// Step 9. Internal iterative deepening
// Minimum depth for use of internal iterative deepening
- const Depth IIDDepthAtPVNodes = 5 * OnePly;
- const Depth IIDDepthAtNonPVNodes = 8 * OnePly;
+ const Depth IIDDepth[2] = { 8 * OnePly /* non-PV */, 5 * OnePly /* PV */};
// At Non-PV nodes we do an internal iterative deepening search
// when the static evaluation is at most IIDMargin below beta.
}
// Step 9. Internal iterative deepening
- // We have different rules for PV nodes and non-pv nodes
- if ( PvNode
- && depth >= IIDDepthAtPVNodes
- && ttMove == MOVE_NONE)
- {
- search<PV>(pos, ss, alpha, beta, depth-2*OnePly, ply, false, threadID);
- ttMove = ss[ply].pv[ply];
- tte = TT.retrieve(posKey);
- }
-
- if ( !PvNode
- && depth >= IIDDepthAtNonPVNodes
+ if ( depth >= IIDDepth[PvNode]
&& ttMove == MOVE_NONE
- && !isCheck
- && ss[ply].eval >= beta - IIDMargin)
+ && (PvNode || (!isCheck && ss[ply].eval >= beta - IIDMargin)))
{
- search<NonPV>(pos, ss, alpha, beta, depth/2, ply, false, threadID);
+ Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
+ search<PvNode>(pos, ss, alpha, beta, d, ply, false, threadID);
ttMove = ss[ply].pv[ply];
tte = TT.retrieve(posKey);
}