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  • Querying a Cassandra column family for rows that have not been updated in X days

    - by knorv
    I'm moving an existing MySQL based application over to Cassandra. So far finding the equivalent Cassandra data model has been quite easy, but I've stumbled on the following problem for which I'd appreciate some input: Consider a MySQL table holding millions of entities: CREATE TABLE entities ( id INT AUTO_INCREMENT NOT NULL, entity_information VARCHAR(...), entity_last_updated DATETIME, PRIMARY KEY (id), KEY (entity_last_updated) ); The table is regularly queried for entities that need to be updated: SELECT id FROM entities WHERE entity_last_updated IS NULL OR entity_last_updated < DATE_ADD(NOW(), INTERVAL -7*24 HOUR) ORDER BY entity_last_updated ASC; The entities returned by this queries are then updated using the following query: UPDATE entities SET entity_information = ?, entity_last_updated = NOW() WHERE id = ?; What would be the corresponding Cassandra data model that would allow me to store the given information and effectively query the entities table for entities that need to be updated (that is: entities that have not been updated in the last seven days)?

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  • Create Class functions on the fly?

    - by JasonS
    Hi, i have a validation class which needs improving. If I require some custom validation I need to specify a custom function. It works a bit like this: The controller tells the validation that a custom validation function is required. The controller runs the validation. --- Gets iffy here --- Validation class creates a new instance of the controller class.... Validation class runs controller-custom_validation_function() Validation class returns true / false Is there someway that I can alter this to do something like this? $validation = new validation; // Insert rules here. $validation-function() = $this-function(); By doing this I could get rid of the step of creating an unneeded class instance.

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  • Can't find how to import as one object or how to merge

    - by Aaron
    I need write a script in blender that creates some birds which fly around some obstacles. The problem is that I need to import a pretty large Collada model (a building) which consists of multiple objects. The import works fine, but the the building is not seen as 1 object. I need to resize and move this building, but I can only get the last object in the building (which is a camera)... Does anyone know how to merge this building in 1 object, group, variable... so I can resize and move it correctly? Part of the code I used: bpy.ops.wm.collada_import(filepath="C:\\Users\\me\\building.dae") building= bpy.context.object building.scale = (100, 100, 100) building.name = "building"

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  • Groovy Prototype Object

    - by Holden
    I have a method with an incoming variable, which represents a script. e.g. hello.groovy Foo.init(this) Foo.groovy class Foo { static init(app) { } } What is the best way to add a ton of new functionality to the app variable in the init method? Basically, I would like to add all the functionality of another object to the app object. For instance, if I had another class: class Bar { def a() { } def b() { } } I would like the app object to basically be a new Bar(). In JavaScript, this is easy by using the prototype object, but I cannot seem to get it working in groovy. What is the best way to accomplish this? Or should I be doing something differently?

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  • How to use Object.GetHashCode() on a type that overrides GetHashCode()

    - by Jimmy
    Hi, I have a class A that implements IEquatable<, using its fields (say, A.b and A.c) for implementing/overriding Equals() and overriding GetHashCode(), and everything works fine, 99% of the time. Class A is part of a hierarchy (class B, C) that all inherit from interface D; they can all be stored together in a dictionary Dictionary, thus it's convenient when they all carry their own default Equals()/GetHashCode(). However, while constructing A I sometime need to do some work to get the values for A.b and A.c; while that's happening, I want to store a reference to the instance that's being built. In that case, I don't want to use the default Equals()/GetHashCode() overrides provided by A. Thus, I was thinking of implementing a ReferenceEqualityComparer, that's meant to force the use of Object's Equals()/GetHashCode(): private class ReferenceEqualityComparer<T> : IEqualityComparer<T> { #region IEqualityComparer<T> Members public bool Equals(T x, T y) { return System.Object.ReferenceEquals(x, y); } public int GetHashCode(T obj) { // what goes here? I want to do something like System.Object.GetHashCode(obj); } #endregion } The question is, since A overrides Object.GetHashCode(), how can I (outside of A) call Object.GetHashCode() for an instance of A? One way of course would be for A to not implement IEquatable< and always supply an IEqualityComparer< to any dictionary that I create, but I'm hoping for a different answer. Thanks

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  • How to test COM object integrity automatically?

    - by sharptooth
    Every COM object must have integrity. In simplified terms this means that if an object implements 3 interfaces - A, B and C and I have A* pointer to the object I must be able to successfully QueryInterface() both B and C and having B I must be able to retrieve A and C and having C I must be able to retrieve A and B. Now my object implements 5 interfaces and I want to test its integrity. Writing checks for all of the above myself will require a substantial effort. Is there a tool or some easily tweakable code or a code pattern that would do it?

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  • When writing a game, should you make objects/enemies/etc. have unique ID numbers?

    - by SLC
    I have recently encountered some issues with merely passing references to objects/enemies in a game I am making, and am wondering if I am using the wrong approach. The main issue I have is disposing of enemies and objects, when other enemies or players may still have links to them. For example, if you have a Rabbit, and a Wolf, the Wolf may have selected the Rabbit to be its target. What I am doing, is the wolf has a GameObject Target = null; and when it decides it is hungry, the Target becomes the Rabbit. If the Rabbit then dies, such as another wolf killing it, it cannot be removed from the game properly because this wolf still has a reference to it. In addition, if you are using a decoupled approach, the rabbit could hit by lightning, reducing its health to below zero. When it next updates itself, it realises it has died, and is removed from the game... but there is no way to update everything that is interested in it. If you gave every enemy a unique ID, you could simply use references to that instead, and use a central lookup class that handled it. If the monster died, the lookup class could remove it from its own index, and subsequently anything trying to access it would be informed that it's dead, and then they could act accordingly. Any thoughts on this?

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  • How to troubleshoot deallocation of object in uitableview?

    - by 4thSpace
    I have a table view with tall cells. About 300 in height. The cells are custom and have an associated nib. In cellForRowAtIndexPath, I access an object in an array using indexPath.row. The object has properties, which I assign to labels on the custom cell. This works fine for the first two cells. Once I scroll enough for the third cell to get created, the app crashes. I have NSZombieEnabled set and here is the output: 2010-04-19 21:48:13.360 MyApp[54463:207] *** -[CALayer release]: message sent to deallocated instance 0xfc4e50 (gdb) continue 2010-04-19 21:48:18.382 MyApp[54463:207] *** NSInvocation: warning: object 0xfc4e50 of class '_NSZombie_CALayer' does not implement methodSignatureForSelector: -- trouble ahead 2010-04-19 21:48:18.383 MyApp[54463:207] *** NSInvocation: warning: object 0xfc4e50 of class '_NSZombie_CALayer' does not implement doesNotRecognizeSelector: -- abort (gdb) continue Program received signal: “EXC_BAD_ACCESS”. (gdb) I'm not sure what is deallocated. How can I trace this to the source?

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  • From a 3D modeler to an iPhone app - what are best practices?

    - by bonkey
    I am quite new in 3D programming on iPhone and I would like to ask for hints about organizing a work between designers and programmers on that platform. Most of all: what kind of tools, libraries or plugins cooperate the best on both sides. Although I consider the question as looking for general best-practices advice I would like to find a solution for my current situation which I describe further, too. I've already done some research and found following libraries: SIO2 Khronos OpenGL ES 1.x SDK for PowerVR MBX Unity3D Oolong Game Engine I've checked modellers or plugins to them giving output formats readable by those tools: obj2opengl Wavefront OBJ to plain header file converter Blender with SIO2 exporter iphonewavefrontloader Cheetah3D PVRGeoPOD for 3DS / Maya Unfortunately I still have no clear vision how to combine any of that tools to get a desinger's work in an application. I look for a way of getting it in the most possible complete way: models, lights, scenes, textures, maybe some simple animations (but rather no game-like physics), but I still got nothing. And here comes my situation: I would like to find right way to present few (but quite complicated) models from a single scene. The designers mostly use 3DS Max 9, sometimes 10 (which partly prevents using PVRGeoPOD) and are rather reluctant to switch to something else but if there's no other choice I suppose it would be possible. The basic rule I've already found in some places "use Wavefront OBJ" not always works. I haven't got any acceptable results with production files, actually. The only things worked fine were some mere examples. Some of my models did imported incomplete, sometimes exporters hung or generated enormous files not really useful on an iPhone, sometimes enabling textures (with GL_TEXTURE_2D) just crashed an app. I know it might be a problem with too complicated models or my mistakes coming from inexeperience but I am not able to find any guidelines for that process to have streamlined cooperation with designers. I am even willing to write some things from scratch in pure OpenGL-ES if it's necessary, but I would like to avoid what might be avoided and get the most from the model files. The best would be the effect I saw on some SIO2 tutorials: export, build & go. But at that moment I've got only "import, wrong", "import, where are textures?", "import, that almost looks fine, export, hang" and so on... Is it really so much frustrating or I am just missed something obvious? Can anybody share his/her experience in that field and tell what kind of software uses for "making things happen"?

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  • How to structure a Genetic Algorithm class hierarchy?

    - by MahlerFive
    I'm doing some work with Genetic Algorithms and want to write my own GA classes. Since a GA can have different ways of doing selection, mutation, cross-over, generating an initial population, calculating fitness, and terminating the algorithm, I need a way to plug in different combinations of these. My initial approach was to have an abstract class that had all of these methods defined as pure virtual, and any concrete class would have to implement them. If I want to try out two GAs that are the same but with different cross-over methods for example, I would have to make an abstract class that inherits from GeneticAlgorithm and implements all the methods except the cross-over method, then two concrete classes that inherit from this class and only implement the cross-over method. The downside to this is that every time I want to swap out a method or two to try out something new I have to make one or more new classes. Is there another approach that might apply better to this problem?

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  • agent-based simulation: performance issue: Python vs NetLogo & Repast

    - by max
    I'm replicating a small piece of Sugarscape agent simulation model in Python 3. I found the performance of my code is ~3 times slower than that of NetLogo. Is it likely the problem with my code, or can it be the inherent limitation of Python? Obviously, this is just a fragment of the code, but that's where Python spends two-thirds of the run-time. I hope if I wrote something really inefficient it might show up in this fragment: UP = (0, -1) RIGHT = (1, 0) DOWN = (0, 1) LEFT = (-1, 0) all_directions = [UP, DOWN, RIGHT, LEFT] # point is just a tuple (x, y) def look_around(self): max_sugar_point = self.point max_sugar = self.world.sugar_map[self.point].level min_range = 0 random.shuffle(self.all_directions) for r in range(1, self.vision+1): for d in self.all_directions: p = ((self.point[0] + r * d[0]) % self.world.surface.length, (self.point[1] + r * d[1]) % self.world.surface.height) if self.world.occupied(p): # checks if p is in a lookup table (dict) continue if self.world.sugar_map[p].level > max_sugar: max_sugar = self.world.sugar_map[p].level max_sugar_point = p if max_sugar_point is not self.point: self.move(max_sugar_point) Roughly equivalent code in NetLogo (this fragment does a bit more than the Python function above): ; -- The SugarScape growth and motion procedures. -- to M ; Motion rule (page 25) locals [ps p v d] set ps (patches at-points neighborhood) with [count turtles-here = 0] if (count ps > 0) [ set v psugar-of max-one-of ps [psugar] ; v is max sugar w/in vision set ps ps with [psugar = v] ; ps is legal sites w/ v sugar set d distance min-one-of ps [distance myself] ; d is min dist from me to ps agents set p random-one-of ps with [distance myself = d] ; p is one of the min dist patches if (psugar >= v and includeMyPatch?) [set p patch-here] setxy pxcor-of p pycor-of p ; jump to p set sugar sugar + psugar-of p ; consume its sugar ask p [setpsugar 0] ; .. setting its sugar to 0 ] set sugar sugar - metabolism ; eat sugar (metabolism) set age age + 1 end On my computer, the Python code takes 15.5 sec to run 1000 steps; on the same laptop, the NetLogo simulation running in Java inside the browser finishes 1000 steps in less than 6 sec. EDIT: Just checked Repast, using Java implementation. And it's also about the same as NetLogo at 5.4 sec. Recent comparisons between Java and Python suggest no advantage to Java, so I guess it's just my code that's to blame? EDIT: I understand MASON is supposed to be even faster than Repast, and yet it still runs Java in the end.

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  • Suggestions for Single-Page Web Application Design?

    - by DaveDev
    My view is that unless you need to change the basic structure of the user interface, you should not have to reload the page at all for any user interactions. I'd like to approach my next ASP.NET MVC project with this in mind. Can anyone suggest any principles, patterns or practices* I should consider? Excellent book, btw. Still trying to wrap my head around some of the concepts though. I thought a question like this would help link the theory to a practical design. Thanks

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  • Disassemble Microsoft Visual Studio 2003 compiler output

    - by Carl Norum
    I'm seeing what I think is strange behaviour from object files output by the Microsoft Visual Studio 2003 tools. The file utility tells me: asmfile.obj: 80386 COFF executable not stripped - version 30821 For objects created by the assembler, but for objects coming from C files, I get just: cfile.obj: data Using Microsoft's dumpbin utility and the objdump I got from cygwin, I can disassemble the assembly-built file, but I get no useful results from either utility for the C-built files. I have a couple of questions related to this difference: What is the object file format generated by the MSVC2003 compiler? How can I disassemble that object file? I am particularly interested in getting the disassembly in AT&T syntax - I'm doing a port of a large source base to make it work with GCC, and I would like to use this method as a shortcut for some of the inline assembly routines in the project. Thanks!

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  • ASIHTTPRequest code design

    - by nico
    I'm using ASIHTTPRequest to communicate with the server asynchronously. It works great, but I'm doing requests in different controllers and now duplicated methods are in all those controllers. What is the best way to abstract that code (requests) in a single class, so I can easily re-use the code, so I can keep the controllers more simple. I can put it in a singleton (or in the app delegate), but I don't think that's a good approach. Or maybe make my own protocol for it with delegate callback. Any advice on a good design approach would be helpful. Thanks.

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  • How to model "target day" in UML Classdiagrams

    - by Tobiask
    Hi there, I want to describe the following situation in an UML Classdiagram: A day, on which a newspaper is send to a customer. This day could be sth. like "every friday" or "every first day of a month". My idea to represent this in a UML Classdiagram: -targetDay:Integer -targetDayGrid:Enumeration targetDay would be sth. like "1" (for monday) oder "5" (for friday) or it could be "1" for the first day of the month or "10" for the 10th day of the month. targetDayGrid is an enum: weekly, monthly. So the enum sets the semantic meaning of the number in targetDay. I´m not happy with this, do you know any other solution to represent my problem? Or do you think my solution is okay?

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  • Persist an object that is not marked as serializable

    - by lasseeskildsen
    Hi, I need to persist an object that is not marked with the serializable attribute. The object is from a 3rd party library which I cannot change. I need to store it in a persist place, like for example the file system, so the optimal solution would be to serialize the object to a file, but since it isn't marked as serializable, that is not a straight forward solution. It's a pretty complex object, which also holds a collection of other objects. Do you guys have any input on how to solve this? The code will never run in a production environment, so I'm ok with almost any solution and performance.

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  • Optimize mysql table ?

    - by fabien-barbier
    Here is my actual table schema (I'm using Mysql) : Table experiment : code(int) sample_1_id sample_2_id ... until ... sample_12_id rna_1_id rna_2_id ... until ... rna_12_id experiment_start How can I optimize both part : sample_n_id and rna_n_id (all are bigint(20) and allow null=true) ? About values : we can have : ex : sample_1_id = 2 , Sample_2_id = 5 , ... Note : values can be updated. Ideas ? Thanks.

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  • iPhone JSON Object

    - by Cosizzle
    Hello, I'm trying to create a application that will retrieve JSON data from an HTTP request, send it to a the application main controller as a JSON object then from there do further processing with it. Where I'm stick is actually creating a class that will serve as a JSON class in which will take a URL, grab the data, and return that object. Alone, im able to make this class work, however I can not get the class to store the object for my main controller to retrieve it. Because im fairly new to Objective-C itself, my thoughts are that im messing up within my init call: -initWithURL:(NSString *) value { responseData = [[NSMutableData data] retain]; NSString *theURL = value; NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:theURL]]; [[NSURLConnection alloc] initWithRequest:request delegate:self]; return self; } The processing of the JSON object takes place here: - (void)connectionDidFinishLoading:(NSURLConnection *)connection { [connection release]; NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding]; [responseData release]; NSError *jsonError; SBJSON *json = [[SBJSON new] autorelease]; NSDictionary *parsedJSON = [json objectWithString:responseString error:&jsonError]; // NSArray object. listings = [parsedJSON objectForKey:@"posts"]; NSEnumerator *enumerator = [listings objectEnumerator]; NSDictionary* item; // to prove that it does work. while (item = (NSDictionary*)[enumerator nextObject]) { NSLog(@"posts:id = %@", [item objectForKey:@"id"]); NSLog(@"posts:address = %@", [item objectForKey:@"address"]); NSLog(@"posts:lat = %@", [item objectForKey:@"lat"]); NSLog(@"posts:lng = %@", [item objectForKey:@"lng"]); } [responseString release]; } Now when calling the object within the main controller I have this bit of code in the viewDidLoad method call: - (void)viewDidLoad { [super viewDidLoad]; JSON_model *jsonObj = [[JSON_model alloc] initWithURL:@"http://localhost/json/faith_json.php?user=1&format=json"]; NSEnumerator *enumerator = [[jsonObj listings] objectEnumerator]; NSDictionary* item; // while (item = (NSDictionary*)[enumerator nextObject]) { NSLog(@"posts:id = %@", [item objectForKey:@"id"]); NSLog(@"posts:address = %@", [item objectForKey:@"address"]); NSLog(@"posts:lat = %@", [item objectForKey:@"lat"]); NSLog(@"posts:lng = %@", [item objectForKey:@"lng"]); } }

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  • WPF - How do I get an object that is bound to a ListBoxItem back

    - by JonBlumfeld
    Hi there here is what I would like to do. I get a List of objects from a database and bind this list to a ListBox Control. The ListBoxItems consist of a textbox and a button. Here is what I came up with. Up to this point it works as intended. The object has a number of Properties like ID, Name. If I click on the button in the ListBoxItem the Item should be erased from the ListBox and also from the database... <ListBox x:Name="taglistBox"> <ListBox.ItemContainerStyle> <Style TargetType="{x:Type ListBoxItem}"> <Setter Property="HorizontalAlignment" Value="Stretch"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="ListBoxItem"> <ContentPresenter HorizontalAlignment="Stretch"/> </ControlTemplate> </Setter.Value> </Setter> <Setter Property="Tag" Value="{Binding TagSelf}"></Setter> </Style> </ListBox.ItemContainerStyle> <ListBox.ItemTemplate> <DataTemplate> <Grid HorizontalAlignment="Stretch"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto"/> <ColumnDefinition/> </Grid.ColumnDefinitions> <Button Grid.Column="0" Name="btTag" VerticalAlignment="Center" Click="btTag_Click" HorizontalAlignment="Left"> <Image Width="16" Height="16" Source="/WpfApplication1;component/Resources/104.png"/> </Button> <TextBlock Name="tbtagBoxTagItem" Margin="5" Grid.Column="1" Text="{Binding Name}" VerticalAlignment="Center" /> </Grid> </DataTemplate> </ListBox.ItemTemplate> </ListBox> The Textblock.Text is bound to object.Name and the ListBoxItem.Tag to object.TagSelf (which is just a copy of the object itself). Now my questions If I click the button in the listboxItem how do I get the listboxitem and the object bound to it back. In order to delete the object from the database I have to retrieve it somehow. I tried something like ListBoxItem lbi1 = (ListBoxItem)(taglistBox.ItemContainerGenerator.ContainerFromItem(taglistBox.Items.CurrentItem)); ObjectInQuestion t = (ObjectInQuestion) lbi1.Tag; Is there a way to automatically update the contents of the ListBox if the Itemssource changes? Right now I'm achieving that by taglistBox.ItemsSource = null; taglistBox.ItemsSource = ObjectInQuestion; I'd appreciate any help you can give :D Thanks in advance

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  • Accessing the Private Constructor

    - by harigm
    I am java developer, went for an interview. I have been asked a question about the Private constructor 1) Can I access a Private Constructor of a Class and Instantiate the class. I was thinking and gave the answer directly--- "NO" But its wrong, can any one help Why NO? and How we can achieve this

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