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• The Importance of Fully Specifying a Problem

  - by Alan

  I had a customer call this week where we were provided a forced crashdump and asked to determine why the system was hung. Normally when you are looking at a hung system, you will find a lot of threads blocked on various locks, and most likely very little actually running on the system (unless it's threads spinning on busy wait type locks). This vmcore showed none of that. In fact we were seeing hundreds of threads actively on cpu in the second before the dump was forced. This prompted the question back to the customer: What exactly were you seeing that made you believe that the system was hung? It took a few days to get a response, but the response that I got back was that they were not able to ssh into the system and when they tried to login to the console, they got the login prompt, but after typing "root" and hitting return, the console was no longer responsive. This description puts a whole new light on the "hang". You immediately start thinking "name services". Looking at the crashdump, yes the sshds are all in door calls to nscd, and nscd is idle waiting on responses from the network. Looking at the connections I see a lot of connections to the secure ldap port in CLOSE_WAIT, but more interestingly I am seeing a few connections over the non-secure ldap port to a different LDAP server just sitting open. My feeling at this point is that we have an either non-responding LDAP server, or one that is responding slowly, the resolution being to investigate that server. Moral When you log a service ticket for a "system hang", it's great to get the forced crashdump first up, but it's even better to get a description of what you observed to make to believe that the system was hung.

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• webhost4life, please give me, my data back. My website will not work without the database.

  - by Shervin Shakibi

  I have about 4 or 5 accounts with WebHost4life.com, these are all my customers that based on my recommendation have been hosting with webhost4life.com. A few days ago for some reason they decided to migrate one of these accounts to a new server. They moved everything created a new database on the new server but the new database is empty. after spending hours with Tech support they acknowledged the problem and assured me it will take up to an hour or two and my database will be populated with the data. this was about 7 hours ago. Oh by the way I pay extra for the backup plan and yes you guessed it, none of my backups are there. Needless to say I’m very scared and disappointed. No one is responding to my emails  or phone calls. After searching the web, I found out, this has happened before, in some cases it took them days to fix the problem and many never got it resolved and switched hosting companies, I would love to do that but I need my 2 GB database before I start shopping around for a new hosting company. Stay away from Webhost4life.

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• Serious problem with mobile modems in UBUNTU to look [on hold]

  - by kitten 94

  I use mobile broadband using data card(modem) with simcard on ubuntu 14.04. My friends,relatives,boss used to make phone call to my sim on modem, & they get the ringsound on their phone but I cannot find any alert on ubuntu about the phone call. They think that I will call back to them & gets disappointed. Some even gets angry "that I am not attending the mobile call intensionally". They even do not not believe me,saying that computer can also pick a mobile call keeping mobile partner in their mind . Is there any way just to find out call & who it is call ? so that I can call to them later. or Is their any software like mobile partner to ubuntu to recive & make phone calls? Modem Manager GUI is helpful only just to send SMS, even USSD not works in it, inorder to receive SMS I have to close & open the windows repeatedly. please,please help me. Any help or ideas is thankful. Waiting for your's reply.

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• Is it considered poor programming to do this with xna components?

  - by Rob

  I created my own Menu System that is event driven. In order to have a loading screen and multithreaded loading to work, I devised this sort of implementation: //Let's check if the game is done loading. if (_game != null) { _gameLoaded = _game.DoneLoading; } //This means the game is loading still, //therefore the loading screen should be active. if (!_gameLoaded && _gameActive) { _gameScreenList[2].UpdateMenu(); } //The loading screen was selected. if (_gameScreenList[2].CurrentState == GameScreen.State.Shown && !_gameActive) { Components.Add(_game = new ParadoxGame(this)); _game.Initialize(); //Initializes the Game so that the loading can begin. _gameActive = true; } In the XNA Game Component that contains the actual game, in the LoadContent method I simply created a new Thread that calls another method ThreadLoad that has all the actual loading. I also have a boolean variable called DoneLoading in the XNA Game Component that is set to true at the end of the ThreadLoad. I am wondering if this is a poor implementation.

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• Cocos2d v2.0 and OpenGL 2.0/1.0: where to start

  - by mm24

  I started developing my very first game 3 months ago using Cocos2d 2.0 for iPhone. I am now in the stage where I'd like to add some cool effects to the bullets and some special weapons (see my waveforms question here). I got a good answer in the cocos2d-iphone forum (see this one). Unfortunately I am a bit paralized now. I don't know if I will be overdoing by learning OpengGL 2.0 or if I should just stick ot the old 1.0. There is a good intro on various tutorial's written in Steffen Itterheims blog (see this post). I would like to add to my game: a blur effect to the bullets (here is a tutorial for OpenGL 1.0) a waveform (see above) some realistic water ripples (here is a nice sample code) So now, given that I don't want to overdo things but at the same time I want to achieve those effects, from where should I start? Should I discard the OpenGL 1.0 tutorials? OR should I use only OpenGL 1.0 code? How can I avoid confusion? I mean, it seems that the compiler recognizes both, but that there are some conflictual calls in some circumnstances, I am fairly sure this has some explanation, is there some reference to this somewhere?

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• Java's Object.wait method with nanoseconds: Is this a joke or am I missing something

  - by Krumia

  I was checking out the Java API source code (Java 8) just out of curiosity. And I found this in java/lang/Object.java. There are three methods named wait: public final native void wait(long timeout): This is the core of all wait methods, which has a native implementation. public final void wait(): Just calls wait(0). And then there is public final void wait(long timeout, int nanos). The JavaDoc for the particular method tells me that, This method is similar to the wait method of one argument, but it allows finer control over the amount of time to wait for a notification before giving up. The amount of real time, measured in nanoseconds, is given by: 1000000*timeout+nanos But this is how the methods achieves "finer control over the amount of time to wait": if (nanos >= 500000 || (nanos != 0 && timeout == 0)) { timeout++; } wait(timeout); So this method basically does a crude rounding up of nanoseconds to milliseconds. Not to mention that anything below 500000ns/0.5ms will be ignored. Is this piece of code bad/unnecessary code, or am I missing some unseen virtue of declaring this method, and it's no argument cousin as the way they are?

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• how to properly implement alpha blending in a complex 3d scene

  - by Gajet

  I know this question might sound a bit easy to answer but It's driving me crazy. There are too many possible situations that a good alpha blending mechanism should handle, and for each Algorithm I can think of there is something missing. these are the methods I've though about so far: first of I though about object sorting by depth, this one simply fails because Objects are not simple shapes, they might have curves and might loop inside each other. so I can't always tell which one is closer to camera. then I thought about sorting triangles but this one also might fail, thought I'm not sure how to implement it there is a rare case that might again cause problem, in which two triangle pass through each other. again no one can tell which one is nearer. the next thing was using depth buffer, at least the main reason we have depth buffer is because of the problems with sorting that I mentioned but now we get another problem. Since objects might be transparent, in a single pixel there might be more than one object visible. So for which Object should I store pixel depth? I then thought maybe I can only store the most front Object depth, and using that determine how should I blend next draw calls at that pixel. But again there was a problem, think about 2 semi transparent planes with a solid plane in middle of them. I was going to render the solid plane at the end, one can see the most distant plane. note that I was going to merge every two planes until there is only one color left for that pixel. Obviously I can use sorting methods too because of the same reasons I've explained above. Finally the only thing I imagine being able to work is to render all objects into different render targets and then sort those layers and display the final output. But this time I don't know how can I implement this algorithm.

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• Writing Java in Java

  - by Skeith

  I have been using Java for several months at work now and am becoming mildly competent in it. The problem I think I am having is that I program C++ in Java . By that I mean I have always used C++ and am treating Java as a simple syntax change instead of appreciate if for its own language. For instance a static variable in C++ is the same as a normal variable in Java as Java is all classes so they maintain there values between function calls. Little things like this are tripping me up constantly as I am self taught. What I want is to invest the time to become a good java programmer not just a C++ programmer that can write in Java. The problem is I do not know how to do this. I have tried reading the Java doc pages but I find them very clinical and hard to understand. So what I am looking for is recommendations on how I can learn to think in Java. Books that teach Java concepts not Java syntax, online tutorials that I can work through that give it a context, established Java traditions/best practices and any other thing that you could recommend.

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• Android - Efficient way to draw tiles in OpenGL ES

  - by Maecky

  Hi, I am trying to write efficient code to render a tile based map in android. I load for each tile the corresponding bitmap (just one time) and then create the according tiles. I have designed a class to do this: public class VertexQuad { private float[] mCoordArr; private float[] mColArr; private float[] mTexCoordArr; private int mTextureName; private static short mCounter = 0; private short mIndex; As you can see, each tile has it's x,y location, a color array, texture coordinates and a texture name. Now, I want to render all my created tiles. To reduce the openGL api calls (I read somewhere that the state changes are costly and therefore I want to keep them to a minimum), I first want to hand ALL the coordinate-arrays, color-arrays and texture-coordinates over to OpenGL. After that I run two for loops. The first one iterates over the textures and binds the texture. The second for loop iterates over all Tiles and puts all tiles with the corresponding texture into an IndexBuffer. After the second for loop has finished, I call gl.gl_drawElements() whith the corresponding index buffer, to draw all tiles with the texture associated. For the next texture I do the same again. Now I run into some problems: Allocating and filling the FloatBuffers at the start of each rendering cycle costs very much time. I just run a test, where i wanted to put 400 coordinates into a FloatBuffer which took me about 200ms. My questions now are: Is there a better way, handling the coordinate and color structures? How is this correctly done, this is obviously not the optimal way? ;) thanks in advance, regards Markus

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• ORM and component-based architecture

  - by EagleBeek

  I have joined an ongoing project, where the team calls their architecture "component-based". The lowest level is one big database. The data access (via ORM) and business layers are combined into various components, which are separated according to business logic. E.g., there's a component for handling bank accounts, one for generating invoices, etc. The higher levels of service contracts and presentation are irrelevant for the question, so I'll omit them here. From my point of view the separation of the data access layer into various components seems counterproductive, because it denies us the relational mapping capabilities of the ORM. E.g., when I want to query all invoices for one customer I have to identify the customer with the "customers" component and then make another call to the "invoices" component to get the invoices for this customer. My impression is that it would be better to leave the data access in one component and separate it from business logic, which may well be cut into various components. Does anybody have some advice? Have I overlooked something?

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• Why is my query soooooo slow?

  - by geekrutherford

  A stored procedure used in our production environment recently became so slow it cause the calling web service to begin timing out. When running the stored procedure in Query Analyzer it took nearly 3 minutes to complete.   The stored procedure itself does little more than create a small bit of dynamic SQL which calls a view with a where clause at the end.   At first the thought was that the query used within the view needed to be optimized. The query is quite long and therefore easy to jump to this conclusion.   Fortunately, after bringing the issue to the attention of a coworker they asked "is there a where clause, and if so, is there an index on the column(s) in it?" I had no idea and quickly said as much. A quick check on the table/column utilized in the where clause indicated indeed there was no index.   Before adding the index, and after admitting I am no SQL wiz, I checked the internet for info on the difference between clustered and non-clustered indexes. I found the following site quite helpful OdeToCode. After adding the non-clustered index on the column, the query that used to take nearly 3 minutes now takes 10 seconds! Ah, if only I'd thought to do this ahead of time!

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• D3DXMatrixDecompose gives different quaternion than D3DXQuaternionRotationMatrix

  - by Fraser

  In trying to solve this problem, I tracked down the problem to the conversion of the rotation matrix to quaternion. In particular, consider the following matrix: -0.02099178 0.9997436 -0.008475631 0 0.995325 0.02009799 -0.09446743 0 0.09427284 0.01041905 0.9954919 0 0 0 0 1 SlimDX.Quaternion.RotationMatrix (which calls D3DXQuaternionRotationMatrix gives a different answer than SlimDX.Matrix.Decompose (which uses D3DXMatrixDecompose). The answers they give (after being normalized) are: X Y Z W Quaternion.RotationMatrix -0.05244324 0.05137424 0.002209336 0.9972991 Matrix.Decompose 0.6989997 0.7135442 -0.03674842 -0.03006023 Which are totally different (note the signs of X, Z, and W are different). Note that these aren't q/-q (two quaternions that represent the same rotation); they face completely different directions. I've noticed that with matrices for rotations very close to that one (successive frames in the animation) that the Matrix.Decompose version gives a solution that flips around wildly and occasionally goes into the desired position, while the Quaternion.RotationMatrix version gives solutions that are stable but go in the wrong direction. This is only for the right arm in my animation -- for the left arm, both functions give the correct solution, which is the same quaternion within error tolerances. This makes me think that there's some sort of numeric instability or weird stuff with signs going on. I tried implementing this and then this, but both gave me a completely incorrect solution (even for the matricies where the SlimDX ones were working correctly) -- maybe the rows and columns are flipped?

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• Enterprise Instrumentation: The 'sessionName' parameter of value 'TraceSession' is not valid

  - by Michael Freidgeim

  We are still using Enterprise Instrumentation(that was created during .Net 1.1 time)In new Server 2008 environment and IIS 7 we have the following errors:The 'sessionName' parameter of value 'TraceSession' is not valid. A trace session of this name does not exist in the TraceSessions configuration file for Windows Trace Session Manager service. Ensure that a session of this name exists in the TraceSessions configuration file and that the Windows Trace Session Manager service is started.   at Microsoft.EnterpriseInstrumentation.EventSinks.TraceEventSink..ctor(IDictionary parameters, EventSource eventSource)   --- End of inner exception stack trace ---   at System.RuntimeMethodHandle._InvokeConstructor(IRuntimeMethodInfo method, Object[] args, SignatureStruct& signature, RuntimeType declaringType)   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)   at Microsoft.EnterpriseInstrumentation.EventSinks.EventSink.CreateNewEventSinks(DataRow[] eventSinkRows, EventSource eventSource)I’ve seen the same errors on development Win7 machines when using IIS. It seems not a problem on Cassini.I've checked ,that Windows Trace Session Manager Service has started and The file C:\Program Files (x86)\Microsoft Enterprise Instrumentation\Bin\Trace Service\TraceSessions.config has corresponding entry<?xml version="1.0" encoding="utf-8" ?><configuration >                <defaultParameters minBuffers="4" maxFileSize="10" maxBuffers="25" bufferSize="20" logFileMode="sequential" flushTimer="3" />                <sessionList>                                 <session name="TraceSession" enabled="false" fileName="C:\Program Files (x86)\Microsoft Enterprise Instrumentation\Bin\Trace Service\Logs\TraceLog.log" />                </sessionList></configuration>The errors still continue, but I was able to disable  the parameter in  eventSink configuration   <eventSink name=" traceSink" description=" Outputs events to the Windows Event Trace." type ="Microsoft.EnterpriseInstrumentation.EventSinks.TraceEventSink ">                <!-- MNF disabled parameter to  avoid error "The 'sessionName' parameter of value 'TraceSession' is not valid"                      < parameter name ="sessionName " value ="TraceSession " />                    -->    </ eventSink>Related old post http://bytes.com/topic/net/answers/104761-enterprise-instrumentation-windows-trace-session-managerOne day I wish to replace all EnterpriseInstrumentation calls with NLog.

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• SSIS Catalog: How to use environment in every type of package execution

  - by Kevin Shyr

  Here is a good blog on how to create a SSIS Catalog and setting up environments.  http://sqlblog.com/blogs/jamie_thomson/archive/2010/11/13/ssis-server-catalogs-environments-environment-variables-in-ssis-in-denali.aspx Here I will summarize 3 ways I know so far to execute a package while using variables set up in SSIS Catalog environment. First way, we have SSIS project having reference to environment, and having one of the project parameter using a value set up in the environment called "Development".  With this set up, you are limited to calling the packages by right-clicking on the packages in the SSIS catalog list and select Execute, but you are free to choose absolute or relative path of the environment. The following screenshot shows the 2 available paths to your SSIS environments.  Personally, I use absolute path because of Option 3, just to keep everything simple for myself. The second option is to call through SQL Job.  This does require you to configure your project to already reference an environment and use its variable.  When a job step is set up, the configuration part will require you to select that reference again.  This is more useful when you want to automate the same package that needs to be run in different environments. The third option is the most important to me as I have a SSIS framework that calls hundreds of packages.  The main part of the stored procedure is in this post (http://geekswithblogs.net/LifeLongTechie/archive/2012/11/14/time-to-stop-using-ldquoexecute-package-taskrdquondash-a-way-to.aspx).  But the top part had to be modified to include the logic to use environment reference. CREATE PROCEDURE [AUDIT].[LaunchPackageExecutionInSSISCatalog] @PackageName NVARCHAR(255) , @ProjectFolder NVARCHAR(255) , @ProjectName NVARCHAR(255) , @AuditKey INT , @DisableNotification BIT , @PackageExecutionLogID INT , @EnvironmentName NVARCHAR(128) = NULL , @Use32BitRunTime BIT = FALSE AS BEGIN TRY DECLARE @execution_id BIGINT = 0; -- Create a package execution IF @EnvironmentName IS NULL BEGIN   EXEC [SSISDB].[catalog].[create_execution]     @package_name=@PackageName,     @execution_id=@execution_id OUTPUT,     @folder_name=@ProjectFolder,     @project_name=@ProjectName,     @use32bitruntime=@Use32BitRunTime; END ELSE BEGIN   DECLARE @EnvironmentID AS INT   SELECT @EnvironmentID = [reference_id]    FROM SSISDB.[internal].[environment_references] WITH(NOLOCK)    WHERE [environment_name] = @EnvironmentName     AND [environment_folder_name] = @ProjectFolder      EXEC [SSISDB].[catalog].[create_execution]     @package_name=@PackageName,     @execution_id=@execution_id OUTPUT,     @folder_name=@ProjectFolder,     @project_name=@ProjectName,     @reference_id=@EnvironmentID,     @use32bitruntime=@Use32BitRunTime; END

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• Versioning APIs

  - by Sharon

  Suppose that you have a large project supported by an API base. The project also ships a public API that end(ish) users can use. Sometimes you need to make changes to the API base that supports your project. For example, you need to add a feature that needs an API change, a new method, or requires altering of one of the objects, or the format of one of those objects, passed to or from the API. Assuming that you are also using these objects in your public API, the public objects will also change any time you do this, which is undesirable as your clients may rely on the API objects remaining identical for their parsing code to work. (cough C++ WSDL clients...) So one potential solution is to version the API. But when we say "version" the API, it sounds like this also must mean to version the API objects as well as well as providing duplicate method calls for each changed method signature. So I would then have a plain old clr object for each version of my api, which again seems undesirable. And even if I do this, I surely won't be building each object from scratch as that would end up with vast amounts of duplicated code. Rather, the API is likely to extend the private objects we are using for our base API, but then we run into the same problem because added properties would also be available in the public API when they are not supposed to be. So what is some sanity that is usually applied to this situation? I know many public services such as Git for Windows maintains a versioned API, but I'm having trouble imagining an architecture that supports this without vast amounts of duplicate code covering the various versioned methods and input/output objects. I'm aware that processes such as semantic versioning attempt to put some sanity on when public API breaks should occur. The problem is more that it seems like many or most changes require breaking the public API if the objects aren't more separated, but I don't see a good way to do that without duplicating code.

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• Threading models when talking to hardware devices

  - by Fuzz

  When writing an interface to hardware over a communication bus, communications timing can sometimes be critical to the operation of a device. As such, it is common for developers to spin up new threads to handle communications. It can also be a terrible idea to have a whole bunch of threads in your system, an in the case that you have multiple hardware devices you may have many many threads that are out of control of the main application. Certainly it can be common to have two threads per device, one for reading and one for writing. I am trying to determine the pros and cons of the two different models I can think of, and would love the help of the Programmers community. Each device instance gets handles it's own threads (or shares a thread for a communication device). A thread may exist for writing, and one for reading. Requested writes to a device from the API are buffered and worked on by the writer thread. The read thread exists in the case of blocking communications, and uses call backs to pass read data to the application. Timing of communications can be handled by the communications thread. Devices aren't given their own threads. Instead read and write requests are queued/buffered. The application then calls a "DoWork" function on the interface and allows all read and writes to take place and fire their callbacks. Timing is handled by the application, and the driver can request to be called at a given specific frequency. Pros for Item 1 include finer grain control of timing at the communication level at the expense of having control of whats going on at the higher level application level (which for a real time system, can be terrible). Pros for Item 2 include better control over the timing of the entire system for the application, at the expense of allowing each driver to handle it's own business. If anyone has experience with these scenarios, I'd love to hear some ideas on the approaches used.

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• Javascript MVC in principle

  - by Michael

  Suppose I want to implement MVC in JavaScript. I am not asking about MVC frameworks. I am asking how to build it in principle. Let's consider a search page of an e-commerce site, which works s follows: User chooses a product and its attributes and press a "search" button. Application sends the search request to the server, receives a list of products. Application displays the list in the web page. I think the Model holds a Query and list of Product objects and "publishes" such events as "query updated", "list of products updated", etc. The Model is not aware of DOM and server, or course. View holds the entire DOM tree and "subscribes" to the Model events to update the DOM. Besides, it "publishes" such events as "user chose a product", "user pressed the search button" etc. Controller does not hold any data. It "subscribes" to the View events, calls the server and updates the Model. Does it make sense?

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• What type of pattern would be used in this case

  - by Admiral Kunkka

  I want to know how to tackle this type of scenario. We are building a person's background, from scratch, and I want to know, conceptually, how to proceed with a secure object pattern in both design and execution... I've been reading on Factory patterns, Model-View-Controller types, Dependency injection, Singleton approaches... and I can't seem to grasp or 'fit' these types of designs decisions into what I'm trying to do.. First and foremost, I started with having a big jack-of-all-trades class, then I read some more, and some tips were to make sure your classes only have a single purpose.. which makes sense and I started breaking down certain things into other classes. Okay, cool. Now I'm looking at dependency injection and kind of didn't really know what's going on. Example/insight of what kind of heirarchy I need to accomplish... class Person needs to access and build from a multitude of different classes. class Culture needs to access a sub-class for culture benefits class Social needs to access class Culture, and other sub-classes class Birth needs to access Social, Culture, and other sub-classes class Childhood/Adolescence/Adulthood need to access everything. Also, depending on different rolls, this class heirarchy needs to create multiple people as well, such as Family, and their backgrounds using some, if not all, of these same classes. Think of it as a people generator, all random, with backgrounds and things that happen to them. Ageing, death of loved ones, military careers, e.t.c. Most of the generation is done randomly, making calls to a mt_rand function to pick from most of the selections inside the classes, guaranteeing the data to be absolutely random. I have most of the bulk-data down, and was looking for some insight from fellow programmers, what do you think?

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• How to convince a client to switch to a framework *now*; also examples of great, large-scale php applications.

  - by cbrandolino

  Hi everybody. I'm about to start working on a very ambitious project that, in my opinion, has some great potential for what concerns the basic concept and the implementation ideas (implementation as in how this ideas will be implemented, not as in programming). The state of the code right now is unluckily subpar. It's vanilla php, no framework, no separation between application and visualization logic. It's been done mostly by amateur students (I know great amateur/student programmers, don't get me wrong: this was not the case though). The clients are really great, and they know the system won't scale and needs a redesign. The problem is, they would like to launch a beta ASAP and then think of rebuilding. Since just the basic functionalities are present now, I suggested it would be a great idea if we (we're a three-people shop, all very proficient) ported that code to some framework (we like CodeIgniter) before launching. We would reasonably be able to do that in < 10 days. Problem is, they don't think php would be a valid long-term solution anyway, so they would prefer to just let it be and fix the bugs for now (there's quite a bit) and then directly switch to some ruby/python based system. Porting to CI now will make future improvements incredibly easier, the current code more secure, changing the style - still being discussed with the designers - a breeze (reminder: there are database calls in template files right now); the biggest obstacle is the lack of trust in php as a valid, scalable technology. So well, I need some examples of great php applications (apart from facebook) and some suggestions on how to try to convince them to port soon. Again, they're great people - it's not like they would like ruby cause it's so hot right now; they just don't trust php since us cool programmers like bashing it, I suppose, but I'm sure going on like this for even one more day would be a mistake. Also, we have some weight in the decision process.

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• Understanding Application binary interface (ABI)

  - by Tim

  I am trying to understand the concept of Application binary interface (ABI). From The Linux Kernel Primer: An ABI is a set of conventions that allows a linker to combine separately compiled modules into one unit without recompilation, such as calling conventions, machine interface, and operating-system interface. Among other things, an ABI defines the binary interface between these units. ... The benefits of conforming to an ABI are that it allows linking object files compiled by different compilers. From Wikipedia: an application binary interface (ABI) describes the low-level interface between an application (or any type of) program and the operating system or another application. ABIs cover details such as data type, size, and alignment; the calling convention, which controls how functions' arguments are passed and return values retrieved; the system call numbers and how an application should make system calls to the operating system; and in the case of a complete operating system ABI, the binary format of object files, program libraries and so on. I was wondering whether ABI depends on both the instruction set and the OS. Are the two all that ABI depends on? What kinds of role does ABI play in different stages of compilation: preprocessing, conversion of code from C to Assembly, conversion of code from Assembly to Machine code, and linking? From the first quote above, it seems to me that ABI is needed for only linking stage, not the other stages. Is it correct? When is ABI needed to be considered? Is ABI needed to be considered during programming in C, Assembly or other languages? If yes, how are ABI and API different? Or is it only for linker or compiler? Is ABI specified for/in machine code, Assembly language, and/or of C?

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• Why would Java app make RPC call to itself?

  - by amphibient

  I am working with a multithreaded homegrown multi-module app in my new job. We use the the Thrift protocol to communicate RPC calls between different stand-alone applications in a distributed system. One of them listens on multiple ports and I just noticed that it actually makes an RPC call to itself from one thread invoked from one socket it listens to (web service call) to another port within the same app. I verified that it could accomplish the same thing if it just went and directly called the method that the remote procedure ultimately invokes as it is all within the same application, same JVM. To make it even more mysterious, the call is completely synchronous, i.e. no callbacks involved. The first thread totally sits and waits until it makes a call across the wire to itself and comes back. Now, I am perplexed why anybody would do it this way. It seems like calling somebody on the phone that sits in the same room as you do. Can anybody provide an explanation why the developer before me would come up with the above mentioned model? Maybe there is a reason and I am missing something.

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• Weird 302 Redirects in Windows Azure

  - by Your DisplayName here!

  In IdentityServer I don’t use Forms Authentication but the session facility from WIF. That also means that I implemented my own redirect logic to a login page when needed. To achieve that I turned off the built-in authentication (authenticationMode="none") and added an Application_EndRequest handler that checks for 401s and does the redirect to my sign in route. The redirect only happens for web pages and not for web services. This all works fine in local IIS – but in the Azure Compute Emulator and Windows Azure many of my tests are failing and I suddenly see 302 status codes where I expected 401s (the web service calls). After some debugging kung-fu and enabling FREB I found out, that there is still the Forms Authentication module in effect turning 401s into 302s. My EndRequest handler never sees a 401 (despite turning forms auth off in config)! Not sure what’s going on (I suspect some inherited configuration that gets in my way here). Even if it shouldn’t be necessary, an explicit removal of the forms auth module from the module list fixed it, and I now have the same behavior in local IIS and Windows Azure. strange. <modules>   <remove name="FormsAuthentication" /> </modules> HTH Update: Brock ran into the same issue, and found the real reason. Read here.

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• Recursion in F#

  - by MarkPearl

  Things are slowly coming together – I was able to look at a bit of F# code and intuitively know what it was going to do (yay)… So today I saw a blog post by Bob Palmer on Fibonacci numbers in F# which inspired me to look at bit into recursion. First the C# example… class Program { public static void CountDown(int n) { switch (n) { case 0: Console.WriteLine("End of Count"); break; default: Console.WriteLine(n); CountDown(n-1); break; } } static void Main(string[] args) { CountDown(10); Console.ReadLine(); } }   In F#, the equivalent would look something like this… open System let rec CountDown n = match n with | 0 -> Console.WriteLine("End of Count"); | n -> Console.WriteLine(n); CountDown (n-1); CountDown 10 Console.ReadLine()   Pretty simple stuff. With F# you when making recursive calls you need to explicitly declare that the function is recursive with the “rec” keyword. Otherwise the code is pretty easy to read and self explanatory.

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• Code execution time out occationally

  - by Athul k Surendran

  I am working on an e-commerce website. There is a case where I need to fetch the whole data in database through third-party API and send it to an indexing engine. This third-party API has many functions like getproducts, getproductprice, etc., and each of that functions will return the data in XML format. From there I will take charge, I will use various API calls and will handle the XML data with XSLT. And will write to a CSV file. This file will be uploaded to an Indexing engine. Right now I have details of 8000 products to feed the engine, and almost all time the this process takes about 15 min to complete, and sometimes fails. I can't find a better solution for this. I am thinking about handling the XML data in C# itself and get rid of XSLT. As I think, XSLT is far slower than C#. Is it a good Idea? Or what else I can do to solve this issue?

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• Dynamic (C# 4.0) &amp; Var in a nutshell.

  - by mbcrump

  A Var is static typed - the compiler and runtime know the type. This can be used to save some keystrokes. The following are identical. Code Snippet var mike = "var demo"; Console.WriteLine(mike.GetType());  //Returns System.String   string mike2 = "string Demo"; Console.WriteLine(mike2.GetType()); //Returns System.String A dynamic behaves like an object, but with dynamic dispatch. The compiler doesn’t know anything about it at compile time. Code Snippet dynamic duo = "dynamic duo"; Console.WriteLine(duo.GetType()); //System.String //duo.BlowUp(); //A dynamic type does not know if this exist until run-time. Console.ReadLine(); To further illustrate this point, the dynamic type called “duo” calls a method that does not exist called BlowUp(). As you can see from the screenshot below, the compiler is reporting no errors even though BlowUp() does not exist. The program will compile fine. It will however throw a runtimebinder exception after it hits that line of code in runtime. Let’s try the same thing with a Var. This time, we get a compiler error that says BlowUp() does not exist. This program will not compile until we add a BlowUp() method.  I hope this helps with your understand of the two. If not, then drop me a line and I’ll be glad to answer it.

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