From: Joona Kiiski <joona.kiiski@gmail.com>
Date: Sun, 12 Apr 2009 20:30:40 +0000 (+0300)
Subject: Revert "Implement a fallback system when aspiration search fails low and we are out... 
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=3e7e1a7c53c251c244d8271082b602e6b9a9b208;hp=0ea716463bf2722931c160edcc9b68e9a800a93a

Revert "Implement a fallback system when aspiration search fails low and we are out of time."

This reverts commit 55dd98f7c717b94a659931cd20e088334b1cf7a6.

Revert fallback-system for root_search

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

diff --git a/src/search.cpp b/src/search.cpp
index 76b79dda..b8d6a3a5 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -259,7 +259,7 @@ namespace {
   // Time managment variables
   int SearchStartTime;
   int MaxNodes, MaxDepth;
-  int MaxSearchTime, AbsoluteMaxSearchTime, EmergencyMaxSearchTime, ExtraSearchTime;
+  int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
   Move EasyMove;
   int RootMoveNumber;
   bool InfiniteSearch;
@@ -520,11 +520,9 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
       {
           MaxSearchTime = myTime / 30 + myIncrement;
           AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100);
-          EmergencyMaxSearchTime = Max(myTime / 2, myIncrement - 100);
       } else { // Blitz game without increment
           MaxSearchTime = myTime / 30;
           AbsoluteMaxSearchTime = myTime / 8;
-          EmergencyMaxSearchTime = myTime / 4;
       }
   }
   else // (x moves) / (y minutes)
@@ -533,11 +531,9 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move,
       {
           MaxSearchTime = myTime / 2;
           AbsoluteMaxSearchTime = Min(myTime / 2, myTime - 500);
-          EmergencyMaxSearchTime = myTime - 500;
       } else {
           MaxSearchTime = myTime / Min(movesToGo, 20);
           AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3);
-          EmergencyMaxSearchTime = Min((8 * myTime) / movesToGo, myTime / 2);
       }
   }
 
@@ -704,9 +700,6 @@ namespace {
     Position p(pos);
     SearchStack ss[PLY_MAX_PLUS_2];
 
-    Value alpha;
-    Value beta;
-
     // searchMoves are verified, copied, scored and sorted
     RootMoveList rml(p, searchMoves);
 
@@ -736,6 +729,9 @@ namespace {
         std::cout << "info depth " << Iteration << std::endl;
 
         //Calculate dynamic search window based on previous iterations.
+        Value alpha;
+        Value beta;
+
         if (MultiPV == 1 && Iteration >= 6) {
           Value prevDelta1 = IterationInfo[Iteration - 1].speculated_value() - IterationInfo[Iteration - 2].speculated_value();
           Value prevDelta2 = IterationInfo[Iteration - 2].speculated_value() - IterationInfo[Iteration - 3].speculated_value();
@@ -754,14 +750,13 @@ namespace {
 
         // Search to the current depth
         Value value = root_search(p, ss, rml, alpha, beta);
+        if (AbortSearch)
+          break; //Value cannot be trusted. Break out immediately!
 
         // Write PV to transposition table, in case the relevant entries have
         // been overwritten during the search:
         TT.insert_pv(p, ss[0].pv);
 
-        if (AbortSearch)
-          break; //Value cannot be trusted. Break out immediately!
-
         //Save info about search result
         Value speculated_value = value;
         bool fHigh = false;
@@ -831,6 +826,7 @@ namespace {
 
             if (stopSearch)
             {
+                //FIXME: Implement fail-low emergency measures
                 if (!PonderSearch)
                     break;
                 else
@@ -842,34 +838,6 @@ namespace {
             break;
     }
 
-    if (FailLow)
-    {
-      //Here we face the rare, but extremely difficult case:
-      //Our aspiration search has failed low and we've run out of time!
-      //So we have no move to play!
-      //Now use the emergency time and try as quickly as possible to
-      //find even one playable move.
-
-      //FIXME: this is only for grepping logs purpose. Remove me when we are sure that this stuff really works!!
-      if (AbortSearch)
-        std::cout << "info depth " << 999 << std::endl;
-      else
-        std::cout << "info depth " << 998 << std::endl;
-
-      //Prepare variables for emergency search
-      AbortSearch = false;
-      FailLow = false;
-      AbsoluteMaxSearchTime = EmergencyMaxSearchTime;
-      MaxSearchTime = EmergencyMaxSearchTime;
-      ExtraSearchTime = 0;
-      rml.sort();
-
-      std::cout << "info depth " << Iteration << std::endl;
-
-     //Cause we failed low, it's _likely_ that we couldn't get over alpha anyway.
-      root_search(p, ss, rml, -VALUE_INFINITE, alpha);
-    }
-
     rml.sort();
 
     // If we are pondering, we shouldn't print the best move before we
@@ -923,6 +891,7 @@ namespace {
 
   Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) {
 
+    //FIXME: Implement bestValue
     Value oldAlpha = alpha;
     Value value;
     Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());