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  • Creating Objects

    - by user1424667
    I have a general coding standard question. Is it bad practice to initialize and create an object in multiple methods depending on the outcome of a users choice. So for example if the user quits a poker game, create the poker hand with the cards the user has received, even if < 5, and if the user played till the end create object to show completed hand to show outcome of the game. The key is that the object will only be created once in actuality, there are just different paths and parameters is will receive depending on if the user folded, or played on to the showdown.

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  • How to get experience in large scale databases?

    - by Justin
    I have written applications that are very small scale and the code I write works fine for them. But I have often wondered how the server side code I write would scale up from 100s of queries per day to millions. Also when looking at possible jobs/projects, people are often looking for developers with experience in this sort of high traffic database design so I would at least like to be able to say, I havent gotten to work on a project that was this popular, but I at least have tried to simulate it. Are there tools or frameworks that can generate a lot of traffic or at least simulate what would happen with traffic on different orders of magnitude so I could get some practice writing optimized code for higher traffic applicaitons?

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  • Am I sending large amounts of data sensibly?

    - by Sofus Albertsen
    I am about to design a video conversion service, that is scalable on the conversion side. The architecture is as follows: Webpage for video upload When done, a message gets sent out to one of several resizing servers The server locates the video, saves it on disk, and converts it to several formats and resolutions The resizing server uploads the output to a content server, and messages back that the conversion is done. Messaging is something I have covered, but right now I am transferring via FTP, and wonder if there is a better way? is there something faster, or more reliable? All the servers will be sitting in the same gigabit switch or neighboring switch, so fast transfer is expected.

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  • Passing class names or objects?

    - by nischayn22
    I have a switch statement switch ( $id ) { case 'abc': return 'Animal'; case 'xyz': return 'Human'; //many more } I am returning class names,and use them to call some of their static functions using call_user_func(). Instead I can also create a object of that class, return that and then call the static function from that object as $object::method($param) switch ( $id ) { case 'abc': return new Animal; case 'xyz': return new Human; //many more } Which way is efficient? To make this question broader : I have classes that have mostly all static methods right now, putting them into classes is kind of a grouping idea here (for example the DB table structure of Animal is given by class Animal and so for Human class). I need to access many functions from these classes so the switch needs to give me access to the class

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  • Replicating A Volume Of Large Data via Transactional Replication

    During weekend maintenance, members of the support team executed an UPDATE statement against the database on the OLTP Server. This database was a part of Transactional Replication, and once the UPDATE statement was executed the Replication procedure came to a halt with an error message. Satnam Singh decided to work on this case and try to find an efficient solution to rebuild the procedure without significant downtime.

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  • Split large file, have arbitrary start index number

    - by nEJC
    I do a lot of file manipulation on my system and in one particular batch job I end up with around 16 Gb file. I need to prepare this data into smaller chunks for another process. I split it into 10k lines per file and numeric index, padded to 5 digits split -a 5 -d -l 10000 large_input_file /out_path/out. This way I end up with files named out.00000 out.00001 ... The problem is that this way indexing always starts with 0. Is there a way to set it to arbitrary starting index? man reveals nothing ...

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  • Canonicalization Within Large Corporations

    As you probably have heard, canonicalization is one of the latest announcements sweeping the SEO industry. What you probably haven't heard, however, is how to pronounce it - or how it will effect your website. I'll do my best to explain canonicalization in layman's terms, but forgive me if it's still tough to understand.

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  • How to quickly search through a very large list of strings / records on a database

    - by Giorgio
    I have the following problem: I have a database containing more than 2 million records. Each record has a string field X and I want to display a list of records for which field X contains a certain string. Each record is about 500 bytes in size. To make it more concrete: in the GUI of my application I have a text field where I can enter a string. Above the text field I have a table displaying the (first N, e.g. 100) records that match the string in the text field. When I type or delete one character in the text field, the table content must be updated on the fly. I wonder if there is an efficient way of doing this using appropriate index structures and / or caching. As explained above, I only want to display the first N items that match the query. Therefore, for N small enough, it should not be a big issue loading the matching items from the database. Besides, caching items in main memory can make retrieval faster. I think the main problem is how to find the matching items quickly, given the pattern string. Can I rely on some DBMS facilities, or do I have to build some in-memory index myself? Any ideas? EDIT I have run a first experiment. I have split the records into different text files (at most 200 records per file) and put the files in different directories (I used the content of one data field to determine the directory tree). I end up with about 50000 files in about 40000 directories. I have then run Lucene to index the files. Searching for a string with the Lucene demo program is pretty fast. Splitting and indexing took a few minutes: this is totally acceptable for me because it is a static data set that I want to query. The next step is to integrate Lucene in the main program and use the hits returned by Lucene to load the relevant records into main memory.

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  • Continuing to code on large projects

    - by user3487347
    I am a hobbyist programmer, and I've started many medium - sized projects to work on just by myself. These include games, a raytracer, physics simulations etc. By the time these projects get to a certain size (around 5000 lines), I begin to slow down in adding features to the program. This is not because of a lack of ideas of what to implement in a program, but rather a struggle in how to go about it. In particular, I'm afraid of breaking what I already have working in order to implement a new feature. I've tried using version control like Git and Subversion, but these seem unnecessary when you are a one man team. I simply have a folder of "versions" of my program, one for each major change I make. How do I keep coding past this 5000 line mark? What about the 50000 line mark?

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  • Display large amount of data to client through pagination

    - by ebram tharwat
    I have a web application in which i need to show a big number of data or records for clients. Now i 'll use pagination but i was wondering should I: Load all the data once then pagination, sorting and sarching 'll be easy..But it 'll takes big time(using local DB it takes up to 9 sec.) Or each time i show new page(from the pagination) i make a new request to server and then new request to DB to get the next records..But then what if the client click on Prev button, i 'll make a new request to get data that I had previously..Should i cach data that are loaded before and how if that's good technique? So load all data once or make a new request every time i need data that maybe have been loaded before. I'm using ASP.NET MVC SPA with durandaljs and knockoutjs

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  • Sharing Large Database Backup Among Team

    - by MattGWagner
    I work on a team of three - five developers that work on an ASP.net web application remotely. We currently run a full local database from a recent backup on all of our machines during development. The current backup, compressed, is about 18 GB. I'm looking to see if there's an easier way to keep all of our local copies relatively fresh without each of us individually downloading the 18 GB file over HTTP from our web server on a regular basis. I guess FTP is an option, but it won't speed the process up at all. I'm familiar with torrents and the thought keeps hitting me that something like that would be effective, but I'm unsure of the security or the process.

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  • Separating Db from business with Inherited classes using multiple views

    - by catalinux
    I have a software that has a car model that will be used in different views (listing, ads, detail page, carousel, up sell widget,etc). class CarModel extends DbModel{ } I look for a "nice way" (a combination of flexible, easy to maintain,etc) to have this used in views. I'm thinking at two different ways Having object views for each context CarViewBase{ var car;// of type CarModel function constructor(args){ //will instantienta internal variable car based on args } function getThumb(){ } function getTitle(){ } } CarListingView extends CarViewBase{ function getListing(){ } } CarAdsView extends CarViewBase{ //the busines rule changes for ads widget function getThumb(){ } } Extending directly the CarModel The challenges comes when My Car Model might need an abstract factory. Let's say I have a field on my car object that states the type of the car : a truck, or a bike, or van. How would affect that my object view? Let's say that getTitle() rule would be different for each type of it. How would you do it?

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  • Ubuntu 12.04 tilts when trying to open large excel file with libreoffice or matlab

    - by user1565754
    I have an xlsx-file of size 27.3MB and when I try to open it either in Libreoffice or Matlab the whole system slows down My processor is AMD Sempron(tm) 140 Processor (should be about 2.7Ghz) Memory I have about 1.7GB Any ideas? I opened this file in Windows no problem...of course it took a few seconds to load but Ubuntu freezes with this file completely...smaller files of size 3MB, 5MB etc open just fine... thnx for support =)

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  • Java ExecutorService java heap space ptoblems

    - by Sergey Aganezov jr
    I have a little bit of a problem in a multitasking java department. I have a class, called public class ThreadWorker implements Runnable { //some code in here public void run(){ // invokes some recursion method in the ThreadWorker itself, // which will stop eventually { } all in all, pretty simple "worker" that can work on it's on. To work with threads I'm using public static int THREAD_NUMBER = 4; public static ExecutorServide es = Executors.newFixedThreadPool(THREAD_NUMBER); adding instances of ThreadWroker class happens here: public void recursiveMethod(Arraylist<Integers> elements, MyClass data){ if (elements.size() == 0 && data.qualifies()){ ThreadWorker tw = new ThreadWorker(data); es.execute(tw); return; } for (int i=0; i< elements.size(); i++){ // some code to prevent my problem MyClass data1 = new MyClass(data); MyClass data2 = new MyClass(data); ArrayList<Integer> newElements = (ArrayList<Integer>)elements.clone(); data1.update(elements.get(i)); data2.update(-1 * elements.get(i)); newElements.remove(i); recursiveMethod(newElements, data1); recursiveMethod(newElements, data2); { } and the problem is that the depth of the recursion tree is quite big, so as it's width, so a lot of ThreadWorkers are added to the ExecutorService, so after some time on the big input a get Exception in thread "pool-1-thread-2" java.lang.OutOfMemoryError: Java heap space which is caused, as I think because of a ginormous number of ThreadWorkers i'm adding to ExecutorSirvice to be executed, so it runs out of memory. Every ThreadWorker takes about 40 Mb of RAM for all it needs. Is there a method to get how many threads (instances of classes implementing runnable interface) have been added to ExecutorService? So I can add it in the shown above code (int the " // some code to prevent my problem"), as while ("number of threads in the ExecutorService" > 10){ Thread.sleep(10000); } so I won't go to deep or to broad with my recursion and prevent those exception-throwing situations. Sincerely, Sergey Aganezov jr.

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  • How to maxmise the largest contiguous block of memory in the Large Object Heap

    - by Unsliced
    The situation is that I am making a WCF call to a remote server which is returns an XML document as a string. Most of the time this return value is a few K, sometimes a few dozen K, very occasionally a few hundred K, but very rarely it could be several megabytes (first problem is that there is no way for me to know). It's these rare occasions that are causing grief. I get a stack trace that starts: System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown. at System.Xml.BufferBuilder.AddBuffer() at System.Xml.BufferBuilder.AppendHelper(Char* pSource, Int32 count) at System.Xml.BufferBuilder.Append(Char[] value, Int32 start, Int32 count) at System.Xml.XmlTextReaderImpl.ParseText() at System.Xml.XmlTextReaderImpl.ParseElementContent() at System.Xml.XmlTextReaderImpl.Read() at System.Xml.XmlTextReader.Read() at System.Xml.XmlReader.ReadElementString() at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderMDRQuery.Read2_getMarketDataResponse() at Microsoft.Xml.Serialization.GeneratedAssembly.ArrayOfObjectSerializer2.Deserialize(XmlSerializationReader reader) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle) at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) I've read around and it is because the Large Object Heap is just getting too fragmented, so even preceding the call with a quick check to StringBuilder.EnsureCapacity just causes the OutOfMemoryException to be thrown earlier (and because I'm guessing at what's needed, it might not actually need that much so my check is causing more problems than it is solving). Some opinions are that there's not much I can do about it. Some of the questions I've asked myself: Use less memory - have you checked for leaks? Yes. The memory usage goes up and down, but there's no fundamental growth that guarantees this to happen. Some of the times it fails, it succeeded at that stage previously. Transfer smaller amounts Not an option, this is a third party web service over which I have no control (or at least it would take a long time to resolve, in the meantime I still have a problem) Can you do something to the LOH to make it less likely to fail? ... now this is most fruitful course. It's a 32-bit process (it has to be for various political, technical and boring reasons) but there's normally hundreds of meg free (multiples of the largest amount for which we've seen failures). Can we monitor the LOH? Using perfmon I can track the size of the heaps, but I don't think there's a way to monitor the largest available contiguous block of memory. Question is: any advice or suggestions for things to try?

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  • How do I get the file size of a large (> 4 GB) file?

    - by endeavormac
    How can I get the file size of a file in C when the file size is greater than 4gb? ftell returns a 4 byte signed long, limiting it to two bytes. stat has a variable of type off_t which is also 4 bytes (not sure of sign), so at most it can tell me the size of a 4gb file. What if the file is larger than 4 gb?

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  • Problem with large number of markers on the map...

    - by bobetko
    I am working on an Android app that already exists on iPhone. In the app, there is a Map activity that has (I counted) around 800 markers in four groups marked by drawable in four different colors. Each group can be turned on or off. Information about markers I have inside List. I create a mapOverlay for each group, then I attach that overlay to the map. I strongly believe that coding part I did properly. But I will attach my code anyway... The thing is, my Nexus One can't handle map with all those markers. It takes around 15 seconds just to draw 500 markers. Then when all drawn, map is not quite smooth. It is sort of hard to zoom and navigate around. It can be done, but experience is bad and I would like to see if something can be done there. iPhone seems doesn't have problems showing all these markers. It takes roughly about 1-2 seconds to show all of them and zooming and panning is not that bad. Slow down is noticeable but still acceptable. I personally think it is no good to draw all those markers, but app is designed by somebody else and I am not supposed to make any drastic changes. I am not sure what to do here. It seems I will have to come up with different functionality, maybe use GPS location, if known, and draw only markers within some radius, or, if location not known, use center of the screen(map) and draw markers around that. I will have to have reasonable explanation for my bosses in case I make these changes. I appreciate if anybody has any idas. And the code: ... for (int m = 0; m < ArrList.size(); m++) { tName = ArrList.get(m).get("name").toString(); tId = ArrList.get(m).get("id").toString(); tLat = ArrList.get(m).get("lat").toString();; tLng = ArrList.get(m).get("lng").toString();; try { lat = Double.parseDouble(tLat); lng = Double.parseDouble(tLng); p1 = new GeoPoint( (int) (lat * 1E6), (int) (lng * 1E6)); OverlayItem overlayitem = new OverlayItem(p1, tName, tId); itemizedoverlay.addOverlay(overlayitem); } catch (NumberFormatException e) { Log.d(TAG, "NumberFormatException" + e); } } mapOverlays.add(itemizedoverlay); mapView.postInvalidate(); ................................ public class HelloItemizedOverlay extends ItemizedOverlay<OverlayItem> { private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>(); private Context mContext; public HelloItemizedOverlay(Drawable defaultMarker, Context context) { super(boundCenterBottom(defaultMarker)); mContext = context; } public void addOverlay(OverlayItem overlay) { mOverlays.add(overlay); populate(); } @Override protected OverlayItem createItem(int i) { return mOverlays.get(i); } @Override public int size() { return mOverlays.size(); } @Override protected boolean onTap(int index) { final OverlayItem item = mOverlays.get(index); ... EACH MARKER WILL HAVE ONCLICK EVENT THAT WILL PRODUCE CLICABLE ... BALOON WITH MARKER'S NAME. return true; } }

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  • Reading from a very large table using multiple threads (Java ) and writing them to a single file

    - by user2534926
    I am currently facing a situation where i have a table with almost 80 millions data and i have to take a dump of that table and store it into a csv file. Currently i am using a not so professional approach( with a perl script+DBI interface , printing the values to stdout and redirecting to a csv file). Now i am planning to use java threading approach. Can you suggest a way forward. Thanks in advance

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  • .NET 4.0 Dynamic object used statically?

    - by Kevin Won
    I've gotten quite sick of XML configuration files in .NET and want to replace them with a format that is more sane. Therefore, I'm writing a config file parser for C# applications that will take a custom config file format, parse it, and create a Python source string that I can then execute in C# and use as a static object (yes that's right--I want a static (not the static type dyanamic) object in the end). Here's an example of what my config file looks like: // my custom config file format GlobalName: ExampleApp Properties { ExternalServiceTimeout: "120" } Python { // this allows for straight python code to be added to handle custom config def MyCustomPython: return "cool" } Using ANTLR I've created a Lexer/Parser that will convert this format to a Python script. So assume I have that all right and can take the .config above and run my Lexer/Parser on it to get a Python script out the back (this has the added benefit of giving me a validation tool for my config). By running the resultant script in C# // simplified example of getting the dynamic python object in C# // (not how I really do it) ScriptRuntime py = Python.CreateRuntime(); dynamic conf = py.UseFile("conftest.py"); dynamic t = conf.GetConfTest("test"); I can get a dynamic object that has my configuration settings. I can now get my config file settings in C# by invoking a dynamic method on that object: //C# calling a method on the dynamic python object var timeout = t.GetProperty("ExternalServiceTimeout"); //the config also allows for straight Python scripting (via the Python block) var special = t.MyCustonPython(); of course, I have no type safety here and no intellisense support. I have a dynamic representation of my config file, but I want a static one. I know what my Python object's type is--it is actually newing up in instance of a C# class. But since it's happening in python, it's type is not the C# type, but dynamic instead. What I want to do is then cast the object back to the C# type that I know the object is: // doesn't work--can't cast a dynamic to a static type (nulls out) IConfigSettings staticTypeConfig = t as IConfigSettings Is there any way to figure out how to cast the object to the static type? I'm rather doubtful that there is... so doubtful that I took another approach of which I'm not entirely sure about. I'm wondering if someone has a better way... So here's my current tactic: since I know the type of the python object, I am creating a C# wrapper class: public class ConfigSettings : IConfigSettings that takes in a dynamic object in the ctor: public ConfigSettings(dynamic settings) { this.DynamicProxy = settings; } public dynamic DynamicProxy { get; private set; } Now I have a reference to the Python dynamic object of which I know the type. So I can then just put wrappers around the Python methods that I know are there: // wrapper access to the underlying dynamic object // this makes my dynamic object appear 'static' public string GetSetting(string key) { return this.DynamicProxy.GetProperty(key).ToString(); } Now the dynamic object is accessed through this static proxy and thus can obviously be passed around in the static C# world via interface, etc: // dependency inject the dynamic object around IBusinessLogic logic = new BusinessLogic(IConfigSettings config); This solution has the benefits of all the static typing stuff we know and love while at the same time giving me the option of 'bailing out' to dynamic too: // the DynamicProxy property give direct access to the dynamic object var result = config.DynamicProxy.MyCustomPython(); but, man, this seems rather convoluted way of getting to an object that is a static type in the first place! Since the whole dynamic/static interaction world is new to me, I'm really questioning if my solution is optimal or if I'm missing something (i.e. some way of casting that dynamic object to a known static type) about how to bridge the chasm between these two universes.

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  • Where is meta.local_fields set in django.db.models.base.py ?

    - by BryanWheelock
    I'm getting the error: Exception Value: (1110, "Column 'about' specified twice") As I was reviewing the Django error page, I noticed that the customizations the model User, seem to be appended to the List twice. This seems to be happening here in django/db/model/base.py in base_save(): values = [(f, f.get_db_prep_save(raw and getattr(self, f.attname) or f.pre_save(self, True))) for f in meta.local_fields] this is what Django error page shows values to be: values = [(<django.db.models.fields.CharField object at 0xa78996c>, u'kallie'), (<django.db.models.fields.CharField object at 0xa7899cc>, ''), (<django.db.models.fields.CharField object at 0xa789a2c>, ''), (<django.db.models.fields.EmailField object at 0xa789a8c>, u'[email protected]'), (<django.db.models.fields.CharField object at 0xa789b2c>, 'sha1$d4a80$0e5xxxxxxxxxxxxxxxxxxxxddadfb07'), (<django.db.models.fields.BooleanField object at 0xa789bcc>, False), (<django.db.models.fields.BooleanField object at 0xa789c6c>, True), (<django.db.models.fields.BooleanField object at 0xa789d2c>, False), (<django.db.models.fields.DateTimeField object at 0xa789dcc>, u'2010-02-03 14:54:35'), (<django.db.models.fields.DateTimeField object at 0xa789e2c>, u'2010-02-03 14:54:35'), # this is where the values from the User model customizations show up (<django.db.models.fields.BooleanField object at 0xa8c69ac>, False), (<django.db.models.fields.CharField object at 0xa8c688c>, None), (<django.db.models.fields.PositiveIntegerField object at 0xa8c69cc>, 1), (<django.db.models.fields.CharField object at 0xa8c69ec>, 'b5ab1603b2308xxxxxxxxxxx75bca1'), (<django.db.models.fields.SmallIntegerField object at 0xa8c6dac>, 0), (<django.db.models.fields.SmallIntegerField object at 0xa8c6e4c>, 0), (<django.db.models.fields.SmallIntegerField object at 0xa8c6e8c>, 0), (<django.db.models.fields.SmallIntegerField object at 0xa8c6ecc>, 10), (<django.db.models.fields.DateTimeField object at 0xa8c6eec>, u'2010-02-03 14:54:35'), (<django.db.models.fields.CharField object at 0xa8c6f2c>, ''), (<django.db.models.fields.URLField object at 0xa8c6f6c>, ''), (<django.db.models.fields.CharField object at 0xa8c6fac>, ''), (<django.db.models.fields.DateField object at 0xa8c6fec>, None), (<django.db.models.fields.TextField object at 0xa8cb04c>, ''), # at this point User model customizations repeats itself (<django.db.models.fields.BooleanField object at 0xa663b0c>, False), (<django.db.models.fields.CharField object at 0xaa1e94c>, None), (<django.db.models.fields.PositiveIntegerField object at 0xaa1e34c>, 1), (<django.db.models.fields.CharField object at 0xaa1e40c>, 'b5ab1603b2308050ebd62f49ca75bca1'), (<django.db.models.fields.SmallIntegerField object at 0xa8c6d8c>, 0), (<django.db.models.fields.SmallIntegerField object at 0xaa2378c>, 0), (<django.db.models.fields.SmallIntegerField object at 0xaa237ac>, 0), (<django.db.models.fields.SmallIntegerField object at 0xaa237ec>, 10), (<django.db.models.fields.DateTimeField object at 0xaa2380c>, u'2010-02-03 14:54:35'), (<django.db.models.fields.CharField object at 0xaa2384c>, ''), (<django.db.models.fields.URLField object at 0xaa2388c>, ''), (<django.db.models.fields.CharField object at 0xaa238cc>, ''), (<django.db.models.fields.DateField object at 0xaa2390c>, None), (<django.db.models.fields.TextField object at 0xaa2394c>, '')] Since this app is in Production, I can't figure out how to use pdb.set_trace() to see what's going on inside of save_base. The customizations to User are: User.add_to_class('email_isvalid', models.BooleanField(default=False)) User.add_to_class('email_key', models.CharField(max_length=16, null=True)) User.add_to_class('reputation', models.PositiveIntegerField(default=1)) User.add_to_class('gravatar', models.CharField(max_length=32)) User.add_to_class('email_feeds', generic.GenericRelation(EmailFeed)) User.add_to_class('favorite_questions', models.ManyToManyField(Question, through=FavoriteQuestion, related_name='favorited_by')) User.add_to_class('badges', models.ManyToManyField(Badge, through=Award, related_name='awarded_to')) User.add_to_class('gold', models.SmallIntegerField(default=0)) User.add_to_class('silver', models.SmallIntegerField(default=0)) User.add_to_class('bronze', models.SmallIntegerField(default=0)) User.add_to_class('questions_per_page', models.SmallIntegerField(choices=QUESTIONS_PER_PAGE_CHOICES, default=10)) User.add_to_class('last_seen', models.DateTimeField(default=datetime.datetime.now)) User.add_to_class('real_name', models.CharField(max_length=100, blank=True)) User.add_to_class('website', models.URLField(max_length=200, blank=True)) User.add_to_class('location', models.CharField(max_length=100, blank=True)) User.add_to_class('date_of_birth', models.DateField(null=True, blank=True)) User.add_to_class('about', models.TextField(blank=True)) Django1.1.1 Python 2.5

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  • Problem using delete[] (Heap corruption) when implementing operator+= (C++)

    - by Darel
    I've been trying to figure this out for hours now, and I'm at my wit's end. I would surely appreciate it if someone could tell me when I'm doing wrong. I have written a simple class to emulate basic functionality of strings. The class's members include a character pointer data (which points to a dynamically created char array) and an integer strSize (which holds the length of the string, sans terminator.) Since I'm using new and delete, I've implemented the copy constructor and destructor. My problem occurs when I try to implement the operator+=. The LHS object builds the new string correctly - I can even print it using cout - but the problem comes when I try to deallocate the data pointer in the destructor: I get a "Heap Corruption Detected after normal block" at the memory address pointed to by the data array the destructor is trying to deallocate. Here's my complete class and test program: #include <iostream> using namespace std; // Class to emulate string class Str { public: // Default constructor Str(): data(0), strSize(0) { } // Constructor from string literal Str(const char* cp) { data = new char[strlen(cp) + 1]; char *p = data; const char* q = cp; while (*q) *p++ = *q++; *p = '\0'; strSize = strlen(cp); } Str& operator+=(const Str& rhs) { // create new dynamic memory to hold concatenated string char* str = new char[strSize + rhs.strSize + 1]; char* p = str; // new data char* i = data; // old data const char* q = rhs.data; // data to append // append old string to new string in new dynamic memory while (*p++ = *i++) ; p--; while (*p++ = *q++) ; *p = '\0'; // assign new values to data and strSize delete[] data; data = str; strSize += rhs.strSize; return *this; } // Copy constructor Str(const Str& s) { data = new char[s.strSize + 1]; char *p = data; char *q = s.data; while (*q) *p++ = *q++; *p = '\0'; strSize = s.strSize; } // destructor ~Str() { delete[] data; } const char& operator[](int i) const { return data[i]; } int size() const { return strSize; } private: char *data; int strSize; }; ostream& operator<<(ostream& os, const Str& s) { for (int i = 0; i != s.size(); ++i) os << s[i]; return os; } // Test constructor, copy constructor, and += operator int main() { Str s = "hello"; // destructor for s works ok Str x = s; // destructor for x works ok s += "world!"; // destructor for s gives error cout << s << endl; cout << x << endl; return 0; }

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  • Putting a C++ Vector as a Member in a Class that Uses a Memory Pool

    - by Deep-B
    Hey, I've been writing a multi-threaded DLL for database access using ADO/ODBC for use with a legacy application. I need to keep multiple database connections for each thread, so I've put the ADO objects for each connection in an object and thinking of keeping an array of them inside a custom threadInfo object. Obviously a vector would serve better here - I need to delete/rearrange objects on the go and a vector would simplify that. Problem is, I'm allocating a heap for each thread to avoid heap contention and stuff and allocating all my memory from there. So my question is: how do I make the vector allocate from the thread-specific heap? (Or would it know internally to allocate memory from the same heap as its wrapper class - sounds unlikely, but I'm not a C++ guy) I've googled a bit and it looks like I might need to write an allocator or something - which looks like so much of work I don't want. Is there any other way? I've heard vector uses placement-new for all its stuff inside, so can overloading operator new be worked into it? My scant knowledge of the insides of C++ doesn't help, seeing as I'm mainly a C programmer (even that - relatively). It's very possible I'm missing something elementary somewhere. If nothing easier comes up - I might just go and do the array thing, but hopefully it won't come to that. I'm using MS-VC++ 6.0 (hey, it's rude to laugh! :-P ). Any/all help will be much appreciated.

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