Do no initialize TM in all cases

Avoid doing full TM initialization if it won't be used, avoids division by zero.

closes #4484

No functional change

src/timeman.cpp

@@ -36,6 +36,12 @@ TimeManagement Time; // Our global time management object
 
 void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
 
+  // if we have no time, no need to initialize TM, except for the start time,
+  // which is used by movetime.
+  startTime = limits.startTime;
+  if (limits.time[us] == 0)
+      return;
+
   TimePoint moveOverhead    = TimePoint(Options["Move Overhead"]);
   TimePoint slowMover       = TimePoint(Options["Slow Mover"]);
   TimePoint npmsec          = TimePoint(Options["nodestime"]);
@@ -59,8 +65,6 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
       limits.npmsec = npmsec;
   }
 
-  startTime = limits.startTime;
-
   // Maximum move horizon of 50 moves
   int mtg = limits.movestogo ? std::min(limits.movestogo, 50) : 50;