// Perform a Principle Variation Search
// https://chessprogramming.wikispaces.com/Principal+Variation+Search
static score_t searchPV(searchNode *node, int depth, uint64_t *node_count_serial) {
// Initialize the searchNode data structure.
initialize_pv_node(node, depth);
// Pre-evaluate the node to determine if we need to search further.
leafEvalResult pre_evaluation_result = evaluate_as_leaf(node, SEARCH_PV);
// use some information from the pre-evaluation
int hash_table_move = pre_evaluation_result.hash_table_move;
if (pre_evaluation_result.type == MOVE_EVALUATED) {
return pre_evaluation_result.score;
}
if (pre_evaluation_result.score > node->best_score) {
node->best_score = pre_evaluation_result.score;
if (node->best_score > node->alpha) {
node->alpha = node->best_score;
}
}
// Get the killer moves at this node.
move_t killer_a = killer[KMT(node->ply, 0)];
move_t killer_b = killer[KMT(node->ply, 1)];
// sortable_move_t move_list
//
// Contains a list of possible moves at this node. These moves are "sortable"
// and can be compared as integers. This is accomplished by using high-order
// bits to store a sort key.
//
// Keep track of the number of moves that we have considered at this node.
// After we finish searching moves at this node the move_list array will
// be organized in the following way:
//
// m0, m1, ... , m_k-1, m_k, ... , m_N-1
//
// where k = num_moves_tried, and N = num_of_moves
//
// This will allow us to update the best_move_history table easily by
// scanning move_list from index 0 to k such that we update the table
// only for moves that we actually considered at this node.
sortable_move_t move_list[MAX_NUM_MOVES];
int num_of_moves = get_sortable_move_list(node, move_list, hash_table_move);
int num_moves_tried = 0;
// Start searching moves.
for (int mv_index = 0; mv_index < num_of_moves; mv_index++) {
// Incrementally sort the move list.
sort_incremental(move_list, num_of_moves, mv_index);
move_t mv = get_move(move_list[mv_index]);
num_moves_tried++;
(*node_count_serial)++;
moveEvaluationResult result = evaluateMove(node, mv, killer_a, killer_b,
SEARCH_PV,
node_count_serial);
if (result.type == MOVE_ILLEGAL || result.type == MOVE_IGNORE) {
continue;
}
// A legal move is a move that's not KO, but when we are in quiescence
// we only want to count moves that has a capture.
if (result.type == MOVE_EVALUATED) {
node->legal_move_count++;
}
// Check if we should abort due to time control.
if (abortf) {
return 0;
}
bool cutoff = search_process_score(node, mv, mv_index, &result, SEARCH_PV);
if (cutoff) {
break;
}
}
if (node->quiescence == false) {
update_best_move_history(&(node->position), node->best_move_index,
move_list, num_moves_tried);
}
tbassert(abs(node->best_score) != -INF, "best_score = %d\n",
node->best_score);
// Update the transposition table.
//
// Note: This function reads node->best_score, node->orig_alpha,
// node->position.key, node->depth, node->ply, node->beta,
// node->alpha, node->subpv
update_transposition_table(node);
return node->best_score;
}
static score_t scout_search(searchNode *node, int depth,
uint64_t *node_count_serial) {
// Initialize the search node.
initialize_scout_node(node, depth);
// check whether we should abort
if (should_abort_check() || parallel_parent_aborted(node)) {
return 0;
}
// Pre-evaluate this position.
leafEvalResult pre_evaluation_result = evaluate_as_leaf(node, SEARCH_SCOUT);
// If we decide to stop searching, return the pre-evaluation score.
if (pre_evaluation_result.type == MOVE_EVALUATED) {
return pre_evaluation_result.score;
}
// Populate some of the fields of this search node, using some
// of the information provided by the pre-evaluation.
int hash_table_move = pre_evaluation_result.hash_table_move;
node->best_score = pre_evaluation_result.score;
node->quiescence = pre_evaluation_result.should_enter_quiescence;
// Grab the killer-moves for later use.
move_t killer_a = killer[KMT(node->ply, 0)];
move_t killer_b = killer[KMT(node->ply, 1)];
// Store the sorted move list on the stack.
// MAX_NUM_MOVES is all that we need.
sortable_move_t move_list[MAX_NUM_MOVES];
// Obtain the sorted move list.
int num_of_moves = get_sortable_move_list(node, move_list, hash_table_move);
int number_of_moves_evaluated = 0;
// A simple mutex. See simple_mutex.h for implementation details.
simple_mutex_t node_mutex;
init_simple_mutex(&node_mutex);
// Sort the move list.
sort_incremental(move_list, num_of_moves, 0);
moveEvaluationResult result;
for (int mv_index = 0; mv_index < num_of_moves; mv_index++) {
if (mv_index == 1) {
sort_full(move_list, num_of_moves);
// sortable_move_t new_move_list[MAX_NUM_MOVES];
//memcpy(new_move_list, move_list, num_of_moves*sizeof(sortable_move_t));
//: sort_incremental_full(move_list,num_of_moves);
}
// Get the next move from the move list.
int local_index = number_of_moves_evaluated++;
move_t mv = get_move(move_list[local_index]);
if (TRACE_MOVES) {
print_move_info(mv, node->ply);
}
// increase node count
__sync_fetch_and_add(node_count_serial, 1);
evaluateMove(&result, node, mv, killer_a, killer_b,
SEARCH_SCOUT,
node_count_serial);
undo_move(&result.next_node, mv);
if (result.type == MOVE_ILLEGAL || result.type == MOVE_IGNORE
|| abortf || parallel_parent_aborted(node)) {
continue;
}
// A legal move is a move that's not KO, but when we are in quiescence
// we only want to count moves that has a capture.
if (result.type == MOVE_EVALUATED) {
node->legal_move_count++;
}
// process the score. Note that this mutates fields in node.
bool cutoff = search_process_score(node, mv, local_index, &result, SEARCH_SCOUT);
if (cutoff) {
node->abort = true;
break;
}
}
if (parallel_parent_aborted(node)) {
return 0;
}
if (node->quiescence == false) {
update_best_move_history(node->position, node->best_move_index,
move_list, number_of_moves_evaluated);
}
tbassert(abs(node->best_score) != -INF, "best_score = %d\n",
node->best_score);
// Reads node->position->key, node->depth, node->best_score, and node->ply
update_transposition_table(node);
return node->best_score;
}
static score_t scout_search(searchNode *node, int depth,
uint64_t *node_count_serial, full_board_t* board) {
// Initialize the search node.
initialize_scout_node(node, depth);
// check whether we should abort
if (should_abort_check() || parallel_parent_aborted(node)) {
return 0;
}
// Pre-evaluate this position.
leafEvalResult pre_evaluation_result = evaluate_as_leaf(node, SEARCH_SCOUT, board);
// If we decide to stop searching, return the pre-evaluation score.
if (pre_evaluation_result.type == MOVE_EVALUATED) {
return pre_evaluation_result.score;
}
// Populate some of the fields of this search node, using some
// of the information provided by the pre-evaluation.
int hash_table_move = pre_evaluation_result.hash_table_move;
node->best_score = pre_evaluation_result.score;
node->quiescence = pre_evaluation_result.should_enter_quiescence;
// Grab the killer-moves for later use.
move_t killer_a = killer[KMT(node->ply, 0)];
move_t killer_b = killer[KMT(node->ply, 1)];
// Store the sorted move list on the stack.
// MAX_NUM_MOVES is all that we need.
sortable_move_t move_list[MAX_NUM_MOVES];
// Obtain the sorted move list.
int num_of_moves = get_sortable_move_list(node, move_list, hash_table_move, board);
int num_of_special_moves = move_list[num_of_moves];
int num_of_nonzero_moves = move_list[num_of_moves + 1];
if (num_of_special_moves == 0) {
selectionSort(move_list, num_of_moves, 1);
num_of_special_moves = 1;
}
int number_of_moves_evaluated = 0;
bool generated_early_cutoff = false;
for (int mv_index = 0; mv_index < num_of_special_moves; mv_index++) {
int local_index = number_of_moves_evaluated++;
move_t mv = get_move(move_list[local_index]);
// increase node count
REDUCER_VIEW(node_count_reducer)++;
smallMoveEvaluationResult result = evaluateMove(node, mv, killer_a, killer_b,
SEARCH_SCOUT,
node_count_serial);
if (result.type == MOVE_ILLEGAL || result.type == MOVE_IGNORE) {
continue;
}
if (abortf || parallel_parent_aborted(node)) {
return 0;
}
// A legal move is a move that's not KO, but when we are in quiescence
// we only want to count moves that has a capture.
if (result.type == MOVE_EVALUATED) {
node->legal_move_count++;
}
// process the score. Note that this mutates fields in node.
bool cutoff = search_process_score(node, mv, local_index, &result, SEARCH_SCOUT);
if (cutoff) {
generated_early_cutoff = true;
break;
}
}
// ABOVE IS YOUNG BROTHER'S WAIT CODE. IT SHOULD RUN IN SERIAL
//
// BELOW IS PARALLELIZED SCOUT SEARCH. IT SHOULD RUN IN PARALLEL
// if this happens, we generated an early cutoff in young brother's wait and can just skip to the end
if (generated_early_cutoff)
goto finish_scout_search;
sort_incremental(move_list + num_of_special_moves, num_of_nonzero_moves - num_of_special_moves);
// A simple mutex. See simple_mutex.h for implementation details.
simple_mutex_t node_mutex;
init_simple_mutex(&node_mutex);
// TODO: see if changing this depth is better
if (depth >= 2) {
cilk_for (int mv_index = num_of_special_moves; mv_index < num_of_moves; mv_index++) {
do {
if (node->abort) continue;
int local_index = __sync_fetch_and_add(&number_of_moves_evaluated, 1);
move_t mv = get_move(move_list[local_index]);
// increase node count
REDUCER_VIEW(node_count_reducer)++;
smallMoveEvaluationResult result = evaluateMove(node, mv, killer_a, killer_b,
SEARCH_SCOUT,
node_count_serial);
// TODO: change this to break if we want to abort
if (result.type == MOVE_ILLEGAL || result.type == MOVE_IGNORE) {
continue;
}
if (abortf || parallel_parent_aborted(node)) {
node->abort = true;
continue;
}
// A legal move is a move that's not KO, but when we are in quiescence
// we only want to count moves that has a capture.
if (result.type == MOVE_EVALUATED) {
__sync_fetch_and_add(&node->legal_move_count, 1);
}
bool cutoff = false;
if (result.score > node->best_score) {
simple_acquire(&node_mutex);
// process the score. Note that this mutates fields in node.
cutoff = search_process_score(node, mv, local_index, &result, SEARCH_SCOUT);
simple_release(&node_mutex);
}
if (cutoff) {
node->abort = true;
continue;
}
} while (false);
}
} else {