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  • Netty options for real-time distribution of small messages to a large number of clients?

    - by user439407
    I am designing a (near) real-time Netty server to distribute a large number of very small messages to a large number of clients across the internet. In internal, go as fast as you can testing, I found that I could do 10k clients no sweat, but now that we are trying to go across the internet, where the latency, bandwidth etc varies pretty wildly we are running into the dreaded outOfMemory issues, even with 2 gigs of RAM. I have tried various workarounds(setting the socket stack sizes smaller, setting high and low water marks, cancelling things that are too old), and they help a little, but they seem to only help a little bit. What would some good ways to optimize Netty for sending large #s of small messages without significant delays? Also, the bulk of the message only consists of one kind of message that I don't particularly care if it doesn't arrive. I would use UDP but because we don't control the client, thats not really a possibility. Is it possible to set a separate timeout solely for this kind of message without affecting the other messages? Any insight you could offer would be greatly appreciated.

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  • Can the Singleton be replaced by Factory?

    - by lostiniceland
    Hello Everyone There are already quite some posts about the Singleton-Pattern around, but I would like to start another one on this topic since I would like to know if the Factory-Pattern would be the right approach to remove this "anti-pattern". In the past I used the singleton quite a lot, also did my fellow collegues since it is so easy to use. For example, the Eclipse IDE or better its workbench-model makes heavy usage of singletons as well. It was due to some posts about E4 (the next big Eclipse version) that made me start to rethink the singleton. The bottom line was that due to this singletons the dependecies in Eclipse 3.x are tightly coupled. Lets assume I want to get rid of all singletons completely and instead use factories. My thoughts were as follows: hide complexity less coupling I have control over how many instances are created (just store the reference I a private field of the factory) mock the factory for testing (with Dependency Injection) when it is behind an interface In some cases the factories can make more than one singleton obsolete (depending on business logic/component composition) Does this make sense? If not, please give good reasons for why you think so. An alternative solution is also appreciated. Thanks Marc

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  • JAVASCRIPT ENABLED [closed]

    - by kirchoffs415
    HI, I hope somebody can help, i keep getting the following message when i log on-- Your Javascript is disabled. Limited functionality is available. it will stay for maybe a day sometimes two.I have uninstalled javascript and reinstalled but still the same. Iam using chrome. any help would be gratefull many thanks Dominic p.s. my system spec is as follows System InformationOS Name Microsoft® Windows Vista™ Home Premium Version 6.0.6002 Service Pack 2 Build 6002 Other OS Description Not Available OS Manufacturer Microsoft Corporation System Name DOM-PC System Manufacturer Dell Inc. System Model Inspiron 1545 System Type X86-based PC Processor Pentium(R) Dual-Core CPU T4200 @ 2.00GHz, 2000 Mhz, 2 Core(s), 2 Logical Processor(s) BIOS Version/Date Dell Inc. A05, 25/02/2009 SMBIOS Version 2.4 Windows Directory C:\Windows System Directory C:\Windows\system32 Boot Device \Device\HarddiskVolume3 Locale United Kingdom Hardware Abstraction Layer Version = "6.0.6002.18005" User Name DOM-PC\DOM Time Zone GMT Standard Time Installed Physical Memory (RAM) 3.00 GB Total Physical Memory 2.96 GB Available Physical Memory 1.38 GB Total Virtual Memory 5.89 GB Available Virtual Memory 4.25 GB Page File Space 3.00 GB Page File C:\pagefile.sys My System Specs

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  • using EventToCommand & PassEventArgsToCommand :: how to get sender, or better metaphor?

    - by JoeBrockhaus
    The point of what I'm doing is that there are a lot of things that need to happen in the viewmodel, but when the view has been loaded, not on constructor. I could wire up event handlers and send messages, but that just seems kinda sloppy to me. I'm implementing a base view and base viewmodel where this logic is contained so all my views get it by default, hopefully. Perhaps I can't even get what I'm wanting: the sender. I just figured this is what RoutedEventArgs.OriginalSource was supposed to be? [Edit] In the meantime, I've hooked up an EventHandler in the xaml.cs, and sure enough, OriginalSource is null there as well. So I guess really I need to know if it's possible to get a reference to the view/sender in the Command as well? [/Edit] My implementation requires that a helper class to my viewmodels which is responsible for creating 'windows' knows of the 'host' control that all the windows get added to. i'm open to suggestions for accomplishing this outside the scope of using eventtocommand. :) (the code for Unloaded is the same) #region ViewLoadedCommand private RelayCommand<RoutedEventArgs> _viewLoadedCommand = null; /// <summary> /// Command to handle the control's Loaded event. /// </summary> public RelayCommand<RoutedEventArgs> ViewLoadedCommand { get { // lazy-instantiate the RelayCommand on first usage if (_viewLoadedCommand == null) { _viewLoadedCommand = new RelayCommand<RoutedEventArgs>( e => this.OnViewLoadedCommand(e)); } return _viewLoadedCommand; } } #endregion ViewLoadedCommand #region View EventHandlers protected virtual void OnViewLoadedCommand(RoutedEventArgs e) { EventHandler handler = ViewLoaded; if (handler != null) { handler(this, e); } } #endregion

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  • Can it be done in a more elegant way with the Swing Timer?

    - by Roman
    Bellow is the code for the simplest GUI countdown. Can the same be done in a shorter and more elegant way with the usage of the Swing timer? import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities; public class CountdownNew { static JLabel label; // Method which defines the appearance of the window. public static void showGUI() { JFrame frame = new JFrame("Simple Countdown"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); label = new JLabel("Some Text"); frame.add(label); frame.pack(); frame.setVisible(true); } // Define a new thread in which the countdown is counting down. public static Thread counter = new Thread() { public void run() { for (int i=10; i>0; i=i-1) { updateGUI(i,label); try {Thread.sleep(1000);} catch(InterruptedException e) {}; } } }; // A method which updates GUI (sets a new value of JLabel). private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater( new Runnable() { public void run() { label.setText("You have " + i + " seconds."); } } ); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { showGUI(); counter.start(); } }); } }

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  • Database for Python Twisted

    - by Will
    There's an API for Twisted apps to talk to a database in a scalable way: twisted.enterprise.dbapi The confusing thing is, which database to pick? The database will have a Twisted app that is mostly making inserts and updates and relatively few selects, and then other strictly-read-only clients that are accessing the database directly making selects. (The read-only users are not necessarily selecting the data that the Twisted app is inserting; its not as though the database is being used as a message-queue) My understanding - which I'd like corrected/adviced - is that: Postgres is a great DB, but all the Python bindings - and there is a confusing maze of them - are abandonware There is psycopg2, but that makes a lot of noise about doing its own connection-pooling and things; does this co-exist gracefully/usefully/transparently with the Twisted async database connection pooling and such? SQLLite is a great database for little things but if used in a multi-user way it does whole-database locking, so performance would suck in the usage pattern I envisage MySQL - after the Oracle takeover, who'd want to adopt it now or adopt a fork? Is there anything else out there?

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  • Making GUI applications on Linux/Windows. What languages/tools to use?

    - by Javed Ahamed
    My student group and I are trying to continue working on a project we worked on this semester over the summer to become a professional, deployable app. We originally did it in Adobe AIR but it seems now that the computers this program will be running on will be very slow, maybe 600mhz and 128-256mb ram so flash just isn't going to cut it. It is basically a health diagnosis application that we will be shipping out to impoverished countries. Now comes the real question. We are wondering what language to rebuild our application in. It has to have a good gui builder associated with it, like adobe flex/air gui builder or visual studio's gui builder but the application should run on linux primarily, and if it can run on windows thats just a plus. We are all students too without really any outside help so whatever we decide to do this in there must be ample documentation available when we hit problems. Some things we have considered so far are using python and glade or c# and monodevelop, but again we really are not experts on any of this which is why I am asking for help as I would rather spend the time now choosing the right tools instead of wasting time down the line when we hit a roadblock. Thanks in advance!

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  • Mysql Database Question about Large Columns

    - by murat
    Hi, I have a table that has 100.000 rows, and soon it will be doubled. The size of the database is currently 5 gb and most of them goes to one particular column, which is a text column for PDF files. We expect to have 20-30 GB or maybe 50 gb database after couple of month and this system will be used frequently. I have couple of questions regarding with this setup 1-) We are using innodb on every table, including users table etc. Is it better to use myisam on this table, where we store text version of the PDF files? (from memory usage /performance perspective) 2-) We use Sphinx for searching, however the data must be retrieved for highlighting. Highlighting is done via sphinx API but still we need to retrieve 10 rows in order to send it to Sphinx again. This 10 rows may allocate 50 mb memory, which is quite large. So I am planning to split these PDF files into chunks of 5 pages in the database, so these 100.000 rows will be around 3-4 million rows and couple of month later, instead of having 300.000-350.000 rows, we'll have 10 million rows to store text version of these PDF files. However, we will retrieve less pages, so again instead of retrieving 400 pages to send Sphinx for highlighting, we can retrieve 5 pages and it will have a big impact on the performance. Currently, when we search a term and retrieve PDF files that have more than 100 pages, the execution time is 0.3-0.35 seconds, however if we retrieve PDF files that have less than 5 pages, the execution time reduces to 0.06 seconds, and it also uses less memory. Do you think, this is a good trade-off? We will have million of rows instead of having 100k-200k rows but it will save memory and improve the performance. Is it a good approach to solve this problem and do you have any ideas how to overcome this problem? The text version of the data is used only for indexing and highlighting. So, we are very flexible. Thanks,

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  • question about MySQL database migration

    - by WilliamLou
    Hi there: If I have a MySQL database with several tables on a live server, now I would like to migrate this database to another server. Of course, the migration I mean here involves some database tables, for example: add some new columns to several tables, add some new tables etc.. Now, the only method I can think of is to use some php/python(two scripts I know) script, connect two databases, dump the data from the old database, and then write into the new database. However, this method is not efficient at all. For example: in old database, table A has 28 columns; in new database, table A has 29 columns, but the extra column will have default value 0 for all the old rows. My script still needs to dump the data row by row and insert each row into the new database. Is there any tools or a better method than writing a script yourself? Here, I dont need to worry about multithread writing problems etc.., I mean the old database will be down (not open to public usage etc.., only for upgrade ) for a while. Thanks!!

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  • Sending an email with browser capabilities and screen size etc.

    - by talkingnews
    A lot of my visitors are blind (with it being a site for the blind), and often when trying to diagnose problems, I'd like to know what version of browser etc they're using, whether flash is installed. Because more often than not, someone will swear they are using X, when in fact Y is installed. Currently, I'm using http://jsbrwsniff.sourceforge.net/usage.html piped into an email, but I've got 2 problems here: First of all, jsbrwsniff is quite "heavy" and hasn't been updated since early 2007, so there's a lot of -1's in the result. Secondly, if I call it as follows, the page reloads: <a href="#" onclick="sendEmail()">Email feedback</a> And if I call it like this, the page goes blank and looks like it's trying to infinitely load a blank page: <a href="javascript:sendEmail()">Email feedback</a> See the nightmare for yourself here: http://kingston.talking-newspapers.co.uk/ Now, I know there are 1001 articles and comments here and elsewhere saying "don't use browser sniffers, they can be spoofed (etc)", but honestly, you'll have to trust me that this is a significantly useful tool when you're talking someone in their more "senior years" and using a screenreader through "help about", when they've clicked the wrong window to start with! I'm using jquery anyway in the site, and I'm aware of $jQuery.browser and $jQuery.support, but these don't tell me the elements I need (like whether Flash is installed, and what version etc). I've looked everywhere for a jquery plugin for my needs, with no luck. Finally, if I have to stick to the current method of jsbrwsniff then it's not the end of the world, but if anyone knows a way of launching the user's email client populated with the information I need but WITHOUT refreshing or blanking the page, I'd love to know. BTW - there's a good reason for not using a webform, which is simply because it's easier for the screen-reader user to use an email client they are used to. Thanks!

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  • Using SVN post-commit hook to update only files that have been commited

    - by fondie
    I am using an SVN repository for my web development work. I have a development site set up which holds a checkout of the repository. I have set up an SVN post-commit hook so that whenever a commit is made to the repository the development site is updated: cd /home/www/dev_ssl /usr/bin/svn up This works fine but due to the size of the repository the updates take a long time (approx. 3 minutes) which is rather frustrating when making regular commits. What I'd like is to change the post-commit hook to only update those files/directories that have been committed but I don't know how to go about doing this. Updating the "lowest common directory" would probably be the best solution, e.g. If committing the follow files: /branches/feature_x/images/logo.jpg /branches/feature_x/css/screen.css It would update the directory: /branches/feature_x/ Can anyone help me create a solution that achieves this please? Thanks! Update: The repository and development site are located on the same server so network issues shouldn't be involved. CPU usage is very low, and I/O should be ok (it's running on hi-spec dedicated server) The development site is approx. 7.5GB in size and contains approx. 600,000 items, this is mainly due to having multiple branches/tags

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  • Should a setter return immediately if assigned the same value?

    - by Andrei Rinea
    In classes that implement INotifyPropertyChanged I often see this pattern : public string FirstName { get { return _customer.FirstName; } set { if (value == _customer.FirstName) return; _customer.FirstName = value; base.OnPropertyChanged("FirstName"); } } Precisely the lines if (value == _customer.FirstName) return; are bothering me. I've often did this but I am not that sure it's needed nor good. After all if a caller assigns the very same value I don't want to reassign the field and, especially, notify my subscribers that the property has changed when, semantically it didn't. Except saving some CPU/RAM/etc by freeing the UI from updating something that will probably look the same on the screen/whatever_medium what do we obtain? Could some people force a refresh by reassigning the same value on a property (NOT THAT THIS WOULD BE A GOOD PRACTICE HOWEVER)? 1. Should we do it or shouldn't we? 2. Why?

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  • Dataflow Pipeline holding on to memory

    - by Jesse Carter
    I've created a Dataflow pipeline consisting of 4 blocks (which includes one optional block) which is responsible for receiving a query object from my application across HTTP and retrieving information from a database, doing an optional transform on that data, and then writing the information back in the HTTP response. In some testing I've done I've been pulling down a significant amount of data from the database (570 thousand rows) which are stored in a List object and passed between the different blocks and it seems like even after the final block has been completed the memory isn't being released. Ram usage in Task Manager will spike up to over 2 GB and I can observe several large spikes as the List hits each block. The signatures for my blocks look like this: private TransformBlock<HttpListenerContext, Tuple<HttpListenerContext, QueryObject>> m_ParseHttpRequest; private TransformBlock<Tuple<HttpListenerContext, QueryObject>, Tuple<HttpListenerContext, QueryObject, List<string>>> m_RetrieveDatabaseResults; private TransformBlock<Tuple<HttpListenerContext, QueryObject, List<string>>, Tuple<HttpListenerContext, QueryObject, List<string>>> m_ConvertResults; private ActionBlock<Tuple<HttpListenerContext, QueryObject, List<string>>> m_ReturnHttpResponse; They are linked as follows: m_ParseHttpRequest.LinkTo(m_RetrieveDatabaseResults); m_RetrieveDatabaseResults.LinkTo(m_ConvertResults, tuple => tuple.Item2 is QueryObjectA); m_RetrieveDatabaseResults.LinkTo(m_ReturnHttpResponse, tuple => tuple.Item2 is QueryObjectB); m_ConvertResults.LinkTo(m_ReturnHttpResponse); Is it possible that I can set up the pipeline such that once each block is done with the list they no longer need to hold on to it as well as once the entire pipeline is completed that the memory is released?

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  • Native functions throw UnsatisfiedLinkError in custom view, despite working in main activity

    - by Mark Ingram
    For some reason I can only call native functions from my main activity and not any custom views that I've created. Here is an example file (I followed a tutorial, but renamed the classes http://mindtherobot.com/blog/452/android-beginners-ndk-setup-step-by-step/) See the usage of the native function "getNewString". package com.example.native; import android.app.Activity; import android.app.AlertDialog; import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.os.Bundle; import android.view.View; public class NativeTestActivity extends Activity { static { System.loadLibrary("nativeTest"); } private native String getNewString(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.setContentView(new BitmapView(this)); String hello = getNewString(); // This line works fine new AlertDialog.Builder(this).setMessage(hello).show(); } } class BitmapView extends View { static { System.loadLibrary("nativeTest"); } private native String getNewString(); public BitmapView(Context context) { super(context); String hello = getNewString(); // This line throws the UnsatisfiedLinkError new AlertDialog.Builder(this.getContext()).setMessage(hello).show(); } } How can I call native functions in my custom views? I've built the application as an Android 2.2 app. I'm running the application on my HTC Desire. I have the latest SDK (9) and latest NDK (r5).

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  • drop down and post data to data base

    - by DAFFODIL
    This is a form which retrieves data from db and displays them in table. At the beginning of each row there will be a check box. If there are 10 rows fetched, I ii check 5 rows and insert them in to diff db but here when, I click drop down box data is getting in to db automatically,bcoz I use onchange event. Any alternative to prevent this to happen. Data should be inserted only when, I click submit button. Any help will be appreciated <?php $con = mysql_connect("localhost","root",""); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("form1", $con); error_reporting(E_ALL ^ E_NOTICE); $nam=$_REQUEST['select1']; $row=mysql_query("select * from inv where name='$nam'"); while($row1=mysql_fetch_array($row)) { $Name=$row1['Name']; $Address =$row1['Address']; $City=$row1['City']; $Pincode=$row1['Pincode']; $No=$row1['No']; $Date=$row1['Date']; $DCNo=$row1['DCNo']; $DcDate=$row1['DcDate']; $YourOrderNo=$row1['YourOrderNo']; $OrderDate=$row1['OrderDate']; $VendorCode=$row1['VendorCode']; $SNo=$row1['SNo']; $descofgoods=$row1['descofgoods']; $Qty=$row1['Qty']; $Rate=$row1['Rate']; $Amount=$row1['Amount']; } ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Untitled Document</title> <script type="text/javascript"> function ram(id) { var q=document.getElementById('qty_'+id).value; var r=document.getElementById('rate_'+id).value; document.getElementById('amt_'+id).value=q*r; } </script> </head> <body> <form id="form1" name="form1" method="post" action=""> <table width="1315" border="0"> <script type="text/javascript"> function g() { form1.submit(); } </script> <tr> <th>Name</th> <th align="left"><select name="select1" onchange="g();"> <option value="" selected="selected">select</option> <?php $row=mysql_query("select Name from inv "); while($row1=mysql_fetch_array($row)) { ?> <option value="<?php echo $row1['Name'];?>"><?php echo $row1['Name'];?></option> <?php } ?> </select></th> </tr> <tr> <th>Address</th> <th align="left"><textarea name="Address"><?php echo $Address;?></textarea></th> </tr> <tr> <th>City</th> <th align="left"><input type="text" name="City" value='<?php echo $City;?>' /></th> </tr> <tr> <th>Pincode</th> <th align="left"><input type="text" name="Pincode" value='<?php echo $Pincode;?>'></th> </tr> <tr> <th>No</th> <th align="left"><input type="text" name="No2" value='<?php echo $No;?>' readonly="" /></th> </tr> <tr> <th>Date</th> <th align="left"><input type="text" name="Date" value='<?php echo $Date;?>' /></th> </tr> <tr> <th>DCNo</th> <th align="left"><input type="text" name="DCNo" value='<?php echo $DCNo;?>' readonly="" /></th> </tr> <tr> <th>DcDate:</th> <th align="left"><input type="text" name="DcDate" value='<?php echo $DcDate;?>' /></th> </tr> <tr> <th>YourOrderNo</th> <th align="left"><input type="text" name="YourOrderNo" value='<?php echo $YourOrderNo;?>' readonly="" /></th> </tr> <tr> <th>OrderDate</th> <th align="left"><input type="text" name="OrderDate" value='<?php echo $OrderDate;?>' /></th> </tr> <tr> <th width="80">VendorCode</th> <th width="1225" align="left"><input type="text" name="VendorCode" value='<?php echo $VendorCode;?>' readonly="" /></th> </tr> </table> <table width="1313" border="0"> <tr> <td width="44">&nbsp;</td> <td width="71">SNO</td> <td width="527">DESCRIPTION</td> <td width="214">QUANTITY</td> <td width="214">RATE/UNIT</td> <td width="217">AMOUNT</td> </tr> <?php $i=1; $row=mysql_query("select * from inv where Name='$nam'"); while($row1=mysql_fetch_array($row)) { $SNo=$row1['SNo']; $descofgoods=$row1['descofgoods']; $Qty=$row1['Qty']; $Rate=$row1['Rate']; $Amount=$row1['Amount']; ?> <tr> <td><input type="checkbox" name="checkbox" value="checkbox" checked="checked"/></td> <td><input type="text" name="No[<?php echo $i?>]" value='<?php echo $SNo;?>' readonly=""/></td> <td><input type="text" name="descofgoods[<?php echo $i?>]" value='<?php echo $descofgoods;?>' /></td> <td><input type="text" name="qty[<?php echo $i?>]" maxlength="50000000" id="qty_<?PHP echo($i) ?>"/></td> <td><input type="text" name="Rate[<?php echo $i?>]" value='<?php echo $Rate;?>' id="rate_<?PHP echo($i) ?>" onclick="ram('<?PHP echo($i) ?>')";></td> <td><input type="text" name="Amount[<?php echo $i?>]" id="amt_<?PHP echo($i) ?>"/></td> </tr> <?php $i++;} ?> <tr> <td><input type="submit" value="submit" header("location:values to be brought for print page.php");/></td> </tr> </table> <label></label> </form> </body> </html> <?php /*error_reporting(E_ALL ^ E_NOTICE); $con = mysql_connect("localhost","root",""); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("form1", $con); /*if(checked=checkbox) { mysql_query="INSERT INTO invo (Name, Address, City, Pincode, No, Date, DCNo, DcDate, YourOrderNo, OrderDate, VendorCode, SNo, descofgoods, Qty, Rate, Amount) VALUES ('$_POST[Name]','$_POST[Address]','$_POST[City]','$_POST[Pincode]','$_POST[No]','$_POST[Date]','$_POST[DCNo]','$_POST[DcDate]','$_POST[YourOrderNo]','$_POST[OrderDate]','$_POST[VendorCode]','$_POST[SNo]','$_POST[descofgoods]','$_POST[qty]','$_POST[Rate]','$_POST[Amount]')"; } else { header("location:values to be brought for print page.php"); }*/ header("ins.php"); ?>

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  • Java Random Slowdowns on Mac OS cont'd

    - by javajustice
    I asked this question a few weeks ago, but I'm still having the problem and I have some new hints. The original question is here: http://stackoverflow.com/questions/1651887/java-random-slowdowns-on-mac-os Basically, I have a java application that splits a job into independent pieces and runs them in separate threads. The threads have no synchronization or shared memory items. The only resources they do share are data files on the hard disk, with each thread having an open file channel. Most of the time it runs very fast, but occasionally it will run very slow for no apparent reason. If I attach a CPU profiler to it, then it will start running quickly again. If I take a CPU snapshot, it says its spending most of its time in "self time" in a function that doesn't do anything except check a few (unshared unsynchronized) booleans. I don't know how this could be accurate because 1, it makes no sense, and 2, attaching the profiler seems to knock the threads out of whatever mode they're in and fix the problem. Also, regardless of whether it runs fast or slow, it always finishes and gives the same output, and it never dips in total cpu usage (in this case ~1500%), implying that the threads aren't getting blocked. I have tried different garbage collectors, different sizings the parts of the memory space, writing data output to non-raid drives, and putting all data output in threads separate the main worker threads. Does anyone have any idea what kind of problem this could be? Could it be the operating system (OS X 10.6.2) ? I have not been able to duplicate it on a windows machine, but I don't have one with a similar hardware configuration.

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  • PostgreSQL, Foreign Keys, Insert speed & Django

    - by Miles
    A few days ago, I ran into an unexpected performance problem with a pretty standard Django setup. For an upcoming feature, we have to regenerate a table hourly, containing about 100k rows of data, 9M on the disk, 10M indexes according to pgAdmin. The problem is that inserting them by whatever method literally takes ages, up to 3 minutes of 100% disk busy time. That's not something you want on a production site. It doesn't matter if the inserts were in a transaction, issued via plain insert, multi-row insert, COPY FROM or even INSERT INTO t1 SELECT * FROM t2. After noticing this isn't Django's fault, I followed a trial and error route, and hey, the problem disappeared after dropping all foreign keys! Instead of 3 minutes, the INSERT INTO SELECT FROM took less than a second to execute, which isn't too surprising for a table <= 20M on the disk. What is weird is that PostgreSQL manages to slow down inserts by 180x just by using 3 foreign keys. Oh, disk activity was pure writing, as everything is cached in RAM; only writes go to the disks. It looks like PostgreSQL is working very hard to touch every row in the referred tables, as 3MB/sec * 180s is way more data than the 20MB this new table takes on disk. No WAL for the 180s case, I was testing in psql directly, in Django, add ~50% overhead for WAL logging. Tried @commit_on_success, same slowness, I had even implemented multi row insert and COPY FROM with psycopg2. That's another weird thing, how can 10M worth of inserts generate 10x 16M log segments? Table layout: id serial primary, a bunch of int32, 3 foreign keys to small table, 198 rows, 16k on disk large table, 1.2M rows, 59 data + 89 index MB on disk large table, 2.2M rows, 198 + 210MB So, am I doomed to either drop the foreign keys manually or use the table in a very un-Django way by defining saving bla_id x3 and skip using models.ForeignKey? I'd love to hear about some magical antidote / pg setting to fix this.

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  • Problem using Lazy<T> from within a generic abstract class

    - by James Black
    I have a generic class that all my DAO classes derive from, which is defined below. I also have a base class for all my entities, but that is not generic. The method GetIdOrSave is going to be a different type than how I defined SabaAbstractDAO, as I am trying to get the primary key to fulfill the foreign key relationships, so this function goes out to either get the primary key or save the entity and then get the primary key. The last code snippet has a solution on how it will work if I get rid of the generic part, so I think this can be solved by using variance, but I can't figure out how to write an interface that will compile. public abstract class SabaAbstractDAO<T> { ... public K GetIdOrSave<K>(K item, Lazy<SabaAbstractDAO<BaseModel>> lazyitemdao) where K : BaseModel { if (item != null && item.Id.IsNull()) { var itemdao = lazyitemdao.Value; item.Id = itemdao.retrieveID(item); if (item.Id.IsNull()) { return itemdao.SaveData(item); } } return item; } } I am getting this error, when I try to compile: Argument 2: cannot convert from 'System.Lazy<ORNL.HRD.LMS.Dao.SabaCourseDAO>' to 'System.Lazy<ORNL.HRD.LMS.Dao.SabaAbstractDAO<ORNL.HRD.LMS.Models.BaseModel>>' I am trying to call it this way: GetIdOrSave(input.OfferingTemplate, new Lazy<SabaCourseDAO>( () => { return new SabaCourseDAO() { Dao = Dao }; }) ); If I change the definition to this, it works. public K GetIdOrSave<K>(K item, Lazy<SabaCourseDAO> lazyitemdao) where K : BaseModel { So, how can I get this to compile using variance (if needed) and generics, so I can have a very general method that will only work with BaseModel and AbstractDAO<BaseModel>? I expect I should only need to make the change in the method and perhaps abstract class definition, the usage should be fine.

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  • Ultra-Portable Laptop or Tablet PC for Development and Sketching

    - by Nelson LaQuet
    I am a software developer that primarily writes in PHP, [X]HTML, CSS, Javascript, C# and C++. I use Eclipse for web development, Visual Studio 2008 for C++ and C# work, TortoiseSVN, Subversion server for local repositories, SQL Server Express, Apache and MYSQL. I also use Office 2007 for word processing and spreadsheets and use Vista Ultimate 64 as my primary operating system. The only other things I do on my laptop are watch movies, surf the internet and listen to music. I currently have a Acer Aspire 5100 (1.4 GHz AMD Turion X2, 2 GB of RAM and a 15.4" screen). This thing does not cut it in performance or portability, and in addition, my DVD drive failed. And before anybody posts about vista: I have had XP Professional 32 on it for the last two years, and recently upgraded to Vista 64. It is actually faster (with areo disabled) then XP; so it is not the OS that is causing the laptop to be slow. I usually sketch a lot, for explaining things, developing user interfaces and software architecture. Because of my requirements, I was thinking about a Lenovo X61 Tablet PC. It outperforms my current laptop, is significantly more portable, and... is a tablet. My question is: do any other software developers use this (or other tablets) for programming? Does it help to be able to sketch on the computer itself? And is it capable of being a good development machine? Will it handle the above software listed? If not, what is the best ultra-portable laptop that is good for programming? Or are ultra-portable laptops even good for programming? I could manage with my 15.4" screen, but am spoiled by my two 19" at my home desktop and my job's workstation.

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  • What would you write in a consitution (law book) for a programmers' country?

    - by Developer Art
    After we have got our great place to talk about professional matters and sozialize online - on SO, I believe the next logical step would be to found our own country! I invite you all to participate and bring together your available resources. We will buy an island, better even a group of island so that we could establish states like .NET territories, Java land, Linux republic etc. We will build a society of programmers (girls - we need you too). To the organizational side, we're going to need some constitution or a law book. I suggest we write it together. I make it a wiki as it should be a cooperative effort. I'll open the work. Section 1. Programmers' rights. Every citizen has a right to an Internet connection 24/7. Every citizen can freely choose the field of interest Section 2. Programmers' obligations. Every citizen must embrace the changing nature of the profession and constanly educate himself Section 3. Law enforcement. Code duplication when can be avoided is punished by limiting the bandwith speed to 64Kbit for a period of one week. Using ugly hacks instead of refactoring code is punished by cutting the Internet connection for a period of one month. Usage of technologies older than 5/10 years is punished by restricting the web access to the sites last updated 5/10 years ago for a period of one month. Please feel free to modify and extend the list. We'll need to have it ready before we proceed formally with the country foundation. A purchase fund will be established shortly. Everyone is invited to participate.

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  • Modify XML existing content in C#

    - by Nano HE
    Purpose: I plan to Create a XML file with XmlTextWriter and Modify/Update some Existing Content with XmlNode SelectSingleNode(), node.ChildNode[?].InnerText = someting, etc. After I created the XML file with XmlTextWriter as below. XmlTextWriter textWriter = new XmlTextWriter("D:\\learning\\cs\\myTest.xml", System.Text.Encoding.UTF8); I practiced the code below. But failed to save my XML file. XmlDocument doc = new XmlDocument(); doc.Load("D:\\learning\\cs\\myTest.xml"); XmlNode root = doc.DocumentElement; XmlNode myNode; myNode= root.SelectSingleNode("descendant::books"); .... textWriter.Close(); doc.Save("D:\\learning\\cs\\myTest.xml"); I found it is not good to produce like my way. Is there any suggestion about it? I am not clear about the concepts and usage of both XmlTextWriter and XmlNode in the same project. Thank you for reading and replies.

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  • Why does Perl's DBI complain about "failed: ERROR OCIEnvNlsCreate" when I try to connect to Oracle 1

    - by John
    I am getting the following error connecting to an Oracle 11g database using a simple Perl script: failed: ERROR OCIEnvNlsCreate. Check ORACLE_HOME (Linux) env var or PATH (Windows) and or NLS settings, permissions, etc. at The script is as follows: #!/usr/local/bin/perl use strict; use DBI; if ($#ARGV < 3) { print "Usage: perl testDbAccess.pl dataBaseUser dataBasePassword SID dataBasePort\n"; exit 0; } my ($user, $pwd, $sid, $port) = @ARGV; my $host = `hostname`; my $dbh; my $sth; my $dbname = "dbi:Oracle:HOST=$host;SID=$sid;PORT=$port"; openDbConnection(); closeDbConnection(); sub openDbConnection() { $dbh = DBI->connect ($dbname, $user ,$pwd , { RaiseError => 1}) || die "Database connection not made: $DBI::errstr"; } sub closeDbConnection() { #$sth->finish(); $dbh->disconnect(); } Anyone seen this problem before?

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  • Using a php://memory wrapper causes errors...

    - by HorusKol
    I'm trying to extend the PHP mailer class from Worx by adding a method which allows me to add attachments using string data rather than path to the file. I came up with something like this: public function addAttachmentString($string, $name='', $encoding = 'base64', $type = 'application/octet-stream') { $path = 'php://memory/' . md5(microtime()); $file = fopen($path, 'w'); fwrite($file, $string); fclose($file); $this->AddAttachment($path, $name, $encoding, $type); } However, all I get is a PHP warning: PHP Warning: fopen() [<a href='function.fopen'>function.fopen</a>]: Invalid php:// URL specified There aren't any decent examples with the original documentation, but I've found a couple around the internet (including one here on SO), and my usage appears correct according to them. Has anyone had any success with using this? My alternative is to create a temporary file and clean up - but that will mean having to write to disc, and this function will be used as part of a large batch process and I want to avoid slow disc operations (old server) where possible. This is only a short file but has different information for each person the script emails.

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  • Jquery - xml parsing

    - by lmkk
    I have the following xml: <?xml version="1.0" encoding="utf-8"?> <Area xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Scenes> <Scene Index="1" Name="Scene1" /> <Scene Index="2" Name="Scene2" /> </Scenes> </Area> Which i am trying to parse with jquery: <script> $(document).ready(function(){ $.ajax({ type: "GET", url: "list.xml", dataType: "xml", success: function(xml) { $(xml).find('scenes').each(function(){ $(this).find('scene').each(function(){ var name = $(this).attr('name'); $('<div class="items" ></div>').html('<p>'+name+'</p>').appendTo('#page-wrap'); }); }); } }); }); </script> Why is this not working? Help!! first attempt at javascript/jquery This is based on a example I found, but have so far been unable to adapt it to my usage. / Lars

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  • Improving Performance on this Image Creation function

    - by Abs
    Hello all, I am making use of GD2 and the image functions to take in a string and then convert that into an image using different fonts at different sizes. The function I use is below. Currently, its pretty quick but not quick enough. The function gets called about 20 times per user and the images generated are always new ones (different) so caching isn't going to help! I was hoping to get some ideas on how to make this function faster. Maybe supply more RAM to the script running? Anything else that is specific to this PHP function? Anything else that I can do to tweak performance of this function? function generate_image($save_path, $text, $font_path, $font_size){ $font = $font_path; /* * I have simplifed the line below, its actually a function that works out the size of the box * that is need for each image as the image size is different based on font type, font size etc */ $measure = array('width' => 300, 'height'=> 120); if($measure['width'] > 900){ $measure['width'] = 900; } $im = imagecreatetruecolor($measure['width'], $measure['height']); $white = imagecolorallocate($im, 255, 255, 255); $black = imagecolorallocate($im, 0, 0, 0); imagefilledrectangle($im, 0, 0, $measure['width'], $measure['height'], $white); imagettftext($im, $font_size, 0, $measure['left'], $measure['top'], $black, $font, ' '.$text); if(imagepng($im, $save_path)){ $status = true; }else{ $status = false; } imagedestroy($im); return $status; } Thanks all for any help

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