From: erbsenzaehler <erbsenzaehler@users.noreply.github.com>
Date: Sun, 27 Jan 2019 08:20:38 +0000 (+0100)
Subject: Make ONE_PLY value independent again
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=49a1fdd3fe894d170a2c2781238c0f0f907c08cc

Make ONE_PLY value independent again

And a Trevis CI test to catch future issues.

No functional change.
---

diff --git a/.travis.yml b/.travis.yml
index c4f68ae5..f27f9c95 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -55,6 +55,9 @@ script:
   - make clean && make -j2 ARCH=x86-64 optimize=no debug=yes build && ../tests/signature.sh $benchref
   - make clean && make -j2 ARCH=x86-32 optimize=no debug=yes build && ../tests/signature.sh $benchref
   - make clean && make -j2 ARCH=x86-32 build && ../tests/signature.sh $benchref
+
+  # Verify bench number is ONE_PLY independent by doubling its value
+  - sed -i 's/.*\(ONE_PLY = [0-9]*\),.*/\1 * 2,/g' types.h
   - make clean && make -j2 ARCH=x86-64 build && ../tests/signature.sh $benchref
   #
   # Check perft and reproducible search
diff --git a/src/search.cpp b/src/search.cpp
index 36c8a5eb..a9a62dbf 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -86,8 +86,8 @@ namespace {
 
   // Add a small random component to draw evaluations to avoid 3fold-blindness
   Value value_draw(Depth depth, Thread* thisThread) {
-    return depth < 4 ? VALUE_DRAW
-                     : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
+    return depth < 4 * ONE_PLY ? VALUE_DRAW
+                               : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
   }
 
   // Skill structure is used to implement strength limit
@@ -785,7 +785,7 @@ namespace {
 
             // Do verification search at high depths, with null move pruning disabled
             // for us, until ply exceeds nmpMinPly.
-            thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4;
+            thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / (4 * ONE_PLY);
             thisThread->nmpColor = us;
 
             Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
@@ -912,8 +912,9 @@ moves_loop: // When in check, search starts from here
           &&  pos.legal(move))
       {
           Value singularBeta = ttValue - 2 * depth / ONE_PLY;
+          Depth halfDepth = depth / (2 * ONE_PLY) * ONE_PLY; // ONE_PLY invariant
           ss->excludedMove = move;
-          value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, depth / 2, cutNode);
+          value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode);
           ss->excludedMove = MOVE_NONE;
 
           if (value < singularBeta)
@@ -961,7 +962,8 @@ moves_loop: // When in check, search starts from here
                   continue;
 
               // Reduced depth of the next LMR search
-              int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
+              int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO);
+              lmrDepth /= ONE_PLY;
 
               // Countermoves based pruning (~20 Elo)
               if (   lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)