Updated the Android benchmark with more accurate timing and better results output. Also fixed walking the tree to use a consistent order to make comparison between the device and emulator easier.

git-svn-id: https://zxing.googlecode.com/svn/trunk@644 59b500cc-1b3d-0410-9834-0bbf25fbcc57

androidtest/src/com/google/zxing/client/androidtest/BenchmarkActivity.java

@@ -24,7 +24,6 @@ import android.util.Log;
 import android.view.View;
 import android.widget.Button;
 import android.widget.TextView;
-import com.google.zxing.BarcodeFormat;
 
 import java.util.Vector;
 
@@ -82,11 +81,7 @@ public class BenchmarkActivity extends Activity {
     for (int x = 0; x < items.size(); x++) {
       BenchmarkItem item = items.get(x);
       if (item != null) {
-        BarcodeFormat format = item.getFormat();
-        Log.v(TAG, (item.getDecoded() ? "DECODED: " : "FAILED: ") + item.getPath());
-        Log.v(TAG, "  Ran " + item.getCount() + " tests on " +
-            (format != null ? format.toString() : "unknown") + " format with an average of " +
-            item.getAverageMilliseconds() + " ms");
+        Log.v(TAG, item.toString());
         count++;
       }
     }

androidtest/src/com/google/zxing/client/androidtest/BenchmarkItem.java

@@ -28,14 +28,13 @@ public class BenchmarkItem {
 
   public BenchmarkItem(String path, int runs) {
     mPath = path;
+    assert(runs > 0);
     mTimes = new int[runs];
     mPosition = 0;
     mDecoded = false;
     mFormat = null;
   }
 
-  // I'm storing these separately instead of as a running total so I can add features like
-  // calculating the min and max later, or ignoring outliers.
   public void addResult(int milliseconds) {
     mTimes[mPosition] = milliseconds;
     mPosition++;
@@ -49,16 +48,40 @@ public class BenchmarkItem {
     mFormat = format;
   }
 
-  public String getPath() {
-    return mPath;
+  @Override
+  public String toString() {
+    StringBuffer result = new StringBuffer();
+    result.append(mDecoded ? ("DECODED " + mFormat.toString() + ": ") : "FAILED: ");
+    result.append(mPath);
+    result.append(" (");
+    result.append(getAverageTime());
+    result.append(" ms average)\n  ");
+    int size = mTimes.length;
+    for (int x = 0; x < size; x++) {
+      result.append(mTimes[x]);
+      result.append(" ");
+    }
+    return result.toString();
   }
 
-  public int getAverageMilliseconds() {
+  /**
+   * Calculates the average time but throws out the maximum as an outlier first.
+   *
+   * @return The average decoding time in milliseconds.
+   */
+  private int getAverageTime() {
     int size = mTimes.length;
     int total = 0;
+    int max = mTimes[0];
     for (int x = 0; x < size; x++) {
-      total += mTimes[x];
+      int time = mTimes[x];
+      total += time;
+      if (time > max) {
+        max = time;
+      }
     }
+    total -= max;
+    size--;
     if (size > 0) {
       return total / size;
     } else {
@@ -66,16 +89,4 @@ public class BenchmarkItem {
     }
   }
 
-  public int getCount() {
-    return mTimes.length;
-  }
-
-  public boolean getDecoded() {
-    return mDecoded;
-  }
-
-  public BarcodeFormat getFormat() {
-    return mFormat;
-  }
-
 }

androidtest/src/com/google/zxing/client/androidtest/BenchmarkThread.java

@@ -16,6 +16,7 @@
 
 package com.google.zxing.client.androidtest;
 
+import android.os.Debug;
 import android.os.Message;
 import android.util.Log;
 import com.google.zxing.MultiFormatReader;
@@ -24,7 +25,7 @@ import com.google.zxing.Result;
 
 import java.io.File;
 import java.io.FileNotFoundException;
-import java.util.Date;
+import java.util.Arrays;
 import java.util.Vector;
 
 final class BenchmarkThread extends Thread {
@@ -45,6 +46,8 @@ final class BenchmarkThread extends Thread {
   public void run() {
     mMultiFormatReader = new MultiFormatReader();
     mMultiFormatReader.setHints(null);
+    // Try to get in a known state before starting the benchmark
+    System.gc();
 
     Vector<BenchmarkItem> items = new Vector<BenchmarkItem>();
     walkTree(mPath, items);
@@ -58,6 +61,7 @@ final class BenchmarkThread extends Thread {
     File file = new File(path);
     if (file.isDirectory()) {
       String[] files = file.list();
+      Arrays.sort(files);
       for (int x = 0; x < files.length; x++) {
         walkTree(file.getAbsolutePath() + "/" + files[x], items);
       }
@@ -80,21 +84,23 @@ final class BenchmarkThread extends Thread {
 
     BenchmarkItem item = new BenchmarkItem(path, RUNS);
     for (int x = 0; x < RUNS; x++) {
-      Date startDate = new Date();
       boolean success;
       Result result = null;
+      // Using this call instead of getting the time should eliminate a lot of variability due to
+      // scheduling and what else is happening in the system.
+      long now = Debug.threadCpuTimeNanos();
       try {
         result = mMultiFormatReader.decodeWithState(source);
         success = true;
       } catch (ReaderException e) {
         success = false;
       }
-      Date endDate = new Date();
+      now = Debug.threadCpuTimeNanos() - now;
       if (x == 0) {
         item.setDecoded(success);
         item.setFormat(result != null ? result.getBarcodeFormat() : null);
       }
-      item.addResult((int) (endDate.getTime() - startDate.getTime()));
+      item.addResult((int) (now / 1000));
     }
     return item;
   }