/**
* @brief Recursive function used to traverse the game tree.
*
* @param [in] result a reference to the exact solution data structure
* @param [in] gp the game position to traverse
* @return a pointer to a new serch node structure
*/
static SearchNode *
game_position_solve_impl ( ExactSolution * const result,
const GamePosition * const gp_old)
{
SearchNode *node;
SearchNode *node2;
node = NULL;
node2 = NULL;
result->node_count++;
NodeInfo * const node_info = &stack->nodes[++stack->fill_point];
//NodeInfo * const next_node_info = &stack->nodes[stack->fill_point];
LegalMoveList * const moves = &node_info->moves;
const SquareSet move_set = game_position_legal_moves(gp_old);
legal_move_list_from_set(move_set, moves);
//GamePositionX * const gp = &node_info->gp;
//GamePositionX * const next_gp = &next_node_info->gp;
/*
GamePosition gp;
uint64 hash;
*/
if (move_set == empty_square_set) {
GamePosition *flipped_players = game_position_pass(gp_old);
const int previous_move_count = stack->nodes[stack->fill_point - 1].moves.move_count;
const SquareSet empties = board_empties(gp_old->board);
if (empties != empty_square_set && previous_move_count != 0) {
node = search_node_negated(game_position_solve_impl(result, flipped_players));
} else {
result->leaf_count++;
node = search_node_new((Square) -1, game_position_final_value(gp_old));
}
flipped_players = game_position_free(flipped_players);
} else {
node = search_node_new((Square) -1, -65);
for (int i = 0; i < moves->move_count; i++) {
const Square move = moves->squares[i];
GamePosition *gp2 = game_position_make_move(gp_old, move);
node2 = search_node_negated(game_position_solve_impl(result, gp2));
gp2 = game_position_free(gp2);
if (node2->value > node->value) {
search_node_free(node);
node = node2;
node->move = move;
node2 = NULL;
} else {
node2 = search_node_free(node2);
}
}
}
stack->fill_point--;
return node;
}
/*
* Main recursive search function.
*/
static SearchNode *
game_position_solve_impl (ExactSolution *const result,
const GamePosition *const gp,
const int achievable,
const int cutoff,
PVCell ***pve_parent_line_p)
{
result->node_count++;
SearchNode *node = NULL;
SearchNode *node2 = NULL;
PVCell **pve_line = NULL;
if (log_env->log_is_on) {
call_count++;
gp_hash_stack_fill_point++;
LogDataH log_data;
log_data.sub_run_id = 0;
log_data.call_id = call_count;
log_data.hash = game_position_hash(gp);
gp_hash_stack[gp_hash_stack_fill_point] = log_data.hash;
log_data.parent_hash = gp_hash_stack[gp_hash_stack_fill_point - 1];
log_data.blacks = (gp->board)->blacks;
log_data.whites = (gp->board)->whites;
log_data.player = gp->player;
gchar *json_doc = game_tree_log_data_h_json_doc(gp_hash_stack_fill_point, gp);
log_data.json_doc = json_doc;
log_data.json_doc_len = strlen(json_doc);
game_tree_log_write_h(log_env, &log_data);
g_free(json_doc);
}
const SquareSet moves = game_position_legal_moves(gp);
if (0ULL == moves) {
pve_line = pve_line_create(pve);
GamePosition *flipped_players = game_position_pass(gp);
if (game_position_has_any_legal_move(flipped_players)) {
node = search_node_negated(game_position_solve_impl(result, flipped_players, -cutoff, -achievable, &pve_line));
} else {
result->leaf_count++;
node = search_node_new(pass_move, game_position_final_value(gp));
}
pve_line_add_move(pve, pve_line, pass_move, flipped_players);
pve_line_delete(pve, *pve_parent_line_p);
*pve_parent_line_p = pve_line;
game_position_free(flipped_players);
} else {
MoveList move_list;
bool branch_is_active = false;
move_list_init(&move_list);
sort_moves_by_mobility_count(&move_list, gp);
for (MoveListElement *element = move_list.head.succ; element != &move_list.tail; element = element->succ) {
const Square move = element->sq;
if (!node) node = search_node_new(move, (pv_full_recording) ? achievable - 1 : achievable);
GamePosition *gp2 = game_position_make_move(gp, move);
pve_line = pve_line_create(pve);
node2 = search_node_negated(game_position_solve_impl(result, gp2, -cutoff, -node->value, &pve_line));
if (node2->value > node->value || (!branch_is_active && node2->value == node->value)) {
branch_is_active = true;
search_node_free(node);
node = node2;
node->move = move;
node2 = NULL;
pve_line_add_move(pve, pve_line, move, gp2);
game_position_free(gp2);
pve_line_delete(pve, *pve_parent_line_p);
*pve_parent_line_p = pve_line;
if (node->value > cutoff) goto out;
if (!pv_full_recording && node->value == cutoff) goto out;
} else {
if (pv_full_recording && node2->value == node->value) {
pve_line_add_move(pve, pve_line, move, gp2);
pve_line_add_variant(pve, *pve_parent_line_p, pve_line);
} else {
pve_line_delete(pve, pve_line);
}
search_node_free(node2);
game_position_free(gp2);
}
}
}
out:
if (log_env->log_is_on) {
gp_hash_stack_fill_point--;
}
return node;
}