Output from a fix depth onward, instead of 3s.

To avoid output that depends on timing, output currmove and similar only from depth > 30
onward.  Current choice of 3s makes the output of the same search depending on
the system load, and doesn't always start at move 1. Depth 30 is nowadays
reached in a few seconds on most systems.

closes https://github.com/official-stockfish/Stockfish/pull/5436

No functional change

src/search.cpp

@@ -349,10 +349,10 @@ void Search::Worker::iterative_deepening() {
                 if (threads.stop)
                     break;
 
-                // When failing high/low give some update (without cluttering
-                // the UI) before a re-search.
+                // When failing high/low give some update before a re-search.
+                // To avoid excessive output, only start at rootDepth > 30.
                 if (mainThread && multiPV == 1 && (bestValue <= alpha || bestValue >= beta)
-                    && elapsed_time() > 3000)
+                    && rootDepth > 30)
                     main_manager()->pv(*this, threads, tt, rootDepth);
 
                 // In case of failing low/high increase aspiration window and
@@ -383,7 +383,7 @@ void Search::Worker::iterative_deepening() {
             std::stable_sort(rootMoves.begin() + pvFirst, rootMoves.begin() + pvIdx + 1);
 
             if (mainThread
-                && (threads.stop || pvIdx + 1 == multiPV || elapsed_time() > 3000)
+                && (threads.stop || pvIdx + 1 == multiPV || rootDepth > 30)
                 // A thread that aborted search can have mated-in/TB-loss PV and score
                 // that cannot be trusted, i.e. it can be delayed or refuted if we would have
                 // had time to fully search other root-moves. Thus we suppress this output and
@@ -974,7 +974,7 @@ moves_loop:  // When in check, search starts here
 
         ss->moveCount = ++moveCount;
 
-        if (rootNode && is_mainthread() && elapsed_time() > 3000)
+        if (rootNode && is_mainthread() && rootDepth > 30)
         {
             main_manager()->updates.onIter(
               {depth, UCIEngine::move(move, pos.is_chess960()), moveCount + thisThread->pvIdx});