Fix incorrect assert(PvNode == (alpha != beta - 1))

In case of a PvNode could happen that alpha == beta - 1,
for instance in case the same previous node was visited
with same beta during a non-pv search, the node failed low
and stored beta-1 in TT. Then the node is searched again
in PV mode, TT value beta-1 is retrieved and updates alpha
that now happens to be beta-1.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/search.cpp b/src/search.cpp
index 437eb4a258cf50fb36c14e9fbd3bd0784d63a5dc..eb9f63f15bca317f4fa148bf304472f7eb204edf 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -544,7 +544,7 @@ namespace {
     const bool RootNode = (NT == Root || NT == SplitPointRoot);
 
     assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
     const bool RootNode = (NT == Root || NT == SplitPointRoot);
 
     assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);

-    assert(PvNode == (alpha != beta - 1));
+    assert((alpha == beta - 1) || PvNode);

     assert(depth > DEPTH_ZERO);
     assert(pos.thread() >= 0 && pos.thread() < Threads.size());
 
     assert(depth > DEPTH_ZERO);
     assert(pos.thread() >= 0 && pos.thread() < Threads.size());
 


@@ -1154,7 +1154,7 @@ split_point_start: // At split points actual search starts from here
 
     assert(NT == PV || NT == NonPV);
     assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
 
     assert(NT == PV || NT == NonPV);
     assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);

-    assert(PvNode == (alpha != beta - 1));
+    assert((alpha == beta - 1) || PvNode);

     assert(depth <= DEPTH_ZERO);
     assert(pos.thread() >= 0 && pos.thread() < Threads.size());
 
     assert(depth <= DEPTH_ZERO);
     assert(pos.thread() >= 0 && pos.thread() < Threads.size());