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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "chess.h"
#include "data.h"
#include "epdglue.h"
/* modified 10/23/01 */
/*
*******************************************************************************
* *
* SearchRoot() is the recursive routine used to implement the alpha/beta *
* negamax search (similar to minimax but simpler to code.) SearchRoot() is *
* only called when ply=1. it is somewhat different from Search() in that *
* some things (null move search, hash lookup, etc.) are not useful at the *
* root of the tree. SearchRoot() calls Search() to search any positions *
* that are below ply=1. *
* *
*******************************************************************************
*/
int SearchRoot(TREE * RESTRICT tree, int alpha, int beta, int wtm, int depth)
{
register int first_move = 1;
register int value;
register int extensions, extended;
BITBOARD begin_root_nodes;
/*
************************************************************
* *
* initialize. set NextMove() status to 0 so it will *
* know what has to be done. *
* *
************************************************************
*/
tree->in_check[2] = 0;
tree->in_check[1] = Check(wtm);
tree->next_status[1].phase = ROOT_MOVES;
/*
************************************************************
* *
* now iterate through the move list and search the *
* resulting positions. note that Search() culls any *
* move that is not legal by using Check(). the special *
* case is that we must find one legal move to search to *
* confirm that it's not a mate or draw. *
* *
************************************************************
*/
while ((tree->phase[1] = NextRootMove(tree, tree, wtm))) {
#if defined(TRACE)
if (1 <= trace_level)
SearchTrace(tree, 1, depth, wtm, alpha, beta, "SearchRoot",
tree->phase[1]);
#endif
/*
************************************************************
* *
* now make the move and search the resulting position. *
* *
************************************************************
*/
MakeMove(tree, 1, tree->current_move[1], wtm);
/*
************************************************************
* *
* if the move to be made checks the opponent, then we *
* need to remember that he's in check and also extend *
* the depth by one ply for him to get out. *
* *
************************************************************
*/
extended = 0;
if (Check(Flip(wtm))) {
tree->in_check[2] = 1;
tree->check_extensions_done++;
extended += incheck_depth;
} else
tree->in_check[2] = 0;
/*
************************************************************
* *
* if we push a passed pawn, we need to look deeper to *
* see if it is a legitimate threat. *
* *
************************************************************
*/
if (Piece(tree->current_move[1]) == pawn &&
push_extensions[To(tree->current_move[1])]) {
tree->passed_pawn_extensions_done++;
extended += pushpp_depth;
}
/*
************************************************************
* *
* now call Search to produce a value for this move. *
* *
************************************************************
*/
begin_root_nodes = tree->nodes_searched;
LimitExtensions(extended, 1);
extensions = extended - INCPLY;
if (first_move) {
if (depth + extensions >= INCPLY)
value =
-Search(tree, -beta, -alpha, Flip(wtm), depth + extensions, 2,
DO_NULL, 0);
else
value = -Quiesce(tree, -beta, -alpha, Flip(wtm), 2);
if (abort_search) {
UnmakeMove(tree, 1, tree->current_move[1], wtm);
return (alpha);
}
first_move = 0;
} else {
if (depth + extensions >= INCPLY)
value =
-Search(tree, -alpha - 1, -alpha, Flip(wtm), depth + extensions, 2,
DO_NULL, 0);
else
value = -Quiesce(tree, -alpha - 1, -alpha, Flip(wtm), 2);
if (abort_search) {
UnmakeMove(tree, 1, tree->current_move[1], wtm);
return (alpha);
}
if ((value > alpha) && (value < beta)) {
if (depth + extensions >= INCPLY)
value =
-Search(tree, -beta, -alpha, Flip(wtm), depth + extensions, 2,
DO_NULL, 0);
else
value = -Quiesce(tree, -beta, -alpha, Flip(wtm), 2);
if (abort_search) {
UnmakeMove(tree, 1, tree->current_move[1], wtm);
return (alpha);
}
}
}
root_moves[tree->root_move].nodes = tree->nodes_searched - begin_root_nodes;
if (value > alpha) {
SearchOutput(tree, value, beta);
root_value = alpha;
if (value >= beta) {
History(tree, 1, depth, wtm, tree->current_move[1]);
UnmakeMove(tree, 1, tree->current_move[1], wtm);
return (value);
}
alpha = value;
}
root_value = alpha;
UnmakeMove(tree, 1, tree->current_move[1], wtm);
#if defined(SMP)
if (split_at_root && smp_idle && NextRootMoveParallel()) {
tree->alpha = alpha;
tree->beta = beta;
tree->value = alpha;
tree->wtm = wtm;
tree->ply = 1;
tree->depth = depth;
tree->mate_threat = 0;
tree->lp_recapture = 0;
if (Thread(tree)) {
if (abort_search || tree->stop)
return (0);
if (tree->thread_id == 0 && CheckInput())
Interrupt(1);
value = tree->search_value;
if (value > alpha) {
if (value >= beta) {
History(tree, 1, depth, wtm, tree->current_move[1]);
tree->fail_high++;
return (value);
}
alpha = value;
break;
}
}
}
#endif
}
/*
************************************************************
* *
* all moves have been searched. if none were legal, *
* return either MATE or DRAW depending on whether the *
* side to move is in check or not. *
* *
************************************************************
*/
if (abort_search || time_abort)
return (0);
if (first_move == 1) {
value = (Check(wtm)) ? -(MATE - 1) : DrawScore(wtm);
if (value >= alpha && value < beta) {
tree->pv[0].pathl = 0;
tree->pv[0].pathh = 0;
tree->pv[0].pathd = iteration_depth;
SearchOutput(tree, value, beta);
#if defined(TRACE)
if (1 <= trace_level)
printf("Search() no moves! ply=1\n");
#endif
}
return (value);
} else {
History(tree, 1, depth, wtm, tree->pv[1].path[1]);
return (alpha);
}
}
/* modified 03/11/98 */
/*
*******************************************************************************
* *
* SearchOutput() is used to print the principal variation whenever it *
* changes. one additional feature is that SearchOutput() will try to do *
* something about variations truncated by the transposition table. if the *
* variation was cut short by a transposition table hit, then we can make the*
* last move, add it to the end of the variation and extend the depth of the *
* variation to cover it. *
* *
*******************************************************************************
*/
void SearchOutput(TREE * RESTRICT tree, int value, int bound)
{
register int wtm;
int i;
ROOT_MOVE temp_rm;
/*
************************************************************
* *
* first, move the best move to the top of the ply-1 move *
* list if it's not already there, so that it will be the *
* first move tried in the next iteration. *
* *
************************************************************
*/
root_print_ok = root_print_ok || tree->nodes_searched > noise_level;
wtm = root_wtm;
if (!abort_search) {
kibitz_depth = iteration_depth;
for (i = 0; i < n_root_moves; i++)
if (tree->current_move[1] == root_moves[i].move)
break;
if (i && i < n_root_moves) {
temp_rm = root_moves[i];
for (; i > 0; i--)
root_moves[i] = root_moves[i - 1];
root_moves[0] = temp_rm;
easy_move = 0;
}
end_time = ReadClock(time_type);
/*
************************************************************
* *
* if this is not a fail-high move, then output the PV *
* by walking down the path being backed up. *
* *
************************************************************
*/
if (value < bound) {
UnmakeMove(tree, 1, tree->pv[1].path[1], root_wtm);
DisplayPV(tree, 6, wtm, end_time - start_time, value, &tree->pv[1]);
MakeMove(tree, 1, tree->pv[1].path[1], root_wtm);
} else {
if (tree->current_move[1] != tree->pv[1].path[1]) {
tree->pv[1].path[1] = tree->current_move[1];
tree->pv[1].pathl = 1;
tree->pv[1].pathh = 0;
tree->pv[1].pathd = iteration_depth;
}
}
tree->pv[0] = tree->pv[1];
local[0]->pv[0] = tree->pv[1];
}
}
/* modified 03/11/98 */
/*
*******************************************************************************
* *
* SearchTrace() is used to print the search trace output each time a node is*
* traversed in the tree. *
* *
*******************************************************************************
*/
void SearchTrace(TREE * RESTRICT tree, int ply, int depth, int wtm, int alpha,
int beta, char *name, int phase)
{
int i;
Lock(lock_io);
for (i = 1; i < ply; i++)
printf(" ");
printf("%d %s d:%5.2f [%s,", ply, OutputMove(tree, tree->current_move[ply],
ply, wtm), (float) depth / (float) INCPLY, DisplayEvaluation(alpha,
1));
printf("%s] n:" BMF " %s(%d)", DisplayEvaluation(beta, 1),
(tree->nodes_searched), name, phase);
if (max_threads > 1)
printf(" (t=%d) ", tree->thread_id);
printf("\n");
Unlock(lock_io);
}
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