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• Hadoop Map/Reduce - simple use example to do the following...

  - by alexeypro

  I have MySQL database, where I store the following BLOB (which contains JSON object) and ID (for this JSON object). JSON object contains a lot of different information. Say, "city:Los Angeles" and "state:California". There are about 500k of such records for now, but they are growing. And each JSON object is quite big. My goal is to do searches (real-time) in MySQL database. Say, I want to search for all JSON objects which have "state" to "California" and "city" to "San Francisco". I want to utilize Hadoop for the task. My idea is that there will be "job", which takes chunks of, say, 100 records (rows) from MySQL, verifies them according to the given search criteria, returns those (ID's) which qualify. Pros/cons? I understand that one might think that I should utilize simple SQL power for that, but the thing is that JSON object structure is pretty "heavy", if I put it as SQL schemas, there will be at least 3-5 tables joins, which (I tried, really) creates quite a headache, and building all the right indexes eats RAM faster than I one can think. ;-) And even then, every SQL query has to be analyzed to be utilizing the indexes, otherwise with full scan it literally is a pain. And with such structure we have the only way "up" is just with vertical scaling. But I am not sure it's the best option for me, as I see how JSON objects will grow (the data structure), and I see that the number of them will grow too. :-) Help? Can somebody point me to simple examples of how this can be done? Does it make sense at all? Am I missing something important? Thank you.

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• NHibernate: how to handle entity-based validation using session-per-request pattern, without control

  - by Seth Petry-Johnson

  What is the best way to do entity-based validation (each entity class has an IsValid() method that validates its internal members) in ASP.NET MVC, with a "session-per-request" model, where the controller has zero (or limited) knowledge of the ISession? Here's the pattern I'm using: Get an entity by ID, using an IFooRepository that wraps the current NH session. This returns a connected entity instance. Load the entity with potentially invalid data, coming from the form post. Validate the entity by callings its IsValid() method. If valid, call IFooRepository.Save(entity). Otherwise, display error message. The session is currently opened when the request begins and flushed when the request ends. Since my entity is connected to a session, flushing the session attempts to save the changes even if the object is invalid. What's the best way to keep validation logic in the entity class, limit controller knowledge of NH, and avoid saving invalid changes at the end of a request? Option 1: Explicitly evict on validation failure, implicitly flush: if the validation fails, I could manually evict the invalid object in the action method. If successful, I do nothing and the session is automatically flushed. Con: error prone and counter-intuitive ("I didn't call .Save(), why are my invalid changes being saved anyways?") Option 2: Explicitly flush, do nothing by default: By default I can dispose of the session on request end, only flushing if the controller indicates success. I'd probably create a SaveChanges() method in my base controller that sets a flag indicating success, and then query this flag when closing the session at request end. Pro: More intuitive to troubleshoot if dev forgets this step [relative to option 1] Con: I have to call IRepository.Save(entity)' and SaveChanges(). Option 3: Always work with disconnected objects: I could modify my repositories to return disconnected/transient objects, and modify the Repo.Save() method to re-attach them. Pro: Most intuitive, given that controllers don't know about NH. Con: Does this defeat many of the benefits I'd get from NH?

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• Pattern for limiting number of simultaneous asynchronous calls

  - by hitch

  I need to retrieve multiple objects from an external system. The external system supports multiple simultaneous requests (i.e. threads), but it is possible to flood the external system - therefore I want to be able to retrieve multiple objects asynchronously, but I want to be able to throttle the number of simultaneous async requests. i.e. I need to retrieve 100 items, but don't want to be retrieving more than 25 of them at once. When each request of the 25 completes, I want to trigger another retrieval, and once they are all complete I want to return all of the results in the order they were requested (i.e. there is no point returning the results until the entire call is returned). Are there any recommended patterns for this sort of thing? Would something like this be appropriate (pseudocode, obviously)? private List<externalSystemObjects> returnedObjects = new List<externalSystemObjects>; public List<externalSystemObjects> GetObjects(List<string> ids) { int callCount = 0; int maxCallCount = 25; WaitHandle[] handles; foreach(id in itemIds to get) { if(callCount < maxCallCount) { WaitHandle handle = executeCall(id, callback); addWaitHandleToWaitArray(handle) } else { int returnedCallId = WaitHandle.WaitAny(handles); removeReturnedCallFromWaitHandles(handles); } } WaitHandle.WaitAll(handles); return returnedObjects; } public void callback(object result) { returnedObjects.Add(result); }

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• Why is my html getting mal-formed?

  - by alkaloids

  I have the following table in a form that's embedded in a formtastic form (semantic_form_for). Everything I ask to be generated by ruby shows up, but the table gets badly mangled (essentially, the tags NEVER get formed. The table headers get drawn correctly There are 14 available_date objects that get passed, and they alternate between having a time value of 1 or 2, so this is just terribly boggling, but probably simple to fix... <table class="availability_table"> <tr> <th>Date</th> <th>Early</th> <th>Late</th> </tr> <% f.fields_for :available_dates do |ad| %> <% if ad.object.time == 1 #if this is an early shift, then start the new row %> <tr><td><%= ad.object.date.strftime('%a, %b %d, %Y') %></td> <td><%= ad.collection_select(:availability , LookupAvailability.all.collect, :id, :name) %></td> <% else #otherwise end the row with just a box%> <td><%= ad.collection_select(:availability , LookupAvailability.all.collect, :id, :name) %></td></tr> <% end %> <% end %> </table> So like I said, the form functions properly, and the objects all get updated and displayed correctly and all that, it's just that the HTML isn't getting echo'd out properly so my table is all mangled. Help!

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• Django m2m form appearing fields

  - by dana

  I have a classroom application,and a follow relation. Users can follow each other and can create classrooms.When a user creates a classroom, he can invite only the people that are following him. The Classroom model is a m2m to User table. i have in models. py: class Classroom(models.Model): creator = models.ForeignKey(User) classname = models.CharField(max_length=140, unique = True) date = models.DateTimeField(auto_now=True) open_class = models.BooleanField(default=True) members = models.ManyToManyField(User,related_name="list of invited members") and in models.py of the follow application: class Relations(models.Model): initiated_by = models.ForeignKey(User, editable=False) date_initiated = models.DateTimeField(auto_now=True, editable = False) follow = models.ForeignKey(User, editable = False, related_name = "follow") date_follow = models.DateTimeField(auto_now=True, editable = False) and in views.py of the classroom app: def save_classroom(request, username): if request.method == 'POST': u = User.objects.get(username=username) form = ClassroomForm(request.POST, request.FILES) if form.is_valid(): new_obj = form.save(commit=False) new_obj.creator = request.user r = Relations.objects.filter(initiated_by = request.user) # new_obj.members = new_obj.save() return HttpResponseRedirect('.') else: form = ClassroomForm() return render_to_response('classroom/classroom_form.html', { 'form': form, }, context_instance=RequestContext(request)) i'm using a ModelForm for the classroom form, and the default view, taking in consideration my many to many relation with User table, in the field Members, is a list of all Users in my database. But i only want in that list the users that are in a follow relationship with the logged in user - the one who creates the classroom. How can i do that? Thanks!

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• IntegrityError: foreign key violation upon delete

  - by Lukasz Korzybski

  I have Order and Shipment model. Shipment has a foreign key to Order. class Order(...): ... class Shipment() order = m.ForeignKey('Order') ... Now in one of my views I want do delete order object along with all related objects. So I invoke order.delete(). I have Django 1.0.4, PostgreSQL 8.4 and I use transaction middleware, so whole request is enclosed in single transaction. The problem is that upon order.delete() I get: ... File "/usr/local/lib/python2.6/dist-packages/django/db/backends/__init__.py", line 28, in _commit return self.connection.commit() IntegrityError: update or delete on table "main_order" violates foreign key constraint "main_shipment_order_id_fkey" on table "main_shipment" DETAIL: Key (id)=(45) is still referenced from table "main_shipment". I checked in connection.queries that proper queries are executed in proper order. First shipment is deleted, after that django executes delete on order row: {'time': '0.000', 'sql': 'DELETE FROM "main_shipment" WHERE "id" IN (17)'}, {'time': '0.000', 'sql': 'DELETE FROM "main_order" WHERE "id" IN (45)'} Foreign key have ON DELETE NO ACTION (default) and is initially deferred. I don't know why I get foreign key constraint violation. I also tried to register pre_delete signal and manually delete shipment objects before delete on order is called, but it resulted in the same error. I can change ON DELETE behaviour for this key in Postgres but it would be just a hack, I wonder if anyone has a better idea what's going on here. There is also a small detail, my Order model inherits from Cart model, so it actually doesn't have id field but cart_ptr_id and after DELETE on order is executed there is also DELETE on cart, but it seems unrelated? to the shipment-order problem so I simplified it in the example.

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• casting Collection<SomeClass> to Collection<SomeSuperClass>

  - by skrebbel

  Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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• Broken ssl, what to do

  - by TIT

  I have a site and i implemented ssl there. but when i browse it, the security seals dont come. i asked to godaddy, they replaid: Thank you for contacting online support. I cannot replicate the issue you have described. The error you described is caused by the way your site has been designed. If you receive this error, you have a combination of secure and non-secure objects on the page. For example, if your secure website was https://www.domain.tld and you added an object (an image, script, flash file, etc.) to that page that was located at http://www.domain.tld/image.jpg, you would break the seal. You will need to change your design to link to objects using https (ie https://www.domain.tld/image.jpg) or modify your site design to use relative paths (/image.jpg). This error can only be corrected by modifying your site design. Please contact your web designer or the manufacturer of your web design software if you require additional assistance modifying your site design. but the problem is i made everything,all my images javascripts are unders https, but the seal still not coming, saying: some content insecure. what is the problem.

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• Alternative to as3isolib?

  - by tedw4rd

  Hi everyone, I've been working on a Flash game that involves an isometric space. I've been using as3isolib for a while now, and I'm less than impressed with how easy it is to use. Whether I'm approaching it the wrong way or it's just not that great to use is a question for another post. Anyways, I've been thinking of a different way to approach the problem of isometric positions, and I think I've got an idea that might work. Essentially, each object that is to be rendered to the iso-space maintains a 3-coordinate position. Those items are then registered with a camera that projects that 3-coordinate position to a 2-coordinate point on the screen according to the math on this Wikipedia article. Then, the MovieClip is added to the stage (or to the camera's MovieClip, perhaps) at that point, and at a child index of the point's y-value. That way, I figure objects that are closer to the camera will be "above" the objects further away, and will get rendered over them. So my question, then, is two-fold: Do you think this idea will work the way I think it will? Are there any existing 3D matrix/vector packages that I should look at? I know there's a Matrix3 class in Flex 3, but we're not using Flex for this game. Thanks!

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• How can I programmatically add more than just one view object to my view controller?

  - by BeachRunnerJoe

  I'm diving into iPhone OS development and I'm trying to understand how I can add multiple view objects to the "Left/Root" view of my SplitView iPad app. I've figured out how to programmatically add a TableView to that view based on the example code I found in Apple's online documentation... RootViewController.h @interface RootViewController : UITableViewController <NSFetchedResultsControllerDelegate, UITableViewDelegate, UITableViewDataSource> { DetailViewController *detailViewController; UITableView *tableView; NSFetchedResultsController *fetchedResultsController; NSManagedObjectContext *managedObjectContext; } RootViewController.m - (void)loadView { UITableView *newTableView = [[UITableView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame] style:UITableViewStylePlain]; newTableView.autoresizingMask = UIViewAutoresizingFlexibleHeight|UIViewAutoresizingFlexibleWidth; newTableView.delegate = self; newTableView.dataSource = self; [newTableView reloadData]; self.view = newTableView; [newTableView release]; } but there are a few things I don't understand about it and I was hoping you veterans could help clear up some confusion. In the statement self.view = newTableView, I assume I'm setting the entire view to a single UITableView. If that's the case, then how can I add additional view objects to that view alongside the table view? For example, if I wanted to have a DatePicker view object and the TableView object instead of just the TableView object, then how would I programmatically add that? Referencing the code above, how can I resize the table view to make room for the DatePicker view object that I'd like to add? Thanks so much in advance for your help! I'm going to continue researching these questions right now.

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• OpenCV shape matching

  - by MAckerman

  I'm new to OpenCV (am actually using Emgu CV C# wrapper) and am attempting to do some object detection. I'm attempting to determine if an object matches a predefined set of objects (that I will have to define). The background is well lit and does not move. My objects that I am starting with are bottles and cans. My current approach is: Do absDiff with a previously taken background image to separate the background. Then dilate 4x to make the lighter areas (in labels) shrink. Then I do a binary threshold to get a big blog, followed by finding contours in this image. I then take the largest contour and draw it, which becomes my shape to either save to the accepted set or compare with the accepted set. Currently I'm using cvMatchShapes, but the double return value seems to vary widely. I'm guessing it is because it doesn't take into account rotation. Is this approach a good one? It isn't working well for glass bottles since the edges are hard to find... I've read about haar classifiers, but thinking that might be overkill for my task.

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• Yaml::load_file acting different between development and production (Rails)

  - by James

  Hi, I am completely stumped at the nature of this problem. We export data from our application into a 'cleaned' YAML file (stripping out IDs, created_at etc). Then we (will) allow users to import these files back into the application - it is the import that is completely bugging me out. In development, YAML::load_file(params[:uploaded_data].local_path) returns an array of YAML::Objects's (and it doesn't matter which of the number of different ways the file could be loaded): [#{"exception_count"="0", "title"="Start", "amount"="70.00", "colour"=nil, "repeat_type_id"="0", "repeat_interval"="1"}}, etc etc] Which is very nice, as the attributes also include the (associated model) exceptions that you see an exception_count for. However on production (rails 2.3.2, running REE 1.8.7 and 1.8.6 for testing, tested on two different production env's, and running production locally) it returns an array of the Objects within the YAML - in this case, Event: [#, repeat_type_id: 0, colour: nil, repeat_interval: 1, exception_count: 0, etc etc] Now this would be just perplexing if it also included the associated model Exception with it - however it doesn't. Can anyone at all shed some light on why the Yaml parser would behave so differently between production and development? I'm on rails 2.3.2, running REE 1.8.7; however I've also tested running Ruby 1.8.6 with exactly the same results. Thanks for any help!

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• Code bacteria: evolving mathematical behavior

  - by Stefano Borini

  It would not be my intention to put a link on my blog, but I don't have any other method to clarify what I really mean. The article is quite long, and it's in three parts (1,2,3), but if you are curious, it's worth the reading. A long time ago (5 years, at least) I programmed a python program which generated "mathematical bacteria". These bacteria are python objects with a simple opcode-based genetic code. You can feed them with a number and they return a number, according to the execution of their code. I generate their genetic codes at random, and apply an environmental selection to those objects producing a result similar to a predefined expected value. Then I let them duplicate, introduce mutations, and evolve them. The result is quite interesting, as their genetic code basically learns how to solve simple equations, even for values different for the training dataset. Now, this thing is just a toy. I had time to waste and I wanted to satisfy my curiosity. however, I assume that something, in terms of research, has been made... I am reinventing the wheel here, I hope. Are you aware of more serious attempts at creating in-silico bacteria like the one I programmed? Please note that this is not really "genetic algorithms". Genetic algorithms is when you use evolution/selection to improve a vector of parameters against a given scoring function. This is kind of different. I optimize the code, not the parameters, against a given scoring function.

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• Creating Multiple TextFields in runtime AS2

  - by ortho

  Hi lads, I have an issue generating multiple text fields in AS2. My AS2 Flash application calls database (via PHP) and then receives XML file that contains a few objects. All I want to do is to loop throught this XML objects and then create a TextField (actually a Component that contains graphics and TextField, but this will come later) based on the information from XML object. I know that I can create something like: _root.createTextField("myText1",1,0,0,100,20); myText1.text = "this is text ONE"; _root.createTextField("myText2",2,0,30,100,20); myText2.text = "this is text TWO"; which will result in 2 text fields, but the problem is when I try to create it dynamicly (e.g. I have item: myNode[0].attributes.name (but when I use it in: _root.createTextField(myNode[0].attributes.name, 1, 0, 0, 100, 20), then I got compile error). var myXML:XML = new XML(); myXML.ignoreWhite=true; myXML.load("tekst.xml"); var tekst:String = new String(); myXML.onLoad = function(success){ if (success){ var myNode = myXML.firstChild.childNodes; for (i=0; i trace("height: "+myNode[i].attributes.height); trace("color: "+myNode[i].attributes.color); trace(myNode[i].firstChild.nodeValue); } } } This actualy traces the values and I can actualy use them when creating the component, but it doesn't create the component that has the same name (obviously both instances point to the same object so the last is only visible). Please help, I tried many things, but no joy. Thank you in advance.

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• how do i execute a stored procedure with vici coolstorage?

  - by lincolnk

  I'm building an app around Vici Coolstorage (asp.net version). I have my classes created and mapped to my database tables and can pull a list of all records fine. I've written a stored procedure where the query jumps across databases that aren't mapped with Coolstorage, however, the fields in the query result map directly to one of my classes. The procedure takes 1 parameter. so 2 questions here: how do i execute the stored procedure? i'm doing this CSParameterCollection collection = new CSParameterCollection(); collection.Add("@id", id); var result = Vici.CoolStorage.CSDatabase.RunQuery("procedurename", collection); and getting the exception "Incorrect syntax near 'procedurename'." (i'm guessing this is because it's trying to execute it as text rather than a procedure?) and also, since the class representing my table is defined as abstract, how do i specify that result should create a list of MyTable objects instead of generic or dynamic or whatever objects? if i try Vici.CoolStorage.CSDatabase.RunQuery<MyTable>(...) the compiler yells at me for it being an abstract class.

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• Excel::Shape object getting released automatically after the count reaches 18 in List<T>

  - by A9S6

  I have a Excel addin written in C# 2.0 in which I am experiencing a strange behavior.Please note that this behavior is only seen in Excel 2003 and NOT in Excel 2007 or 2010. Issue: When the user clicks an import command button, a file is read and a number of Shapes are created/added to the worksheet using Worksheet::Shapes::AddPicture() method. A reference to these Shape objects are kept in a generic list: List<Excel.Shape> list = new List<Excel.Shape>(); Everything works fine till the list has less than 18 references. When the count reaches 18, and a new Shape reference is added, the first one i.e. @ index [0] is released. I am unable to call any method or property on that reference and calling a method/property throws a COMException (0x800A1A8) i.e. Object Required. If I add one more, then the reference @ [1] is not accessible and so on. Strange enough... this happens with Shape object only i.e. If I add one Shape and then 17 nulls to the list then this wont happen until 17 more Shape objects are added. Does anyone has an idea why it happens after the count reaches 18? I thought it might be something with the List's default capacity. Something like relocating the references during which they get released so I initialized it with a capacity of 1000 but still no luck. List<Excel.Shape> list = new List<Excel.Shape>(1000); Any Idea??

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• Does Ctypes Structures and POINTERS automatically free the memory when the Python object is deleted?

  - by jsbueno

  When using Python CTypes there are the Structures, that allow you to clone c-structures on the Python side, and the POINTERS objects that create a sofisticated Python Object from a memory address value and can be used to pass objects by reference back and forth C code. What I could not find on the documentation or elsewhere is what happens when a Python object containing a Structure class that was de-referenced from a returning pointer from C Code (that is - the C function alocated memory for the structure) is itself deleted. Is the memory for the original C structure freed? If not how to do it? Furthermore -- what if the Structure contains Pointers itself, to other data that was also allocated by the C function? Does the deletion of the Structure object frees the Pointers onits members? (I doubt so) Else - -how to do it? Trying to call the system "free" from Python for the Pointers in the Structure is crashing Python for me. In other words, I have this structure filled up by a c Function call: class PIX(ctypes.Structure): """Comments not generated """ _fields_ = [ ("w", ctypes.c_uint32), ("h", ctypes.c_uint32), ("d", ctypes.c_uint32), ("wpl", ctypes.c_uint32), ("refcount", ctypes.c_uint32), ("xres", ctypes.c_uint32), ("yres", ctypes.c_uint32), ("informat", ctypes.c_int32), ("text", ctypes.POINTER(ctypes.c_char)), ("colormap", ctypes.POINTER(PIXCOLORMAP)), ("data", ctypes.POINTER(ctypes.c_uint32)) ] And I want to free the memory it is using up from Python code.

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• Help with copy and deepcopy in Python

  - by Az

  Hi there, I think I tried to ask for far too much in my previous question so apologies for that. Let me lay out my situation in as simple a manner as I can this time. Basically, I've got a bunch of dictionaries that reference my objects, which are in turn mapped using SQLAlchemy. All fine with me. However, I want to make iterative changes to the contents of those dictionaries. The problem is that doing so will change the objects they reference---and using copy.copy() does no good since it only copies the references contained within the dictionary. Thus even if copied something, when I try to, say print the contents of the dictionary, I'll only get the latest updated values for the object. This is why I wanted to use copy.deepcopy() but that does not work with SQLAlchemy. Now I'm in a dilemma since I need to copy certain attributes of my object before making said iterative changes. In summary, I need to use SQLAlchemy and at the same time make sure I can have a copy of my object attributes when making changes so I don't change the referenced object itself. Any advice, help, suggestions, etc.?

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• Flash/Flex sending XML to Rails App

  - by bdicasa

  I'm trying to send some XML to a rails app in Flex. I'm using the URLRequest and URLLoader objects. However, I'm having trouble determining how to send the XML and _method parameter to the rails app using these flash objects. Below is how I'm currently trying to achieve this. var request:URLRequest = new URLRequest(); request.method = URLRequestMethod.POST; request.data = new Object(); request.data.xml = Blog.xml.toXMLString(); request.contentType = "text/xml"; var loader:URLLoader = new URLLoader(); loader.addEventListener(Event.COMPLETE, saveCompleteHandler); var saveUrl:String = ""; saveUrl = BASE_URL; if (Blog.isNewBlog) { // Set the rails REST method. request.data._method = "POST"; saveUrl += "blogs.xml"; } else { // Set the rails REST method. request.data._method = "PUT"; saveUrl += "blogs/" + Blog.id.toString() + ".xml"; } request.url = saveUrl; //trace(request.data.toString()); loader.load(request); However the only data that is getting sent to the server is [Object object]. If some one could let me know where I'm going wrong I'd greatly appreciate it. Thanks.

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• Bi-directional view model syncing with "live" collections and properties (MVVM)

  - by Schneider

  I am getting my knickers in a twist recently about View Models (VM). Just like this guy I have come to the conclusion that the collections I need to expose on my VM typically contain a different type to the collections exposed on my business objects. Hence there must be a bi-directional mapping or transformation between these two types. (Just to complicate things, on my project this data is "Live" such that as soon as you change a property it gets transmitted to other computers) I can just about cope with that concept, using a framework like Truss, although I suspect there will be a nasty surprise somewhere within. Not only must objects be transformed but a synchronization between these two collections is required. (Just to complicate things I can think of cases where the VM collection might be a subset or union of business object collections, not simply a 1:1 synchronization). I can see how to do a one-way "live" sync, using a replicating ObservableCollection or something like CLINQ. The problem then becomes: What is the best way to create/delete items? Bi-directinal sync does not seem to be on the cards - I have found no such examples, and the only class that supports anything remotely like that is the ListCollectionView. Would bi-directional sync even be a sensible way to add back into the business object collection? All the samples I have seen never seem to tackle anything this "complex". So my question is: How do you solve this? Is there some technique to update the model collections from the VM? What is the best general approach to this?

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• Defining < for STL sort algorithm - operator overload, functor or standalone function?

  - by Andy

  I have a stl::list containing Widget class objects. They need to be sorted according to two members in the Widget class. For the sorting to work, I need to define a less-than comparator comparing two Widget objects. There seems to be a myriad of ways to do it. From what I can gather, one can either: a. Define a comparison operator overload in the class: bool Widget::operator< (const Widget &rhs) const b. Define a standalone function taking two Widgets: bool operator<(const Widget& lhs, const Widget& rhs); And then make the Widget class a friend of it: class Widget { // Various class definitions ... friend bool operator<(const Widget& lhs, const Widget& rhs); }; c. Define a functor and then include it as a parameter when calling the sort function: class Widget_Less : public binary_function<Widget, Widget, bool> { bool operator()(const Widget &lhs, const Widget& rhs) const; }; Does anybody know which method is better? In particular I am interested to know if I should do 1 or 2. I searched the book Effective STL by Scott Meyer but unfortunately it does not have anything to say about this. Thank you for your reply.

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• x86 .net application with system.OutOfMemoryException

  - by Allen

  Hi,Guys I got OutOfMemoryException after the app running for 1 day, the app totally use 1.5G memory , all consumed by managed heap, gen 2 used 200mb , and LOB used 1.3mb, however the weired thing is, 900mb of space are Free. from perf counter I saw there had number of gen 2 gc collection happened, why GC collector cannot collect those 900mb free space in gen2 and LOB? I'm really appreicate for your help. following info are from windbg: 0:000> !eeheap -gc Number of GC Heaps: 1 generation 0 starts at 0x183153f0 generation 1 starts at 0x182aa834 generation 2 starts at 0x02131000 ephemeral segment allocation context: none segment begin allocated size 02130000 02131000 0312f284 0xffe284(16769668) 07750000 07751000 0874fc5c 0xffec5c(16772188) 09e30000 09e31000 0ae2fc2c 0xffec2c(16772140) 0b230000 0b231000 0c22ffec 0xffefec(16773100) 0c230000 0c231000 0d22f6f0 0xffe6f0(16770800) 0d230000 0d231000 0e22ea10 0xffda10(16767504) 0e230000 0e231000 0f22c1c4 0xffb1c4(16757188) 10390000 10391000 1138ddf4 0xffcdf4(16764404) 154e0000 154e1000 164da90c 0xff990c(16750860) 34aa0000 34aa1000 35a9dbfc 0xffcbfc(16763900) 7aca0000 7aca1000 7bc9edfc 0xffddfc(16768508) 49760000 49761000 4a75ef64 0xffdf64(16768868) 7bca0000 7bca1000 7cc99bac 0xff8bac(16747436) 17a70000 17a71000 183313fc 0x8c03fc(9176060) Large object heap starts at 0x03131000 segment begin allocated size 03130000 03131000 041250c8 0xff40c8(16728264) 08920000 08921000 099102f8 0xfef2f8(16708344) .... .... 4c760000 4c761000 4d71d578 0xfbc578(16500088) 1bb10000 1bb11000 1ca110d0 0xf000d0(15728848) 57760000 57761000 5862d7f8 0xecc7f8(15517688) Total Size: Size: 0x5ab13450 (1521562704) bytes. ------------------------------ GC Heap Size: Size: 0x5ab13450 (1521562704) bytes. 0:000> !dumpheap -stat total 0 objects Statistics: MT Count TotalSize Class Name 73037c78 1 12 System.Configuration.GenericEnumConverter 73036da0 1 12 System.Configuration.InfiniteIntConverter .... .... 69161c3c 35025 6809420 System.Windows.EffectiveValueEntry[] 69164748 54 12471072 MS.Internal.WeakEventTable+EventKey[] 710e2228 9540 190389260 System.Byte[] 710dd2b8 1317031 339257932 System.String 0035a670 6427 902224056 Free Total 3615631 objects

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• Why does the Java Collections Framework offer two different ways to sort?

  - by dvanaria

  If I have a list of elements I would like to sort, Java offers two ways to go about this. For example, lets say I have a list of Movie objects and I’d like to sort them by title. One way I could do this is by calling the one-argument version of the static java.util.Collections.sort( ) method with my movie list as the single argument. So I would call Collections.sort(myMovieList). In order for this to work, the Movie class would have to be declared to implement the java.lang.Comparable interface, and the required method compareTo( ) would have to be implemented inside this class. Another way to sort is by calling the two-argument version of the static java.util.Collections.sort( ) method with the movie list and a java.util.Comparator object as it’s arguments. I would call Collections.sort(myMovieList, titleComparator). In this case, the Movie class wouldn’t implement the Comparable interface. Instead, inside the main class that builds and maintains the movie list itself, I would create an inner class that implements the java.util.Comparator interface, and implement the one required method compare( ). Then I'd create an instance of this class and call the two-argument version of sort( ). The benefit of this second method is you can create an unlimited number of these inner class Comparators, so you can sort a list of objects in different ways. In the example above, you could have another Comparator to sort by the year a movie was made, for example. My question is, why bother to learn both ways to sort in Java, when the two-argument version of Collections.sort( ) does everything the first one-argument version does, but with the added benefit of being able to sort the list’s elements based on several different criteria? It would be one less thing to have to keep in your mind while coding. You’d have one basic mechanism of sorting lists in Java to know.

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• Building a formset dynamically

  - by vorpyg

  I initially wrote code to build a form dynamically, based on data from the DB, similar to what I described in my previous SO post. As SO user Daniel Roseman points out, he would use a formset for this, and now I've come to the realization that he must be completely right. :) My approach works, basically, but I can't seem to get validation across the entire form to be working properly (I believe it's possible, but it's getting quite complex, and there has to be a smarter way of doing it = Formsets!). So now my question is: How can I build a formset dynamically? Not in an AJAX way, I want each form's label to be populated with an FK value (team) from the DB. As I have a need for passing parameters to the form, I've used this technique from a previous SO post. With the former approach, my view code is (form code in previous link): def render_form(request): teams = Team.objects.filter(game=game) form_collection = [] for team in teams: f = SuggestionForm(request.POST or None, team=team, user=request.user) form_collection.append(f) Now I want to do something like: def render_form(request): teams = Team.objects.filter(game=game) from django.utils.functional import curry from django.forms.formsets import formset_factory formset = formset_factory(SuggestionForm) for team in teams: formset.form.append(staticmethod(curry(SuggestionForm, request.POST or None, team=team, user=request.user))) But the append bit doesn't work. What's the proper way of doing this? Thanks!

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• Best strategy for moving data between physical tiers in ASP.net

  - by Pete Lunenfeld

  Building a new ASP.net application, and planning to separate DB, 'service' tier and Web/UI tier into separate physical layers. What is the best/easiest strategy to move serialized objects between the service tier and the UI tier? I was considering serializing POCOs into JSON using simple ASP.net pages to serve the middle tier. Meaning that the UI/Web tier will request data from a (hidden to the outside user) web server that will return a JSON string. This kind of JSON 'emitter' seems easily testable. It also seems easily compressible for efficiently moving data over the WAN between tiers. I know that some folks use .asmx webservices for this kind of task, but this seems like there is excess overhead with SOAP, and the package is not as human readable (testable) as POCOs serialized as JSON. Others are using more complex technology like WCF which we have never used. Does anyone have advice for choosing a method for moving data/objects between the data (db) tier and the web (UI) tier over the WAN using .net technologies? Thanks!!!

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