1 files changed, 37 insertions, 19 deletions
diff --git a/src/root.c b/src/root.c
index ed450b4..bfcf034 100755
--- a/src/root.c
+++ b/src/root.c
@@ -950,27 +950,45 @@ _IterateSetSearchGlobals(ULONG uDepth)
     //
     g_uSoftExtendLimit = g_uIterateDepth * 2;
     g_uHardExtendLimit = g_uIterateDepth * 4;
-    for (u = 0; u < MAX_PLY_PER_SEARCH; u++)
+
+    // g_uExtensionReduction[]'s own bands, below, must stay reachable
+    // within [0, MAX_PLY_PER_SEARCH) regardless of how deep g_uIterateDepth
+    // is -- naive g_uSoftExtendLimit/g_uHardExtendLimit (2x/4x iterate
+    // depth) can hugely exceed MAX_PLY_PER_SEARCH for a deep requested
+    // search (e.g. sd=30 -> hard limit 120 >> 64), which would leave every
+    // reachable u in the loop below permanently in the "0 penalty" band --
+    // no taper at all for the entire representable ply range. Deliberately
+    // a LOCAL, separately-capped depth for this table only --
+    // g_uSoftExtendLimit/g_uHardExtendLimit themselves stay uncapped (raw
+    // g_uIterateDepth * 2/4) since g_uHardExtendLimit is also read directly
+    // elsewhere (searchsup.c's QSearch runaway-depth cutoff) where capping
+    // it would be an unrelated, unintended behavior change.
     {
-        if (u < g_uSoftExtendLimit)
-        {
-            g_uExtensionReduction[u] = 0;
-        }
-        else if (u < (g_uSoftExtendLimit + g_uIterateDepth / 2))
-        {
-            g_uExtensionReduction[u] = QUARTER_PLY;
-        }
-        else if (u < (g_uSoftExtendLimit + g_uIterateDepth))
-        {
-            g_uExtensionReduction[u] = HALF_PLY;
-        }
-        else if (u < g_uHardExtendLimit)
-        {
-            g_uExtensionReduction[u] = THREE_QUARTERS_PLY;
-        }
-        else
+        ULONG uEffIterateDepth = MIN(g_uIterateDepth, (MAX_PLY_PER_SEARCH - 4) / 4);
+        ULONG uEffSoftLimit = uEffIterateDepth * 2;
+        ULONG uEffHardLimit = uEffIterateDepth * 4;
+        for (u = 0; u < MAX_PLY_PER_SEARCH; u++)
         {
-            g_uExtensionReduction[u] = 5 * ONE_PLY;
+            if (u < uEffSoftLimit)
+            {
+                g_uExtensionReduction[u] = 0;
+            }
+            else if (u < (uEffSoftLimit + uEffIterateDepth / 2))
+            {
+                g_uExtensionReduction[u] = QUARTER_PLY;
+            }
+            else if (u < (uEffSoftLimit + uEffIterateDepth))
+            {
+                g_uExtensionReduction[u] = HALF_PLY;
+            }
+            else if (u < uEffHardLimit)
+            {
+                g_uExtensionReduction[u] = THREE_QUARTERS_PLY;
+            }
+            else
+            {
+                g_uExtensionReduction[u] = 5 * ONE_PLY;
+            }
         }
     }