Search ply and game ply are rwo different things !
Revert bogus commit.
No functional change on bench, but it changes in real games
when engine sends all the moves up to current one.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
// pointer to point to the new, ready to be updated, state.
struct ReducedStateInfo {
Key pawnKey, materialKey;
// pointer to point to the new, ready to be updated, state.
struct ReducedStateInfo {
Key pawnKey, materialKey;
- int castleRights, rule50, ply, pliesFromNull;
+ int castleRights, rule50, gamePly, pliesFromNull;
Square epSquare;
Score value;
Value npMaterial[2];
Square epSquare;
Score value;
Value npMaterial[2];
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
- history[st->ply++] = key;
+ history[st->gamePly++] = key;
// Update side to move
key ^= zobSideToMove;
// Update side to move
key ^= zobSideToMove;
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
// Save the current key to the history[] array, in order to be able to
// detect repetition draws.
- history[st->ply++] = st->key;
+ history[st->gamePly++] = st->key;
// Update the necessary information
if (st->epSquare != SQ_NONE)
// Update the necessary information
if (st->epSquare != SQ_NONE)
// Update the necessary information
sideToMove = opposite_color(sideToMove);
st->rule50--;
// Update the necessary information
sideToMove = opposite_color(sideToMove);
st->rule50--;
-/// Position::reset_ply() simply sets ply to 0. It is used from the
+/// Position::reset_game_ply() simply sets gamePly to 0. It is used from the
/// UCI interface code, whenever a non-reversible move is made in a
/// 'position fen <fen> moves m1 m2 ...' command. This makes it possible
/// for the program to handle games of arbitrary length, as long as the GUI
/// handles draws by the 50 move rule correctly.
/// UCI interface code, whenever a non-reversible move is made in a
/// 'position fen <fen> moves m1 m2 ...' command. This makes it possible
/// for the program to handle games of arbitrary length, as long as the GUI
/// handles draws by the 50 move rule correctly.
-void Position::reset_ply() {
+void Position::reset_game_ply() {
if (st->rule50 > 100 || (st->rule50 == 100 && !is_check()))
return true;
if (st->rule50 > 100 || (st->rule50 == 100 && !is_check()))
return true;
- assert(st->ply >= st->rule50);
-
- for (int i = 4, e = Min(st->rule50, st->pliesFromNull); i <= e; i += 2)
- if (history[st->ply - i] == st->key)
+ for (int i = 4, e = Min(Min(st->gamePly, st->rule50), st->pliesFromNull); i <= e; i += 2)
+ if (history[st->gamePly - i] == st->key)
return true;
return false;
return true;
return false;
struct StateInfo {
Key pawnKey, materialKey;
struct StateInfo {
Key pawnKey, materialKey;
- int castleRights, rule50, ply, pliesFromNull;
+ int castleRights, rule50, gamePly, pliesFromNull;
Square epSquare;
Score value;
Value npMaterial[2];
Square epSquare;
Score value;
Value npMaterial[2];
bool opposite_colored_bishops() const;
bool has_pawn_on_7th(Color c) const;
bool opposite_colored_bishops() const;
bool has_pawn_on_7th(Color c) const;
- // Game ply information
+ // Current thread ID searching on the position
- int ply() const;
- void reset_ply();
+
+ // Reset the gamePly variable to 0
+ void reset_game_ply();
// Position consistency check, for debugging
bool is_ok(int* failedStep = NULL) const;
// Position consistency check, for debugging
bool is_ok(int* failedStep = NULL) const;
-inline int Position::ply() const {
- return st->ply;
-}
-
#endif // !defined(POSITION_H_INCLUDED)
#endif // !defined(POSITION_H_INCLUDED)
void idle_loop(int threadID, SplitPoint* sp);
template <bool Fake>
void idle_loop(int threadID, SplitPoint* sp);
template <bool Fake>
- void split(const Position& pos, SearchStack* ss, Value* alpha, const Value beta, Value* bestValue,
+ void split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode);
private:
Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode);
private:
Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
template <NodeType PvNode>
Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
template <NodeType PvNode>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
+ Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
template <NodeType PvNode>
template <NodeType PvNode>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
+ Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
template <NodeType PvNode>
void sp_search(SplitPoint* sp, int threadID);
template <NodeType PvNode>
void sp_search(SplitPoint* sp, int threadID);
H.clear();
init_ss_array(ss, PLY_MAX_PLUS_2);
ValueByIteration[1] = rml.get_move_score(0);
H.clear();
init_ss_array(ss, PLY_MAX_PLUS_2);
ValueByIteration[1] = rml.get_move_score(0);
Iteration = 1;
// Is one move significantly better than others after initial scoring ?
Iteration = 1;
// Is one move significantly better than others after initial scoring ?
alpha = -VALUE_INFINITE;
// Full depth PV search, done on first move or after a fail high
alpha = -VALUE_INFINITE;
// Full depth PV search, done on first move or after a fail high
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
assert(newDepth-ss->reduction >= OnePly);
// Reduced depth non-pv search using alpha as upperbound
assert(newDepth-ss->reduction >= OnePly);
// Reduced depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
doFullDepthSearch = (value > alpha);
}
doFullDepthSearch = (value > alpha);
}
assert(newDepth - OnePly >= OnePly);
ss->reduction = OnePly;
assert(newDepth - OnePly >= OnePly);
ss->reduction = OnePly;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
doFullDepthSearch = (value > alpha);
}
ss->reduction = Depth(0); // Restore original reduction
doFullDepthSearch = (value > alpha);
}
ss->reduction = Depth(0); // Restore original reduction
if (doFullDepthSearch)
{
// Full depth non-pv search using alpha as upperbound
if (doFullDepthSearch)
{
// Full depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
// If we are above alpha then research at same depth but as PV
// to get a correct score or eventually a fail high above beta.
if (value > alpha)
// If we are above alpha then research at same depth but as PV
// to get a correct score or eventually a fail high above beta.
if (value > alpha)
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+ value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
// search<>() is the main search function for both PV and non-PV nodes
template <NodeType PvNode>
// search<>() is the main search function for both PV and non-PV nodes
template <NodeType PvNode>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
+ Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
- assert(pos.ply() > 0 && pos.ply() < PLY_MAX);
+ assert(ply > 0 && ply < PLY_MAX);
assert(pos.thread() >= 0 && pos.thread() < TM.active_threads());
Move movesSearched[256];
assert(pos.thread() >= 0 && pos.thread() < TM.active_threads());
Move movesSearched[256];
bool mateThreat = false;
int moveCount = 0;
int threadID = pos.thread();
bool mateThreat = false;
int moveCount = 0;
int threadID = pos.thread();
refinedValue = bestValue = value = -VALUE_INFINITE;
oldAlpha = alpha;
refinedValue = bestValue = value = -VALUE_INFINITE;
oldAlpha = alpha;
TT.store(posKey, ss->eval, VALUE_TYPE_EXACT, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]);
Value rbeta = beta - razor_margin(depth);
TT.store(posKey, ss->eval, VALUE_TYPE_EXACT, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]);
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, Depth(0));
+ Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, Depth(0), ply);
if (v < rbeta)
// Logically we should return (v + razor_margin(depth)), but
// surprisingly this did slightly weaker in tests.
if (v < rbeta)
// Logically we should return (v + razor_margin(depth)), but
// surprisingly this did slightly weaker in tests.
pos.do_null_move(st);
(ss+1)->skipNullMove = true;
pos.do_null_move(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R*OnePly < OnePly ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, Depth(0))
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly);
+ nullValue = depth-R*OnePly < OnePly ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, Depth(0), ply+1)
+ : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly, ply+1);
(ss+1)->skipNullMove = false;
pos.undo_null_move();
(ss+1)->skipNullMove = false;
pos.undo_null_move();
return nullValue;
ss->skipNullMove = true;
return nullValue;
ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly);
+ Value v = search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, ply);
ss->skipNullMove = false;
if (v >= beta)
ss->skipNullMove = false;
if (v >= beta)
Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
ss->skipNullMove = true;
Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
ss->skipNullMove = true;
- search<PvNode>(pos, ss, alpha, beta, d);
+ search<PvNode>(pos, ss, alpha, beta, d, ply);
ss->skipNullMove = false;
ttMove = ss->pv[0];
ss->skipNullMove = false;
ttMove = ss->pv[0];
Value b = ttValue - SingularExtensionMargin;
ss->excludedMove = move;
ss->skipNullMove = true;
Value b = ttValue - SingularExtensionMargin;
ss->excludedMove = move;
ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2);
+ Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
if (v < ttValue - SingularExtensionMargin)
ext = OnePly;
}
if (v < ttValue - SingularExtensionMargin)
ext = OnePly;
}
// Step extra. pv search (only in PV nodes)
// The first move in list is the expected PV
if (PvNode && moveCount == 1)
// Step extra. pv search (only in PV nodes)
// The first move in list is the expected PV
if (PvNode && moveCount == 1)
- value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0))
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0), ply+1)
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
else
{
// Step 14. Reduced depth search
else
{
// Step 14. Reduced depth search
if (ss->reduction)
{
Depth d = newDepth - ss->reduction;
if (ss->reduction)
{
Depth d = newDepth - ss->reduction;
- value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0))
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
+ value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0), ply+1)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
doFullDepthSearch = (value > alpha);
}
doFullDepthSearch = (value > alpha);
}
assert(newDepth - OnePly >= OnePly);
ss->reduction = OnePly;
assert(newDepth - OnePly >= OnePly);
ss->reduction = OnePly;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1);
doFullDepthSearch = (value > alpha);
}
ss->reduction = Depth(0); // Restore original reduction
doFullDepthSearch = (value > alpha);
}
ss->reduction = Depth(0); // Restore original reduction
// Step 15. Full depth search
if (doFullDepthSearch)
{
// Step 15. Full depth search
if (doFullDepthSearch)
{
- value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0))
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
+ value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0), ply+1)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
// Step extra. pv search (only in PV nodes)
// Search only for possible new PV nodes, if instead value >= beta then
// parent node fails low with value <= alpha and tries another move.
if (PvNode && value > alpha && value < beta)
// Step extra. pv search (only in PV nodes)
// Search only for possible new PV nodes, if instead value >= beta then
// parent node fails low with value <= alpha and tries another move.
if (PvNode && value > alpha && value < beta)
- value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0))
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0), ply+1)
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
&& !AbortSearch
&& !TM.thread_should_stop(threadID)
&& Iteration <= 99)
&& !AbortSearch
&& !TM.thread_should_stop(threadID)
&& Iteration <= 99)
- TM.split<FakeSplit>(pos, ss, &alpha, beta, &bestValue, depth,
+ TM.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
mateThreat, &moveCount, &mp, PvNode);
}
mateThreat, &moveCount, &mp, PvNode);
}
// less than OnePly).
template <NodeType PvNode>
// less than OnePly).
template <NodeType PvNode>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
+ Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
assert(depth <= 0);
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
assert(depth <= 0);
- assert(pos.ply() > 0 && pos.ply() < PLY_MAX);
+ assert(ply > 0 && ply < PLY_MAX);
assert(pos.thread() >= 0 && pos.thread() < TM.active_threads());
EvalInfo ei;
assert(pos.thread() >= 0 && pos.thread() < TM.active_threads());
EvalInfo ei;
bool isCheck, deepChecks, enoughMaterial, moveIsCheck, evasionPrunable;
const TTEntry* tte;
Value oldAlpha = alpha;
bool isCheck, deepChecks, enoughMaterial, moveIsCheck, evasionPrunable;
const TTEntry* tte;
Value oldAlpha = alpha;
TM.incrementNodeCounter(pos.thread());
ss->pv[0] = ss->pv[1] = ss->currentMove = MOVE_NONE;
TM.incrementNodeCounter(pos.thread());
ss->pv[0] = ss->pv[1] = ss->currentMove = MOVE_NONE;
// Make and search the move
pos.do_move(move, st, ci, moveIsCheck);
// Make and search the move
pos.do_move(move, st, ci, moveIsCheck);
- value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-OnePly);
+ value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-OnePly, ply+1);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
{
Value localAlpha = sp->alpha;
Depth d = newDepth - ss->reduction;
{
Value localAlpha = sp->alpha;
Depth d = newDepth - ss->reduction;
- value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0))
- : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d);
+ value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), sp->ply+1)
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d, sp->ply+1);
+
doFullDepthSearch = (value > localAlpha);
}
doFullDepthSearch = (value > localAlpha);
}
ss->reduction = OnePly;
Value localAlpha = sp->alpha;
ss->reduction = OnePly;
Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction);
+ value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, sp->ply+1);
doFullDepthSearch = (value > localAlpha);
}
ss->reduction = Depth(0); // Restore original reduction
doFullDepthSearch = (value > localAlpha);
}
ss->reduction = Depth(0); // Restore original reduction
if (doFullDepthSearch)
{
Value localAlpha = sp->alpha;
if (doFullDepthSearch)
{
Value localAlpha = sp->alpha;
- value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0))
- : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth);
+ value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), sp->ply+1)
+ : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1);
// Step extra. pv search (only in PV nodes)
// Search only for possible new PV nodes, if instead value >= beta then
// parent node fails low with value <= alpha and tries another move.
if (PvNode && value > localAlpha && value < sp->beta)
// Step extra. pv search (only in PV nodes)
// Search only for possible new PV nodes, if instead value >= beta then
// parent node fails low with value <= alpha and tries another move.
if (PvNode && value > localAlpha && value < sp->beta)
- value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -sp->beta, -sp->alpha, Depth(0))
- : - search<PV>(pos, ss+1, -sp->beta, -sp->alpha, newDepth);
+ value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -sp->beta, -sp->alpha, Depth(0), sp->ply+1)
+ : - search<PV>(pos, ss+1, -sp->beta, -sp->alpha, newDepth, sp->ply+1);
// split() returns.
template <bool Fake>
// split() returns.
template <bool Fake>
- void ThreadsManager::split(const Position& p, SearchStack* ss, Value* alpha, const Value beta,
- Value* bestValue, Depth depth, bool mateThreat, int* moveCount,
- MovePicker* mp, bool pvNode) {
+ void ThreadsManager::split(const Position& p, SearchStack* ss, int ply, Value* alpha,
+ const Value beta, Value* bestValue, Depth depth, bool mateThreat,
+ int* moveCount, MovePicker* mp, bool pvNode) {
+ assert(ply > 0 && ply < PLY_MAX);
assert(*bestValue >= -VALUE_INFINITE);
assert(*bestValue <= *alpha);
assert(*alpha < beta);
assert(*bestValue >= -VALUE_INFINITE);
assert(*bestValue <= *alpha);
assert(*alpha < beta);
// Initialize the split point object
splitPoint->parent = threads[master].splitPoint;
splitPoint->stopRequest = false;
// Initialize the split point object
splitPoint->parent = threads[master].splitPoint;
splitPoint->stopRequest = false;
splitPoint->depth = depth;
splitPoint->mateThreat = mateThreat;
splitPoint->alpha = *alpha;
splitPoint->depth = depth;
splitPoint->mateThreat = mateThreat;
splitPoint->alpha = *alpha;
init_ss_array(ss, PLY_MAX_PLUS_2);
pos.do_move(cur->move, st);
moves[count].move = cur->move;
init_ss_array(ss, PLY_MAX_PLUS_2);
pos.do_move(cur->move, st);
moves[count].move = cur->move;
- moves[count].score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0));
+ moves[count].score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1);
moves[count].pv[0] = cur->move;
moves[count].pv[1] = MOVE_NONE;
pos.undo_move(cur->move);
moves[count].pv[0] = cur->move;
moves[count].pv[1] = MOVE_NONE;
pos.undo_move(cur->move);
Depth depth;
bool pvNode, mateThreat;
Value beta;
Depth depth;
bool pvNode, mateThreat;
Value beta;
SearchStack sstack[MAX_THREADS][PLY_MAX_PLUS_2];
// Const pointers to shared data
SearchStack sstack[MAX_THREADS][PLY_MAX_PLUS_2];
// Const pointers to shared data
move = move_from_string(RootPosition, token);
RootPosition.do_move(move, st);
if (RootPosition.rule_50_counter() == 0)
move = move_from_string(RootPosition, token);
RootPosition.do_move(move, st);
if (RootPosition.rule_50_counter() == 0)
- RootPosition.reset_ply();
+ RootPosition.reset_game_ply();
}
// Our StateInfo st is about going out of scope so copy
// its content inside RootPosition before they disappear.
}
// Our StateInfo st is about going out of scope so copy
// its content inside RootPosition before they disappear.