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• Implement looped movement animation with tap to cancel

  - by Nader

  Hi All; My app is based around a grid and an image that moves within a grid that is contained within a scrollview. I have an imageview that I am animating from one cell to another in time with a slow finger movement and recentering the scrollview. That is rather straight forward. I have also implement the ability to detect a swipe and therefore move the image all the way to the end of the grid and the uiscrollview recentering. I have even implemented the ability to detect a subsequent tap and freeze the swiped movement. The issue with the swipe movement is that the UIScrollView will scroll all the way to the end before the Image reaches the end and so I have to wait for the image to arrive. Also, when I freeze the movement of the image, I have to re-align the image to a cell (which I can do). I have come to the realization that I have to animate the image one cell at a time for swipes and recentering the uiscrollview before moving the image to the next cell. I have attempted to implement this but I cannot come up with a solution that works or works properly. Can anyone suggest how I go about implementing this? Even if you are able to put up code from a different example or sudo code, it would help a lot as I cannot workout how this should be done, should I be using selectors, a listener in delegates, I just simply lack the experience to solve this design pattern. Here is some code: Note that the sprite is an UIImageView - (void)animateViewToPosition:(SpriteView *)sprite Position:(CGPoint)pos Duration:(CFTimeInterval)duration{ CGMutablePathRef traversePath = CGPathCreateMutable(); CGPathMoveToPoint(traversePath, NULL, sprite.center.x, sprite.center.y); CGPathAddLineToPoint(traversePath, NULL, pos.x, pos.y); CAKeyframeAnimation *traverseAnimation = [CAKeyframeAnimation animationWithKeyPath:kAnimatePosition]; traverseAnimation.duration = duration; traverseAnimation.removedOnCompletion = YES; traverseAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; traverseAnimation.delegate = sprite; traverseAnimation.path = traversePath; CGPathRelease(traversePath); [sprite.layer addAnimation:traverseAnimation forKey:kAnimatePosition]; sprite.center = pos; }

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• Optimizing multiple dispatch notification algorithm in C#?

  - by Robert Fraser

  Sorry about the title, I couldn't think of a better way to describe the problem. Basically, I'm trying to implement a collision system in a game. I want to be able to register a "collision handler" that handles any collision of two objects (given in either order) that can be cast to particular types. So if Player : Ship : Entity and Laser : Particle : Entity, and handlers for (Ship, Particle) and (Laser, Entity) are registered than for a collision of (Laser, Player), both handlers should be notified, with the arguments in the correct order, and a collision of (Laser, Laser) should notify only the second handler. A code snippet says a thousand words, so here's what I'm doing right now (naieve method): public IObservable<Collision<T1, T2>> onCollisionsOf<T1, T2>() where T1 : Entity where T2 : Entity { Type t1 = typeof(T1); Type t2 = typeof(T2); Subject<Collision<T1, T2>> obs = new Subject<Collision<T1, T2>>(); _onCollisionInternal += delegate(Entity obj1, Entity obj2) { if (t1.IsAssignableFrom(obj1.GetType()) && t2.IsAssignableFrom(obj2.GetType())) obs.OnNext(new Collision<T1, T2>((T1) obj1, (T2) obj2)); else if (t1.IsAssignableFrom(obj2.GetType()) && t2.IsAssignableFrom(obj1.GetType())) obs.OnNext(new Collision<T1, T2>((T1) obj2, (T2) obj1)); }; return obs; } However, this method is quite slow (measurable; I lost ~2 FPS after implementing this), so I'm looking for a way to shave a couple cycles/allocation off this. I thought about (as in, spent an hour implementing then slammed my head against a wall for being such an idiot) a method that put the types in an order based on their hash code, then put them into a dictionary, with each entry being a linked list of handlers for pairs of that type with a boolean indication whether the handler wanted the order of arguments reversed. Unfortunately, this doesn't work for derived types, since if a derived type is passed in, it won't notify a subscriber for the base type. Can anyone think of a way better than checking every type pair (twice) to see if it matches? Thanks, Robert

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• Accurately display upload progress in Silverilght upload

  - by Matt

  I'm trying to debug a file upload / download issue I'm having. I've got a Silverlight file uploader, and to transmit the files I make use of the HttpWebRequest class. So I create a connection to my file upload handler on the server and begin transmitting. While a file uploads I keep track of total bytes written to the RequestStream so I can figure out a percentage. Now working at home I've got a rather slow connection, and I think Silverlight, or the browser, is lying to me. It seems that my upload progress logic is inaccurate. When I do multiple file uploads (24 images of 3-6mb big in my testing), the logic reports the files finish uploading but I believe that it only reflects the progress of written bytes to the RequestStream, not the actual amount of bytes uploaded. What is the most accurate way to measure upload progress. Here's the logic I'm using. public void Upload() { if( _TargetFile != null ) { Status = FileUploadStatus.Uploading; Abort = false; long diff = _TargetFile.Length - BytesUploaded; UriBuilder ub = new UriBuilder( App.siteUrl + "upload.ashx" ); bool complete = diff <= ChunkSize; ub.Query = string.Format( "{3}name={0}&StartByte={1}&Complete={2}", fileName, BytesUploaded, complete, string.IsNullOrEmpty( ub.Query ) ? "" : ub.Query.Remove( 0, 1 ) + "&" ); HttpWebRequest webrequest = ( HttpWebRequest ) WebRequest.Create( ub.Uri ); webrequest.Method = "POST"; webrequest.BeginGetRequestStream( WriteCallback, webrequest ); } } private void WriteCallback( IAsyncResult asynchronousResult ) { HttpWebRequest webrequest = ( HttpWebRequest ) asynchronousResult.AsyncState; // End the operation. Stream requestStream = webrequest.EndGetRequestStream( asynchronousResult ); byte[] buffer = new Byte[ 4096 ]; int bytesRead = 0; int tempTotal = 0; Stream fileStream = _TargetFile.OpenRead(); fileStream.Position = BytesUploaded; while( ( bytesRead = fileStream.Read( buffer, 0, buffer.Length ) ) != 0 && tempTotal + bytesRead < ChunkSize && !Abort ) { requestStream.Write( buffer, 0, bytesRead ); requestStream.Flush(); BytesUploaded += bytesRead; tempTotal += bytesRead; int percent = ( int ) ( ( BytesUploaded / ( double ) _TargetFile.Length ) * 100 ); UploadPercent = percent; if( UploadProgressChanged != null ) { UploadProgressChangedEventArgs args = new UploadProgressChangedEventArgs( percent, bytesRead, BytesUploaded, _TargetFile.Length, _TargetFile.Name ); SmartDispatcher.BeginInvoke( () => UploadProgressChanged( this, args ) ); } } //} // only close the stream if it came from the file, don't close resizestream so we don't have to resize it over again. fileStream.Close(); requestStream.Close(); webrequest.BeginGetResponse( ReadCallback, webrequest ); }

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• Updating Checked Checkboxes using CodeIgniter + MySQL

  - by Tim

  Hello I have about 8 check boxes that are being generated dynamically from my database. This is the code in my controller //Start Get Processes Query $this->db->select('*'); $this->db->from('projects_processes'); $this->db->where('process_enabled', '1'); $data['getprocesses'] = $this->db->get(); //End Get Processes Query //Start Get Checked Processes Query $this->db->select('*'); $this->db->from('projects_processes_reg'); $this->db->where('project_id', $project_id); $data['getchecked'] = $this->db->get(); //End Get Processes Query This is the code in my view. <?php if($getprocesses->result_array()) { ?> <?php foreach($getprocesses->result_array() as $getprocessrow): ?> <tr> <td><input <?php if($getchecked->result_array()) { foreach($getchecked->result_array() as $getcheckedrow): if($getprocessrow['process_id'] == $getcheckedrow['process_id']) { echo 'checked'; } endforeach; }?> type="checkbox" name="progresscheck[]" value="<?php echo $getprocessrow['process_id']; ?>"><?php echo $getprocessrow['process_name']; ?><br> </td> </tr> <?php endforeach; ?> This generates the checkboxes into the form and also checks the appropriate ones as specified by the database. The problem is updating them. What I have been doing so far is simply deleting all checkbox entries for the project and then re-inserting all the values into the database. This is bad because 1. It's slow and horrible. 2. I lose all my meta data of when the check boxes were checked. So I guess my question is, how do I update only the checkboxes that have been changed? Thanks, Tim

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• UIImagePickerController Memory Leak

  - by Watson

  I am seeing a huge memory leak when using UIImagePickerController in my iPhone app. I am using standard code from the apple documents to implement the control: UIImagePickerController* imagePickerController = [[UIImagePickerController alloc] init]; imagePickerController.delegate = self; if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) { switch (buttonIndex) { case 0: imagePickerController.sourceType = UIImagePickerControllerSourceTypeCamera; [self presentModalViewController:imagePickerController animated:YES]; break; case 1: imagePickerController.sourceType = UIImagePickerControllerSourceTypePhotoLibrary; [self presentModalViewController:imagePickerController animated:YES]; break; default: break; } } And for the cancel: -(void) imagePickerControllerDidCancel:(UIImagePickerController *)picker { [[picker parentViewController] dismissModalViewControllerAnimated: YES]; [picker release]; } The didFinishPickingMediaWithInfo callback is just as stanard, although I do not even have to pick anything to cause the leak. Here is what I see in instruments when all I do is open the UIImagePickerController, pick photo library, and press cancel, repeatedly. As you can see the memory keeps growing, and eventually this causes my iPhone app to slow down tremendously. As you can see I opened the image picker 24 times, and each time it malloc'd 128kb which was never released. Basically 3mb out of my total 6mb is never released. This memory stays leaked no matter what I do. Even after navigating away from the current controller, is remains the same. I have also implemented the picker control as a singleton with the same results. Here is what I see when I drill down into those two lines: Any help here would be greatly appreciated! Again, I do not even have to choose an image. All I do is present the controller, and press cancel. Update 1 I downloaded and ran apple's example of using the UIIMagePickerController and I see the same leak happening there when running instruments (both in simulator and on the phone). http://developer.apple.com/library/ios/#samplecode/PhotoPicker/Introduction/Intro.html%23//apple_ref/doc/uid/DTS40010196 All you have to do is hit the photo library button and hit cancel over and over, you'll see the memory keep growing. Any ideas? Update 2 I only see this problem when viewing the photo library. I can choose take photo, and open and close that one over and over, without a leak.

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• How to optimize Core Data query for full text search

  - by dk

  Can I optimize a Core Data query when searching for matching words in a text? (This question also pertains to the wisdom of custom SQL versus Core Data on an iPhone.) I'm working on a new (iPhone) app that is a handheld reference tool for a scientific database. The main interface is a standard searchable table view and I want as-you-type response as the user types new words. Words matches must be prefixes of words in the text. The text is composed of 100,000s of words. In my prototype I coded SQL directly. I created a separate "words" table containing every word in the text fields of the main entity. I indexed words and performed searches along the lines of SELECT id, * FROM textTable JOIN (SELECT DISTINCT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) ON id=textTableId LIMIT 50 This runs very fast. Using an IN would probably work just as well, i.e. SELECT * FROM textTable WHERE id IN (SELECT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) LIMIT 50 The LIMIT is crucial and allows me to display results quickly. I notify the user that there are too many to display if the limit is reached. This is kludgy. I've spent the last several days pondering the advantages of moving to Core Data, but I worry about the lack of control in the schema, indexing, and querying for an important query. Theoretically an NSPredicate of textField MATCHES '.*\bfoo.*' would just work, but I'm sure it will be slow. This sort of text search seems so common that I wonder what is the usual attack? Would you create a words entity as I did above and use a predicate of "word BEGINSWITH 'foo'"? Will that work as fast as my prototype? Will Core Data automatically create the right indexes? I can't find any explicit means of advising the persistent store about indexes. I see some nice advantages of Core Data in my iPhone app. The faulting and other memory considerations allow for efficient database retrievals for tableview queries without setting arbitrary limits. The object graph management allows me to easily traverse entities without writing lots of SQL. Migration features will be nice in the future. On the other hand, in a limited resource environment (iPhone) I worry that an automatically generated database will be bloated with metadata, unnecessary inverse relationships, inefficient attribute datatypes, etc. Should I dive in or proceed with caution?

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• How to bind DataTable to Chart series?

  - by user175908

  Hello, How to do bind data from DataTable to Chart series? I get null reference exception. I tried binding with square brackets and it did not worked either. So, how to do the binding? Thanks. P.S: I included DataGrid XAML and CS which works just fine. Converting data to List<KeyValuePair<string,int>> works good but it is kinda slow and is unnessesary trash in code. I use WPFToolkit (the latest version). XAML: <Window x:Class="BindingzTest.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="606" Width="988" xmlns:charting="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"> <Grid Name="LayoutRoot"> <charting:Chart Title="Letters and Numbers" VerticalAlignment="Top" Height="400"> <charting:Chart.Series> <charting:ColumnSeries Name="myChartSeries" IndependentValueBinding="{Binding Letter}" DependentValueBinding="{Binding Number}" ItemsSource="{Binding}" /> </charting:Chart.Series> </charting:Chart> <DataGrid Name="myDataGrid" VerticalAlignment="Stretch" Margin="0,400,0,50" ItemsSource="{Binding}" AutoGenerateColumns="False"> <DataGrid.Columns> <DataGridTextColumn Header="Letter" Binding="{Binding Letter}"/> <DataGridTextColumn Header="Number" Binding="{Binding Number}"/> </DataGrid.Columns> </DataGrid> <Button Content="Generate" HorizontalAlignment="Left" Name="generateButton" Width="128" Click="GenerateButtonClicked" Height="52" VerticalAlignment="Bottom" /> </Grid> CS: public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); } DataTable GenerateMyTable() { var myTable = new DataTable("MyTable"); myTable.Columns.Add("Letter"); myTable.Columns.Add("Number"); myTable.Rows.Add("A", 500); myTable.Rows.Add("B", 400); myTable.Rows.Add("C", 500); myTable.Rows.Add("D", 600); myTable.Rows.Add("E", 300); myTable.Rows.Add("F", 200); return myTable; } private void GenerateButtonClicked(object sender, RoutedEventArgs e) { var myGeneratedTable = GenerateMyTable(); myDataGrid.DataContext = myGeneratedTable; myChartSeries.DataContext = myGeneratedTable; // Calling this throws "Object reference not set to an instance of an object" exception } }

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• Non-linear regression models in PostgreSQL using R

  - by Dave Jarvis

  Background I have climate data (temperature, precipitation, snow depth) for all of Canada between 1900 and 2009. I have written a basic website and the simplest page allows users to choose category and city. They then get back a very simple report (without the parameters and calculations section): The primary purpose of the web application is to provide a simple user interface so that the general public can explore the data in meaningful ways. (A list of numbers is not meaningful to the general public, nor is a website that provides too many inputs.) The secondary purpose of the application is to provide climatologists and other scientists with deeper ways to view the data. (Using too many inputs, of course.) Tool Set The database is PostgreSQL with R (mostly) installed. The reports are written using iReport and generated using JasperReports. Poor Model Choice Currently, a linear regression model is applied against annual averages of daily data. The linear regression model is calculated within a PostgreSQL function as follows: SELECT regr_slope( amount, year_taken ), regr_intercept( amount, year_taken ), corr( amount, year_taken ) FROM temp_regression INTO STRICT slope, intercept, correlation; The results are returned to JasperReports using: SELECT year_taken, amount, year_taken * slope + intercept, slope, intercept, correlation, total_measurements INTO result; JasperReports calls into PostgreSQL using the following parameterized analysis function: SELECT year_taken, amount, measurements, regression_line, slope, intercept, correlation, total_measurements, execute_time FROM climate.analysis( $P{CityId}, $P{Elevation1}, $P{Elevation2}, $P{Radius}, $P{CategoryId}, $P{Year1}, $P{Year2} ) ORDER BY year_taken This is not an optimal solution because it gives the false impression that the climate is changing at a slow, but steady rate. Questions Using functions that take two parameters (e.g., year [X] and amount [Y]), such as PostgreSQL's regr_slope: What is a better regression model to apply? What CPAN-R packages provide such models? (Installable, ideally, using apt-get.) How can the R functions be called within a PostgreSQL function? If no such functions exist: What parameters should I try to obtain for functions that will produce the desired fit? How would you recommend showing the best fit curve? Keep in mind that this is a web app for use by the general public. If the only way to analyse the data is from an R shell, then the purpose has been defeated. (I know this is not the case for most R functions I have looked at so far.) Thank you!

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• mysql index optimization for a table with multiple indexes that index some of the same columns

  - by Sean

  I have a table that stores some basic data about visitor sessions on third party web sites. This is its structure: id, site_id, unixtime, unixtime_last, ip_address, uid There are four indexes: id, site_id/unixtime, site_id/ip_address, and site_id/uid There are many different types of ways that we query this table, and all of them are specific to the site_id. The index with unixtime is used to display the list of visitors for a given date or time range. The other two are used to find all visits from an IP address or a "uid" (a unique cookie value created for each visitor), as well as determining if this is a new visitor or a returning visitor. Obviously storing site_id inside 3 indexes is inefficient for both write speed and storage, but I see no way around it, since I need to be able to quickly query this data for a given specific site_id. Any ideas on making this more efficient? I don't really understand B-trees besides some very basic stuff, but it's more efficient to have the left-most column of an index be the one with the least variance - correct? Because I considered having the site_id being the second column of the index for both ip_address and uid but I think that would make the index less efficient since the IP and UID are going to vary more than the site ID will, because we only have about 8000 unique sites per database server, but millions of unique visitors across all ~8000 sites on a daily basis. I've also considered removing site_id from the IP and UID indexes completely, since the chances of the same visitor going to multiple sites that share the same database server are quite small, but in cases where this does happen, I fear it could be quite slow to determine if this is a new visitor to this site_id or not. The query would be something like: select id from sessions where uid = 'value' and site_id = 123 limit 1 ... so if this visitor had visited this site before, it would only need to find one row with this site_id before it stopped. This wouldn't be super fast necessarily, but acceptably fast. But say we have a site that gets 500,000 visitors a day, and a particular visitor loves this site and goes there 10 times a day. Now they happen to hit another site on the same database server for the first time. The above query could take quite a long time to search through all of the potentially thousands of rows for this UID, scattered all over the disk, since it wouldn't be finding one for this site ID. Any insight on making this as efficient as possible would be appreciated :) Update - this is a MyISAM table with MySQL 5.0. My concerns are both with performance as well as storage space. This table is both read and write heavy. If I had to choose between performance and storage, my biggest concern is performance - but both are important. We use memcached heavily in all areas of our service, but that's not an excuse to not care about the database design. I want the database to be as efficient as possible.

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• Faster Matrix Multiplication in C#

  - by Kyle Lahnakoski

  I have as small c# project that involves matrices. I am processing large amounts of data by splitting it into n-length chunks, treating the chucks as vectors, and multiplying by a Vandermonde** matrix. The problem is, depending on the conditions, the size of the chucks and corresponding Vandermonde** matrix can vary. I have a general solution which is easy to read, but way too slow: public byte[] addBlockRedundancy(byte[] data) { if (data.Length!=numGood) D.error("Expecting data to be just "+numGood+" bytes long"); aMatrix d=aMatrix.newColumnMatrix(this.mod, data); var r=vandermonde.multiplyBy(d); return r.ToByteArray(); }//method This can process about 1/4 megabytes per second on my i5 U470 @ 1.33GHz. I can make this faster by manually inlining the matrix multiplication: int o=0; int d=0; for (d=0; d<data.Length-numGood; d+=numGood) { for (int r=0; r<numGood+numRedundant; r++) { Byte value=0; for (int c=0; c<numGood; c++) { value=mod.Add(value, mod.Multiply(vandermonde.get(r, c), data[d+c])); }//for output[r][o]=value; }//for o++; }//for This can process about 1 meg a second. (Please note the "mod" is performing operations over GF(2^8) modulo my favorite irreducible polynomial.) I know this can get a lot faster: After all, the Vandermonde** matrix is mostly zeros. I should be able to make a routine, or find a routine, that can take my matrix and return a optimized method which will effectively multiply vectors by the given matrix, but faster. Then, when I give this routine a 5x5 Vandermonde matrix (the identity matrix), there is simply no arithmetic to perform, and the original data is just copied. ** Please note: What I use the term "Vandermonde", I actually mean an Identity matrix with some number of rows from the Vandermonde matrix appended (see comments). This matrix is wonderful because of all the zeros, and because if you remove enough rows (of your choosing) to make it square, it is an invertible matrix. And, of course, I would like to use this same routine to convert any one of those inverted matrices into an optimized series of instructions. How can I make this matrix multiplication faster? Thanks! (edited to correct my mistake with Vandermonde matrix)

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• Comparing two large sets of attributes

  - by andyashton

  Suppose you have a Django view that has two functions: The first function renders some XML using a XSLT stylesheet and produces a div with 1000 subelements like this: <div id="myText"> <p id="p1"><a class="note-p1" href="#" style="display:none" target="bot">?</a></strong>Lorem ipsum</p> <p id="p2"><a class="note-p2" href="#" style="display:none" target="bot">?</a></strong>Foo bar</p> <p id="p3"><a class="note-p3" href="#" style="display:none" target="bot">?</a></strong>Chocolate peanut butter</p> (etc for 1000 lines) <p id="p1000"><a class="note-p1000" href="#" style="display:none" target="bot">?</a></strong>Go Yankees!</p> </div> The second function renders another XML document using another stylesheet to produce a div like this: <div id="myNotes"> <p id="n1"><cite class="note-p1">¹<span>Trololo</span></cite></p> <p id="n2"><cite class="note-p1">²<span>Trololo</span></cite></p> <p id="n3"><cite class="note-p2">³<span>lololo</span></cite></p> (etc for n lines) <p id="n"><cite class="note-p885">ⁿ<span>lololo</span></cite></p> </div> I need to see which elements in #myText have classes that match elements in #myNotes, and display them. I can do this using the following jQuery: $('#myText').find('a').each(function() { var $anchor = $(this); $('#myNotes').find('cite').each(function() { if($(this).attr('class') == $anchor.attr('class')) { $anchor.show(); }); }); However this is incredibly slow and inefficient for a large number of comparisons. What is the fastest/most efficient way to do this - is there a jQuery/js method that is reasonable for a large number of items? Or do I need to reengineer the Django code to do the work before passing it to the template?

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• performance problem looping through table rows

  - by Sridhar

  Hi, I am using jquery to loop through table rows and save the data. If the table has 200 rows it is performing slow. I am getting the javascript message "Stop Running this script" in IE when I call this method. Following is the code I am using to loop through table rows. Can you please let me know if there is a better way to do this. function SaveData() { var $table = $('#' + gridid); var rows = $table.find('tbody > tr').get(); var transactions = []; var $row, empno, newTransaction, $rowChildren; $.each(rows, function(index, row) { $row = $(row); $rowChildren = $row.children("td"); if ($rowChildren.find("input[id*=hRV]").val() === '1') { empno = $rowChildren.find("input[id*=tEmpno]").val(); newTransaction = new Array(); newTransaction[0] = company; newTransaction[1] = $rowChildren.find("input[id*=tEmpno]").val(); newTransaction[2] = $rowChildren.find("input[id*=tPC]").val(); newTransaction[3] = $rowChildren.find("input[id*=hQty]").val(); newTransaction[4] = $rowChildren.find("input[id*=hPR]").val(); newTransaction[5] = $rowChildren.find("input[id*=tJC]").val(); newTransaction[6] = $rowChildren.find("input[id*=tL1]").val(); newTransaction[7] = $rowChildren.find("input[id*=tL2]").val(); newTransaction[8] = $rowChildren.find("input[id*=tL3]").val(); newTransaction[9] = $rowChildren.find("input[id*=tL4]").val(); newTransaction[10] = $rowChildren.find("input[id*=tL5]").val(); newTransaction[11] = $rowChildren.find("input[id*=tL6]").val(); newTransaction[12] = $rowChildren.find("input[id*=tL7]").val(); newTransaction[13] = $rowChildren.find("input[id*=tL8]").val(); newTransaction[14] = $rowChildren.find("input[id*=tL9]").val(); newTransaction[15] = $rowChildren.find("input[id*=tL10]").val(); newTransaction[16] = $rowChildren.find("input[id*=tSF]").val(); newTransaction[17] = $rowChildren.find("input[id*=tCG]").val(); newTransaction[18] = $rowChildren.find("input[id*=tTF]").val(); newTransaction[19] = $rowChildren.find("input[id*=tWK]").val(); newTransaction[20] = $rowChildren.find("input[id*=tAI]").val(); newTransaction[21] = $rowChildren.find("input[id*=tWC]").val(); newTransaction[22] = $rowChildren.find("input[id*=tPI]").val(); newTransaction[23] = "E"; var record = newTransaction.join(';'); transactions.push(record); } }); if (transactions.length > 0) { var strTransactions = transactions.join('|'); //send data to server //here ajax function is called to save data. } }

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• Asp.net hosting equivalent of Dreamhost (pricing, features and support)

  - by Cherian

  Disclaimer: I have browsed http://stackoverflow.com/questions/tagged/asp.net+hosting and didn’t find anything quite similar in value to Dreamhost. One of the biggest impediments IMHO for developing web applications on asp.net is the cost of deployment. I am not talking about building sites like Stackoverflow.com or plentyoffish.com. This is about sites that are bigger than brochureware and smaller than ones that require dedicated servers. Let me give you an example. xmec.org is an asp.net site I maintain for my college alumni. On an average it’s slated to hit around 1000-1100 views per day. At present it’s hosted on godaddy. The service is so damn pathetic; I am using it only because of the lack of options. The site doesn’t scale (no, it’s not the code) and the web control panels are extremely slow. The money I pay doesn’t justify the service or the performance. Every deployment push is a visit to the infuriating web control panel to set the permissions and the root directories. Had I developed it in python, this would have been deployed on Dreamhost.com with $10/year hosting fees (they have offers running all throughout) 50 GB space 5 MySQL Databases Shell / FTP Users POP / SMTP Access Unlimited Domains hosting Unlimited Sub domains hosting Unlimited Domains Forwarded/Mirrored Custom DNS (These are the only ones I could think of. More at the feature page) With a dream host shell, I even have a svn checked-out version of wordpress for my blog. Now, that’s control! To my question: Is there any asp.net (preferably .net 3.5. Dreamhost keeps on updating versions every fortnight) hosting company providing remotely similar feature-sets and pricing like Dreamhost. My requirements are: Less than $15-25/ year Typical WISP minus PHP .net 3.5 SP1 Full Trust mode(I can live with medium trust, if not for the IL emitting libraries) Isolated Application Pool 5 – 10 MySQL db’s Unlimited domain hosting MsSql 2005 or 2008 FTP support At Least 5 GB space SMTP IIS 7 Log files Accessibility Moderately good control panel Scripting, shell support Nominal bandwidth Another case in point: Recently I’ve been contemplating building a tool-website to find duplicates and weird characters in my Google contacts and fix them. With asp.net, the best part is that I can do this with LINQ to XML in less than 100 lines of code. What’s bad is the hosting part. I don’t think I stand to make any money out of this and therefore can’t afford to host it on GoGrid or DiscountAsp.net. Godaddy is not an option either. If I do this in python, I can push to this my existing $10 Dreamhost account with another domain pointed. No extra cost. Svn exported with scripts (capability) to change the connection string! Looking at the problem holistically, I think I represent a large breed of programmers playing it cheap and experimenting different things on a regular basis, one of which will become the next twitter/digg.

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• Adding unique objects to Core Data

  - by absolut

  I'm working on an iPhone app that gets a number of objects from a database. I'd like to store these using Core Data, but I'm having problems with my relationships. A Detail contains any number of POIs (points of interest). When I fetch a set of POI's from the server, they contain a detail ID. In order to associate the POI with the Detail (by ID), my process is as follows: Query the ManagedObjectContext for the detailID. If that detail exists, add the poi to it. If it doesn't, create the detail (it has other properties that will be populated lazily). The problem with this is performance. Performing constant queries to Core Data is slow, to the point where adding a list of 150 POI's takes a minute thanks to the multiple relationships involved. In my old model, before Core Data (various NSDictionary cache objects) this process was super fast (look up a key in a dictionary, then create it if it doesn't exist) I have more relationships than just this one, but pretty much every one has to do this check (some are many to many, and they have a real problem). Does anyone have any suggestions for how I can help this? I could perform fewer queries (by searching for a number of different ID's), but I'm not sure how much this will help. Some code: POI *poi = [NSEntityDescription insertNewObjectForEntityForName:@"POI" inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]]; poi.POIid = [attributeDict objectForKey:kAttributeID]; poi.detailId = [attributeDict objectForKey:kAttributeDetailID]; Detail *detail = [self findDetailForID:poi.POIid]; if(detail == nil) { detail = [NSEntityDescription insertNewObjectForEntityForName:@"Detail" inManagedObjectContext:[(AppDelegate*)[UIApplication sharedApplication].delegate managedObjectContext]]; detail.title = poi.POIid; detail.subtitle = @""; detail.detailType = [attributeDict objectForKey:kAttributeType]; } -(Detail*)findDetailForID:(NSString*)detailID { NSManagedObjectContext *moc = [[UIApplication sharedApplication].delegate managedObjectContext]; NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Detail" inManagedObjectContext:moc]; NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; [request setEntity:entityDescription]; NSPredicate *predicate = [NSPredicate predicateWithFormat: @"detailid == %@", detailID]; [request setPredicate:predicate]; NSLog(@"%@", [predicate description]); NSError *error; NSArray *array = [moc executeFetchRequest:request error:&error]; if (array == nil || [array count] != 1) { // Deal with error... return nil; } return [array objectAtIndex:0]; }

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• Cases of companies taking IP rights of your own personal projects developed outside company time

  - by GSS

  Hi, I have heard of cases where a developer working for a company is also making his own personal projects in his own time, using his own equipment yet the company he works for tries to claim ownership for the project. I really find this annoying, and bang out of order. It should also be illegal. I am in this position (work for a company and working on my own systems - from small class libraries used to practise what I learn in my exam revision to a large commercial-scale system). While I don't know if the company will try to take ownership, all I know is they say they do not want a conflict of interest. Fair enough, my system is developed in my own time using my own equipment. They also say that work time should be for work only, which it is. Funny thing that as work is so boring, easy and slow that I have plenty of free time, which I wish I could spend on something productive - said system. The problem is, my company does not take hiring technical talent seriously. This is my first job, I am a junior coder (but my status/position doesn't really reflect what I can do), but I am the only developer. Likewise with the guy who controls Windows Server. As the contract does not say anything about taking ownership, I would assume they would. They would try to milk my success (I've made a good impression so I am sure they would). How can this be allowed? Are there any examples of this happening to any fellow Stacker here? It really makes my blood boil. What I find funny is that my company hardly has the expertise and resources to even be able to successfully run a project of my size. What I do at work is an ASP.NET application consisting of five pages, and even then there are flaws in the project. If I told them that they would also have to take responsibility for flaws in the project, then they would think twice! It's exactly because of this I save the best code for myself and at work I write rubbish code full of code smells. The company don't really care about error handling, as long as the business functionality works (ie a scheduled email sends, but there is no error handling). They'd think twice when they see the embarassment and business cost of a YSOD...

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• Floating point vs integer calculations on modern hardware

  - by maxpenguin

  I am doing some performance critical work in C++, and we are currently using integer calculations for problems that are inherently floating point because "its faster". This causes a whole lot of annoying problems and adds a lot of annoying code. Now, I remember reading about how floating point calculations were so slow approximately circa the 386 days, where I believe (IIRC) that there was an optional co-proccessor. But surely nowadays with exponentially more complex and powerful CPUs it makes no difference in "speed" if doing floating point or integer calculation? Especially since the actual calculation time is tiny compared to something like causing a pipeline stall or fetching something from main memory? I know the correct answer is to benchmark on the target hardware, what would be a good way to test this? I wrote two tiny C++ programs and compared their run time with "time" on Linux, but the actual run time is too variable (doesn't help I am running on a virtual server). Short of spending my entire day running hundreds of benchmarks, making graphs etc. is there something I can do to get a reasonable test of the relative speed? Any ideas or thoughts? Am I completely wrong? The programs I used as follows, they are not identical by any means: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { int accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += rand( ) % 365; } std::cout << accum << std::endl; return 0; } Program 2: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { float accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += (float)( rand( ) % 365 ); } std::cout << accum << std::endl; return 0; } Thanks in advance!

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• Replace HTML entities in a string avoiding <img> tags

  - by Xeos

  I have the following input: Hi! How are you? <script>//NOT EVIL!</script> Wassup? :P LOOOL!!! :D :D :D Which is then run through emoticon library and it become this: Hi! How are you? <script>//NOT EVIL!</script> Wassup? <img class="smiley" alt="" title="tongue, :P" src="ui/emoticons/15.gif"> LOOOL!!! <img class="smiley" alt="" title="big grin, :D" src="ui/emoticons/5.gif"> <img class="smiley" alt="" title="big grin, :P" src="ui/emoticons/5.gif"> <img class="smiley" alt="" title="big grin, :P" src="ui/emoticons/5.gif"> I have a function that escapes HTML entites to prevent XSS. So running it on raw input for the first line would produce: Hi! How are you? &lt;script&gt;//NOT EVIL!&lt;/script&gt; Now I need to escape all the input, but at the same time I need to preserve emoticons in their initial state. So when there is <:-P emoticon, it stays like that and does not become &lt;:-P. I was thinking of running a regex split on the emotified text. Then processing each part on its own and then concatenating the string together, but I am not sure how easily can Regex be bypassed? I know the format will always be this: [<img class="smiley" alt="] [empty string] [" title="] [one of the values from a big list] [, ] [another value from the list (may be matching original emoticon)] [" src="ui/emoticons/] [integer from Y to X] [.gif">] Using the list MAY be slow, since I need to run that regex on text that may have 20-30-40 emoticons. Plus there may be 5-10-15 text messages to process. What could be an elegant solution to this? I am ready to use third-party library or jQuery for this. PHP preprocessing is possible as well.

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• Bulk inserts into sqlite db on the iphone...

  - by akaii

  I'm inserting a batch of 100 records, each containing a dictonary containing arbitrarily long HTML strings, and by god, it's slow. On the iphone, the runloop is blocking for several seconds during this transaction. Is my only recourse to use another thread? I'm already using several for acquiring data from HTTP servers, and the sqlite documentation explicitly discourages threading with the database, even though it's supposed to be thread-safe... Is there something I'm doing extremely wrong that if fixed, would drastically reduce the time it takes to complete the whole operation? NSString* statement; statement = @"BEGIN EXCLUSIVE TRANSACTION"; sqlite3_stmt *beginStatement; if (sqlite3_prepare_v2(database, [statement UTF8String], -1, &beginStatement, NULL) != SQLITE_OK) { printf("db error: %s\n", sqlite3_errmsg(database)); return; } if (sqlite3_step(beginStatement) != SQLITE_DONE) { sqlite3_finalize(beginStatement); printf("db error: %s\n", sqlite3_errmsg(database)); return; } NSTimeInterval timestampB = [[NSDate date] timeIntervalSince1970]; statement = @"INSERT OR REPLACE INTO item (hash, tag, owner, timestamp, dictionary) VALUES (?, ?, ?, ?, ?)"; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, [statement UTF8String], -1, &compiledStatement, NULL) == SQLITE_OK) { for(int i = 0; i < [items count]; i++){ NSMutableDictionary* item = [items objectAtIndex:i]; NSString* tag = [item objectForKey:@"id"]; NSInteger hash = [[NSString stringWithFormat:@"%@%@", tag, ownerID] hash]; NSInteger timestamp = [[item objectForKey:@"updated"] intValue]; NSData *dictionary = [NSKeyedArchiver archivedDataWithRootObject:item]; sqlite3_bind_int( compiledStatement, 1, hash); sqlite3_bind_text( compiledStatement, 2, [tag UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_text( compiledStatement, 3, [ownerID UTF8String], -1, SQLITE_TRANSIENT); sqlite3_bind_int( compiledStatement, 4, timestamp); sqlite3_bind_blob( compiledStatement, 5, [dictionary bytes], [dictionary length], SQLITE_TRANSIENT); while(YES){ NSInteger result = sqlite3_step(compiledStatement); if(result == SQLITE_DONE){ break; } else if(result != SQLITE_BUSY){ printf("db error: %s\n", sqlite3_errmsg(database)); break; } } sqlite3_reset(compiledStatement); } timestampB = [[NSDate date] timeIntervalSince1970] - timestampB; NSLog(@"Insert Time Taken: %f",timestampB); // COMMIT statement = @"COMMIT TRANSACTION"; sqlite3_stmt *commitStatement; if (sqlite3_prepare_v2(database, [statement UTF8String], -1, &commitStatement, NULL) != SQLITE_OK) { printf("db error: %s\n", sqlite3_errmsg(database)); } if (sqlite3_step(commitStatement) != SQLITE_DONE) { printf("db error: %s\n", sqlite3_errmsg(database)); } sqlite3_finalize(beginStatement); sqlite3_finalize(compiledStatement); sqlite3_finalize(commitStatement);

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• Parsing a .NET DataSet returned from a .NET Web Service in Java

  - by Chris Dail

  I have to consume a .NET hosted web service from a Java application. Interoperability between the two is usually very good. The problem I'm running into is that the .NET application developer chose to expose data using the .NET DataSet object. There are lots of articles written as to why you should not do this and how it makes interoperability difficult: http://www.hanselman.com/blog/ReturningDataSetsFromWebServicesIsTheSpawnOfSatanAndRepresentsAllThatIsTrulyEvilInTheWorld.aspx http://www.lhotka.net/weblog/ThoughtsOnPassingDataSetObjectsViaWebServices.aspx http://aspnet.4guysfromrolla.com/articles/051805-1.aspx http://www.theserverside.net/tt/articles/showarticle.tss?id=Top5WSMistakes My problem is that despite this not being recommended practice, I am stuck with having to consume a web service returning a DataSet with Java. When you generate a proxy for something like this with anything other than .NET you basically end up with an object that looks like this: @XmlElement(namespace = "http://www.w3.org/2001/XMLSchema", required = true) protected Schema schema; @XmlAnyElement(lax = true) protected Object any; This first field is the actual schema that should describe the DataSet. When I process this using JAX-WS and JAXB in Java, it bring all of XS-Schema in as Java objects to be represented here. Walking the object tree of JAXB is possible but not pretty. The any field represents the raw XML for the DataSet that is in the schema specified by the schema. The structure of the dataset is pretty consistent but the data types do change. I need access to the type information and the schema does vary from call to call. I've though of a few options but none seem like 'good' options. Trying to generate Java objects from the schema using JAXB at runtime seems to be a bad idea. This would be way too slow since it would need to happen everytime. Brute force walk the schema tree using the JAXB objects that JAX-WS brought in. Maybe instead of using JAXB to parse the schema it would be easier to deal with it as XML and use XPath to try and find the type information I need. Are there other options I have not considered? Is there a Java library to parse DataSet objects easily? What have other people done who may have similar situations?

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• Delay keyboard input help

  - by Stradigos

  I'm so close! I'm using the XNA Game State Management example found here and trying to modify how it handles input so I can delay the key/create an input buffer. In GameplayScreen.cs I've declared a double called elapsedTime and set it equal to 0. In the HandleInput method I've changed the Key.Right button press to: if (keyboardState.IsKeyDown(Keys.Left)) movement.X -= 50; if (keyboardState.IsKeyDown(Keys.Right)) { elapsedTime -= gameTime.ElapsedGameTime.TotalMilliseconds; if (elapsedTime <= 0) { movement.X += 50; elapsedTime = 10; } } else { elapsedTime = 0; } The pseudo code: If the right arrow key is not pressed set elapsedTime to 0. If it is pressed, the elapsedTime equals itself minus the milliseconds since the last frame. If the difference then equals 0 or less, move the object 50, and then set the elapsedTime to 10 (the delay). If the key is being held down elapsedTime should never be set to 0 via the else. Instead, after elapsedTime is set to 10 after a successful check, the elapsedTime should get lower and lower because it's being subtracted by the TotalMilliseconds. When that reaches 0, it successfully passes the check again and moves the object once more. The problem is, it moves the object once per press but doesn't work if you hold it down. Can anyone offer any sort of tip/example/bit of knowledge towards this? Thanks in advance, it's been driving me nuts. In theory I thought this would for sure work. CLARIFICATION Think of a grid when your thinking about how I want the block to move. Instead of just fluidly moving across the screen, it's moving by it's width (sorta jumping) to the next position. If I hold down the key, it races across the screen. I want to slow this whole process down so that holding the key creates an X millisecond delay between it 'jumping'/moving by it's width. EDIT: Turns out gameTime.ElapsedGameTime.TotalMilliseconds is returning 0... all of the time. I have no idea why.

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• iPhone: Speeding up a search that's polling 17,000 Core Data objects

  - by randombits

  I have a class that conforms to UISearchDisplayDelegate and contains a UISearchBar. This view is responsible for allowing the user to poll a store of about 17,000 objects that are currently managed by Core Data. Everytime the user types in a character, I created an instance of a SearchOperation (subclasses NSOperation) that queries Core Data to find results that might match the search. The code in the search controller looks something like: - (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope { // Update the filtered array based on the search text and scope in a secondary thread if ([searchText length] < 3) { [filteredList removeAllObjects]; // First clear the filtered array. [self setFilteredList:NULL]; [self.tableView reloadData]; return; } NSDictionary *searchdict = [NSDictionary dictionaryWithObjectsAndKeys:scope, @"scope", searchText, @"searchText", nil]; [aSearchQueue cancelAllOperations]; SearchOperation *searchOp = [[SearchOperation alloc] initWithDelegate:self dataDict:searchdict]; [aSearchQueue addOperation:searchOp]; } And my search is rather straight forward. SearchOperation is a subclass of NSOperation. I overwrote the main method with the following code: - (void)main { if ([self isCancelled]) { return; } NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"MyEntity" inManagedObjectContext:managedObjectContext]; NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; [fetchRequest setEntity:entity]; NSPredicate *predicate = NULL; predicate = [NSPredicate predicateWithFormat:@"(someattr contains[cd] %@)", searchText]; [fetchRequest setPredicate:predicate]; NSError *error = NULL; NSArray *fetchResults = [managedObjectContext executeFetchRequest:fetchRequest error:&error]; [fetchRequest release]; if (self.delegate != nil) [self.delegate didFinishSearching:fetchResults]; [pool drain]; } This code works, but it has several issues. It's slow. Even though I have the search happening in a separate thread other than the UI thread, querying 17,000 objects is clearly not optimal. If I'm not careful, crashes can happen. I set the max concurrent searches in my NSOperationQueue to 1 to avoid this. What else can I do to make this search faster? I think preloading all 17,000 objects into memory might be risky. There has to be a smarter way to conduct this search to give results back to the user faster.

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• Calculations in a table of data

  - by Christian W

  I have a table of data with survey results, and I want to do certain calculations on this data. The datastructure is somewhat like this: ____________________________________________________________________________________ | group |individual | key | key | key | | | |subkey|subkey|subkey|subkey|subkey|subkey|subkey|subkey|subkey| | | |q|q|q |q |q |q|q|q |q|q|q |q |q |q|q|q |q|q|q |q |q |q|q|q | |-------|-----------|-|-|--|--|---|-|-|--|-|-|--|--|---|-|-|--|-|-|--|--|---|-|-|--| | 1 | 0001 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 1 | 0002 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 1 | 0003 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 2 | 0004 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 2 | 0005 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 3 | 0006 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 4 | 0007 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | ------------------------------------------------------------------------------------ Excuse my poor ascii skills... So, every individual belongs to a group, and has answered some questions. These questions are always grouped in keys and subkeys. Is there any simple method to calculate averages, deviations and similar based on the groupings. Something like public float getAverage(int key, int individual); float avg = getAverage(5,7); I think what I'm asking is what would be the best way to structure the data in C# to make it as easy as possible to work with? I have started making classes for every entity, but I got confused somewhere and something stopped working. So before I continue along this path, I was wondering if there are any other, better, ways of doing this? (Every individual can also have describing variables, like agegroup and such, but that's not important for the base functionality.) Our current solution does all calculations inline in the queries when requesting the data from the database. This works, but it's slow and the number of queries equals questions * individuals + keys * individuals, which could be alot if individual queries. Any suggestions?

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• Using JUnit as an acceptance test framework

  - by Chris Knight

  OK, so I work for a company who has openly adopted agile practices for development in recent years. Our unit tests and code quality are improving. One area we still are working on is to find what works best for us in the automated acceptance test arena. We want to take our well formed user stories and use these to drive the code in a test driven manner. This will also give us acceptance level tests for each user story which we can then automate. To date, we've tried Fit, Fitnesse and Selenium. Each have their advantages, but we've also had real issues with them as well. With Fit and Fitnesse, we can't help but feel they overcomplicate things and we've had many technical issues using them. The business haven't fully bought in these tools and aren't particularly keen on maintaining the scripts all the time (and aren't big fans of the table style). Selenium is really good, but slow and relies on real time data and resources. One approach we are now considering is the use of the JUnit framework to provide similiar functionality. Rather than testing just a small unit of work using JUnit, why not use it to write a test (using the JUnit framework) to cover an acceptance level swath of the application? I.e. take a new story ("As a user I would like to see basic details of my policy...") and write a test in JUnit which starts executing application code at the point of entry for the policy details link but covers all code and logic down to the stubbed data access layer and back to the point of forwarding to the next page in the application, asserting on what data the user should see on that page. This seems to me to have the following advantages: Simplicity (no additional frameworks required) Zero effort to integrate with our Continuous Integration build server (since it already handles our JUnit tests) Full skillset already present in the team (its just a JUnit test after all) And the downsides being: Less customer involvement (though they are heavily involved in writing the user stories in the first place from which the acceptance tests will be written) Perhaps more difficult to understand (or make understood) the user story and acceptance criteria in a JUnit class verses a freetext specification ala Fit or Fitnesse So, my question is really, have you ever tried this method? Ever considered it? What are your thoughts? What do you like and dislike about this approach? Finally, please only mention alternative frameworks if you can say why you like or dislike them more than this approach.

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• ActiveMQ 5.2.0 + REST + HTTP POST = java.lang.OutOfMemoryError

  - by Bruce Loth

  First off, I am a newbie when it comes to JMS & ActiveMQ. I have been looking into a messaging solution to serve as middleware for a message producer that will insert XML messages into a queue via HTTP POST. The producer is an existing system written in C++ that cannot be modified (so Java and the C++ API are out). Using the "demo" examples and some trial and error, I have cobbled together a working example of what I want to do (on a windows box). The web.xml I configured in a test directory under "webapps" specifies that the HTTP POST messages received from the producer are to be handled by the MessageServlet. I added a line for the text app in "activemq.xml" ('ow' is the test app dir): I created a test script to "insert" messages into the queue which works well. The problem I am running into is that it as I continue to insert messages via REST/HTTP POST, the memory consumption and thread count used by ActiveMQ continues to rise (It happens when I have timely consumers as well as slow or non-existent consumers). When memory consumption gets around 250MB's and the thread count exceeds 5000 (as shown in windows task manager), ActiveMQ crashes and I see this in the log: Exception in thread "ActiveMQ Transport Initiator: vm://localhost#3564" java.lang.OutOfMemoryError: unable to create new native thread It is as if Jetty is spawning a new thread to handle each HTTP POST and the thread never dies. I did look at this page: http://activemq.apache.org/javalangoutofmemory.html and tried but that didn't fix the problem (although I didn't fully understand the implications of the change either). Does anyone have any ideas? Thanks! Bruce Loth PS - I included the "test message producer" python script below for what it is worth. I created batches of 100 messages and continued to run the script manually from the command line while watching the memory consumption and thread count of ActiveMQ in task manager. def foo(): import httplib, urllib body = "<?xml version='1.0' encoding='UTF-8'?>\n \ <ROOT>\n \ [snip: xml deleted to save space] </ROOT>" headers = {"content-type": "text/xml", "content-length": str(len(body))} conn = httplib.HTTPConnection("127.0.0.1:8161") conn.request("POST", "/ow/message/RDRCP_Inbox?type=queue", body, headers) response = conn.getresponse() print response.status, response.reason data = response.read() conn.close() ## end method definition ## Begin test code count = 0; while(count < 100): # Test with batches of 100 msgs count += 1 foo()

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• how to implement a "soft barrier" in multithreaded c++

  - by Jason

  I have some multithreaded c++ code with the following structure: do_thread_specific_work(); update_shared_variables(); //checkpoint A do_thread_specific_work_not_modifying_shared_variables(); //checkpoint B do_thread_specific_work_requiring_all_threads_have_updated_shared_variables(); What follows checkpoint B is work that could have started if all threads have reached only checkpoint A, hence my notion of a "soft barrier". Typically multithreading libraries only provide "hard barriers" in which all threads must reach some point before any can continue. Obviously a hard barrier could be used at checkpoint B. Using a soft barrier can lead to better execution time, especially since the work between checkpoints A and B may not be load-balanced between the threads (i.e. 1 slow thread who has reached checkpoint A but not B could be causing all the others to wait at the barrier just before checkpoint B). I've tried using atomics to synchronize things and I know with 100% certainty that is it NOT guaranteed to work. For example using openmp syntax, before the parallel section start with: shared_thread_counter = num_threads; //known at compile time #pragma omp flush Then at checkpoint A: #pragma omp atomic shared_thread_counter--; Then at checkpoint B (using polling): #pragma omp flush while (shared_thread_counter > 0) { usleep(1); //can be removed, but better to limit memory bandwidth #pragma omp flush } I've designed some experiments in which I use an atomic to indicate that some operation before it is finished. The experiment would work with 2 threads most of the time but consistently fail when I have lots of threads (like 20 or 30). I suspect this is because of the caching structure of modern CPUs. Even if one thread updates some other value before doing the atomic decrement, it is not guaranteed to be read by another thread in that order. Consider the case when the other value is a cache miss and the atomic decrement is a cache hit. So back to my question, how to CORRECTLY implement this "soft barrier"? Is there any built-in feature that guarantees such functionality? I'd prefer openmp but I'm familiar with most of the other common multithreading libraries. As a workaround right now, I'm using a hard barrier at checkpoint B and I've restructured my code to make the work between checkpoint A and B automatically load-balancing between the threads (which has been rather difficult at times). Thanks for any advice/insight :)

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