabeta(2, -maxeval, maxeval);
+                               moves1[i].eval = 0.1*moves1[i].eval +
+                                       this.alphabeta(VariantRules.SEARCH_DEPTH-1, -maxeval, maxeval);
                                this.undo(moves1[i]);
                        }
                        moves1.sort( (a,b) => { return (color=="w" ? 1 : -1) * (b.eval - a.eval); });
                }
+               else
+                       return currentBest;
 
-               let candidates = [0]; //indices of candidates moves
+               candidates = [0];
                for (let j=1; j<moves1.length && moves1[j].eval == moves1[0].eval; j++)
                        candidates.push(j);
 //             console.log(moves1.map(m => { return [this.getNotation(m), m.eval]; }));