DroidFish: Run the engine process with lower priority.

DroidFish/src/org/petero/droidfish/engine/EngineUtil.java

@@ -107,6 +107,9 @@ public class EngineUtil {
     /** Executes chmod 744 exePath. */
     final static native boolean chmod(String exePath);
 
+    /** Change the priority of a process. */
+    final static native void reNice(int pid, int prio);
+
     /** For synchronizing non thread safe native calls. */
     public static Object nativeLock = new Object();
 }

DroidFish/src/org/petero/droidfish/engine/ExternalEngine.java

@@ -77,6 +77,7 @@ public class ExternalEngine extends UCIEngineBase {
             synchronized (EngineUtil.nativeLock) {
                 engineProc = pb.start();
             }
+            reNice(engineProc);
 
             startupThread = new Thread(new Runnable() {
                 @Override
@@ -168,6 +169,17 @@ public class ExternalEngine extends UCIEngineBase {
         }
     }
 
+    /** Try to change the engine process priority to 5. */
+    private void reNice(Process proc) {
+        try {
+            java.lang.reflect.Field f = engineProc.getClass().getDeclaredField("pid");
+            f.setAccessible(true);
+            int pid = f.getInt(engineProc);
+            EngineUtil.reNice(pid, 10);
+        } catch (Throwable t) {
+        }
+    }
+
     /** Remove all files except exePath from exeDir. */
     private void cleanUpExeDir(File exeDir, String exePath) {
         try {