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  • Android: Crashed when single contact is clicked

    - by Sean Tan
    My application is always crashed at this moment, guru here please help me to solved. Thanks.The situation now is as mentioned in title above. Hereby is my AndroidManifest.xml <?xml version="1.0" encoding="utf-8"?> <!-- Copyright (C) 2009 The Android Open Source Project Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.contactmanager" android:versionCode="1" android:versionName="1.0"> <uses-sdk android:minSdkVersion="10" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.MANAGE_ACCOUNTS"/> <uses-permission android:name="android.permission.WRITE_OWNER_DATA"/> <uses-permission android:name="android.permission.CAMERA"/> <uses-permission android:name="android.permission.CALL_PHONE"/> <uses-permission android:name="android.permission.GET_ACCOUNTS" /> <uses-permission android:name="android.permission.READ_CONTACTS" /> <uses-permission android:name="android.permission.WRITE_CONTACTS" /> <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/> <uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.CAMERA"/> <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/> <uses-permission android:name="android.permission.GET_ACCOUNTS"/> <application android:label="@string/app_name" android:icon="@drawable/icon" android:allowBackup="true"> <!-- --><activity android:name=".ContactManager" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="ContactAdder" android:label="@string/addContactTitle"> </activity> <activity android:name=".SingleListContact" android:label="Contact Person Details"> </activity> </application> </manifest> The SingleListContact.java package com.example.android.contactmanager; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.widget.TextView; public class SingleListContact extends Activity{ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.setContentView(R.layout.single_list_contact_view); TextView txtContact = (TextView) findViewById(R.id.contactList); Intent i = getIntent(); // getting attached intent data String contact = i.getStringExtra("contact"); // displaying selected product name txtContact.setText(contact); } } My ContactManager.java as below /* * Copyright (C) 2009 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.contactmanager; import android.app.Activity; import android.content.Intent; import android.database.Cursor; import android.net.Uri; import android.os.Bundle; import android.provider.ContactsContract; import android.util.Log; import android.view.View; import android.widget.AdapterView; import android.widget.AdapterView.OnItemClickListener; import android.widget.Button; import android.widget.CheckBox; import android.widget.CompoundButton; import android.widget.CompoundButton.OnCheckedChangeListener; import android.widget.ListView; import android.widget.SimpleCursorAdapter; import android.widget.TextView; public final class ContactManager extends Activity implements OnItemClickListener { public static final String TAG = "ContactManager"; private Button mAddAccountButton; private ListView mContactList; private boolean mShowInvisible; //public BooleanObservable ShowInvisible = new BooleanObservable(false); private CheckBox mShowInvisibleControl; /** * Called when the activity is first created. Responsible for initializing the UI. */ @Override public void onCreate(Bundle savedInstanceState) { Log.v(TAG, "Activity State: onCreate()"); super.onCreate(savedInstanceState); setContentView(R.layout.contact_manager); // Obtain handles to UI objects mAddAccountButton = (Button) findViewById(R.id.addContactButton); mContactList = (ListView) findViewById(R.id.contactList); mShowInvisibleControl = (CheckBox) findViewById(R.id.showInvisible); // Initialise class properties mShowInvisible = false; mShowInvisibleControl.setChecked(mShowInvisible); // Register handler for UI elements mAddAccountButton.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Log.d(TAG, "mAddAccountButton clicked"); launchContactAdder(); } }); mShowInvisibleControl.setOnCheckedChangeListener(new OnCheckedChangeListener() { public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { Log.d(TAG, "mShowInvisibleControl changed: " + isChecked); mShowInvisible = isChecked; populateContactList(); } }); mContactList = (ListView) findViewById(R.id.contactList); mContactList.setOnItemClickListener(this); // Populate the contact list populateContactList(); } /** * Populate the contact list based on account currently selected in the account spinner. */ private void populateContactList() { // Build adapter with contact entries Cursor cursor = getContacts(); String[] fields = new String[] { ContactsContract.Data.DISPLAY_NAME }; SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.contact_entry, cursor, fields, new int[] {R.id.contactEntryText}); mContactList.setAdapter(adapter); } /** * Obtains the contact list for the currently selected account. * * @return A cursor for for accessing the contact list. */ private Cursor getContacts() { // Run query Uri uri = ContactsContract.Contacts.CONTENT_URI; String[] projection = new String[] { ContactsContract.Contacts._ID, ContactsContract.Contacts.DISPLAY_NAME }; String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" + (mShowInvisible ? "0" : "1") + "'"; //String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" + (mShowInvisible.get() ? "0" : "1") + "'"; String[] selectionArgs = null; String sortOrder = ContactsContract.Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC"; return this.managedQuery(uri, projection, selection, selectionArgs, sortOrder); } /** * Launches the ContactAdder activity to add a new contact to the selected account. */ protected void launchContactAdder() { Intent i = new Intent(this, ContactAdder.class); startActivity(i); } public void onItemClick(AdapterView<?> l, View v, int position, long id) { Log.i("TAG", "You clicked item " + id + " at position " + position); // Here you start the intent to show the contact details // selected item TextView tv=(TextView)v.findViewById(R.id.contactList); String allcontactlist = tv.getText().toString(); // Launching new Activity on selecting single List Item Intent i = new Intent(getApplicationContext(), SingleListContact.class); // sending data to new activity i.putExtra("Contact Person", allcontactlist); startActivity(i); } } contact_entry.xml <?xml version="1.0" encoding="utf-8"?> <!-- Copyright (C) 2009 The Android Open Source Project Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical"> <ListView android:layout_width="wrap_content" android:id="@+id/contactList" android:layout_height="0dp" android:padding="10dp" android:textSize="200sp" android:layout_weight="10"/> <CheckBox android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/showInvisible" android:text="@string/showInvisible"/> <Button android:layout_width="fill_parent" android:layout_height="wrap_content" android:id="@+id/addContactButton" android:text="@string/addContactButtonLabel"/> </LinearLayout> Logcat result: 12-05 05:00:31.289: E/AndroidRuntime(642): FATAL EXCEPTION: main 12-05 05:00:31.289: E/AndroidRuntime(642): java.lang.NullPointerException 12-05 05:00:31.289: E/AndroidRuntime(642): at com.example.android.contactmanager.ContactManager.onItemClick(ContactManager.java:148) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.widget.AdapterView.performItemClick(AdapterView.java:284) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.widget.ListView.performItemClick(ListView.java:3513) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.widget.AbsListView$PerformClick.run(AbsListView.java:1812) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.os.Handler.handleCallback(Handler.java:587) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.os.Handler.dispatchMessage(Handler.java:92) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.os.Looper.loop(Looper.java:123) 12-05 05:00:31.289: E/AndroidRuntime(642): at android.app.ActivityThread.main(ActivityThread.java:3683) 12-05 05:00:31.289: E/AndroidRuntime(642): at java.lang.reflect.Method.invokeNative(Native Method) 12-05 05:00:31.289: E/AndroidRuntime(642): at java.lang.reflect.Method.invoke(Method.java:507) 12-05 05:00:31.289: E/AndroidRuntime(642): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 12-05 05:00:31.289: E/AndroidRuntime(642): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 12-05 05:00:31.289: E/AndroidRuntime(642): at dalvik.system.NativeStart.main(Native Method)

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  • Building v8 without JIT

    - by rames
    Hello, I would like to run some tests on v8 with and without JIT to compare performances. I know JIT will improve my average speed performance, but it would be nice for me to have some actual more detailed tests results as I want to work with mobile platforms. I haven't found how to enable or disable JIT like it exists on Squirrelfish (cf. ENABLE_JIT in JavaScriptCore/wtf/Platform.h). Does somebody knows how to do that with v8? Thanks. Alexandre

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  • SQL 2003 Distance Latitude Longitude

    - by J.Hendrix
    I have a table full of Dealers along with their latitude and longitude. I am trying to determine the top n closest dealers to any given lat and lon. I already have the function to calculate distance between locations, but I want to do as few calculations as possible (my table can contain many thousands of entries). Currently I have to calculate the distance for each entry then sort them. Is there any way to sort before I do the calculation to improve performance? This question is good, but I will not always know my range. Should I just pick an arbitrarily high range then refine my results? I am thankful for any help the community can offer. declare @Lat real declare @lon real Set @lat = 41.05 Set @lon = -73.53 SELECT top 10 MemberID, Address1, City, State, Zip, Phone, Lat, Lon, (SELECT fun_DistanceLatLon] (@Lat,@lon,Lat,Lon)) as mDistance --Calculate distance FROM Dealers Order by (SELECT fun_DistanceLatLon] (@Lat,@lon,Lat,Lon))

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  • wowza vs Flash Media Server (FMS / FMIS) - ease of integration with ASP.Net

    - by alchemical
    We're creating a web site offering one to many video chat and trying to decide on which of these streaming servers to go with. Looking at around 256kbps live streams, hoping to achieve at least 1000 simultaneous streams on one 8-core server. Wowza is cheaper (1k vs 5k for FMS), and appears to be used successfully by many sites (StreamLive, Justin.TV, etc.). However, some people have expressed that it may be more difficult to work with. I.e. fine-tuning it, less documentation, integration with ASP.Net code, etc. Wondering if anyone with real-world experience with either of these servers can advise regarding how easy or difficult to use and integrate they are for a site like this. Also wondering if there is any performance difference (lag, etc.).

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  • Postgresql - one database for everyone, or one-database per customer

    - by user337876
    I'm working on a web-based business application where each customer will need to have their own data (think basecamphq.com type model) For scalability and ease-of-upgrades, I'd prefer to have a single database where each customer gets a filtered version of the data. The problem is how to guarantee that they stay sandboxed to their own data. Trying to enforce it in code seems like a disaster waiting to happen. I know Oracle has a way to append a where clause to every query based on a login id, but does Postgresql have anything similar? If not, is there a different design pattern I could use (like creating a view of each table for each customer that filters)? Worse case scenario, what is the performance/memory overhead of having 1000 100M databases vs having a single 1Tb database? I will need to provide backup/restore functionality on a per-customer basis which is dead-simple on a single database but quite a bit trickier if they are sharing the database with other customers.

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  • Cheetah pre-compiled template usage quesion

    - by leo
    For performance reason as suggested here, I am studying how to used the pr-compiled template. I edit hello.tmpl in template directory as #attr title = "This is my Template" \${title} Hello \${who}! then issued cheetah-compile.exe .\hello.tmpl and get the hello.py In another python file runner.py , i have !/usr/bin/env python from Cheetah.Template import Template from template import hello def myMethod(): tmpl = hello.hello(searchList=[{'who' : 'world'}]) results = tmpl.respond() print tmpl if name == 'main': myMethod() But the outcome is ${title} Hello ${who}! Debugging for a while, i found that inside hello.py def respond(self, trans=None): ## CHEETAH: main method generated for this template if (not trans and not self._CHEETAH__isBuffering and not callable(self.transaction)): trans = self.transaction # is None unless self.awake() was called if not trans: trans = DummyTransaction() it looks like the trans is None, so it goes to DummyTransaction, what did I miss here? Any suggestions to how to fix it?

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  • how to automate upsizing from Access to SQL Server?

    - by Arne
    Hi, I need to automate the migration from an Access (2003) to an SQL Server DB (2005 or 2008). The upsizing should be done automatically as part of a build process. I need that because there are 2 versions of the software, a single user rich client and a web version. Access DB is used for single user to minimize setup effort, SQL Server to improve performance and scaling with many simultanious users. Access should be the "leading" DB, meaning devs do changes in Access DB and those are propagated to the SQL server within the build process. Many changes will occur, so doing it manually is not an option. I am new to the Microsoft world, so I dont know appropriate tools for that. What tools can I use and how? I know how to do it (by clicking) with the upsizing assistant. Perhaps I can automate that somehow? Thanks in advance for your answers. Cheers, Arne

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  • bundle .NET dlls to run application in .NET-less machine?

    - by Camilo Martin
    AFAIK, ngen turns MSIL into native code (also reffered to as pre-JIT), however I never payed too much attention at it's startup performance impact. Ngen'd applications still require the .NET base class libraries (the runtime). Since the base class libraries have everything our .NET assemblies need (correct?) would it be possible to ship the framework's DLLs with my ngen'd application so that it does not require the runtime to be installed? (e.g., the scenario for most Windows XP machines) Oh, and please don't bother mentioning Remotesoft's Salamander Linker or Xenocode's Postbuild. They are not for my (and many's) current budget (and they seem to simply bundle the framework in a virtualized enviroinment, which means big download sizes and slow startup times I believe) EDIT: I know now, ngen doesn't do what I thought it did. But is it possible to bundle the .NET files with an application, without using a VM?

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  • How can a Delphi TForm / TPersistent object calculate its own construction and deserialization time?

    - by mjustin
    For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": start of the deserialization process after the deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event So the log for TMyForm.Create(nil) could look like: - 00.000 instance created - 00.010 before deserialization - 01.823 after deserialization - 02.340 before OnFormCreate Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions. Background: for some of our app forms which have a very basic structure (with some PageControls and QuantumGrids) I realized that it is not database access and other stuff in OnFormShow but the construction which took most of the time (around 2 seconds) which makes me wonder where this time is spent. As a reference object I will also build a mock form which has a similar structure but no code or datamodule connections and measure its creation time.

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  • Compiler optimization of repeated accessor calls

    - by apocalypse9
    I've found recently that for some types of financial calculations that the following pattern is much easier to follow and test especially in situations where we may need to get numbers from various stages of the computation. public class nonsensical_calculator { ... double _rate; int _term; int _days; double monthlyRate { get { return _rate / 12; }} public double days { get { return (1 - i); }} double ar { get { return (1+ days) /(monthlyRate * days) double bleh { get { return Math.Pow(ar - days, _term) public double raar { get { return bleh * ar/2 * ar / days; }} .... } Obviously this often results in multiple calls to the same accessor within a given formula. I was curious as to whether or not the compiler is smart enough to optimize away these repeated calls with no intervening change in state, or whether this style is causing a decent performance hit. Further reading suggestions are always appreciated

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  • Persist an object that is not marked as serializable

    - by lasseeskildsen
    Hi, I need to persist an object that is not marked with the serializable attribute. The object is from a 3rd party library which I cannot change. I need to store it in a persist place, like for example the file system, so the optimal solution would be to serialize the object to a file, but since it isn't marked as serializable, that is not a straight forward solution. It's a pretty complex object, which also holds a collection of other objects. Do you guys have any input on how to solve this? The code will never run in a production environment, so I'm ok with almost any solution and performance.

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  • grouping draggable objects with jquery-ui draggable

    - by Jim Robert
    Hello, I want to use jquery draggable/droppable to let the user select a group of objects (each one has a checkbox in the corner) and then drag all the selected objects as a group... I can't figure out for the life of me how to do it haha. Here is what I'm thinking will lead to a usable solution, on each draggable object, use the start() event and somehow grab all the other selected objects and add them to the selection I was also considering just making the dragged object look like a group of objects (they're images, so a pile of photos maybe) for performance reasons. I think using the draggable functionality might fall over if you drag several dozen objects at once, does that sound like a better idea?

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  • DefaultSchedulerService in ASP.NET application

    - by Samir P
    Hi, My project has a requirement to implement look-ahead caching i.e. triggering another request on invokation of a specific request. The following details in short the implementation - HttpModule parses the SOAPRequest and matches entry in a configuration file for look-ahead candidate. If the request matches, it prepares the Parameters dictionary and starts appropriate workflow. Single workflow runtime is used across all requests is ensured through initializing the runtime instance at Application_Start event and stored in Application Dictionary. Using persistence service and DefaultScheduler service. We can't implement windows service model, as current requirement mandates passing the SOAPRequest parameters as arguments. ManualSchedulerService is not in contention due to synchronous nature of it's actual behaviour. Still the performance is pretty bad and product team is not happy. Can anybody suggest me better solution? Thanks, Samir

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  • PHP voting system with sessions?

    - by pingu
    Hi guys, I've been reading up on stackoverflow about creating voting systems in PHP that minimize abuse/multiple voting from the same user, but I haven't come across the answer to my question. I've got an application where users don't need to register to vote or "like" an entry. Obviously, I want to minimize abuse and I don't want to limit votes per IP address because some organisations (mine included) use shared IP addresses. I've never used sessions in a non-authenticated system before, but since this application is centered around entry votes I was wondering if this approach would work and whether there were any disadvantages such as performance implications, and whether it's even possible to use sessions in this way: start a session when the website is loaded allow one vote per item per session If this is a bad idea, my alternative options would be to allow a reasonable number of votes per IP address (say 25), or put a time limit between votes from the same IP address. What do you guys recommend?

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  • reasons to not use typekit?

    - by Haroldo
    I'm launching a new site soon and would like to use one nice font (for headings etc). I've experimented with scripts like cufon and find them very disappointing. The way I see it I have to legal options: create my own font stacks using fonts that are licensed for @font-face (like fontsquirrel) subscribe to typekit use standard font stacks including some of MS Office's nicer fonts (not keen on!) I'm looking for comments from someone with experience here, not speculation please (i can do that myself!). Has anyone used typekit? Have you noticed any performance issues?

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  • OpenCL: does it play well with OpenMP, can I connect other languages to it, etc.

    - by Cem Karan
    The 1.0 spec for OpenCL just came out a few days ago (Spec is here) and I've just started to read through it. I want to know if it plays well with other high performance multiprocessing APIs like OpenMP (spec) and I want to know what I should learn. So, here are my basic questions: If I am already using OpenMP, will that break OpenCL or vice-versa? Is OpenCL more powerful than OpenMP? Or are they intended to be complementary? Is there a standard way of connecting an OpenCL program to a standard C99 program (or any other language)? What is it? Does anyone know if anyone is writing an OpenCL book? I'm reading the spec, but I've found books to be more helpful.

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  • Spinlocks, How Much Useful Are They?

    - by unknown
    How often do you find yourself actually using spinlocks in your code? How common is it to come across a situation where using a busy loop actually outperforms the usage of locks? Personally, when I write some sort of code that requires thread safety, I tend to benchmark it with different synchronization primitives, and as far as it goes, it seems like using locks gives better performance than using spinlocks. No matter for how little time I actually hold the lock, the amount of contention I receive when using spinlocks is far greater than the amount I get from using locks (of course, I run my tests on a multiprocessor machine). I realize that it's more likely to come across a spinlock in "low-level" code, but I'm interested to know whether you find it useful in even a more high-level kind of programming?

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  • How to recognize touch events and control a script object inside UIWebView?

    - by Markus S.
    Situation: I have an UIView with an UIWebView in it. When the viewDidLoad the Javascript Object inside the UIWebView is called (Microsoft Seadragon AJAX JS). For your Understanding: Seadragon loads a specified megapixel image(JPEG) and in a Desktop Browser like Firefox i can Zoom into the image and I can drag the crop for example from the middle to the left. In the iPhone Simulator (for iPad) only the Zooming Function is working on one single tap but when i try to drag the crop (with left mouse button click and holding it) I'm dragging the whole UIWebView but not the crop of course! Is that feature which the simulator isn't able to handle or what's yout solutin guys? Special Thanks!! P.S.: It's a bit jiggling when the zooming function of Seadragon is called. Is that authentic to the real performance of the iPad or does the simulator not have the power as the iPad has?

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  • Perfmon on Vista to monitor .Net CLR memory for dutch dummies

    - by Dabblernl
    OK... My managed .Net program is eating memory leading it to crash after a few hours with a OutOfMemoryException. I want to investigate this starting with using perfmon.exe. I found a description on how to do this here However, I have a dutch Vista and the terms used differ widely from the ones used in this blog and I find myself simply unable to set it up. Can someone point me the way by stating "first from the top,second from the left" how to set up a performance monitor for my .Net program?

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  • Polling duplex does not scale... what's the alternative?

    - by user80855
    Our tests showed that the polling duplex binding simply does not scale and can not be used on a service within a web-farm or even a web garden. We have looked at TCP/IP sockets for a client push method, but the firewall issue is does allow us to use sockets. I was wondering what is the alternative "free" solution to this problem? allowing us to scale and allowing us to push data to client... I have also tried the solution in this article http://tomasz.janczuk.org/2009/09/scale-out-of-silverlight-http-polling.html but at the end, there was too much polling on a database, and performance was affected. Our Silverlight application need a pub/sub design, but it needs to be reliable and scalable... any ideas?

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  • Django - categories & sub-categories

    - by Bluey
    Some advice needed on how I can structure my models for my site. I have seen this post from Django project but still a little lost. Also come across Django-MPTT - but that's no help and possibly overkill. I'm looking to have categories & subcategories that are shown in the URLs like this: mysite.com/Level1/Maths/Calculations/Addition/ mysite.com/Level3/English/ mysite.com/Level2/English/Storytelling/ In my admin interface I'm looking to have drop downs for each level of category or subcategory. Also at each level I will be querying items (another model) like get all items that have the category 'Level1' AND 'Maths'. There could also be a situation where I have five or more subcategories. How is it best to create my models for best performance? It it worth using tagging instead?

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  • Laws of Computer Science and Programming

    - by Jonas
    We have Amdahl's law that basically states that if your program is 10% sequential you can get a maximum 10x performance boost by parallelizing your application. Another one is Wadler's law which states that In any language design, the total time spent discussing a feature in this list is proportional to two raised to the power of its position. 0. Semantics 1. Syntax 2. Lexical syntax 3. Lexical syntax of comments My question is this: What are the most important (or at least significant / funny but true / sad but true) laws of Computer Science and programming? I want named laws, and not random theorems, So an answer should look something like Surname's (law|theorem|conjecture|corollary...) Please state the law in your answer, and not only a link. Edit: The name of the law does not need to contain it's inventors surname. But I do want to know who stated (and perhaps proved) the law

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  • Filtering in E4X

    - by FB55
    This is just a simple question. I'm currently using Mozilla's Rhino to develop a little webapp. As one step, I need to get a webpage and filter all of it's nodes. For doing that, I use E4X. I thought I could do this like that: var pnodes = doc..*(p); But that produces an error. How is it done right? (BTW: this is just a step for increasing performance. The code already does well, it's just a bit slow.)

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  • Troubleshooting latency spikes on ESXi NFS datastores

    - by exo_cw
    I'm experiencing fsync latencies of around five seconds on NFS datastores in ESXi, triggered by certain VMs. I suspect this might be caused by VMs using NCQ/TCQ, as this does not happen with virtual IDE drives. This can be reproduced using fsync-tester (by Ted Ts'o) and ioping. For example using a Grml live system with a 8GB disk: Linux 2.6.33-grml64: root@dynip211 /mnt/sda # ./fsync-tester fsync time: 5.0391 fsync time: 5.0438 fsync time: 5.0300 fsync time: 0.0231 fsync time: 0.0243 fsync time: 5.0382 fsync time: 5.0400 [... goes on like this ...] That is 5 seconds, not milliseconds. This is even creating IO-latencies on a different VM running on the same host and datastore: root@grml /mnt/sda/ioping-0.5 # ./ioping -i 0.3 -p 20 . 4096 bytes from . (reiserfs /dev/sda): request=1 time=7.2 ms 4096 bytes from . (reiserfs /dev/sda): request=2 time=0.9 ms 4096 bytes from . (reiserfs /dev/sda): request=3 time=0.9 ms 4096 bytes from . (reiserfs /dev/sda): request=4 time=0.9 ms 4096 bytes from . (reiserfs /dev/sda): request=5 time=4809.0 ms 4096 bytes from . (reiserfs /dev/sda): request=6 time=1.0 ms 4096 bytes from . (reiserfs /dev/sda): request=7 time=1.2 ms 4096 bytes from . (reiserfs /dev/sda): request=8 time=1.1 ms 4096 bytes from . (reiserfs /dev/sda): request=9 time=1.3 ms 4096 bytes from . (reiserfs /dev/sda): request=10 time=1.2 ms 4096 bytes from . (reiserfs /dev/sda): request=11 time=1.0 ms 4096 bytes from . (reiserfs /dev/sda): request=12 time=4950.0 ms When I move the first VM to local storage it looks perfectly normal: root@dynip211 /mnt/sda # ./fsync-tester fsync time: 0.0191 fsync time: 0.0201 fsync time: 0.0203 fsync time: 0.0206 fsync time: 0.0192 fsync time: 0.0231 fsync time: 0.0201 [... tried that for one hour: no spike ...] Things I've tried that made no difference: Tested several ESXi Builds: 381591, 348481, 260247 Tested on different hardware, different Intel and AMD boxes Tested with different NFS servers, all show the same behavior: OpenIndiana b147 (ZFS sync always or disabled: no difference) OpenIndiana b148 (ZFS sync always or disabled: no difference) Linux 2.6.32 (sync or async: no difference) It makes no difference if the NFS server is on the same machine (as a virtual storage appliance) or on a different host Guest OS tested, showing problems: Windows 7 64 Bit (using CrystalDiskMark, latency spikes happen mostly during preparing phase) Linux 2.6.32 (fsync-tester + ioping) Linux 2.6.38 (fsync-tester + ioping) I could not reproduce this problem on Linux 2.6.18 VMs. Another workaround is to use virtual IDE disks (vs SCSI/SAS), but that is limiting performance and the number of drives per VM. Update 2011-06-30: The latency spikes seem to happen more often if the application writes in multiple small blocks before fsync. For example fsync-tester does this (strace output): pwrite(3, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 1048576, 0) = 1048576 fsync(3) = 0 ioping does this while preparing the file: [lots of pwrites] pwrite(3, "********************************"..., 4096, 1036288) = 4096 pwrite(3, "********************************"..., 4096, 1040384) = 4096 pwrite(3, "********************************"..., 4096, 1044480) = 4096 fsync(3) = 0 The setup phase of ioping almost always hangs, while fsync-tester sometimes works fine. Is someone capable of updating fsync-tester to write multiple small blocks? My C skills suck ;) Update 2011-07-02: This problem does not occur with iSCSI. I tried this with the OpenIndiana COMSTAR iSCSI server. But iSCSI does not give you easy access to the VMDK files so you can move them between hosts with snapshots and rsync. Update 2011-07-06: This is part of a wireshark capture, captured by a third VM on the same vSwitch. This all happens on the same host, no physical network involved. I've started ioping around time 20. There were no packets sent until the five second delay was over: No. Time Source Destination Protocol Info 1082 16.164096 192.168.250.10 192.168.250.20 NFS V3 WRITE Call (Reply In 1085), FH:0x3eb56466 Offset:0 Len:84 FILE_SYNC 1083 16.164112 192.168.250.10 192.168.250.20 NFS V3 WRITE Call (Reply In 1086), FH:0x3eb56f66 Offset:0 Len:84 FILE_SYNC 1084 16.166060 192.168.250.20 192.168.250.10 TCP nfs > iclcnet-locate [ACK] Seq=445 Ack=1057 Win=32806 Len=0 TSV=432016 TSER=769110 1085 16.167678 192.168.250.20 192.168.250.10 NFS V3 WRITE Reply (Call In 1082) Len:84 FILE_SYNC 1086 16.168280 192.168.250.20 192.168.250.10 NFS V3 WRITE Reply (Call In 1083) Len:84 FILE_SYNC 1087 16.168417 192.168.250.10 192.168.250.20 TCP iclcnet-locate > nfs [ACK] Seq=1057 Ack=773 Win=4163 Len=0 TSV=769110 TSER=432016 1088 23.163028 192.168.250.10 192.168.250.20 NFS V3 GETATTR Call (Reply In 1089), FH:0x0bb04963 1089 23.164541 192.168.250.20 192.168.250.10 NFS V3 GETATTR Reply (Call In 1088) Directory mode:0777 uid:0 gid:0 1090 23.274252 192.168.250.10 192.168.250.20 TCP iclcnet-locate > nfs [ACK] Seq=1185 Ack=889 Win=4163 Len=0 TSV=769821 TSER=432716 1091 24.924188 192.168.250.10 192.168.250.20 RPC Continuation 1092 24.924210 192.168.250.10 192.168.250.20 RPC Continuation 1093 24.924216 192.168.250.10 192.168.250.20 RPC Continuation 1094 24.924225 192.168.250.10 192.168.250.20 RPC Continuation 1095 24.924555 192.168.250.20 192.168.250.10 TCP nfs > iclcnet_svinfo [ACK] Seq=6893 Ack=1118613 Win=32625 Len=0 TSV=432892 TSER=769986 1096 24.924626 192.168.250.10 192.168.250.20 RPC Continuation 1097 24.924635 192.168.250.10 192.168.250.20 RPC Continuation 1098 24.924643 192.168.250.10 192.168.250.20 RPC Continuation 1099 24.924649 192.168.250.10 192.168.250.20 RPC Continuation 1100 24.924653 192.168.250.10 192.168.250.20 RPC Continuation 2nd Update 2011-07-06: There seems to be some influence from TCP window sizes. I was not able to reproduce this problem using FreeNAS (based on FreeBSD) as a NFS server. The wireshark captures showed TCP window updates to 29127 bytes in regular intervals. I did not see them with OpenIndiana, which uses larger window sizes by default. I can no longer reproduce this problem if I set the following options in OpenIndiana and restart the NFS server: ndd -set /dev/tcp tcp_recv_hiwat 8192 # default is 128000 ndd -set /dev/tcp tcp_max_buf 1048575 # default is 1048576 But this kills performance: Writing from /dev/zero to a file with dd_rescue goes from 170MB/s to 80MB/s. Update 2011-07-07: I've uploaded this tcpdump capture (can be analyzed with wireshark). In this case 192.168.250.2 is the NFS server (OpenIndiana b148) and 192.168.250.10 is the ESXi host. Things I've tested during this capture: Started "ioping -w 5 -i 0.2 ." at time 30, 5 second hang in setup, completed at time 40. Started "ioping -w 5 -i 0.2 ." at time 60, 5 second hang in setup, completed at time 70. Started "fsync-tester" at time 90, with the following output, stopped at time 120: fsync time: 0.0248 fsync time: 5.0197 fsync time: 5.0287 fsync time: 5.0242 fsync time: 5.0225 fsync time: 0.0209 2nd Update 2011-07-07: Tested another NFS server VM, this time NexentaStor 3.0.5 community edition: Shows the same problems. Update 2011-07-31: I can also reproduce this problem on the new ESXi build 4.1.0.433742.

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  • iPhone - Is it ok to override UITableViewCell setSelected:animated

    - by Brian
    I am drawing custom UITableViewCells. My cells are opaque and are completely drawn in the drawRect of the cell to help with performance. I want to handle the look of a selected cell myself. If I don't, then the contents of my cell is covered up by the selectedBackgroundView that is added. Is it common or acceptable to override the setSelected:animated method of my cell so this is done properly. I guess if I did that, then I would not call the super's setSelected method since I would be handling how the cell will show that its selected. I would also have to set the selected property of the cell. Any help would be great. Thanks.

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