};
+ // FIXME: document me
+
+ enum NullStatus {
+ ALLOW_NULLMOVE,
+ FORBID_NULLMOVE,
+ VERIFY_NULLMOVE
+ };
// RootMove struct is used for moves at the root at the tree. For each
// root move, we store a score, a node count, and a PV (really a refutation
Value id_loop(const Position& pos, Move searchMoves[]);
Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
- Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
+ Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, NullStatus nullStatus, int threadID, Move excludedMove = MOVE_NONE);
Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
void sp_search(SplitPoint* sp, int threadID);
void sp_search_pv(SplitPoint* sp, int threadID);
if (ss[0].reduction)
{
// Reduced depth non-pv search using alpha as upperbound
- value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
+ value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, ALLOW_NULLMOVE, 0);
doFullDepthSearch = (value > alpha);
}
}
{
// Full depth non-pv search using alpha as upperbound
ss[0].reduction = Depth(0);
- value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
+ value = -search(pos, ss, -alpha, newDepth, 1, ALLOW_NULLMOVE, 0);
// 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 (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
+ Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, FORBID_NULLMOVE, threadID, move);
if (excValue < ttValue - SingularExtensionMargin)
ext = OnePly;
ss[ply].reduction = pv_reduction(depth, moveCount);
if (ss[ply].reduction)
{
- value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
+ value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, ALLOW_NULLMOVE, threadID);
doFullDepthSearch = (value > alpha);
}
}
if (doFullDepthSearch)
{
ss[ply].reduction = Depth(0);
- value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
+ value = -search(pos, ss, -alpha, newDepth, ply+1, ALLOW_NULLMOVE, threadID);
// Step extra. pv search (only in PV nodes)
if (value > alpha && value < beta)
// search() is the search function for zero-width nodes.
Value search(Position& pos, SearchStack ss[], Value beta, Depth depth,
- int ply, bool allowNullmove, int threadID, Move excludedMove) {
+ int ply, NullStatus nullStatus, int threadID, Move excludedMove) {
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
assert(ply >= 0 && ply < PLY_MAX);
tte = TT.retrieve(posKey);
ttMove = (tte ? tte->move() : MOVE_NONE);
- if (tte && ok_to_use_TT(tte, depth, beta, ply, allowNullmove))
+ if (tte && ok_to_use_TT(tte, depth, beta, ply, nullStatus != VERIFY_NULLMOVE))
{
ss[ply].currentMove = ttMove; // Can be MOVE_NONE
return value_from_tt(tte->value(), ply);
// Step 7. Static null move pruning
// We're betting that the opponent doesn't have a move that will reduce
// the score by more than futility_margin(depth) if we do a null move.
- if ( allowNullmove
+ if ( nullStatus == ALLOW_NULLMOVE
&& depth < RazorDepth
&& !isCheck
&& !value_is_mate(beta)
// When we jump directly to qsearch() we do a null move only if static value is
// at least beta. Otherwise we do a null move if static value is not more than
// NullMoveMargin under beta.
- if ( allowNullmove
+ if ( nullStatus == ALLOW_NULLMOVE
&& depth > OnePly
&& !isCheck
&& !value_is_mate(beta)
pos.do_null_move(st);
- nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
+ nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, FORBID_NULLMOVE, threadID);
pos.undo_null_move();
// Do zugzwang verification search for high depths, don't store in TT
// if search was stopped.
if ( ( depth < 6 * OnePly
- || search(pos, ss, beta, depth-5*OnePly, ply, false, threadID) >= beta)
+ || search(pos, ss, beta, depth-5*OnePly, ply, VERIFY_NULLMOVE, threadID) >= beta)
&& !AbortSearch
&& !TM.thread_should_stop(threadID))
{
assert(value_to_tt(nullValue, ply) == nullValue);
- TT.store(posKey, nullValue, VALUE_TYPE_NS_LO, depth, MOVE_NONE);
+ if (!tte)
+ TT.store(posKey, nullValue, VALUE_TYPE_NS_LO, depth, MOVE_NONE);
+
return nullValue;
}
} else {
&& !isCheck
&& ss[ply].eval >= beta - IIDMargin)
{
- search(pos, ss, beta, depth/2, ply, false, threadID);
+ search(pos, ss, beta, depth/2, ply, FORBID_NULLMOVE, threadID);
ttMove = ss[ply].pv[ply];
tte = TT.retrieve(posKey);
}
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, false, threadID, move);
+ Value excValue = search(pos, ss, ttValue - SingularExtensionMargin, depth / 2, ply, FORBID_NULLMOVE, threadID, move);
if (excValue < ttValue - SingularExtensionMargin)
ext = OnePly;
ss[ply].reduction = nonpv_reduction(depth, moveCount);
if (ss[ply].reduction)
{
- value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
+ value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, ALLOW_NULLMOVE, threadID);
doFullDepthSearch = (value >= beta);
}
}
if (doFullDepthSearch)
{
ss[ply].reduction = Depth(0);
- value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
+ value = -search(pos, ss, -(beta-1), newDepth, ply+1, ALLOW_NULLMOVE, threadID);
}
// Step 16. Undo move
ss[sp->ply].reduction = nonpv_reduction(sp->depth, moveCount);
if (ss[sp->ply].reduction)
{
- value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
+ value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, ALLOW_NULLMOVE, threadID);
doFullDepthSearch = (value >= sp->beta && !TM.thread_should_stop(threadID));
}
}
if (doFullDepthSearch)
{
ss[sp->ply].reduction = Depth(0);
- value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
+ value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, ALLOW_NULLMOVE, threadID);
}
// Step 16. Undo move
if (ss[sp->ply].reduction)
{
Value localAlpha = sp->alpha;
- value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
+ value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, ALLOW_NULLMOVE, threadID);
doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID));
}
}
{
Value localAlpha = sp->alpha;
ss[sp->ply].reduction = Depth(0);
- value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, true, threadID);
+ value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, ALLOW_NULLMOVE, threadID);
if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID))
{