- // build_pv() extends a PV by adding moves from the transposition table at
- // the end. This should ensure that the PV is almost always at least two
- // plies long, which is important, because otherwise we will often get
- // single-move PVs when the search stops while failing high, and a
- // single-move PV means that we don't have a ponder move.
-
- void build_pv(const Position& pos, Move pv[]) {
- int ply;
- Position p(pos);
- StateInfo st[100];
-
- for (ply = 0; pv[ply] != MOVE_NONE; ply++)
- p.do_move(pv[ply], st[ply]);
-
- bool stop;
- const TTEntry* tte;
- for (stop = false, tte = TT.retrieve(p.get_key());
- tte && tte->move() != MOVE_NONE && !stop;
- tte = TT.retrieve(p.get_key()), ply++)
- {
- if (!move_is_legal(p, tte->move(), p.pinned_pieces(p.side_to_move())))
- break;
- pv[ply] = tte->move();
- p.do_move(pv[ply], st[ply]);
- for (int j = 0; j < ply; j++)
- if (st[j].key == p.get_key()) stop = true;
- }
- pv[ply] = MOVE_NONE;
- }
-
-