Implement maxNPS UCI option for CuckooChess

This is an alternative way to limit the engine strength. It also has
the advantage of reducing heat and battery drain.

CuckooChess/src/main/java/uci/EngineControl.java

@@ -73,6 +73,7 @@ public class EngineControl {
 
     // Reduced strength variables
     private int strength = 1000;
+    private int maxNPS = 0;
     private long randomSeed = 0;
 
     /**
@@ -226,7 +227,7 @@ public class EngineControl {
         sc = new Search(pos, posHashList, posHashListSize, tt, ht);
         sc.timeLimit(minTimeLimit, maxTimeLimit);
         sc.setListener(new SearchListener(os));
-        sc.setStrength(strength, randomSeed);
+        sc.setStrength(strength, randomSeed, maxNPS);
         MoveGen.MoveList moves = moveGen.pseudoLegalMoves(pos);
         MoveGen.removeIllegal(pos, moves);
         if ((searchMoves != null) && (searchMoves.size() > 0))
@@ -374,6 +375,7 @@ public class EngineControl {
         os.printf("option name UCI_EngineAbout type string default %s by Peter Osterlund, see %s%n",
                 ComputerPlayer.engineName, "http://hem.bredband.net/petero2b/javachess/index.html");
         os.print("option name Strength type spin default 1000 min 0 max 1000\n");
+        os.print("option name maxNPS type spin default 0 min 0 max 10000000\n");
         
         for (String pName : Parameters.instance().getParamNames()) {
             ParamBase p = Parameters.instance().getParam(pName);
@@ -424,6 +426,8 @@ public class EngineControl {
                 analyseMode = Boolean.parseBoolean(optionValue);
             } else if (optionName.equals("strength")) {
                 strength = Integer.parseInt(optionValue);
+            } else if (optionName.equals("maxnps")) {
+                maxNPS = Integer.parseInt(optionValue);
             } else {
                 Parameters.instance().set(optionName, optionValue);
             }

CuckooChessEngine/src/main/java/chess/Search.java

@@ -66,6 +66,7 @@ public class Search {
 
     // Reduced strength variables
     private int strength = 1000; // Strength (0-1000)
+    private int maxNPS = 0;      // If > 0, reduce strength by limiting NPS
     private boolean weak = false;        // Set to strength < 1000
     private long randomSeed = 0;
 
@@ -170,12 +171,16 @@ public class Search {
         maxTimeMillis = maxTimeLimit;
     }
 
-    final public void setStrength(int strength, long randomSeed) {
+    final public void setStrength(int strength, long randomSeed, int maxNPS) {
         if (strength < 0) strength = 0;
         if (strength > 1000) strength = 1000;
         this.strength = strength;
         weak = strength < 1000;
         this.randomSeed = randomSeed;
+        this.maxNPS = maxNPS;
+        nodesBetweenTimeCheck = 5000;
+        if (maxNPS > 0)
+            nodesBetweenTimeCheck = Math.min(Math.max(maxNPS / 100, 1), nodesBetweenTimeCheck);
     }
 
     final public Move iterativeDeepening(MoveGen.MoveList scMovesIn,
@@ -264,6 +269,9 @@ public class Search {
                         mi, "-", alpha, beta, "-", "-");
                 System.out.printf("%-6s...\n", TextIO.moveToUCIString(m)); */
                 pos.makeMove(m, ui);
+                nodes++;
+                totalNodes++;
+                nodesToGo--;
                 SearchTreeInfo sti = searchTreeInfo[0];
                 sti.currentMove = m;
                 sti.lmr = lmrS;
@@ -301,6 +309,9 @@ public class Search {
                         nodes = qNodes = 0;
                         posHashList[posHashListSize++] = pos.zobristHash();
                         pos.makeMove(m, ui);
+                        nodes++;
+                        totalNodes++;
+                        nodesToGo--;
                         int score2 = -negaScout(-beta, -score, 1, depthS - plyScale, -1, givesCheck);
                         score = Math.max(score, score2);
                         nodesThisMove += nodes + qNodes;
@@ -320,6 +331,9 @@ public class Search {
                         nodes = qNodes = 0;
                         posHashList[posHashListSize++] = pos.zobristHash();
                         pos.makeMove(m, ui);
+                        nodes++;
+                        totalNodes++;
+                        nodesToGo--;
                         score = -negaScout(-score, -alpha, 1, depthS - plyScale, -1, givesCheck);
                         nodesThisMove += nodes + qNodes;
                         posHashListSize--;
@@ -459,7 +473,7 @@ public class Search {
             long idx = log.logNodeStart(sti.nodeIdx, sti.currentMove, alpha, beta, ply, depth/plyScale);
             searchTreeInfo[ply].nodeIdx = idx;
         }
-        if (--nodesToGo <= 0) {
+        if (nodesToGo <= 0) {
             nodesToGo = nodesBetweenTimeCheck;
             long tNow = System.currentTimeMillis();
             long timeLimit = searchNeedMoreTime ? maxTimeMillis : minTimeMillis;
@@ -467,6 +481,15 @@ public class Search {
                     ((maxNodes >= 0) && (totalNodes >= maxNodes))) {
                 throw new StopSearch();
             }
+            if (maxNPS > 0) {
+                long time = tNow - tStart;
+                if (totalNodes * 1000.0 > maxNPS * Math.max(1, time)) {
+                    long wantedTime = totalNodes * 1000 / maxNPS;
+                    long sleepTime = wantedTime - time;
+                    if (sleepTime > 0)
+                        try { Thread.sleep(sleepTime); } catch (InterruptedException ignore) {}
+                }
+            }
             if (tNow - tLastStats >= 1000) {
                 notifyStats();
             }
@@ -797,6 +820,7 @@ public class Search {
                 pos.makeMove(m, ui);
                 nodes++;
                 totalNodes++;
+                nodesToGo--;
                 sti.currentMove = m;
 /*              long nodes0 = nodes;
                 long qNodes0 = qNodes;
@@ -1021,6 +1045,7 @@ public class Search {
             pos.makeMove(m, ui); 
             qNodes++;
             totalNodes++;
+            nodesToGo--;
             score = -quiesce(-beta, -alpha, ply + 1, depth - 1, nextInCheck);
             pos.unMakeMove(m, ui);
             if (score > bestScore) {

DroidFishApp/src/main/java/org/petero/droidfish/engine/cuckoochess/DroidEngineControl.java

@@ -70,6 +70,7 @@ public class DroidEngineControl {
 
     // Reduced strength variables
     private int strength = 1000;
+    private int maxNPS = 0;
     private long randomSeed = 0;
     private Random rndGen = new Random();
 
@@ -224,8 +225,8 @@ public class DroidEngineControl {
         sc = new Search(pos, posHashList, posHashListSize, tt, ht);
         sc.timeLimit(minTimeLimit, maxTimeLimit);
         sc.setListener(new SearchListener(os));
-        sc.setStrength(strength, randomSeed);
+        sc.setStrength(strength, randomSeed, maxNPS);
-        sc.nodesBetweenTimeCheck = 500;
+        sc.nodesBetweenTimeCheck = Math.min(500, sc.nodesBetweenTimeCheck);
         MoveGen.MoveList moves = moveGen.pseudoLegalMoves(pos);
         MoveGen.removeIllegal(pos, moves);
         if ((searchMoves != null) && (searchMoves.size() > 0))
@@ -367,9 +368,10 @@ public class DroidEngineControl {
         os.printLine("option name OwnBook type check default false");
         os.printLine("option name Ponder type check default true");
         os.printLine("option name UCI_AnalyseMode type check default false");
-        os.printLine("option name UCI_EngineAbout type string default %s by Peter Osterlund, see http://web.comhem.se/petero2home/javachess/index.html",
+        os.printLine("option name UCI_EngineAbout type string default %s by Peter Osterlund, see http://hem.bredband.net/petero2b/javachess/index.html",
                 ComputerPlayer.engineName);
         os.printLine("option name Strength type spin default 1000 min 0 max 1000");
+        os.printLine("option name maxNPS type spin default 0 min 0 max 10000000");
     }
 
     final void setOption(String optionName, String optionValue) {
@@ -385,6 +387,8 @@ public class DroidEngineControl {
                 analyseMode = Boolean.parseBoolean(optionValue);
             } else if (optionName.equals("strength")) {
                 strength = Integer.parseInt(optionValue);
+            } else if (optionName.equals("maxnps")) {
+                maxNPS = Integer.parseInt(optionValue);
             }
         } catch (NumberFormatException ignore) {
         }