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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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• C# - Dictionary with generic array as value

  - by alhazen

  In my class, I want to use a dictionary with the following declaration: Dictionary<string, T[]> Since the operations of my class are exactly the same for all generic types, I do not wish to define my class as generic (which means I would have to create a separate instance of my class for each generic type I insert into the dictionary ?). One alternative I'm attempting is to use Dictionary<string, object> instead: public void Add<T>(string str, T value) { // Assuming key already exists var array = (T[]) dictionary[str]; array[0] = value; } However, when iterating over the dictionary, how do I cast the object value back to an array ? foreach(string strKey in dictionary.Keys) { var array = (T[]) dictionary[strKey]; // How to cast here ? //... array[0] = default(T); } Thanks.

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• C++ overloading virtual = operator

  - by taz

  Hello, here is the code for my question: class ICommon { public: virtual ICommon& operator=(const ICommon & p)const=0; }; class CSpecial : public ICommon { public: CSpecial& operator=(const CSpecial & cs) { //custom operations return *this; } }; CSpecial obj; Basically: I want the interface ICommon to force it's descendants to implement = operator but don't want to have any typecasts in the implementation. The compiler says "can't instantiate an abstract class. Any help/advice will be appreciated.

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• Loading a DB table into nested dictionaries in Python

  - by Hossein

  Hi, I have a table in MySql DB which I want to load it to a dictionary in python. the table columns is as follows: id,url,tag,tagCount tagCount is the number of times that a tag has been repeated for a certain url. So in that case I need a nested dictionary, in other words a dictionary of dictionary, to load this table. Because each url have several tags for which there are different tagCounts.the code that I used is this:( the whole table is about 22,000 records ) cursor.execute( ''' SELECT url,tag,tagCount FROM wtp ''') urlTagCount = cursor.fetchall() d = defaultdict(defaultdict) for url,tag,tagCount in urlTagCount: d[url][tag]=tagCount print d first of all I want to know if this is correct.. and if it is why it takes so much time? Is there any faster solutions? I am loading this table into memory to have fast access to get rid of the hassle of slow database operations, but with this slow speed it has become a bottleneck itself, it is even much slower than DB access. and anyone help? thanks

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• Can this loop be sped up in pure Python?

  - by Noctis Skytower

  I was trying out an experiment with Python, trying to find out how many times it could add one to an integer in one minute's time. Assuming two computers are the same except for the speed of the CPUs, this should give an estimate of how fast some CPU operations may take for the computer in question. The code below is an example of a test designed to fulfill the requirements given above. This version is about 20% faster than the first attempt and 150% faster than the third attempt. Can anyone make any suggestions as to how to get the most additions in a minute's time span? Higher numbers are desireable. EDIT: This experiment is being written in Python 3.1 and is 15% faster than the fourth speed-up attempt. def start(seconds): import time, _thread def stop(seconds, signal): time.sleep(seconds) signal.pop() total, signal = 0, [None] _thread.start_new_thread(stop, (seconds, signal)) while signal: total += 1 return total if __name__ == '__main__': print('Testing the CPU speed ...') print('Relative speed:', start(60))

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• How to manage db connections on server?

  - by simpatico

  I have a severe problem with my database connection in my web application. Since I use a single database connection for the whole application from singleton Database class, if i try concurrent db operations (two users) the database rollsback the transactions. This is my static method used: All threads/servlets call static Database.doSomething(...) methods, which in turn call the the below method. private static /* synchronized*/ Connection getConnection(final boolean autoCommit) throws SQLException { if (con == null) { con = new MyRegistrationBean().getConnection(); } con.setAutoCommit(true); //TODO return con; } What's the recommended way to manage this db connection/s I have, so that I don't incurr in the same problem.

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• Convert String value format of YYYYMMDDHHMMSS to C# DateTime

  - by SARAVAN

  I have a need to convert a string value in the form "YYYYMMDDHHMMSS" to a DateTime. But not sure on how, may be a DateTime.Tryparse can be used to make this happen. Or is there any other way to do it. I can do this using some string operations to take "YYYYMMDD" alone, convert to a datetime and then add HH, MM, SS separately to that DateTime. But is there any DateTime.TryParse() methods that I can use in one line to convert a "YYYYMMDDHHMMSS" format string value to a DateTime value?

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• IHTMLTxtRange.execCommand("Copy",false,null) fails due to IE settings

  - by srirambalaji-s

  We have a .Net application that is used for editing/rendering customized HTML documents. It is hosted in IE using the AxSHDocVw.AxWebBrowser controls. We proceed with navigating to "about:blank" page initially then we change the Document by writing our custom values into it. The problem we are facing is the call to IHTMLTxtRange.execCommand("Copy",false,null) is failing if we don't enable the IE Security Settings in the Internet Security zone (Scripting-Allow Programmatic Access to Clipboard ). In order to bypass the security setting ,I tried to point to a local html file initially while navigating. But this fails as soon as I modify the Document. I want to use the IHTMLTxtRange.execCommand("Copy",false,null) command so that I can customize our Copy/Paste operations. Is there any other way I can do this. Please share your ideas inorder to overcome this situation. Thanks. Sriram

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• iPhone: One Object, One Thread

  - by GingerBreadMane

  On the iPhone, I would like to do some operations on an image in a separate thread. Rather than dealing with semiphores, locking, etc., I'd like to use the 'One Object, One Thread' method of safely writing this concurrent operation. I'm not sure what is the correct way to copy my object into a new thread so that the object is not accessed in the main thread. Do I use the 'copy' method? If so, do I do this before the thread or inside the thread? ... -(void)someMethod{ UIImage *myImage; [NSThread detachNewThreadSelector:@selector(getRotatedImage:) toTarget:self withObject:myImage]; } -(void)getRotatedImage:(UIImage *)image{ ... ... UIImage *copiedImage = [image copy]; ... ... }

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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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• swing: event listener support class

  - by Jason S

  Is there any preexisting class that helps support add/remove EventListener operations? (kind of like PropertyChangeSupport) I'm trying to partition my code into a model and view in Java. I have some data that arrives erratically, and would like the model to support some kind of EventListener so that a view can subscribe to changes in the model. The data is numerous + complicated enough that I don't want to have to do the whole fine-grained Javabeans property change support; rather I would just like to allow notification that the model has changed in a coarse way. how can I best do this?

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• What data is actually stored in a B-tree database in CouchDB?

  - by Andrey Vlasovskikh

  I'm wondering what is actually stored in a CouchDB database B-tree? The CouchDB: The Definitive Guide tells that a database B-tree is used for append-only operations and that a database is stored in a single B-tree (besides per-view B-trees). So I guess the data items that are appended to the database file are revisions of documents, not the whole documents: +---------|### ... | | +------|###|------+ ... ---+ | | | | +------+ +------+ +------+ +------+ | doc1 | | doc2 | | doc1 | ... | doc1 | | rev1 | | rev1 | | rev2 | | rev7 | +------+ +------+ +------+ +------+ Is it true? If it is true, then how the current revision of a document is determined based on such a B-tree? Doesn't it mean, that CouchDB needs a separate "view" database for indexing current revisions of documents to preserve O(log n) access? Wouldn't it lead to race conditions while building such an index? (as far as I know, CouchDB uses no write locks).

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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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• pass php array to jquery with getJSON

  - by robertdd

  i want to pass a php aray to jQuery: $.getimagesarr = function() { $.getJSON('operations.php', {'operation':'getimglist'}, function(data){ var arr = new Array(); arr = data; return arr; }); } var data = $.getimagesarr(); if (data){ jQuery.each(data, function(i, val) { .... }); } it return undefined in php i have this: function getimglist(){ $results = $_SESSION['files']; echo json_encode($results); } it is possible?

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• What are the advantages to use StringBuilder versus XmlDocument or related to create XML documetns?

  - by Rob

  This might be a bit of a code smell, but I have seen it is some production code, namely the use of StringBuilder as opposed to XmlDocument when creating XML documents. In some cases these are write once operations (e.g. create the document and save it to disk) where as others are passing the built string to an XmlDocument to preform an XslTransform to a document that is returned to the client. So obvious question: is there merit to doing things this way, is it something that should be done on a case-by-case basis, or is this the wrong way of doing things?

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• R: simple and short if clauses for combind statements

  - by jorgusch

  Hello, TRUE/FALSE if clauses are easily and quickly done in R. However, if the argument gets more complex, it also gets ugly very soon. For instance: I might want to execute different operations for a row(foo) dependent on the value in one cell (foo[1]). Let the intervals be 0:39 and 40:59 and 60:100 Something like does not exit: (if foo[1] "in" 40:60){... In fact, I only see ways of at least two if clauses and two else statements and the action for the first interval somewhere at the bottom of the code. With more intervals(or any other condition) it is getting more complex. Is there a best practice (for this purpose or others) with a simple construction and nice design to read? Thanks a lot!

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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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• Cuda program results are always zero in HW, correct in EMU??

  - by Orion Nebula

  Hi all! I am having a weird problem .. I have written a CUDA code which executes correctly in emulation and all results show up.. however, when executed on hardware "G210" .. the results in the result memory are always 0 I am passing two vectors to the kernel, one with random variables the other is initialized to zero, the code copies the first vector to shared memory, does some swapping and other operations and then writes back the results on the second vector (the one with the initial 0's) I am using double precision, the -arch sm13 flag is used, all memory allocation also use sizeof(double) .. I have checked if the kernel is invoked, it does .. so no problems here .. the cudaMemCpy has no problems .. what could be the problem .. :( why would it work in emulation but not on HW I am quite confused .. any ideas?

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• Replicating Active Directory - testing scenarios

  - by Naeem Sarfraz

  Replicating a production server's Active Directory is possible through a number of approaches as mentioned here and here. I'm looking for a simpler approach if one exists. I have a mixed-mode authentication site that I need to test. Quite simply AD users (internal) will have more privilege's than someone who logs in via forms (external). We have a web service that cache's an AD structure (users & groups). I'm thinking of building a module (http handler I guess?) that will pick up my specially formed URL (http://impersonateduser@localhost/mywebapp) and use the bit before the @ as the username. That will be the username I use for any subsequent operations. How does that sound? Has anyone got other proposals for testing scenarios like this?

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• How does one implement a truly asynchronous java thread

  - by Ritesh M Nayak

  I have a function that needs to perfom two operations, one which finishes fast and one which takes a long time to run. I want to be able to delegate the long running operation to a thread and I dont care when the thread finishes, but the threads needs to complete. I implemented this as shown below , but, my secondoperation never gets done as the function exits after the start() call. How I can ensure that the function returns but the second operation thread finishes its execution as well and is not dependent on the parent thread ? public void someFunction(String data) { smallOperation() Blah a = new Blah(); Thread th = new Thread(a); th.Start(); } class SecondOperation implements Runnable { public void run(){ // doSomething long running } }

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• What's the most effective way to interpolate between two colors? (pseudocode and bitwise ops expecte

  - by navand

  Making a Blackberry app, want a Gradient class. What's the most effective way (as in, speed and battery life) to interpolate two colors? Please be specific. // Java, of course int c1 = 0xFFAA0055 // color 1, ARGB int c2 = 0xFF00CCFF // color 2, ARGB float st = 0 // the current step in the interpolation, between 0 and 1 /* Help from here on. Should I separate each channel of each color, convert them to decimal and interpolate? Is there a simpler way? interpolatedChannel = red1+((red2-red1)*st) interpolatedChannel = interpolatedChannel.toString(16) ^ Is this the right thing to do? If speed and effectiveness is important in a mobile app, should I use bitwise operations? Help me! */

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• Can I turn off implicit Python unicode conversions to find my mixed-strings bugs?

  - by Tal Weiss

  When profiling our code I was surprised to find millions of calls to C:\Python26\lib\encodings\utf_8.py:15(decode) I started debugging and found that across our code base there are many small bugs, usually comparing a string to a unicode or adding a sting and a unicode. Python graciously decodes the strings and performs the following operations in unicode. How kind. But expensive! I am fluent in unicode, having read Joel Spolsky and Dive Into Python... I try to keep our code internals in unicode only. My question - can I turn off this pythonic nice-guy behavior? At least until I find all these bugs and fix them (usually by adding a u'u')? Some of them are extremely hard to find (a variable that is sometimes a string...). Python 2.6.5 (and I can't switch to 3.x).

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• Connecting std::basic_ofstream<unsigned char> to a FIFO. bad_cast exceptions

  - by Mike B

  Using gcc 4.4.3 on Linux 2.6.32, I get bad_cast exceptions when connecting std::basic_ofstream to a FIFO. Stepping though the debugger, I can see that the error is generated at various places in the standard library because the _M_codecvt member of the stream or filebuf object is NULL. Exactly where it happens depends on the order of operations, but it appears to be the same cause in each. So am I doing something fundamentally stupid here? ofstream and ifstream work fine. Is there some reason that you shouldn't attach a stream of anything besides char to a FIFO? Thanks in advance.

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• How to implement square root and exponentiation on arbitrary length numbers?

  - by tomp

  I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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• Primary reasons why programming language runtimes use stacks?

  - by manuel aldana

  Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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