Duplicate search.c history.

src/search.c-move-to-temp-migration-bitboard__search.c

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+/* search.c - search good moves.
+ *
+ * Copyright (C) 2023 Bruno Raoult ("br")
+ * Licensed under the GNU General Public License v3.0 or later.
+ * Some rights reserved. See COPYING.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+ *
+ */
+
+
+#include <br.h>
+#include <list.h>
+#include "debug.h"
+
+#include "move.h"
+#include "eval.h"
+#include "search.h"
+
+/**
+ * negamax() - search position negamax.
+ * @pos: &position to search
+ * @depth: Wanted depth.
+ * @color: 1 for white, -1 for black.
+ *
+ * Calculate the negamax value of @pos. This is an extensive search, with
+ * absolutely no cutoff.
+ *
+ * @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;
+}
+
+
+/**
+ * pvs() - Principal Variation Search.
+ * @pos: &position to search
+ * @depth: wanted depth.
+ * @alpha: alpha value.
+ * @beta: beta value.
+ * @color: 1 for white, -1 for black.
+ *
+ * Calculate the PVS value of @pos.
+ * See https://en.wikipedia.org/wiki/Principal_variation_search
+ *
+ * Moves list should be first generated and evaluated/sorted.
+ *
+ * @return: The @pos PVS evaluation.
+ */
+eval_t pvs(pos_t *pos, int depth, int alpha, int beta, int color)
+{
+    move_t *move;
+    pos_t *newpos;
+    eval_t score = EVAL_INVALID;
+    bool firstchild = true;
+
+    pos->node_count++;
+
+    if (depth == 0) {
+        //return quiesce(p, alpha, beta);           /* leaf node */
+        moves_gen_all_nomoves(pos);
+        score = eval(pos) * color;
+        log_f(2, "Terminal: depth=%d ", depth);
+        log_f(2, "score=%d alpha=%d beta=%d\n", score, alpha, beta);
+        return score;
+    }
+
+    moves_gen_all(pos);
+    //moves_print(pos, M_PR_EVAL);
+    /* do the full search for first child */
+    //move = list_first_entry_or_null(&pos->moves[pos->turn], move_t, list);
+
+    list_for_each_entry(move, &pos->moves[pos->turn], list) {
+        newpos = move_do(pos, move);
+        log(2, "%.*s", 5 - depth, "                ");
+        if (firstchild) {                               /* first child */
+            score = -pvs(newpos, depth - 1, -beta, -alpha, -color);
+            log_f(2, "First child depth=%d move=", depth);
+            //move_print(0, move, 0);
+            log(2, "score=%d alpha=%d beta=%d\n", score, alpha, beta);
+            pos->bestmove = move;
+        } else {
+            /* search with a null window */
+            score = -pvs(newpos, depth - 1, -alpha - 1, -alpha, -color);
+            log_f(2, "Other child depth=%d move=", depth);
+            //move_print(0, move, 0);
+            log_f(2, "score=%d alpha=%d beta=%d ", score, alpha, beta);
+            /* for fail-soft:  if (score > alpha && score < beta) */
+            if (score > alpha) {
+                /* if failed high, do a full re-search */
+                log_f(2, "doing full search.");
+                score = -pvs(newpos, depth - 1, -beta, -alpha, -color);
+            }
+            log(2, "\n");
+        }
+        pos->node_count += newpos->node_count;
+        move_undo(newpos, move);
+        if (score >= beta) {                      /* fail-hard hard beta cut-off */
+            log(2, "%.*s", 5 - depth, "                ");
+            log_f(2, "depth=%d score=%d alpha=%d beta=%d beta cut-off.\n",
+                  depth, score, alpha, beta);
+            return beta;
+        }
+        if (score > alpha) {
+            log(2, "%.*s", 5 - depth, "                ");
+            log_f(2, "depth=%d setting new alpha from %d to %d\n",
+                  depth, alpha, score);
+            alpha = score;
+            pos->bestmove = move;
+        }
+        move->pos = NULL;
+        move->negamax = score;
+        firstchild = false;
+    }
+
+    return alpha;
+}
+
+/*
+ * int negascout (pos_t *pos, int depth, int alpha, int beta )
+ * {                     /\* compute minimax value of position p *\/
+ *     move_t *move;
+ *     pos_t *newpos;
+ *     eval_t best = EVAL_MIN, score;
+ *
+ *     int a, b, t, i;
+ *
+ *     if (depth == 0) {
+ *         //return quiesce(p, alpha, beta);           /\* leaf node *\/
+ *         moves_gen_all_nomoves(pos);
+ *         score = eval(pos) * color;
+ *         return score;
+ *     }
+ *     moves_gen_all(pos);
+ *     a = alpha;
+ *     b = beta;
+ *     list_for_each_entry(move, &pos->moves[pos->turn], list) {
+ *         log(1, "%.*s", 5 - depth, "                ");
+ *         newpos = move_do(pos, move);
+ * //    for ( i = 1; i <= w; i++ ) {
+ *         t = -negascout (newpos, depth - 1, -b, -alpha);
+ *         if ( (t > a) && (t < beta) && (i > 1) )
+ *             t = -NegaScout ( p_i, -beta, -alpha ); /\* re-search *\/
+ *         alpha = max( alpha, t );
+ *         if ( alpha >= beta )
+ *             return alpha;                            /\* cut-off *\/
+ *         b = alpha + 1;                  /\* set new null window *\/
+ *     }
+ *     return alpha;
+ * }
+ */
+
+/*
+ * int quiesce(pos_t *pos, int alpha, int beta)
+ * {
+ *     int stand_pat = eval(pos);
+ *
+ *     if( stand_pat >= beta )
+ *         return beta;
+ *     if( alpha < stand_pat )
+ *         alpha = stand_pat;
+ *
+ *     /\*
+ *      * until( every_capture_has_been_examined )  {
+ *      *     MakeCapture();
+ *      *     score = -Quiesce( -beta, -alpha );
+ *      *     TakeBackMove();
+ *      *
+ *      *     if( score >= beta )
+ *      *         return beta;
+ *      *     if( score > alpha )
+ *      *        alpha = score;
+ *      * }
+ *      *\/
+ *     return alpha;
+ * }
+ */
+
+/**
+ * ab_negamax() - search position negamax with alpha-beta cutoff.
+ * @pos: &position to search
+ * @depth: Wanted depth.
+ * @color: 1 for white, -1 for black.
+ *
+ * Calculate the negamax value of @pos, with alpha-beta pruning.
+ *
+ * @return: The @pos negamax evaluation.
+ */
+/*int ab_negamax(pos_t *pos, int alpha, int beta, int depth)
+{
+    move_t *move;
+    pos_t *newpos;
+    eval_t best = EVAL_MIN, score;
+
+    if(depth == 0) {
+       //return quiesce( alpha, beta );
+        moves_gen_all_nomoves(pos);
+       score = eval(pos) * color;
+       return score;
+    }
+   for ( all moves)  {
+      score = -alphaBeta( -beta, -alpha, depthleft - 1 );
+      if( score >= beta )
+         return beta;   //  fail hard beta-cutoff
+      if( score > alpha )
+         alpha = score; // alpha acts like max in MiniMax
+   }
+   return alpha;
+}
+*/