Differences

This shows you the differences between two versions of the page.

--- chess:programming:alpha-beta_pruning:transposition_table_enhanced_alpha-beta [2021/11/10 22:44] – created peter
+++ chess:programming:alpha-beta_pruning:transposition_table_enhanced_alpha-beta [2021/11/10 23:04] (current) – peter
@@ Line 5: / Line 5: @@
   // Check if position is in TT and has been searched to sufficient depth.
   if retrieve(n) = found then
-    if n.ƒ+ or n.ƒ+ = n.ƒ then return n.ƒ+;
+    if n.ƒ+ <= alpha or n.ƒ+ = n.ƒ- then return n.ƒ+;
-if n.ƒ then return n.ƒ ;
+    if n.ƒ- >= beta then return n.ƒ-;
-/* Reached the maximum search depth */
-if n = leaf then
+  // Reached the maximum search depth.
-n.ƒ := n.ƒ+ := g := eval(n);
+  if n = leaf then
-else
+    n.ƒ- := n.ƒ+ := g := eval(n);
-g := ; a := ;
+  else
-c := firstchild(n);
+    g := -XXX; a := alpha;
-/* Search until a cutoff occurs or all children have been considered */
+    c := firstchild(n);
-while g < and c = do
-g := max(g, Alpha-Beta(c, , a));
+    // Search until a cutoff occurs or all children have been considered.
-a := max(a, g);
+    while g < beta and c != YYY do
-c := nextbrother(c);
+      g := max(g, -Alpha-Beta(c, -beta, -a));
-/* Save in transposition table */
+      a := max(a, g);
-if g then n.ƒ+ := g;
+      c := nextbrother(c);
-if < g < then n.ƒ+ := n.ƒ := g;
-if g then n.ƒ := g;
+    // Save in transposition table.
+    if g <= alpha then n.ƒ+ := g;
+    if alpha < g < beta then n.ƒ+ := n.ƒ- := g;
+    if g >= beta then n.ƒ- := g;
 store(n);
 return g;
 </code>