From c5fa2ebf21eea205252d740f2ef4101d43ae945c Mon Sep 17 00:00:00 2001
From: "Phu Minh (Catto)" <53084840+nguyenphuminh@users.noreply.github.com>
Date: Wed, 24 Jul 2024 15:42:25 +0700
Subject: [PATCH] Add delta pruning (#15)

Add delta pruning based on futility pruning
---
 README.md       | 1 +
 catto.config.js | 2 +-
 package.json    | 2 +-
 src/core.ts     | 9 +++++++--
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 3d99238..15ad624 100644
--- a/README.md
+++ b/README.md
@@ -76,6 +76,7 @@ Note that the config file is compiled with the engine itself, so if you are usin
 * Transposition table.
 * Null-move pruning.
 * Futility pruning.
+* Delta pruning.
 * Late move reductions.
 * Search extensions:
     * Check extensions.
diff --git a/catto.config.js b/catto.config.js
index 35e0818..90c86f8 100644
--- a/catto.config.js
+++ b/catto.config.js
@@ -1,6 +1,6 @@
 module.exports = {
     // Current version to show in UCI
-    version: "v0.8.0",
+    version: "v0.8.1",
     // Late move reduction config
     lmrFullDepth: 4, // Number of moves to be searched in full depth
     lmrMaxReduction: 3, // Only apply LMR above this depth
diff --git a/package.json b/package.json
index 26fb321..f9bbb0f 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "catto",
-  "version": "0.8.0",
+  "version": "0.8.1",
   "description": "The Catto chess engine",
   "main": "index.js",
   "scripts": {
diff --git a/src/core.ts b/src/core.ts
index f950e0f..1c51d02 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -1,8 +1,7 @@
 import { Chess, Move } from "chess.js";
 import { evaluateBoard } from "./evaluate";
-import { mvv_lva, PIECE_NUM } from "./evaluations";
+import { mvv_lva, PIECE_NUM, mgMaterial } from "./evaluations";
 import { genZobristKey } from "./zobrist";
-import { mgMaterial } from "./evaluations";
 
 export enum HashFlag {
     exact,
@@ -189,6 +188,12 @@ export class Engine {
             return beta;
         }
 
+        // Delta pruning
+        const delta = mgMaterial[4];
+        if (evaluation < alpha - delta) {
+            return alpha;
+        }
+
         // Found a better move
         if (evaluation > alpha) {
             alpha = evaluation;