Simplify IID depth formula

mcostalba · mcostalba · commit 68d61b80c60a · 2015-07-30T09:54:25.000+02:00
Restore original formula messed up during
half-ply removal.

STC
LLR: 4.11 (-2.94,2.94) [-3.00,1.00]
Total: 21349 W: 4091 L: 3909 D: 13349

LTC
LLR: 5.42 (-2.94,2.94) [-3.00,1.00]
Total: 52819 W: 8321 L: 8122 D: 36376

bench: 8040572
diff --git a/src/search.cpp b/src/search.cpp
@@ -769,9 +769,9 @@ namespace {
         && !ttMove
         && (PvNode || ss->staticEval + 256 >= beta))
     {
-        Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
+        Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
         ss->skipEarlyPruning = true;
-        search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
+        search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d, true);
         ss->skipEarlyPruning = false;
 
         tte = TT.probe(posKey, ttHit);
@@ -821,13 +821,11 @@ namespace {
           if (!pos.legal(move, ci.pinned))
               continue;
 
-          moveCount = ++splitPoint->moveCount;
+          ss->moveCount = moveCount = ++splitPoint->moveCount;
           splitPoint->spinlock.release();
       }
       else
-          ++moveCount;
-      
-      ss->moveCount = moveCount;
+          ss->moveCount = ++moveCount;
 
       if (RootNode)
       {
@@ -935,8 +933,7 @@ namespace {
       // Check for legality just before making the move
       if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))
       {
-          moveCount--;
-          ss->moveCount = moveCount;
+          ss->moveCount = --moveCount;
           continue;
       }
 
@@ -1429,7 +1426,7 @@ namespace {
     }
 
     // Extra penalty for PV move in previous ply when it gets refuted
-    if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount==1 && !pos.captured_piece_type())
+    if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount == 1 && !pos.captured_piece_type())
     {
         Square prevPrevSq = to_sq((ss-2)->currentMove);
         HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];

Original file line number	Diff line number	Diff line change
`@@ -769,9 +769,9 @@ namespace {`
`769`	`769`	`&& !ttMove`
`770`	`770`	`&& (PvNode \|\| ss->staticEval + 256 >= beta))`
`771`	`771`	`{`
`772`		`- Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);`
	`772`	`+ Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);`
`773`	`773`	`ss->skipEarlyPruning = true;`
`774`		`- search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);`
	`774`	`+ search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d, true);`
`775`	`775`	`ss->skipEarlyPruning = false;`
`776`	`776`
`777`	`777`	`tte = TT.probe(posKey, ttHit);`
`@@ -821,13 +821,11 @@ namespace {`
`821`	`821`	`if (!pos.legal(move, ci.pinned))`
`822`	`822`	`continue;`
`823`	`823`
`824`		`- moveCount = ++splitPoint->moveCount;`
	`824`	`+ ss->moveCount = moveCount = ++splitPoint->moveCount;`
`825`	`825`	`splitPoint->spinlock.release();`
`826`	`826`	`}`
`827`	`827`	`else`
`828`		`- ++moveCount;`
`829`		`-`
`830`		`- ss->moveCount = moveCount;`
	`828`	`+ ss->moveCount = ++moveCount;`
`831`	`829`
`832`	`830`	`if (RootNode)`
`833`	`831`	`{`
`@@ -935,8 +933,7 @@ namespace {`
`935`	`933`	`// Check for legality just before making the move`
`936`	`934`	`if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))`
`937`	`935`	`{`
`938`		`- moveCount--;`
`939`		`- ss->moveCount = moveCount;`
	`936`	`+ ss->moveCount = --moveCount;`
`940`	`937`	`continue;`
`941`	`938`	`}`
`942`	`939`
`@@ -1429,7 +1426,7 @@ namespace {`
`1429`	`1426`	`}`
`1430`	`1427`
`1431`	`1428`	`// Extra penalty for PV move in previous ply when it gets refuted`
`1432`		`- if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount==1 && !pos.captured_piece_type())`
	`1429`	`+ if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount == 1 && !pos.captured_piece_type())`
`1433`	`1430`	`{`
`1434`	`1431`	`Square prevPrevSq = to_sq((ss-2)->currentMove);`
`1435`	`1432`	`HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];`