Add negamax function (no α β pruning)

src/brchess.c

@@ -29,6 +29,7 @@
 #include "move.h"
 #include "fen.h"
 #include "eval.h"
+#include "search.h"
 
 struct command {
     char *name;                                   /* User printable name */
@@ -62,6 +63,8 @@ int do_eval(pos_t *, char*);
 int do_move(pos_t *, char*);
 int do_quit(pos_t *, char*);
 int do_debug(pos_t *, char*);
+int do_depth(pos_t *, char*);
+int do_search(pos_t *, char*);
 
 struct command commands[] = {
     { "help", do_help, "Display this text" },
@@ -78,10 +81,13 @@ struct command commands[] = {
     { "eval", do_eval, "Eval current position" },
     { "do_move", do_move, "execute nth move on current position" },
     { "debug", do_debug, "Set log level to LEVEL" },
+    { "depth", do_depth, "Set search depth to N" },
+    { "search", do_search, "Search best move" },
     { NULL, (int(*)()) NULL, NULL }
 };
 
 static int done=0;
+static int depth=1;
 
 int brchess(pos_t *pos)
 {
@@ -377,7 +383,7 @@ int do_debug(__unused pos_t *pos, __unused char *arg)
    not present. */
 int do_help(__unused pos_t *pos, __unused char *arg)
 {
-    register int i;
+    int i;
     int printed = 0;
 
     for (i = 0; commands[i].name; i++) {
@@ -407,6 +413,23 @@ int do_help(__unused pos_t *pos, __unused char *arg)
     return 0;
 }
 
+int do_depth(__unused pos_t *pos, char *arg)
+{
+    depth = atoi(arg);
+    printf("depth = %d\n", depth);
+    return 1;
+
+}
+
+int do_search(pos_t *pos, __unused char *arg)
+{
+    printf("++++++++\nnegamax=%d\n", negamax(pos, depth, pos->turn==WHITE? 1:-1));
+    printf("best=");
+    move_print(0, pos->bestmove, 0);
+    printf("score=%d\n", pos->bestmove->negamax);
+    return 1;
+}
+
 #ifdef BIN_brchess
 /** main()
  * options:
@@ -430,7 +453,7 @@ int main(int ac, char **av)
     moves_pool_init();
     pos_pool_init();
     pos = pos_get();
-    debug_init(1, stderr);
+    debug_init(1, stderr, true);
 
     while ((opt = getopt(ac, av, "d:f:")) != -1) {
         switch (opt) {

src/search.c

@@ -24,28 +24,41 @@
  * negamax() - the negamax tree.
  *
  */
-eval_t negamax(pos_t *pos, int depth)
+eval_t negamax(pos_t *pos, int depth, int color)
 {
-    move_t *move, *bestmove;
+    move_t *move, bestmove;
     pos_t *newpos;
     eval_t best = EVAL_MIN, score;
 
+    printf("depth=%d\n", depth);
     moves_gen_all(pos);
-    if (depth == 0)
-        return eval(pos) * pos->turn == WHITE? 1: -1;
-
+    //pos_check(pos);
+    if (depth == 0) {
+        score = eval(pos);
+        printf("evalnega=%d turn=%d color=%d", score, pos->turn, color);
+        score *= color;
+        printf(" --> evalnega=%d\n", score);
+        return score;
+    }
+    moves_print(pos, 0);
     list_for_each_entry(move, &pos->moves[pos->turn], list) {
         newpos = move_do(pos, move);
-        score = -negamax(newpos, depth - 1 );
-        if(score > best) {
+        score = -negamax(newpos, depth - 1, -color);
+        move->negamax = score;
+        printf("move=");
+        move_print(0, move, 0);
+        printf("score=%d\n", score);
+
+        if (score > best) {
             best = score;
-            bestmove = move;
+            pos->bestmove = move;
 #           ifdef DEBUG_SEARCH
-            log_f(2, "depth=%d best move=", best);
-            move_print(0, bestmove, M_PR_LONG);
-            log_f(2, " eval=%d\n", best);
+            printf("depth=%d best move=", depth);
+            move_print(0, &bestmove, 0);
+            printf(" eval=%d\n", best);
 #           endif
         }
+        move_undo(newpos, move);
     }
     return best;
 }

src/search.h

@@ -20,6 +20,6 @@
 #define EVAL_MIN INT_MIN
 #define EVAL_MAX INT_MAX
 
-eval_t negamax(pos_t *pos, int depth);
+eval_t negamax(pos_t *pos, int depth, int color);
 
 #endif  /* SEARCH_H */