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• A way of allocating multidimensional arrays dynamically

  - by C77431

  salute.. I am learning dynamic allocations for multidimensional arrays in a book and I found some ways for that, And now haven't problem in it. But the author of the book shows us a way, but it doesn't work correctly. It is this: pbeans = new double [3][4]; // Allocate memory for a 3x4 array And this is the error: error C2440: '=' : cannot convert from 'int (*)[4]' to 'int *' how should i define pbeans ( if this type of coding is legal)? and what is the problem exactly? Regards.

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• How do I choose a database?

  - by liamzebedee

  I need a comparison table of some sort for database varieties (MySQL, SQLite etc.). I can't find one. My use case is, I am implementing storage of objects in a distributed hash table. I need a database solution that is: Fast for sorting Simplistic (no users, preferably no additional structures like multiple tables etc.) Concurrent (if possible) Multi-platform File based (not stored in memory primarily) Centralized I will be programming in Go. As I understand, I believe I need what is called a Document Orientated Database, because I am storing objects, identified by keys. EDIT: While I am implementing a DHT, I will also be storing metadata about the objects, such as access counts etc. It would also be preferable to have TLL (time to live)

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• Which method should I use to give the perception the computer is thinking in programming?

  - by Roy

  I want to create a simple game like tic tac toe where the human user is playing against the computer. The computer function takes a couple of milliseconds to run but I would like to make the computer take 5 seconds to make a move. Which method should I use? 1) Create two memory threads. One for the computer and one for the human user. When the computer is taking 5 seconds to imitate thinking, the human user thread is paused for 5 seconds. 2) Disable input devices for 5 seconds using timer or dispatchertimer 3) Any better methods you can think of Thanks!

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• How to fire off a asych thread in a web application, and gaurantee only 1 thread fires?

  - by Blankman

  I want to cache a object in memory. Regenerating the object when the cache expires is fairly expensive, so I want to do the following: When the cache is "about" to expire, I want to fire off a asychronous thread that will go and rebuild the object and then reset the cache. One thing I am worry about is multiple threads firing to fetch the object to cache, I only want a single thread doing this, realizing many people will be hitting the website. This might not be the best use case to do this, but I want to know how to do this sort of thing.

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• append versus resize for numpy array

  - by Abruzzo Forte e Gentile

  Hi all I would like to append a value at the end of my numpy.array. I saw numpy.append function but this performs an exact copy of the original array adding at last my new value. I would like to avoid copies since my arrays are big. I am using resize method and then set the last index available to the new value. Can you confirm that resize is the best way to append a value at the end? Is it not moving memory around someway? Thanks AFG oldSize = myArray,shape(0) myArray.resize( oldSize + 1 ) myArray[oldSize] = newValue

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• Inheriting database connection in PHP OOP

  - by vrode

  My abstract class Database is made for database interaction and any child of this class (UserDatabase, ActionDatabase, EventDatabase) inherits its database connection which is defined as static. `abstract class Database { static $connection = mysql_connect( ); } class UserDatabase extends Database { ... public function __construct( ) { $connection ? "connected" : "not connected"; $this-table = "users"; mysql_query( "FROM " . $this-table . " SELECT *" ); } } ` Does that mean, that my database connection is only set up and stored in memory once and passed on to subclasses as reference without being replicated for each instance? Is this how you would implement you OOP-correct database interface?

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• better for-loop syntax for detecting empty sequences?

  - by Dmitry Beransky

  Hi, Is there a better way to write the following: row_counter = 0 for item in iterable_sequence: # do stuff with the item counter += 1 if not row_counter: # handle the empty-sequence-case Please keep in mind that I can't use len(iterable_sequence) because 1) not all sequences have known lengths; 2) in some cases calling len() may trigger loading of the sequence's items into memory (as the case would be with sql query results). The reason I ask is that I'm simply curious if there is a way to make above more concise and idiomatic. What I'm looking for is along the lines of: for item in sequence: #process item *else*: #handle the empty sequence case (assuming "else" here worked only on empty sequences, which I know it doesn't)

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• From xcode not able to execute DISTINCT keyword for sqlite

  - by mac

  -(void) readProductsFromDatabase { // Setup the database object sqlite3 *database; // Init the animals Array products = [[NSMutableArray alloc] init]; // Open the database from the users filessytem if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { NSLog(@"db opened"); // Setup the SQL Statement and compile it for faster access const char *sqlStatement = "SELECT DISTINCT productname FROM iphone "; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { // Loop through the results and add them to the feeds array while(sqlite3_step(compiledStatement) == SQLITE_ROW) { NSLog(@"inside sqlite3 prepare"); // Read the data from the result row NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; } } // Release the compiled statement from memory sqlite3_finalize(compiledStatement); } sqlite3_close(database); } My problem is const char *sqlStatement = "SELECT DISTINCT productname FROM iphone "; This line not executing ,i am using sqlite3, thanks in advance,

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• PHP reporting error. DB verify how to?

  - by iamfab

  Error reporting Notice: Undefined variable: random_chars in wamp\www\php_sandbox\idgen.php on line 21 Call Stack: # Time Memory Function Location 1 0.0045 678928 {main}( ) ..\idgen.php:0 GPB7446 How do I fix this error? Using this code like an automatic unique id generator. How do I connect to DB to verify code is truly unique before allowing it to be assigned to a user creating a new account? Thanks <?php $characters = array( "A","B","E","F","G","H","J","K","M","N","P","R","S","T","W","X","Y","Z"); $keys = array(); while(count($keys) < 3) { $x = mt_rand(0, count($characters)-1); if(!in_array($x, $keys)) { $keys[] = $x; } } foreach($keys as $key){ $random_chars .= $characters[$key];} $randNum = rand(2327,9987); $randLet = rand(2327,9987); echo $random_chars . $randNum; ?>

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• What's your development setup? (Talking right now to my boss)

  - by Flinkman

  How do I tell my boss, that I need endless cpu power to automate my daily job? By the way, what's your setup, now in sep, 2008. How fast disks? How much memory? How many cores? How big screen? (Ok, what the hell are you doing, you may ask. I'm working in multiple environments, vmware. Have couple of build-systems running, for compatibility tests. These build systems are automated. The setup of the build system is also. Is there an another way?) Thanks!

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• Maven easyb plugin java heap space settings?

  - by vinnu

  Hi, I attempted to change my heap size for maven easyb plugin http://www.easyb.org/maven-easyb-plugin/. In my easyb test I added standard code to print the heap size using the code Runtime.getFreeMemory() and Runtime.getTotalMemory(). I tried setting the MAVEN_OPTS=-Xmx1024m -Xms1024m and also set the maven opts in Maven surefire plugin. Now when I run the same class from the Junit I can see the getTotalMemory() displaying a number close 1Gig but the when the same classes are invoked from easyb plugin they do not reflect the memory size. Shouldn't there be a way of passing JVM opts to maven easyb plugin when it runs these easyb tests? At the very minimum it should atleast pick up the MAVEN_OPTS settings from the environment. Has someone bumped into problems like this? (A search on this group's archive does not reveal much)

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• How can I avoid setting some columns if others haven't changed, when working with Linq To SQL?

  - by Patrick Szalapski

  In LINQ to SQL, I want to avoid setting some columns if others haven't changed? Say I have dim row = (From c in dataContext.Customers Where c.Id = 1234 Select c).Single() row.Name = "Example" ' line 3 dataContext.SubmitChanges() ' line 4 Great, so LINQ to SQL fetches a row, sets the name to "Example" in memory, and generates an update SQL query only when necessary--that is, no SQL will be generated if the customer's name was already "Example". So suppose on line 3, I want to detect if row has changed, and if so, set row.UpdateDate = DateTime.Now. If row has not changed, I don't want to set row.UpdateDate so that no SQL is generated. Is there any good way to do this?

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• sharepoint spweb and spsite disposal

  - by user327045

  I've been using the following code in a .NET 1.1 SharePoint 2003 environment and it works great: try { site = SPControl.GetContextSite(Context); web = site.OpenWeb(); ... } catch (Exception export) { output.Write("Caught Exception: <br/><br/>"); output.Write(export.Message + "<br><br>"); output.Write(export.StackTrace); } finally { if (web != null) web.Dispose(); if (site != null) site.Dispose(); } However, I'm currently porting the code to a .NET 2.0 SharePoint 2007 environment and I get the following error message: "Trying to use an SPWeb object that has been closed or disposed and is no longer valid." If I comment out the Dispose() code, it works fine. But won't this cause memory leaks? What's the best way to fix the problem?

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• List of phones that will work with Eclipse?

  - by user1058647

  I need an android phone to test my apps with that will work with Eclipse. It has to be low cost, run Gingerbread with modest memory and CPU. Thinking that any android phone would work I recently purchased a Virgin Mobil Chaser but as it turns out, it cannot be seen by either Eclipse or adb (but device manager does see the phone). Another developer has also had the same identical problem with the Chaser. I could keep buying phones and see if they work but that could be long and frustrating. I hope to find a "no contract" phone. Is there any list of phones that work with Eclipse. Does anyone know of any other Virgin Mobil phones that will work? thanks, Gary

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• iphone - how to properly handle exceptional situations (signals ?)

  - by pmilosev

  Hi In my iphone app, I want to provide some sort of app termination handler that will do some final work (delete some sensitive data) before the application terminates. I want to handle as much of the termination situations as possible: 1) User terminates the app 2) The device runs out of battery 3) The system terminates the app due to some reason (e.g. out of memory or app freeze) 4) Application crashes (EXC_BAD_ACCESS or SIGSEGV) Any other exceptional situation ? What is the best way to achieve this (e.g. is applicationWillTerminate method called in situation 2) ? Is it possible to do the cleanup in a signal handler (includes iPhone Security framework calls) ? regards

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• Total Size of NSMutableArray object

  - by sj wengi

  Hi Folks, I've got an NSMutableArray that holds a bunch of objects, what I'm trying to figure out is how much memory is the array using. After looking at a couple of places I know about the sizeof call, and when I make it I get 32 bits (which is the size of the NSMutableArray object it self). Example code: NSMutableArray *temp = [[NSMutableArray alloc]init]; [temp addObject:objectxyz]; [temp addObject:objectabc]; [temp addObject:object123]; now I want to know the size :) Thanks, Sj

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• How to persist and load an object which conforms to NSCoding protocol?

  - by mystify

  I have made an class which conforms to the NSCoding protocol and does all the encode and decode stuff. For my app, I simply want to persist an object from that class to the device and the next time when the app launches, I want to load that object back into memory. Basically it's just an class which holds some user input information. For example the user starts writing a text but then quits the app. Next time I want to load that data object. I guess I need NSKeyedArchiver? Is there a good tutorial on this? How do I do that?

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• Problem in serializing

  - by Harun

  Hello Guyz, Presently I need to serialize one of my object which contains more my own classes object. But the problem is I dont want to save it in a file and then retrieve it into memory stream. Is there any way to directly serialize my object into stream. I used BinaryFormatter for seializing. First I used a MemoryStream directly to take serialize output but it is giving error at time of deserialization. But later when I serialize it with a file then close it and again reopen it , it works perfectly. But I want to take it direct into stream because in my program I need to do it frequently to pass it into network client. And using file repeatedly might slow down my software. Hope I clear my problem. Any Sugetion ?

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• Codeigniter - Is it ok to add functionality to the constructor in controllers?

  - by Irro

  I'm making a project where I want the user to search for shops in different cities and would like the url to be like this: domain/shop/city/name. So I created a controller in codeigniter called Shop. But I cant create a city function since the city part of the url changes dependent on city name. One easy way to do it would be to add a function called "search" and add the functionality there but then I get url's like: domain/shop/search/city/name which I really would like to avoid. So my question is if it's ok to add my functionality directly into the constructor to avoid that extra "search" part in the url? I'm afraid that there might be some performance tricks involved that potentially keeps the class in memory so the constructor will not be called every time.

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• Java Thread - Synchronization issue

  - by Yatendra Goel

  From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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• How to Return A File and a strongly Typed data at the same time?

  - by chobo2

  Hi I am using asp.net mvc 1.0 and I want to return a XML file but I also want to return a strongly typed data back so I can update some fields. Like the XML file will contain users who failed to be inserted into the database. So I want that to appear as a dialog save box what asp.net mvc return file() would do. However I also want to return on the page like values like how many users failed to be added, how many users where added, etc. So I want to use scafolding with the class file I want to pass it along. If this was a view I could pass it along as an object model but I don't see a parameter for that in File(). I also don't want to save the xml file onto the harddrive I want to do it through memory. So have a link that would display on the page to download the file and show the the data I want would not be desired.

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• Does anyone else think instance variables are problematic in database-backed applications?

  - by Ben Aston

  It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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• Shortest command to calculate the sum of a column of output on Unix?

  - by Andrew

  I'm sure there is a quick and easy way to calculate the sum of a column of values on Unix systems (using something like awk or xargs perhaps), but writing a shell script to parse the rows line by line is the only thing that comes to mind at the moment. For example, what's the simplest way to modify the command below to compute and display the total for the SEGSZ column (70300)? ipcs -mb | head -6 IPC status from /dev/kmem as of Mon Nov 17 08:58:17 2008 T ID KEY MODE OWNER GROUP SEGSZ Shared Memory: m 0 0x411c322e --rw-rw-rw- root root 348 m 1 0x4e0c0002 --rw-rw-rw- root root 61760 m 2 0x412013f5 --rw-rw-rw- root root 8192

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• Performing regex on a stream

  - by takoi

  I have some large text files which im going to preform consecutive matching on (just capturing, not replacing). Im thinking its not such a good idea to keep the whole file in memory, but rather use a Reader. What i know about the input is that if there's a match, its not going to span more than 5 lines. So my idea was to have some sort of buffer which just keeps these 5 lines, or so, do the first search, and continue. But it has to "know" where the regex match ended for this to work. e.g if the match ends at line 2 it should start the next search from here. Is it possible to do something like this in an efficient way?

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• small string optimization for vector?

  - by BuschnicK

  I know several (all?) STL implementations implement a "small string" optimization where instead of storing the usual 3 pointers for begin, end and capacity a string will store the actual character data in the memory used for the pointers if sizeof(characters) <= sizeof(pointers). I am in a situation where I have lots of small vectors with an element size <= sizeof(pointer). I cannot use fixed size arrays, since the vectors need to be able to resize dynamically and may potentially grow quite large. However, the median (not mean) size of the vectors will only be 4-12 bytes. So a "small string" optimization adapted to vectors would be quite useful to me. Does such a thing exist? I'm thinking about rolling my own by simply brute force converting a vector to a string, i.e. providing a vector interface to a string. Good idea?

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