2012/4/20 Kostya Vasilyev <[email protected]>:
> The default is definitely serial on my GNex with 4.0.2.
>
> Did they revert it again for the 4.0.3 that you have?
Here's how I am testing it (sloppy code, but it meets the need):
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import android.util.Log;
public class ParallelTasksActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new SillyTask().execute("A");
new SillyTask().execute("B");
new SillyTask().execute("C");
new SillyTask().execute("D");
new SillyTask().execute("E");
}
class SillyTask extends AsyncTask<String, String, Void> {
@Override
protected Void doInBackground(String... params) {
for (int i=0; i < 5; i++) {
String msg=params[0] + String.valueOf(i);
Log.d("ParallelTasks", msg);
SystemClock.sleep(1000);
}
return(null);
}
}
}
Now, if AsyncTask executes serially, I would expect:
A0
A1
A2
A3
A4
B0
B1
B2
B3
B4
...
Even if the letters were out of order (e.g., C before A), the
numerical index would be in order, because the task would be tying up
the one-and-only thread, so there should be no interleaving between
letter.
Yet, when I run this on 4.0.3 or 4.0.4, I get:
04-20 20:15:34.574: D/ParallelTasks(2965): D0
04-20 20:15:34.574: D/ParallelTasks(2965): C0
04-20 20:15:34.574: D/ParallelTasks(2965): E0
04-20 20:15:34.582: D/ParallelTasks(2965): A0
04-20 20:15:34.586: D/ParallelTasks(2965): B0
04-20 20:15:35.574: D/ParallelTasks(2965): D1
04-20 20:15:35.574: D/ParallelTasks(2965): E1
04-20 20:15:35.574: D/ParallelTasks(2965): C1
04-20 20:15:35.582: D/ParallelTasks(2965): A1
04-20 20:15:35.586: D/ParallelTasks(2965): B1
04-20 20:15:36.578: D/ParallelTasks(2965): E2
04-20 20:15:36.578: D/ParallelTasks(2965): C2
04-20 20:15:36.586: D/ParallelTasks(2965): D2
04-20 20:15:36.586: D/ParallelTasks(2965): A2
04-20 20:15:36.589: D/ParallelTasks(2965): B2
04-20 20:15:37.586: D/ParallelTasks(2965): C3
04-20 20:15:37.593: D/ParallelTasks(2965): D3
04-20 20:15:37.593: D/ParallelTasks(2965): B3
04-20 20:15:37.593: D/ParallelTasks(2965): E3
04-20 20:15:37.593: D/ParallelTasks(2965): A3
04-20 20:15:38.589: D/ParallelTasks(2965): C4
04-20 20:15:38.601: D/ParallelTasks(2965): D4
04-20 20:15:38.601: D/ParallelTasks(2965): E4
04-20 20:15:38.605: D/ParallelTasks(2965): B4
04-20 20:15:38.609: D/ParallelTasks(2965): A4
Since the five AsyncTask instances are interleaving their results, I
have to assume that they are running in parallel.
Even if I change doInBackground() to:
@Override
protected Void doInBackground(String... params) {
Log.d("ParallelTasks", params[0] + " started");
SystemClock.sleep(10000);
Log.d("ParallelTasks", params[0] + " ended");
return(null);
}
so there's a 10-second tie-up, I get:
04-20 20:20:02.886: D/ParallelTasks(3044): D started
04-20 20:20:02.898: D/ParallelTasks(3044): B started
04-20 20:20:02.898: D/ParallelTasks(3044): A started
04-20 20:20:02.898: D/ParallelTasks(3044): E started
04-20 20:20:02.898: D/ParallelTasks(3044): C started
04-20 20:20:12.898: D/ParallelTasks(3044): A ended
04-20 20:20:12.902: D/ParallelTasks(3044): C ended
04-20 20:20:12.910: D/ParallelTasks(3044): D ended
04-20 20:20:12.914: D/ParallelTasks(3044): B ended
04-20 20:20:12.918: D/ParallelTasks(3044): E ended
All five start, 10 seconds elapses, and all five end, indicating that
they are running in parallel.
Where I am going wrong in my analysis?
--
Mark Murphy (a Commons Guy)
http://commonsware.com | http://github.com/commonsguy
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