Fix was wrong becuase search starts from ss+1,
code is a bit tricky here, so rewrite in a way
to be more easy to read and understand.
Spotted by Eelco.
No functional change.
void id_loop(Position& pos) {
void id_loop(Position& pos) {
- Stack ss[MAX_PLY_PLUS_2];
+ Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1)
int depth, prevBestMoveChanges;
Value bestValue, alpha, beta, delta;
int depth, prevBestMoveChanges;
Value bestValue, alpha, beta, delta;
- memset(ss, 0, 4 * sizeof(Stack));
+ memset(ss-1, 0, 4 * sizeof(Stack));
depth = BestMoveChanges = 0;
bestValue = delta = -VALUE_INFINITE;
depth = BestMoveChanges = 0;
bestValue = delta = -VALUE_INFINITE;
- ss->currentMove = MOVE_NULL; // Hack to skip update gains
+ (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
TT.new_search();
History.clear();
Gains.clear();
TT.new_search();
History.clear();
Gains.clear();
// research with bigger window until not failing high/low anymore.
while (true)
{
// research with bigger window until not failing high/low anymore.
while (true)
{
- // Search starts from ss+1 to allow referencing (ss-1). This is
- // needed by update gains and ss copy when splitting at Root.
- bestValue = search<Root>(pos, ss+1, alpha, beta, depth * ONE_PLY);
+ bestValue = search<Root>(pos, ss, alpha, beta, depth * ONE_PLY);
// Bring to front the best move. It is critical that sorting is
// done with a stable algorithm because all the values but the first
// Bring to front the best move. It is critical that sorting is
// done with a stable algorithm because all the values but the first
- Stack ss[MAX_PLY_PLUS_2];
+ Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1)
Position pos(*sp->pos, this);
Position pos(*sp->pos, this);
- memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
- (ss+1)->splitPoint = sp;
+ memcpy(ss-1, sp->ss-1, 4 * sizeof(Stack));
+ ss->splitPoint = sp;
switch (sp->nodeType) {
case Root:
switch (sp->nodeType) {
case Root:
- search<SplitPointRoot>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+ search<SplitPointRoot>(pos, ss, sp->alpha, sp->beta, sp->depth);
- search<SplitPointPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+ search<SplitPointPV>(pos, ss, sp->alpha, sp->beta, sp->depth);
- search<SplitPointNonPV>(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+ search<SplitPointNonPV>(pos, ss, sp->alpha, sp->beta, sp->depth);
break;
default:
assert(false);
break;
default:
assert(false);