Gather stats for max callback time

A small amount of stats analysis, mostly max callback time, with simple
display in the UI.

Also improves pow calculation to use lut implementation instead of
math.h pow(), for a speedup somewhere around 20-30%.

android/jni/Android.mk

@@ -6,6 +6,7 @@ LOCAL_CPP_EXTENSION := .cc
 LOCAL_SRC_FILES := android_glue.cc \
                    dx7note.cc \
                    env.cc \
+                   exp2.cc \
                    fm_core.cc \
                    fm_op_kernel.cc \
                    freqlut.cc \

android/src/com/google/synthesizer/android/stats/JitterStats.java

@@ -0,0 +1,44 @@
+package com.google.synthesizer.android.stats;
+
+import android.util.Log;
+
+public class JitterStats {
+  public JitterStats() {
+    startTime_ = new double[N_STATS];
+    endTime_ = new double[N_STATS];
+
+  }
+
+  // Takes stats buf in format from android_glue
+  public void aggregate(byte[] statsBuf) {
+    String[] lines = new String(statsBuf).split("\n");
+    for (int i = 0; i < lines.length; i++) {
+      String[] toks = lines[i].split(" ");
+      if (toks.length == 3 && "ts".equals(toks[0])) {
+        double startTime = Double.parseDouble(toks[1]);
+        double endTime = Double.parseDouble(toks[2]);
+        startTime_[bufIx_] = startTime;
+        endTime_[bufIx_] = endTime;
+        bufIx_ = (bufIx_ + 1) % N_STATS;
+        double cbTime = endTime - startTime;
+        meanCbTime_ += (cbTime - meanCbTime_) * .01;
+      }
+    }
+  }
+
+  public String report() {
+    double maxCbTime = 0.0;
+    for (int i = 0; i < N_STATS; i++) {
+      double cbTime = endTime_[i] - startTime_[i];
+      maxCbTime = Math.max(maxCbTime, cbTime);
+    }
+    return "max cb = " + Double.toString(maxCbTime * 1000) + "ms";
+  }
+
+  static final int N_STATS = 2000;
+  double meanCbTime_;
+  double startTime_[];
+  double endTime_[];
+  int bufIx_ = 0;
+
+}

android/src/com/google/synthesizer/android/ui/PianoActivity2.java

@@ -18,7 +18,6 @@ package com.google.synthesizer.android.ui;
 
 import java.io.IOException;
 import java.io.InputStream;
-import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.HashMap;
 
@@ -46,6 +45,7 @@ import android.widget.TextView;
 
 import com.google.synthesizer.R;
 import com.google.synthesizer.android.AndroidGlue;
+import com.google.synthesizer.android.stats.JitterStats;
 import com.google.synthesizer.android.widgets.knob.KnobListener;
 import com.google.synthesizer.android.widgets.knob.KnobView;
 import com.google.synthesizer.android.widgets.piano.PianoView;
@@ -120,6 +120,7 @@ public class PianoActivity2 extends Activity {
       tryConnectUsb();
     }
 
+    jitterStats_ = new JitterStats();
     statusHandler_ = new Handler();
     statusRunnable_ = new Runnable() {
       public void run() {
@@ -127,15 +128,11 @@ public class PianoActivity2 extends Activity {
         if (n > 0) {
           byte[] buf = new byte[n];
           androidGlue_.readStatsBytes(buf, 0, n);
+          jitterStats_.aggregate(buf);
           TextView statusTextView = (TextView)findViewById(R.id.status);
-          String statusString = new String(buf);
-          int nlIndex = statusString.indexOf('\n');
-          if (nlIndex >= 0) {
-            statusString = statusString.substring(0, nlIndex);
+          statusTextView.setText(jitterStats_.report());
         }
-          statusTextView.setText(statusString);
-        }
-        statusHandler_.postDelayed(statusRunnable_, 10);
+        statusHandler_.postDelayed(statusRunnable_, 100);
       }
     };
     statusRunnable_.run();
@@ -252,4 +249,5 @@ public class PianoActivity2 extends Activity {
   private Spinner presetSpinner_;
   private Handler statusHandler_;
   private Runnable statusRunnable_;
+  private JitterStats jitterStats_;
 }

cpp/src/android_glue.cc

@@ -27,6 +27,7 @@
 
 #include "synth.h"
 #include "freqlut.h"
+#include "exp2.h"
 #include "sin.h"
 #include "synth_unit.h"
 
@@ -137,6 +138,7 @@ Java_com_google_synthesizer_android_AndroidGlue_start(JNIEnv *env,
 
   buffer_size = buf_size;
   Freqlut::init(sample_rate);
+  Exp2::init();
   Sin::init();
   ring_buffer = new RingBuffer();
   stats_ring_buffer = new RingBuffer();

cpp/src/dx7note.cc

@@ -21,6 +21,7 @@
 #include "synth.h"
 #include "freqlut.h"
 #include "patch.h"
+#include "exp2.h"
 #include "dx7note.h"
 
 using namespace std;
@@ -171,8 +172,8 @@ void Dx7Note::compute(int32_t *buf) {
   for (int op = 0; op < 6; op++) {
     params_[op].gain[0] = params_[op].gain[1];
     int32_t level = env_[op].getsample();
-    // TODO: replace pow with faster calculation
-    int32_t gain = pow(2, 10 + level * (1.0 / (1 << 24)));
+    int32_t gain = Exp2::lookup(level - (14 * (1 << 24)));
+    //int32_t gain = pow(2, 10 + level * (1.0 / (1 << 24)));
     params_[op].gain[1] = gain;
   }
   core_.compute(buf, params_, algorithm_, fb_buf_, fb_shift_);