From f7fd2cb6575ab7eca549c86e4745e798a1c221f9 Mon Sep 17 00:00:00 2001
From: Bruno Raoult <braoult@gmail.com>
Date: Mon, 5 Aug 2024 08:26:33 +0200
Subject: [PATCH] merge perft split

---
 src/perft.c  | 80 ++++++++++++++++++++++++++++++++--------------------
 src/search.c | 58 +++++++++++++++++++------------------
 2 files changed, 80 insertions(+), 58 deletions(-)

diff --git a/src/perft.c b/src/perft.c
index 970f1b3..99fdb87 100644
--- a/src/perft.c
+++ b/src/perft.c
@@ -20,59 +20,79 @@
 #include "move-do.h"
 
 /**
- * perft() - Perform perft on position
+ * do_perft() - perft engine
  * @pos:    &position to search
  * @depth:  Wanted depth.
- * @ply:    current perft depth level (root = 1)
- * @divide: output total for 1st level moves.
  *
- * Run perft on a position. This function displays the available moves at @depth
- * level for each possible first move, and the total of moves.
+ * Run perft on a position.
  *
  * This version uses the algorithm:
- *    if last depth
- *      return 1;
  *    gen legal moves
+ *    if last depth
+ *      return number of legal move
  *    loop for legal move
  *      do-move
- *      perft (depth -1)
+ *      if depth == 2
+ *
+ *      do_perft (depth -1)
  *      undo-move
  *
  * @return: total moves found at @depth level.
  */
 static u64 do_perft(pos_t *pos, int depth)
 {
-    u64 subnodes = 0, nodes = 0;
+    u64 nodes = 0;
     movelist_t movelist;
     move_t *move, *last;
     state_t state;
 
     pos_set_checkers_pinners_blockers(pos);
     pos_legal(pos, pos_gen_pseudo(pos, &movelist));
-    if (depth == 1)
-        return movelist.nmoves;
-    last = movelist.move + movelist.nmoves;
 
-    for (move = movelist.move; move < last; ++move) {
-        move_do(pos, *move, &state);
-        if (depth == 2) {
-            movelist_t movelist2;
-            pos_set_checkers_pinners_blockers(pos);
-            subnodes = pos_legal(pos, pos_gen_pseudo(pos, &movelist2))->nmoves;
-        } else if (pos->plyroot >= 3) {
-            hentry_t *entry = tt_probe_perft(pos->key, depth);
-            if (entry != TT_MISS) {
-                subnodes = HASH_PERFT_VAL(entry->data);
-            } else {
-                subnodes = do_perft(pos, depth - 1);
-                tt_store_perft(pos->key, depth, subnodes);
+    //if (depth == 1)
+    //    return movelist.nmoves;
+
+    last = movelist.move + movelist.nmoves;
+    switch (depth) {
+        case 1:
+            /* This case could be removed if 'case 2' is handled in perft()
+             */
+            return movelist.nmoves;
+            break;
+        case 2:
+            /* For depth 2, we directly calculate the possible legal moves
+             * after each possible moves.
+             */
+            for (move = movelist.move; move < last; ++move) {
+                move_do(pos, *move, &state);
+                movelist_t movelist2;
+                pos_set_checkers_pinners_blockers(pos);
+                nodes += pos_legal(pos, pos_gen_pseudo(pos, &movelist2))->nmoves;
+                move_undo(pos, *move, &state);
             }
-        } else {
-            subnodes = do_perft(pos, depth - 1);
-        }
-        move_undo(pos, *move, &state);
-        nodes += subnodes;
+            break;
+        default:
+            /* Default: Search in TT for same key+depth. Use it if found, create
+             * it otherwise.
+             */
+            for (move = movelist.move; move < last; ++move) {
+                move_do(pos, *move, &state);
+                hentry_t *entry = tt_probe_perft(pos->key, depth);
+                if (entry != TT_MISS) {
+                    nodes += HASH_PERFT_VAL(entry->data);
+                } else {
+                    u64 subnodes = do_perft(pos, depth - 1);
+                    tt_store_perft(pos->key, depth, subnodes);
+                    nodes += subnodes;
+                }
+                move_undo(pos, *move, &state);
+            }
+            //} else {
+            //subnodes = do_perft(pos, depth - 1);
     }
+        //move_undo(pos, *move, &state);
+        //nodes += subnodes;
+    //}
 
     return nodes;
 }
diff --git a/src/search.c b/src/search.c
index 4e558d7..c0633e3 100644
--- a/src/search.c
+++ b/src/search.c
@@ -47,34 +47,36 @@ bool is_draw(pos_t *pos)
  *
  * @return: The @pos negamax evaluation.
  */
-/*
- * eval_t negamax(pos_t *pos, int depth, int color)
- * {
- *     move_t *move;
- *     pos_t *newpos;
- *     eval_t best = EVAL_MIN, score;
- *
- *     pos->node_count++;
- *     if (depth == 0) {
- *         moves_gen_all_nomoves(pos);
- *         score = eval(pos) * color;
- *         return score;
- *     }
- *     moves_gen_all(pos);
- *     list_for_each_entry(move, &pos->moves[pos->turn], list) {
- *         newpos = move_do(pos, move);
- *         score = -negamax(newpos, depth - 1, -color);
- *         pos->node_count += newpos->node_count;
- *         move->negamax = score;
- *         if (score > best) {
- *             best = score;
- *             pos->bestmove = move;
- *         }
- *         move_undo(newpos, move);
- *     }
- *     return best;
- * }
- */
+eval_t negamax(pos_t *pos, int depth, int color)
+{
+    move_t *move, *last;
+    state_t state;
+    eval_t best = EVAL_MIN, score;
+    movelist_t movelist;
+
+    pos->node_count++;
+    if (depth == 0) {
+        score = eval(pos) * color;
+        return score;
+    }
+    pos_set_checkers_pinners_blockers(pos);
+    pos_gen_legal(pos, &movelist);
+    last = movelist.move + movelist.nmoves;
+    //moves_gen_all(pos);
+    for (move = movelist.move; move < last; ++move) {
+        //list_for_each_entry(move, &pos->moves[pos->turn], list) {
+        move_do(pos, *move, &state);
+        score = -negamax(pos, depth - 1, -color);
+        pos->node_count += pos->node_count;
+        //move->negamax = score;
+        if (score > best) {
+            best = score;
+            pos->eval = best;
+        }
+        move_undo(pos, *move, &state);
+    }
+    return best;
+}
 
 
 /**