diff -r 23cd36180bf9 -r 4dde63ac0bb4 ai.js
--- a/ai.js	Thu Sep 25 01:10:01 2014 +0300
+++ b/ai.js	Thu Sep 25 02:05:48 2014 +0300
@@ -22,6 +22,28 @@
     return to;
 }
 
+ai.brdCache = function() {
+    this.cache = [];
+}
+ai.brdCache.prototype.get = function(brd) {
+    var compr = brd.compress();
+    var subCache = this.cache[compr[0]];
+    if (subCache) {
+        return subCache[compr[1]];
+    }
+    return undefined;
+}
+ai.brdCache.prototype.put = function(brd, val) {
+    var compr = brd.compress();
+    var subCache = this.cache[compr[0]];
+    if (subCache) {
+        subCache[compr[1]] = val;
+    } else {
+        this.cache[compr[0]] = [];
+        this.cache[compr[0]][compr[1]] = val;
+    }
+}
+
 // Each strategy is a function that except current board position as 2d array and context from
 // previous call to share state/precomputed values between calls.
 
@@ -343,6 +365,7 @@
     return score;
 }
 ai.expectimax.prototype.analyse = function(brd) {
+    this.brdCache = new ai.brdCache();
     var origBrd = new this.brdEngine(brd);
     var nextBrd = new this.brdEngine();
     var maxW = -1;
@@ -368,15 +391,9 @@
 ai.expectimax.prototype.evalFn = function(brd, depth) {
     if (depth >= this.depthLimit)
         return this.weight(brd);
-    if (this.cache[depth]) {
-        var cache = this.cache[depth];
-        for (var i = cache.length-1; i >= 0; i--) {
-            if (brd.equals(cache[i].brd))
-                return cache[i].weight;
-        }
-    } else {
-        this.cache[depth] = [];
-    }
+    var wCached = this.brdCache.get(brd);
+    if (wCached)
+        return wCached;
     var wMin = +Infinity;
     for (var i = 0; i < 3; i++) {
         for (var j = 0; j < 3; j++) {
@@ -402,11 +419,10 @@
             }
         }
     }
-    this.cache[depth].push({brd: brd, weight: wMin});
+    this.brdCache.put(brd, wMin);
     return wMin;
 }
 /* Mark that next board will be unrelated to previous, so any stored precompution can be cleared. */
 ai.expectimax.prototype.cleanup = function() {
-    this.cache = [];
 }