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• Checking server load with PHP and taking appropriate action

  - by teehoo

  Hi, I'm creating a project in which a server receives operations from clients to apply to a local server document. The server and client both share the same document and therefore each message the client sends contains an MD5 hash, which the server compares to after generating its own hash to ensure the server and client documents are synchronized. My question is, if the server is overloaded, could I somehow detect this in PHP, which would in turn let me decide whether I want to execute the hash generation function or not? Perhaps in the scenario defined, this is not a perfect use-case, but I'm interested in this approach in general.

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• How does git save space and is fast at the same time?

  - by eSKay

  I just saw the first git tutorial at http://blip.tv/play/Aeu2CAI How does git store all the versions of all the files and still be more economical in space than subversion which saves only the latest version of the code? I know this can be done using compression but that would be at the cost of speed, but this also says that git is much faster (though where is gains the max is the fact that most of its operations are offline). So, my guess is that git compresses data extensively it is still faster because uncompression + work is still faster than network_fetch + work Am I correct? even close?

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• Implement a simple class in your favorite language.

  - by Oscar Reyes

  I'm doing this to learn syntax of different programming languages. So, how would you defined the following class along with with it's operations in your favorite programming language? Image generated by http://yuml.me/ And a main method or equivalent to invoke it: For instance, for Java it would be: ... public static void main( String [] args ) { Fraction f = new Fraction(); f.numerator( 2 ); f.denominator( 5 ); f.print(); } ....

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• How should I port this Prototype to JQuery?

  - by blu

  There is currently this Prototype code that does a PUT: new Ajax.Request(someUrl, { method: 'put', parameters: { 'foo': bar }, onSuccess: function(response) { } .bind(this) }); I found this post but the solution uses an extra parameter supported by RoR, however I am targeting an ASP.NET backend. I searched a bit and found that not all browsers support PUT operations so apparently this could fail in certain browsers? This is already in prod, so a direct port would be fine for now I suppose. As an aside, what is the deal with the bind(this) in the onSuccess function?

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• Domain Model and Contracts

  - by devoured elysium

  I am modelling a DVD Rental Store: A Client gives its clientNumber to the System. The System checks whenever the given clientNumber is valid. The Client gives the name of the DVD he wants to rent. ... n. ...I will later have to form an association between a new instance of "RentDVD" class concept to the current Client c. My Domain Model is something like: I've made the Contract for the first and second operations as: Preconditions: none Postconditions: there exists a Client c such that c.clientNumber = clientNumber. Now, I don't know if I should form an association between this Client c and the DVDStore(that I intend to use as front-end). If I don't make the association, how will I later be able to "reference" this same Client? Should I be making an association between Client and a different concept? Thanks

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• WeakReferences are not freed in embedded OS

  - by Carsten König

  I've got a strange behavior here: I get a massive memory leak in production running a WPF application that runs on a DLOG-Terminal (Windows Embedded Standard SP1) that behaves perfectly fine if I run it localy on a normal desktop (Win7 prof.) After many unsucessful attempts to find any problem I put one of those directly beside my monitor, installed the ANTs MemoryProfiler and did one hour test run simulating user operations on both the terminal and my development PC. Result is, that due to some strange reasons the embedded system piles up a huge amount of WeakReference and EffectiveValueEntry[] Objects. Here are are some pictures: Development (PC): And the terminal: Just look at the class list... Has anyone seen something like this before and are there known solutions to this? Where can I get help? (PS the terminals where installed with images prepared for .net4)

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• reading unformatted fortran file in matlab - which precision?

  - by Griff

  I have just written out a file: real*8 :: vol_cel real*8, dimension(256,256,256) :: dense [... some operations] open(unit=8,file=fname,form="unformatted") write(8)dense(:,:,:)/vol_cell close(8) dense and vol_cell are real*8 variables. My code to read this in in Matlab: fid = fopen(fname,'r'); mesh_raw = fread(fid,256*256*256,'double'); fclose(fid); The min and max values clearly show that it is not reading it in correctly (Min is 0 and max is a largish positive real*8). min = 3.3622e+38 max = -3.3661e+38 What precision do I need to set in Matlab to make it read in the unformatted Fortran file? A somewhat related question: This Matlab code I am using reads binary files OK but not unformatted files. Though I am generating this new data on my Mac OSX using gfortran. It doesn't recognize form="binary" so I can't do it that way. Do I need to add some library?

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• Tweak Data in Doctrine Migration (say, by running some arbitrary queries)

  - by timdev

  I've got a migration that creates a couple of columns that act as foreign keys. In particular, I'm adding a creator_id and owner_id column to a model. These foreign keys indicate who created, and who currently owns, a particular kind of domain object. Users are managed by sfDoctrineGuardPlugin. What I'd like to do, for the purpose of the migration, is look up the (active) user with the lowest id, and default creator_id/owner_id to that. I don't see any particularly obvious/proper way to run arbitrary operations on the database during a migration. Does anyone know how?

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• Looking for solution to persist rows sequence in a database table that allow efficient reordering at

  - by Chau Chee Yang

  I have a database table. There is a field name "Sequence" that indicate sequence when user presents the rows in report or grid visually. When the rows are retrieved and presented in a grid, there are few UI gadget that allow user to reorder the rows arbitrary. The new sequence will be persist in database table when user commit the changes. Here are some UI operations: Move to first Move to last Move up 1 row Move down 1 row multi-select rows and move up or down multi-select rows and drag to new position For operation like "Move to first" or "Move to Last", it usually involve many rows and the sequence those rows would need to be updated accordingly. This may not be efficient enough at runtime. It is a common practice to use INTEGER as sequence's data type. Other solution is using "DOUBLE" or "FLOAT" that could overcome the mass update of row sequence but we will face problem if we reach the limit of precision.

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• Explain ML type inference to a C++ programmer

  - by Tsubasa Gomamoto

  How does ML perform the type inference in the following function definition: let add a b = a + b Is it like C++ templates where no type-checking is performed until the point of template instantiation after which if the type supports the necessary operations, the function works or else a compilation error is thrown ? i.e. for example, the following function template template <typename NumType> NumType add(NumType a, NumType b) { return a + b; } will work for add<int>(23, 11); but won't work for add<ostream>(cout, fout); Is what I am guessing is correct or ML type inference works differently? PS: Sorry for my poor English; it's not my native language.

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• Comparison of collection datatypes in C#

  - by Joel in Gö

  Does anyone know of a good overview of the different C# collection types? I am looking for something showing which basic operations such as Add, Remove, RemoveLast etc. are supported, and giving the relative performance. It would be particularly interesting for the various generic classes - and even better if it showed eg. if there is a difference in performance between a List<T> where T is a class and one where T is a struct. A start would be a nice cheat-sheet for the abstract data structures, comparing Linked Lists, Hash Tables etc. etc. Thanks!

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• Best practice for partial updates in a RESTful service

  - by magiconair

  I am writing a RESTful service for a customer management system and I am trying to find the best practice for updating records partially. For example, I want the caller to be able to read the full record with a GET request. But for updating it only certain operations on the record are allowed, like change the status from ENABLED to DISABLED. (I have more complex scenarios than this) I don't want the caller to submit the entire record with just the updated field for security reasons (it also feels like overkill). Is there a recommended way of constructing the URIs? Do I use GET, POST, PUT or is there no agreed way of doing these kind of things? When reading the REST books RPC style calls seem to be frowned upon. Thanks Frank

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• Why might different computers calculate different arithmetic results in VB.NET?

  - by Eyal

  I have some software written in VB.NET that performs a lot of calculations, mostly extracting jpegs to bitmaps and computing calculations on the pixels like convolutions and matrix multiplication. Different computers are giving me different results despite having identical inputs. What might be the reason? Edit: I can't provide the algorithm because it's proprietary but I can provide all the relevant operations: ULong \ ULong (Turuncating division) Bitmap.Load("filename.bmp') (Load a bitmap into memory) Bitmap.GetPixel(Integer, Integer) (Get a pixel's brightness) Double + Double Double * Double Math.Sqrt(Double) Math.PI Math.Cos(Double) ULong - ULong ULong * ULong ULong << ULong List.OrderBy(Of Double)(Func) Hmm... Is it possible that OrderBy is using a non-stable QuickSort and that QuickSort is using a random pivot? Edit: Just tested, nope. The sort is stable.

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• Genetic programming in c++, library suggestions?

  - by shuttle87

  I'm looking to add some genetic algorithms to an Operations research project I have been involved in. Currently we have a program that aids in optimizing some scheduling and we want to add in some heuristics in the form of genetic algorithms. Are there any good libraries for generic genetic programming/algorithms in c++? Or would you recommend I just code my own? I should add that while I am not new to c++ I am fairly new to doing this sort of mathematical optimization work in c++ as the group I worked with previously had tended to use a proprietary optimization package. We have a fitness function that is fairly computationally intensive to evaluate and we have a cluster to run this on so parallelized code is highly desirable. So is c++ a good language for this? If not please recommend some other ones as I am willing to learn another language if it makes life easier. thanks!

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• Best Ruby ORM for Wrapping around Legacy SQL Server Database?

  - by Technocrat

  Hi. I found this answer and it sounds like almost exactly what I'm doing. I have heard mixed answers about whether or not datamapper can support SQL Server through dataobjects. Basically, we have an app that uses a consistently structured database, consistently named tables, etc in SQL Server. We're making all kinds of tools and stuff that have to interact with it, some of them remotely and so I decided that we need to create some common, simple access point to do read/write operations on the SQL Server app since it's API is all C# and other things I despise. Now my question is if anyone has any examples or projects they know of where a ruby ORM can essentially create models for another application's legacy database by defining the conventions of each model's pkeys, fkeys, table names, etc. Sequel is the only ORM I've used with SQL Server but never to do anything quite like this. Any suggestions?

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• Is this an UITableView -beginUpdates documentation error?

  - by mystify

  I can't wrap my head around what they tried to say here in the docs for -beginUpdate: Call this method if you want subsequent insertions, deletion, and selection operations (for example, cellForRowAtIndexPath: and indexPathsForVisibleRows) to be animated simultaneously. Let's see... cellForRowAtIndexPath: and indexPathsForVisibleRows are both GETTER methods. They do not update anything and do not change anything. So why should I call -beginUpdates before calling these? And what's animated regarding these? Well, nothing, huh? Just want to make sure this is really an error in the docs and I didn't miss something.

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• Resetting Objects vs. Constructing New Objects

  - by byronh

  Is it considered better practice and/or more efficient to create a 'reset' function for a particular object that clears/defaults all the necessary member variables to allow for further operations, or to simply construct a new object from outside? I've seen both methods employed a lot, but I can't decide which one is better. Of course, for classes that represent database connections, you'd have to use a reset method rather than constructing a new one resulting in needless connecting/disconnecting, but I'm talking more in terms of abstraction classes. Can anyone give me some real-world examples of when to use each method? In my particular case I'm thinking mostly in terms of ORM or the Model in MVC. For example, if I would want to retrieve a bunch of database objects for display and modify them in one operation.

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• Working with multiple input and output files in Python

  - by Morlock

  I need to open multiple files (2 input and 2 output files), do complex manipulations on the lines from input files and then append results at the end of 2 output files. I am currently using the following approach: in_1 = open(input_1) in_2 = open(input_2) out_1 = open(output_1, "w") out_2 = open(output_2, "w") # Read one line from each 'in_' file # Do many operations on the DNA sequences included in the input files # Append one line to each 'out_' file in_1.close() in_2.close() out_1.close() out_2.close() The files are huge (each potentially approaching 1Go, that is why I am reading through these input files one at a time. I am guessing that this is not a very Pythonic way to do things. :) Would using the following form good? with open("file1") as f1: with open("file2") as f2: # etc. If yes, could I do it while avoiding the highly indented code that would result? Thanks for the insights!

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• ASP.NET MVC Generic Controllers and Spring.NET

  - by Jason

  Hello, I am creating an application using ASP.NET MVC (2) and Spring.NET. Since most of my Controller implementations just implement the similar CRUD operations, I would like to just create a single Generic controller, as explained here: http://stackoverflow.com/questions/848904/in-asp-net-mvc-is-it-possible-to-make-a-generic-controller However, the above example doesn't take DI frameworks into consideration. What I'm thinking is to create this (warning: this is an ugly mass of code I need help with): public SpringGenericControllerFactory : DefaultControllerFactory { public IController CreateController(RequestContext requestContext, string controllerName) { // Determine the controller type to return Type controllerType = Type.GetType("MyController").MakeGenericType(Type.GetType(controllerName)); // Return the controller return Activator.CreateInstance(controllerType) as IController; } } The entries in objects.xml would look something like this: <object id="controllerFactory" type="Application.Controllers.SpringGenericControllerFactory" /> <object id="DepartmentController" factory-method="CreateController" factory-object="controllerFactory" /> Can anyone pick through this and offer advice?

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• Interpreters: How much simplification?

  - by Ray

  In my interpreter, code like the following x=(y+4)*z echo x parses and "optimizes" down to four single operations performed by the interpreter, pretty much assembly-like: add 4 to y multiply <last operation result> with z set x to <last operation result> echo x In modern interpreters (for example: CPython, Ruby, PHP), how simplified are the "opcodes" for which are in end-effect run by the interpreter? Could I achieve better performance when trying to keep the structures and commands for the interpreter more complex and high-level? That would be surely a lot harder, or?

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• Upsert - Efficient Update or Insert in VB.Net, SQL Server

  - by HK1

  I'm trying to understand how to streamline the process of inserting a record if none exists or updating a record if it already exists. I'm not using stored procedures, although maybe that would be the most efficient way of doing this. The actual scenario in which this is necessary is saving a user preference/setting to my SettingsUser table. In MS Access I would typically pull a DAO recordset looking for the specified setting. If the recordset comes back empty then I know I need to add a new record which I can do with the same recordset object. On the other hand, if it isn't empty, I can just update the setting's value right away. In theory, this is only two database operations. What is the recommended way of doing this in .NET?

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• App engine downtime

  - by DutrowLLC

  I've noticed that google app engine seems to have a fair amount of downtime where they place the datastore into read-only mode. Frequently this downtime is in the middle of the day. Is this something that is happening only during early development, or is this something that I can expect to be always be occurring? I've developing an application that helps small businesses handle their operations. One thing that it does is take appointments, another is route phone calls. I'd like some suggestions on how to handle times when the datastore is in read-only such as: What if our client is on the phone with the customer and is taking down an appointment and the datastore is in read-only? It would not be acceptable to ask the client to come back later to save, especially if its in the middle of the day. What if there is an incoming call and the application can not store the record or properly route the call due to database writes being unavailable? How are these types of issues normally handled?

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• What is faster? Drawing or Compositing?

  - by mystify

  I make extensive use of -drawRect: to do some nice animations. A timer tries to fire 30 times per second with -setNeedsDisplay, but it feels like just 20 times. Also I can't use -setNeedsDisplayInRect: because the animation covers the entire thing. Would it help to take some of those drawing operations out of -drawRect: and move them to a subview? -drawRect has to do less then, but instead the OS will have more work with compositing views. Is there a rule of thumb which one is more worse? I remember from an apple text that they claimed Core Animation doesn't redraw during animation. So is that their secret of speed? Using subviews in animations?

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• Prolog - Finding the current directory, relative directory for 'tell' predicate

  - by Bharat

  I'm having trouble trying to figure out how to get prolog to spit out a text file where I want it to. I'm currently doing a bunch of operations and then using tell('output.txt') to record the output. Now the problem is that when I do this, it creates this file in the SWI \bin\ folder. I was wondering if there's a way to make it create this file in the directory containing the actual .pl file. So even if the file was moved (and it will be), the text file gets created right where the source file is. Long story short, is there a way to get the location of the source file once the source file has been consulted? Many Thanks!

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• Strategies for generating Zend Cache Keys

  - by emeraldjava

  ATM i'm manually generating a cache key based on the method name and parameters, then follow to the normal cache pattern. This is all done in the Controller and i'm calling a model class that 'extends Zend_Db_Table_Abstract'. public function indexAction() { $cache = Zend_Registry::get('cache'); $individualleaguekey = sprintf("getIndividualLeague_%d_%s",$leagueid,$division->code); if(!$leaguetable = $cache->load($individualleaguekey)) { $table = new Model_DbTable_Raceresult(); $leaguetable = $table->getIndividualLeague($leagueid,$division,$races); $cache->save($leaguetable, $individualleaguekey); } $this->view->leaguetable = $leaguetable; .... I want to avoid the duplication of parameters to the cache creation method and also to the model method, so i'm thinking of moving the caching logic away from my controller class and into model class packaged in './model/DbTable', but this seems incorrect since the DB model should only handle SQL operations. Any suggestions on how i can implement a clean patterned solution?

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