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• Am I under risk of CSRF attacks in a POST form that doesn't require the user to be logged in?

  - by Monika Sulik

  I'm probably being a total noob here, but I'm still uncertain about what a CSRF (Cross-Site Request Forgery) attack is exactly. So lets look at three situations... 1) I have a POST form that I use to edit data on my site. I want this data to be edited only by users that are logged in. 2) I have a site, which can be used by both users who are logged in as well as guests. Parts of the site are for logged in users only, but there are also POST forms that can be used by all users - anonymous and not (for example a standard contact form). Should the contact form be safeguarded against CSRF attacks? 3) I have a site which doesn't have an authentication system at all (well, perhaps that's unrealistic, so lets say it has an admin site which is separate from the rest of it and the admin part is properly safeguarded). The main part of the site is only used by anonymous users. Do the POST forms on it need to be safeguarded? In the case of 1) the answer is clearly yes. But in the case of 2 and 3 I don't know (and is the difference between 2 and 3 even significant?).

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• C++ .NET DLL vs C# Managed Code ? (File Encrypting AES-128+XTS)

  - by Ranhiru

  I need to create a Windows Mobile Application (WinMo 6.x - C#) which is used to encrypt/decrypt files. However it is my duty to write the encryption algorithm which is AES-128 along with XTS as the mode of operation. RijndaelManaged just doesn't cut it :( Very much slower than DES and 3DES CryptoServiceProviders :O I know it all depends on how good I am at writing the algorithm in the most efficient way. (And yes I my self have to write it from scratch but i can take a look @ other implementations) Nevertheless, does writing a C++ .NET DLL to create the encryption/decryption algorithm + all the file handling and using it from C# have a significant performance advantage OVER writing the encryption algorithm + file handling in completely managed C# code? If I use C++ .NET to create the encryption algorithm, should I use MFC Smart Device DLL or ATL? What is the difference and is there any impact on which one I choose? And can i just add a reference to the C++ DLL from C# or should I use P/Invoke? I am fairly competent with C# than C++ but performance plays a major role as I have convinced my lecturers that AES is a very efficient cryptographic algorithm for resource constrained devices. Thanx a bunch :)

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• How to organize the work when project needs to be re-implemented due to poor code quality?

  - by Dmitriy Nagirnyak

  Hi, I have joined a very small where one main developer has been buiding the web app (.NET 4.0) during ~6 months. The project should be delivered within next 2 months. After first look at the code I can say that I would never allow it to go to production (things like catch { }, not tests at all with WebForms etc). So the code quality is incredibly low. My task is to improve that and still deliver the solution. So I plan to start with unit testing and MVC2 reimplementing most of the functionality (though using some of the existing code). I estimate that I will need about 6 weeks to catch up with the current progress and be on te same functionality level as the application will be in 6 months. The problem is that the main developer who has been working on the project does not seem to be very 'professional' and skillful (he seems to be really starting in IT and many basic things are unknown to him). It will take significant amount of time and effort to educate him how to do the proper testing, development and apply some patterns. I am ready to take responsibility for the reimplemnting the application but at the same time I don't want the main developer to be on idle but as he won't be able to significantly contribute to the better-world project at this stage I am not sure what would the best way to keep productivity high for both of us. Currently I think following solution is good enough: He proceeds doing what he does until I will catch up with him and then start working on a new project together. The problem is that of course this approach is not very productive as one developer will do better-world project while the other will proceed with what he did, effectively doing similar tasks. Can you suggest how we could better organise the work together in order to be most efficient for the overall project? Thanks, Dmitriy.

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• what is the exact way to use Endorsed directory in jdk1.6

  - by raticulin

  I want to upgrade my jaxws to 2.2 (jdk1.6 comes bundled with jaxws 2.1). My jdk is (I did not install public jre): java version "1.6.0_20" Java(TM) SE Runtime Environment (build 1.6.0_20-b02) Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode) In jaxws' own doc they explain how to do it: One way to fix this is to copy jaxws-api.jar and jaxb-api.jar into JRE endorsed directory, which is $JAVA_HOME/lib/endorsed (or $JDK_HOME/jre/lib/endorsed) But I am not sure this is having any effect in my installation. For starters I have only defined %JAVA_HOME%. And folder $JAVA_HOME/lib/endorsed is inexistant, so I created and copied the two jars. But if I do (wsgen is a tool from jaxws) wsgen -version I still get: JAX-WS RI 2.1.6 in JDK 6 I also tried creating folder JAVA_HOME\jre\lib\endorsed (notice that in the doc they say JDK_HOME, but as I only have JAVA_HOME I used this path). Still same wsgen output. My questions are: What is the difference between JAVA_HOME and JDK_HOME in the doc page? anything significant or just two ways to refer to JAVA_HOME ? Is 'wsgen -version' a valid way to check jaxws version that is used or this always calls the exe in the original jdk, but it does not mean endorsed jars will be used? Anyone knows very detailed steps to install jaxws2.2 in a jdk.16?

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• PHP Regex to remove nested form elements but not input elements

  - by that0n3guy

  I'm modifying a PHP script that I have and it is currently outputting a nested form. Something like: <form name="input" action="html_form_action.asp" method="get"> <p>stuff here here, this may or may not be in a div, script, etc..</p> <form name="input" action="html_form_action.asp" method="get"> <div>stuff here possibilly</div> Username: <input type="text" name="user" /> <input type="submit" value="Submit" /> </form> <p>otherstuff this may or may not be in a div, script, etc..</p> </form> Nested form's are a no-no (IE hates them and basically causes the form to stop working), so I need to remove the nested form lines, but not the form items. I need to remove the nested: <form name="input" action="html_form_action.asp" method="get"> and </form> but not the outer <form and </form> or the input or submit stuff. Is this possible to do with regex? Note, the reason I just want to regex out the form rather than find the problem is because I know it will take some significant re-working to get rid of the double form... the regex solution is quick for now.

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• How to pull one commit at a time from a remote git repository?

  - by Norman Ramsey

  I'm trying to set up a darcs mirror of a git repository. I have something that works OK, but there's a significant problem: if I push a whole bunch of commits to the git repo, those commits get merged into a single darcs patchset. I really want to make sure each git commit gets set up as a single darcs patchset. I bet this is possible by doing some kind of git fetch followed by interrogation of the local copy of the remote branch, but my git fu is not up to the job. Here's the (ksh) code I'm using now, more or less: git pull -v # pulls all the commits from remote --- bad! # gets information about only the last commit pulled -- bad! author="$(git log HEAD^..HEAD --pretty=format:"%an <%ae>")" logfile=$(mktemp) git log HEAD^..HEAD --pretty=format:"%s%n%b%n" > $logfile # add all new files to darcs and record a patchset. this part is OK darcs add -q --umask=0002 -r . darcs record -a -A "$author" --logfile="$logfile" darcs push -a rm -f $logfile My idea is Try git fetch to get local copy of the remote branch (not sure exactly what arguments are needed) Somehow interrogate the local copy to get a hash for every commit since the last mirroring operation (I have no idea how to do this) Loop through all the hashes, pulling just that commit and recording the associated patchset (I'm pretty sure I know how to do this if I get my hands on the hash) I'd welcome either help fleshing out the scenario above or suggestions about something else I should try. Ideas?

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• SQL deadlock on delete then bulk insert

  - by StarLite

  I have an issue with a deadlock in SQL Server that I haven't been able to resolve. Basically I have a large number of concurrent connections (from many machines) that are executing transactions where they first delete a range of entries and then re-insert entries within the same range with a bulk insert. Essentially, the transaction looks like this BEGIN TRANSACTION T1 DELETE FROM [TableName] WITH( XLOCK HOLDLOCK ) WHERE [Id]=@Id AND [SubId]=@SubId INSERT BULK [TableName] ( [Id] Int , [SubId] Int , [Text] VarChar(max) COLLATE SQL_Latin1_General_CP1_CI_AS ) WITH(CHECK_CONSTRAINTS, FIRE_TRIGGERS) COMMIT TRANSACTION T1 The bulk insert only inserts items matching the Id and SubId of the deletion in the same transaction. Furthermore, these Id and SubId entries should never overlap. When I have enough concurrent transaction of this form, I start to see a significant number of deadlocks between these statements. I added the locking hints XLOCK HOLDLOCK to attempt to deal with the issue, but they don't seem to be helpling. The canonical deadlock graph for this error shows: Connection 1: Holds RangeX-X on PK_TableName Holds IX Page lock on the table Requesting X Page lock on the table Connection 2: Holds IX Page lock on the table Requests RangeX-X lock on the table What do I need to do in order to ensure that these deadlocks don't occur. I have been doing some reading on the RangeX-X locks and I'm not sure I fully understand what is going on with these. Do I have any options short of locking the entire table here?

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• Where to find algorithms for standard math functions?

  - by dsimcha

  I'm looking to submit a patch to the D programming language standard library that will allow much of std.math to be evaluated at compile time using the compile-time function evaluation facilities of the language. Compile-time function evaluation has several limitations, the most important ones being: You can't use assembly language. You can't call C code or code for which the source is otherwise unavailable. Several std.math functions violate these and compile-time versions need to be written. Where can I get information on good algorithms for computing things such as logarithms, exponents, powers, and trig functions? I prefer just high level descriptions of algorithms to actual code, for two reasons: To avoid legal ambiguity and the need to make my code look "different enough" from the source to make sure I own the copyright. I want simple, portable algorithms. I don't care about micro-optimization as long as they're at least asymptotically efficient. Edit: D's compile time function evaluation model allows floating point results computed at compile time to differ from those computed at runtime anyhow, so I don't care if my compile-time algorithms don't give exactly the same result as the runtime version as long as they aren't less accurate to a practically significant extent.

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• My OpenCL kernel is slower on faster hardware.. But why?

  - by matdumsa

  Hi folks, As I was finishing coding my project for a multicore programming class I came up upon something really weird I wanted to discuss with you. We were asked to create any program that would show significant improvement in being programmed for a multi-core platform. I’ve decided to try and code something on the GPU to try out OpenCL. I’ve chosen the matrix convolution problem since I’m quite familiar with it (I’ve parallelized it before with open_mpi with great speedup for large images). So here it is, I select a large GIF file (2.5 MB) [2816X2112] and I run the sequential version (original code) and I get an average of 15.3 seconds. I then run the new OpenCL version I just wrote on my MBP integrated GeForce 9400M and I get timings of 1.26s in average.. So far so good, it’s a speedup of 12X!! But now I go in my energy saver panel to turn on the “Graphic Performance Mode” That mode turns off the GeForce 9400M and turns on the Geforce 9600M GT my system has. Apple says this card is twice as fast as the integrated one. Guess what, my timing using the kick-ass graphic card are 3.2 seconds in average… My 9600M GT seems to be more than two times slower than the 9400M.. For those of you that are OpenCL inclined, I copy all data to remote buffers before starting, so the actual computation doesn’t require roundtrip to main ram. Also, I let OpenCL determine the optimal local-worksize as I’ve read they’ve done a pretty good implementation at figuring that parameter out.. Anyone has a clue? edit: full source code with makefiles here http://www.mathieusavard.info/convolution.zip cd gimage make cd ../clconvolute make put a large input.gif in clconvolute and run it to see results

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• Fast JSON serialization (and comparison with Pickle) for cluster computing in Python?

  - by user248237

  I have a set of data points, each described by a dictionary. The processing of each data point is independent and I submit each one as a separate job to a cluster. Each data point has a unique name, and my cluster submission wrapper simply calls a script that takes a data point's name and a file describing all the data points. That script then accesses the data point from the file and performs the computation. Since each job has to load the set of all points only to retrieve the point to be run, I wanted to optimize this step by serializing the file describing the set of points into an easily retrievable format. I tried using JSONpickle, using the following method, to serialize a dictionary describing all the data points to file: def json_serialize(obj, filename, use_jsonpickle=True): f = open(filename, 'w') if use_jsonpickle: import jsonpickle json_obj = jsonpickle.encode(obj) f.write(json_obj) else: simplejson.dump(obj, f, indent=1) f.close() The dictionary contains very simple objects (lists, strings, floats, etc.) and has a total of 54,000 keys. The json file is ~20 Megabytes in size. It takes ~20 seconds to load this file into memory, which seems very slow to me. I switched to using pickle with the same exact object, and found that it generates a file that's about 7.8 megabytes in size, and can be loaded in ~1-2 seconds. This is a significant improvement, but it still seems like loading of a small object (less than 100,000 entries) should be faster. Aside from that, pickle is not human readable, which was the big advantage of JSON for me. Is there a way to use JSON to get similar or better speed ups? If not, do you have other ideas on structuring this? (Is the right solution to simply "slice" the file describing each event into a separate file and pass that on to the script that runs a data point in a cluster job? It seems like that could lead to a proliferation of files). thanks.

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• Need help choosing database server

  - by The Pretender

  Good day everyone. Recently I was given a task to develop an application to automate some aspects of stocks trading. While working on initial architecture, the database dilemma emerged. What I need is a fast database engine which can process huge amounts of data coming in very fast. I'm fairly experienced in general programming, but I never faced a task of developing a high-load database architecture. I developed a simple MSSQL database schema with several many-to-many relationships during one of my projects, but that's it. What I'm looking for is some advice on choosing the most suitable database engine and some pointers to various manuals or books which describe high-load database development. Specifics of the project are as follows: OS: Windows NT family (Server 2008 / 7) Primary platform: .NET with C# Database structure: one table to hold primary items and two or three tables with foreign keys to the first table to hold additional information. Database SELECT requirements: Need super-fast selection by foreign keys and by combination of foreign key and one of the columns (presumably DATETIME) Database INSERT requirements: The faster the better :) If there'll be significant performance gain, some parts can be written in C++ with managed interfaces to the rest of the system. So once again: given all that stuff I just typed, please give me some advice on what the best database for my project is. Links or references to some manuals and books on the subject are also greatly appreciated. EDIT: I'll need to insert 3-5 rows in 2 tables approximately once in 30-50 milliseconds and I'll need to do SELECT with 0-2 WHERE clauses queries with similar rate.

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• RIA: how to get functionality, not a data

  - by Budda

  On the server side I have the following class: public class Customer { [Key] public int Id { get; set; } public string FirstName { get; set; } public string SecondName { get; set; } public string FullName { get { return string.Concat(FirstName, " ", SecondName); } } } The problem is that each field is calculated and transferred to the client, for example 'FullName' property: [DataMember()] [Editable(false)] [ReadOnly(true)] public string FullName { get { return this._fullName; } set { if ((this._fullName != value)) { this.ValidateProperty("FullName", value); this.OnFullNameChanging(value); this._fullName = value; this.RaisePropertyChanged("FullName"); this.OnFullNameChanged(); } } } Instead of data transferring (that is traffic consuming, in some cases it introduces significant overhead). I would like to have a calculation on the client side. Is this possible without manual duplication of the property implementation? Thank you.

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• Blocking on DBCP connection pool (open and close connnection). Is database connection pooling in OpenEJB pluggable?

  - by topchef

  We use OpenEJB on Tomcat (used to run on JBoss, Weblogic, etc.). While running load tests we experience significant performance problems with handling JMS messages (queues). Problem was localized to blocking on database connection pool getting or releasing connection to the pool. Blocking prevented concurrent MDB instances (threads) from running hence performance suffered 10-fold and worse. The same code used to run on application servers (with their respective connection pool implementations) with no blocking at all. Example of thread blocked: Name: JMS Resource Adapter-worker-23 State: BLOCKED on org.apache.commons.pool.impl.GenericObjectPool@1ea6b4a owned by: JMS Resource Adapter-worker-19 Total blocked: 18,426 Total waited: 0 Stack trace: org.apache.commons.pool.impl.GenericObjectPool.returnObject(GenericObjectPool.java:916) org.apache.commons.dbcp.PoolableConnection.close(PoolableConnection.java:91) - locked org.apache.commons.dbcp.PoolableConnection@1bcba8 org.apache.commons.dbcp.managed.ManagedConnection.close(ManagedConnection.java:147) com.xxxxx.persistence.DbHelper.closeConnection(DbHelper.java:290) .... Couple of questions. I am almost certain that some transactional attributes and properties contribute to this blocking, but MDBs are defined as non-transactional (we use both annotations and ejb-jar.xml). Some EJBs do use container-managed transactions though (and we can observe blocking there as well). Are there any DBCP configurations that may fix blocking? Is DBCP connection pool implementation replaceable in OpenEJB? How easy (difficult) to replace it with another library? Just in case this is how we define data source in OpenEJB (openejb.xml): <Resource id="MyDataSource" type="DataSource"> JdbcDriver oracle.jdbc.driver.OracleDriver JdbcUrl ${oracle.jdbc} UserName ${oracle.user} Password ${oracle.password} JtaManaged true InitialSize 5 MaxActive 30 ValidationQuery SELECT 1 FROM DUAL TestOnBorrow true </Resource>

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• Where can I find a quick reference for standard Basic?

  - by Steve314

  The reason? Pure nostalgia. Anyway, there was a standard for Basic that was published in the late 80s or early 90s. It was probably ISO/IEC 10279:1991, but I don't have access to that and cannot be sure. Whatever this standard was, some of the syntax made its way into Borlands Turbo Basic and Microsofts Visual Basic. I never learned any significant amount of VB, but Turbo Basic is one of those things I played with in my mis-spent youth. At one time, my main reference was an article published in one of the main programming periodicals - maybe Personal Computer World, maybe Byte. A scan of that article (if anyone can even identify it) would be great, but all I really want is a few pages quick reference of that standard syntax. Must be free (I'm not that nostalgic), but it must describe the standard syntax - the whole point is to sort out what is standard as opposed to VB or whatever. EDIT The more I think about this, the more convinced I am that this standard was available around 1987 or 1988. Maybe it was the earlier non-full version of the standard above, or maybe it was pre-acceptance of the standard.

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• How do I run a command as a different user from a root cronjob?

  - by rob

  I seem to be stuck between an NFS limitation and a Cron limitation. So I've got root cron (on RHEL5) running a shell script that, among other things, needs to rsync some files over an NFS mount. And the files on the NFS mount are owned by the apache user with mode 700, so only the apache user can run the rsync command -- running as root yields a permission error (NFS being a rare case, apparently, where the root user is not all-powerful?) When I just want to run the rsync by hand, I can use "sudo -u apache rsync ..." But sudo no workie in cron -- it says "sudo: sorry, you must have a tty to run sudo". I don't want to run the whole script as apache (i.e. from apache's crontab) because other parts of the script do require root -- it's just that one command that needs to run as apache. And I would really prefer not to change the mode on the files, as that will involve significant changes to other applications. There's gotta be a way to accomplish "sudo -u apache" from cron?? thanks! rob

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• What are the drawbacks of using PHP to create variables in my CSS stylesheet?

  - by Greg

  One significant drawback of CSS is that one can't use variables. For example, I'd like to use variables to control the location of imported CSS, and it would be awesome to create variables for colors that are used repeatedly in a design. One approach is to use a PHP file for the CSS stylesheet. In other words, create a "style.php" with... <?php header("Content-type: text/css"); ?> ...at the top of the file, and then link to it using... <link href="style.php" rel="stylesheet" type="text/css" /> ...in any file that uses these styles. So what's the catch? I think it might be performance -- I did a few quick experiments in Firefox/Firebug and as one would expect, the CSS stylesheet is cached, but the PHP stylesheet isn't. So we're paying the price of an additional GET. The other annoying thing is that TextMate does not syntax highlight properly for CSS in a .php file. Are there other drawbacks? Have you used this approach, and if so, would you recommend it?

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• Bored with CS. What can I study that will make an impact?

  - by Eric Martinez

  So I'm going to an average university, majoring in CS. I haven't learned a damn thing and am in my third year. I've come to be really bored with studying CS. Initially, I was kind of misinformed and thought majoring in CS would make me a good "product creator". I make my money combining programming and business/marketing. But I have always done programming for the love of the art. I find things like algorithms interesting and want to be able to use CS to solve real world problems. I like the idea of bioinformatics and other hybrid studies. I'm not good enough, yet I hope, to really make a significant effort in those areas but I aspire to be. What are some other fields, open problems, and otherwise cool stuff to apply CS knowledge to in the real world? I'm really looking for something that will motivate me and re-excite me to continue studying CS. Edit: Like someone mentioned below. I am very interesting in the idea of being able to use computer science to help answer fundamental questions of life and the universe. But I'm not sure what is possible or how to begin.

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• Merging changes to a workspace with uncommitted changes

  - by Kim L

  We've just recently switched over from SVN to Mercurial, but now we are running into problems with our workflow. Example I have my local clone of the repository which I work on. I'm making some highly experimental changes to our code base, something that I don't want to commit before I'm sure it works the way it is supposed to, I don't want to commit it even locally. Now, simultaneously, my co-worker has made some significant improvements/bug fixes which I need. He pushes his commits to our main repository. The question is, how can I merge his changes to my workspace without the requirement that I have to commit all my changes, since I need his changes to test my own code? A more day-to-day problem we have with the exact same workflow is where we have a couple of configuration files which are in the repository. Each developer makes a couple of small environment specific changes to the configuration files, but do not commit the changes. These couple of uncommitted files hinders us from making any merges to our workspace, just like with the example above. Ideally, the configuration files probably shouldn't be in the repository, unfortunately, that's just how it has to be for here unnamed reasons.

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• MVVM: Thin ViewModels and Rich Models

  - by Dan Bryant

  I'm continuing to struggle with the MVVM pattern and, in attempting to create a practical design for a small/medium project, have run into a number of challenges. One of these challenges is figuring out how to get the benefits of decoupling with this pattern without creating a lot of repetitive, hard-to-maintain code. My current strategy has been to create 'rich' Model classes. They are fully aware that they will be consumed by an MVVM pattern and implement INotifyPropertyChanged, allow their collections to be observed and remain cognizant that they may always be under observation. My ViewModel classes tend to be thin, only exposing properties when data actually needs to be transformed, with the bulk of their code being RelayCommand handlers. Views happily bind to either ViewModels or Models directly, depending on whether any data transformation is required. I use AOP (via Postsharp) to ease the pain of INotifyPropertyChanged, making it easy to make all of my Model classes 'rich' in this way. Are there significant disadvantages to using this approach? Can I assume that the ViewModel and View are so tightly coupled that if I need new data transformation for the View, I can simply add it to the ViewModel as needed?

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• Is NSPasteboard thread-safe?

  - by Joe

  Is it safe to write data to an NSPasteboard object from a background thread? I can't seem to find a definitive answer anywhere. I think the assumption is that the data will be written to the pasteboard before the drag begins. Background: I have an application that is fetching data from Evernote. When the application first loads, it gets the meta data for each note, but not the note content. The note stubs are then listed in an outline view. When the user starts to drag a note, the notes are passed to the background thread that handles getting the note content from Evernote. Having the main thread block until the data is gotten results in a significant delay and a poor user experience, so I have the [outlineView:writeItems:toPasteboard:] function return YES while the background thread processes the data and invokes the main thread to write the data to the pasteboard object. If the note content gets transferred before the user drops the note somewhere, everything works perfectly. If the user drops the note somewhere before the data has been processed... well, everything blocks forever. Is it safe to just have the background thread write the data to the pasteboard?

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• puzzled with java if else performance

  - by user1906966

  I am doing an investigation on a method's performance and finally identified the overhead was caused by the "else" portion of the if else statement. I have written a small program to illustrate the performance difference even when the else portion of the code never gets executed: public class TestIfPerf { public static void main( String[] args ) { boolean condition = true; long time = 0L; int value = 0; // warm up test for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } // benchmark if condition only time = System.nanoTime(); for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } } time = System.nanoTime() - time; System.out.println( "1) performance " + time ); time = System.nanoTime(); // benchmark if else condition for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } time = System.nanoTime() - time; System.out.println( "2) performance " + time ); } } and run the test program with java -classpath . -Dmx=800m -Dms=800m TestIfPerf. I performed this on both Mac and Linux Java with 1.6 latest build. Consistently the first benchmark, without the else is much faster than the second benchmark with the else section even though the code is structured such that the else portion is never executed because of the condition. I understand that to some, the difference might not be significant but the relative performance difference is large. I wonder if anyone has any insight to this (or maybe there is something I did incorrectly). Linux benchmark (in nano) performance 1215488 performance 2629531 Mac benchmark (in nano) performance 1667000 performance 4208000

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• Eclipse (Aptana) Typing Lag

  - by Zack

  Hello SO, I've been using Aptana for some time now, and as of recent I've been dealing with files that are really, really big (500+ lines of code, which is huge for me, being a novice developer). Whenever I deal with smaller files, I get that weird sensation that I'm "in front of" what's typing, but now I'm quite sure of it--there is a significant lag between when I type something and when I see the text appear on screen. I don't have this issue with Dreamweaver CS3, so I know my computer has the capability to edit these files without this happening, but Eclipse still lags. I also don't see when something is being deleted if I hold down backspace, I see the first few characters get deleted, but then everything "hangs." Once I release the backspace key, the characters that would've been shown deleting instantly vanish all at once. The same thing happens with the forward delete key. I'm beginning to think this is an issue with Java, since I have the same feeling that everything is slightly "behind me" when I'm using -any- Java application. The computer is an intel Pentium 4 3.2 GHz Prescott, with 2GB's of DDR400 RAM and a Radeon HD3650 graphics card. If anyone knows how to fix this lagging issue, I'm all ears (eyes?); if anyone can recommend a different IDE with capabilities similar to Aptana (I do Python, HTML, CSS and JS; I use Git for SCM), I'd be glad to give it a try. Thanks!

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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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• why unsigned int 0xFFFFFFFF is equal to int -1?

  - by conejoroy

  perhaps it's a very stupid question but I'm having a hard time figuring this out =) in C or C++ it is said that the maximum number a size_t (an unsigned int data type) can hold is the same as casting -1 to that data type. for example see http://stackoverflow.com/questions/1420982/invalid-value-for-sizet Why?? I'm confused.. I mean, (talking about 32 bit ints) AFAIK the most significant bit holds the sign in a signed data type (that is, bit 0x80000000 to form a negative number). then, 1 is 0x00000001.. 0x7FFFFFFFF is the greatest positive number a int data type can hold. then, AFAIK the binary representation of -1 int should be 0x80000001 (perhaps I'm wrong). why/how this binary value is converted to anything completely different (0xFFFFFFFF) when casting ints to unsigned?? or.. how is it possible to form a binary -1 out of 0xFFFFFFFF? I have no doubt that in C: ((unsigned int)-1) == 0xFFFFFFFF or ((int)0xFFFFFFFF) == -1 is equally true than 1 + 1 == 2, I'm just wondering why. thanks!

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• Fastest PNG decoder for .NET

  - by sboisse

  Our web server needs to process many compositions of large images together before sending the results to web clients. This process is performance critical because the server can receive several thousands of requests per hour. Right now our solution loads PNG files (around 1MB each) from the HD and sends them to the video card so the composition is done on the GPU. We first tried loading our images using the PNG decoder exposed by the XNA API. We saw the performance was not too good. To understand if the problem was loading from the HD or the decoding of the PNG, we modified that by loading the file in a memory stream, and then sending that memory stream to the .NET PNG decoder. The difference of performance using XNA or using System.Windows.Media.Imaging.PngBitmapDecoder class is not significant. We roughly get the same levels of performance. Our benchmarks show the following performance results: Load images from disk: 37.76ms 1% Decode PNGs: 2816.97ms 77% Load images on Video Hardware: 196.67ms 5% Composition: 87.80ms 2% Get composition result from Video Hardware: 166.21ms 5% Encode to PNG: 318.13ms 9% Store to disk: 3.96ms 0% Clean up: 53.00ms 1% Total: 3680.50ms 100% From these results we see that the slowest parts are when decoding the PNG. So we are wondering if there wouldn't be a PNG decoder we could use that would allow us to reduce the PNG decoding time. We also considered keeping the images uncompressed on the hard disk, but then each image would be 10MB in size instead of 1MB and since there are several tens of thousands of these images stored on the hard disk, it is not possible to store them all without compression.

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