1 files changed, 44 insertions, 0 deletions

diff --git a/src/movesup.c b/src/movesup.c
index dec090c..33deae2 100755
--- a/src/movesup.c
+++ b/src/movesup.c
@@ -1017,11 +1017,36 @@ Return value:
     SCORE iVal;
     MOVE mv;
     MOVE_STACK_MOVE_VALUE_FLAGS mvfTemp;
+    MOVE mvLast;
+    ULONG uPrevContKey = 0;
+    FLAG fHaveContinuation = FALSE;
+    COOR cEnprise;
 
     ASSERT(ctx->sMoveStack.uBegin[ctx->uPly] <= uEnd);
     ASSERT(u >= ctx->sMoveStack.uBegin[ctx->uPly]);
     ASSERT(u < uEnd);
 
+    // Continuation history: "did a move like this tend to fail high
+    // right after a move like that?", keyed by (previous move, this
+    // move) at the same [piece][to] coarseness g_HistoryCounters
+    // already uses. Same accumulation/decay math as g_HistoryCounters
+    // (see _IncrementContinuationCounter/_DecrementContinuationCounter,
+    // dynamic.c) so its magnitude is empirically self-calibrated rather
+    // than a hand-picked constant -- a pair seen once contributes
+    // almost nothing, a pair that's fail-highed repeatedly at real
+    // depth naturally grows to compete with PSQT+history.
+    if ((ctx->uPly > 0) && (0 != (mvLast = (ctx->sPlyInfo[ctx->uPly - 1]).mv).uMove))
+    {
+        uPrevContKey = MOVE_TO_CONT_KEY(mvLast);
+        fHaveContinuation = TRUE;
+    }
+
+    // Flee-to-safety: a small, same-tier selection-time nudge (not a
+    // GOOD_MOVE promotion -- that class was retired, see generate.c's
+    // RETIRED comment) for a quiet move whose origin square is
+    // currently en prise.
+    cEnprise = FindEnprisePiece(ctx, ctx->sPosition.uToMove);
+
     //
     // Linear search from u..ctx->sMoveStack.uEnd[ctx->uPly] for the
     // move with the best value.
@@ -1031,6 +1056,16 @@ Return value:
     if (!IS_CAPTURE_OR_PROMOTION(mv))
     {
         iBestVal += g_HistoryCounters[mv.pMoved][mv.cTo];
+        if (TRUE == fHaveContinuation)
+        {
+            iBestVal += CONTINUATION_SCALE *
+                g_ContinuationHistory[(uPrevContKey * CONT_KEY_RANGE) +
+                                      MOVE_TO_CONT_KEY(mv)];
+        }
+        if (mv.cFrom == cEnprise)
+        {
+            iBestVal += FLEE_BONUS;
+        }
     }
     uLoc = u;
 
@@ -1041,6 +1076,15 @@ Return value:
         if (!IS_CAPTURE_OR_PROMOTION(mv))
         {
             iVal += g_HistoryCounters[mv.pMoved][mv.cTo];
+            if (TRUE == fHaveContinuation)
+            {
+                iVal += g_ContinuationHistory[(uPrevContKey * CONT_KEY_RANGE) +
+                                               MOVE_TO_CONT_KEY(mv)];
+            }
+            if (mv.cFrom == cEnprise)
+            {
+                iVal += FLEE_BONUS;
+            }
         }
         if (iVal > iBestVal)
         {