public void run() {
            while (running) {
                if (holder.getSurface().isValid()) {
                    long startTime = System.nanoTime();
                    Canvas canvas = holder.lockCanvas();
                    Thread th1 = new Thread(new Runnable() {
                        public void run() {
                            updateField(0, 0, width, height / 2);
                        }
                    });
                    th1.start();
                    Thread th2 = new Thread(new Runnable() {
                        public void run() {
                            updateField(0, height / 2, width, height);
                        }
                    });
                    th2.start();
                    try {
                        th1.join();
                        th2.join();

                    }
                    catch (InterruptedException e) {};
                    field = field2;
                    onDraw(canvas);
                    holder.unlockCanvasAndPost(canvas);
                    long finishTime = System.nanoTime();
                    Log.i("TIME", "Circle: " + (finishTime-startTime)/1000000);
                    try {
                        Thread.sleep(16);
                    } catch (InterruptedException ignore) {}
                }
            }
        }