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• Optimising local image loading/rendering on iPhone

  - by Tricky

  Hi, I'm looking to create an interface where the user can navigate through large volumes of images. Each image has a thumbnail of 128x128 that I wish to display and will be kind of similar to coverflow in operation. I have this all working in principle but am becoming stuck when navigating through content at speed. The interface begins to stutter and becoming jerky. I believe this is primarily because of disk i/o and the cost of rendering each image. Is there anyway this can be handed over to a seperate thread simply? Defaulting to a greyed out thumbnail until the image has loaded? How have Apple managed to achieve this in coverflow? Many thanks,

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• Concatenation Operator

  - by Chaitanya

  This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: by not using the concatenation operator, does it effect the performance? If it doesn't why at all have the concatenation operator. Why have 2 modes of implementation when one does the work?

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• Multiple ParticleSystems in cocos2d

  - by Mattias Akerman

  I wonder about what road I should go with ParticleSystem. In this particular case I want to create 1-20 small explosions at the same time but with different positions. Right now I'm creating a new ParticleSystem for each explosion and then release it, but of course this is very punishing to the performance. My question is: Is there a way to create one ParticleSystem with multiple emitting sources. If not should I create an array of ParticleSystem in init and then use a free one when an explosion is needed? Or is there another approach I haven't thought of?

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• PostgreSQL 8.3 data types: xml vs varchar

  - by Sejanus

  There's xml data type in Postgres, I never used it before so I'd like to hear opinions. Downsides and upsides vs using regular varchar (or Text) column to store xml. The text I'm going to store is xml, well-formed, UTF-8. No need to search by it (I've read searching by xml is slow). This XML actually is data prepared for PDF generation with Apache FOP. XML can be generated dynamically from data found elsewhere (other Postgres tables), it's stored as is only so that I won't need to generate it twice. Kinda backup#2 for already generated PDF documents. Anything else to know? Good practices, performance, maintenance, etc?

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• Looking for the most painless non-RDBMS storage method in C#

  - by NateD

  I'm writing a simple program that will run entirely client-side. (Desktop programming? do people still do that?) and I need a simple way to store trivial amounts of data in a structured form, but really don't see any need to use a database system. What's more, some of the data needs to be serialized and passed around to different users, like some kind of "file" or perhaps a "document". (has anyone ever done that before?) So, I've looked at using .Net DataSets, LINQ, direct XML manipulation, and they all seem like they would get the job done, but I would like to know before I dive into any of them if there's one method that is generally regarded as easier to code than others. As I said, the amount of data to be stored is trivial, even if one hundred people all used the same machine we're not talking about more than 10 MB, so performance is not as large a concern as is codeability/maintainability. Thank you all in advance!

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• touches event handler for UIImageView

  - by madmik3

  I am just getting stated with iPhone development and can't seem to find the answer I am looking for what I want to do. It seems like I should be able to programmatically create a UIImageView and then set up an event handler for it's touch functions. in c# i would have something that looks like Button b = new Button(); b.Click+= my handler code right now I have this CGRect myImageRect = CGRectMake(0.0f, 0.0f, 141.0f, 151.0f); UIImageView *myImage = [[UIImageView alloc] initWithFrame:myImageRect]; myImage.userInteractionEnabled = YES; [myImage setImage:[UIImage imageNamed:@"myImage.png"]]; myImage.opaque = YES; // explicitly opaque for performance [self.view addSubview:myImage]; [myImage release]; What do I need to do to override the touch events? thanks

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• How do I get the name of the newest file via the Terminal?

  - by Alec

  I'm trying to create a macro for Keyboard Maestro for OS X doing the following: Get name of newest file in a directory on my disk based on date created; Paste the text "newest file: " plus the name of the newest file. One of its options is to "Execute a shell script", so I thought that would do it for 1. After Googling around a bit I came up with this: cd /path/to/directory/ ls -t | head -n1 This sorts it right, and returns the first filename. However, it also seems to includes a line break, which I do not want. As for 2: I can output the text "newest file: " with a different action in the app, and paste the filename behind that. But I'm wondering if you can't return "random text" + the outcome of the ls command. So my question is: can I do this only using the ls command? And how do I get just the name of the latest file without any linebreaks or returns?

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• Tables with no Primary Key

  - by Matt Hamilton

  I have several tables whose only unique data is a uniqueidentifier (a Guid) column. Because guids are non-sequential (and they're client-side generated so I can't use newsequentialid()), I have made a non-primary, non-clustered index on this ID field rather than giving the tables a clustered primary key. I'm wondering what the performance implications are for this approach. I've seen some people suggest that tables should have an auto-incrementing ("identity") int as a clustered primary key even if it doesn't have any meaning, as it means that the database engine itself can use that value to quickly look up a row instead of having to use a bookmark. My database is merge-replicated across a bunch of servers, so I've shied away from identity int columns as they're a bit hairy to get right in replication. What are your thoughts? Should tables have primary keys? Or is it ok to not have any clustered indexes if there are no sensible columns to index that way?

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• What design considerations should one take to receive text and multiple attachments via web?

  - by ramesh.nagul

  I am developing a web application to accept a bunch of text and attachments (1 or more) via email, web and other methods. I am planning to build a single interface, mostly a web service to accept this content. What design considerations should I make? I am building the app using ASP.NET MVC 2. Should the attachments be saved to disk or in the database? Should the unified single interface be a web service? Pros and cons to using web services to upload files

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• Grand Central Strategy for Opening Multiple Files

  - by user276632

  I have a working implementation using Grand Central dispatch queues that (1) opens a file and computes an OpenSSL DSA hash on "queue1", (2) writing out the hash to a new "side car" file for later verification on "queue2". I would like to open multiple files at the same time, but based on some logic that doesn't "choke" the OS by having 100s of files open and exceeding the hard drive's sustainable output. Photo browsing applications such as iPhoto or Aperture seem to open multiple files and display them, so I'm assuming this can be done. I'm assuming the biggest limitation will be disk I/O, as the application can (in theory) read and write multiple files simultaneously. Any suggestions? TIA

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• windows I/O manager - IRP's classification in read-like and write-like

  - by clyfe

  I am writing a windows filesystem minifilter driver that must fail IRP's in a preoperation callback. How can I find out from the callback parameters if the operation is read-like ( only reads data ) or it's write-like ( modifies data on the disk - write, delete etc ) ? I'm thinking on: Data->Iopb->TargetFileObject->ReadAccess Data->Iopb->TargetFileObject->WriteAccess But I'm not sure, I think thees are available only in postoperation callback. The documentation is really cumbersome. Code sample: FLT_PREOP_CALLBACK_STATUS Fail ( __inout PFLT_CALLBACK_DATA Data, __in PCFLT_RELATED_OBJECTS FltObjects, __deref_out_opt PVOID *CompletionContext ) { FLT_PREOP_CALLBACK_STATUS status = FLT_PREOP_SUCCESS_NO_CALLBACK; if ( IS WRITE_LIKE(Data, FltObjects) ) { // ??? HOW DO I FIND OUT???? if( FLT_IS_FASTIO_OPERATION(Data) ){ status = FLT_PREOP_DISALLOW_FASTIO; } else { status = FLT_PREOP_COMPLETE; } Data->IoStatus.Status = STATUS_ACCESS_DENIED; Data->IoStatus.Information = 0; return status; } return status; }

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• which is the best for build a Gantt-chart like application Flex or Flash Action Script?

  - by coderex

  Which is the best for build an application show like in image. For the better graphics and performance wise. I want to know Flash for Flex is more suitable for this. In Flash ca we be able to build a grid kind of applications easily? I headed that Flex have the functions to handle grid and other things. Drag & scroll Zoom like feature. but am not sure able the graphics of flex. Is the components are customizable.. Please help me.

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• Using PHP to place database rows into an array?

  - by Hamed Szilazi

  I was just wondering how i would be able to code perform an SQL query and then place each row into a new array, for example, lets say a table looked like the following: $people= mysql_query("SELECT * FROM friends") Output: | ID | Name | Age | --1----tom----32 --2----dan----22 --3----pat----52 --4----nik----32 --5----dre----65 How could i create a multidimensional array that works in the following way, the first rows second column data could be accessed using $people[0][1] and fifth rows third column could be accessed using $people[4][2]. How would i go about constructing this type of array? Sorry if this is a strange question, its just that i am new to PHP+SQL and would like to know how to directly access data. Performance and speed is not a issue as i am just writing small test scripts to get to grips with the language.

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• Best practices to build a highly configurable software product.

  - by Kabeer

  Hello. I am working on a software product that can substantially change behavior based on the configuration & meta-data supplied. I would like to know best practices to architect / build a highly configurable software product. Considering that there are substantial number of configuration parameters, I'd like to look at something that will not affect the performance before I look at dependency injection. My platform is .Net ... I seek recommendations on architecture / design and implementations fronts.

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• Implementing ma? osx loop device driver.

  - by Inso Reiges

  Hello, I am aware that there is a native implementation of loop device system on osx, the hdiutil/hdix driver. But due to a number of reasons i need to roll out my own custom loop driver. Since hdix is closed-source can anyone give some starting pointers, links, advises, etc. on the subject? I had expirience implementing loop drivers on linux and windows but i don't really have a clue where to start from on osx. The basic functionality i need to implement is the same: given any file on disk, simulate a virtual block device interface for it. I also would like my loop driver to use all the native partition filter stacking available for real and hdix virtual block devices on osx.

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• I want to version control my entire slice

  - by Tom

  I'm renting a slice (i.e., a VPS) from Slicehost. I've a spent a day or two filling up /usr with my favorite packages, /etc with configs and init scripts, and so on. Now I want to: save this whole setup somewhere (e.g., to load onto another machine). see what changes I've made to which files revert changes, tag revisions, and all that other good version control stuff Saving a disk image gives me (1), but not (2) and (3). Using Subversion (svn import / svn://someotherhost) might give me all three, but I expect problems if I actually try to check a project out into / and maintain .svn directories in root-owned areas. And to load my setup onto a fresh slice, I'd need to install an svn client on it first. Is there a good way to do what I want to do?

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• Are C++ meta-templates required knowledge for programmers?

  - by Robert Gould

  In my experience Meta-templates are really fun (when your compilers are compliant), and can give good performance boosts, and luckily I'm surrounded by seasoned C++ programmers that also grok meta-templates, however occasionally a new developer arrives and can't make heads or tails of some of the meta-template tricks we use (mostly Andrei Alenxandrescu stuff), for a few weeks until he gets initiated appropriately. So I was wondering what's the situation for other C++ programmers out there? Should meta-template programming be something C++ programmers should be "required" to know (excluding entry level students of course), or not? Edit: Note my question is related to production code and not little samples or prototypes

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• Writing temporary data from R

  - by Shane

  I want to write some temporary data to disk in an R package, and I want to be sure that it can run on every OS without assuming the user has admin rights. Is there an existing R function that can provide a path to a temporary directory on all major OS's? Or a way to reference a user's home directory? Otherwise, I was thinking of trying this: Sys.getenv("temp") I presume that I can't expect people to have write access to their R locations, otherwise I could reference a path within the package directory: .find.package("package.name").

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• Is it a good idea to create an STL iterator which is noncopyable?

  - by BillyONeal

  Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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• Rails Unit Testing with MyISAM Tables

  - by tadman

  I've got an application that requires the use of MyISAM on a few tables, but the rest are the traditional InnoDB type. The application itself is not concerned with transactions where it applies to these records, but performance is a concern. The Rails testing environment assumes the engine used is transactional, though, so when the test database is generated from the schema.rb it is imported with the same engine. Is it possible to over-ride this behaviour in a simple manner? I've resorted to an awful hack to ensure the tables are the correct type by appending this to test_helper.rb: (ActiveRecord::Base.connection.select_values("SHOW TABLES") - %w[ schema_info ]).each do |table_name| ActiveRecord::Base.connection.execute("ALTER TABLE `#{table_name}` ENGINE=InnoDB") end Is there a better way to make a MyISAM-backed model be testable?

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• fd.seek() IOError: [Errno 22] Invalid argument

  - by Julian Kessel

  My Python Interpreter (v2.6.5) raises the above error in the following codepart: fd = open("some_filename", "r") fd.seek(-2, os.SEEK_END) #same happens if you exchange the second arg. w/ 2 data=fd.read(2); last call is fd.seek() Traceback (most recent call last): File "bot.py", line 250, in <module> fd.seek(iterator, os.SEEK_END); IOError: [Errno 22] Invalid argument The strange thing with this is that the exception occurs just when executing my entire code, not if only the specific part with the file opening. At the runtime of this part of code, the opened file definitely exists, disk is not full, the variable "iterator" contains a correct value like in the first codeblock. What could be my mistake? Thanks in advance

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• Whats faster in Javascript a bunch of small setInterval loops, or one big one?

  - by RobertWHurst

  Just wondering if its worth it to make a monolithic loop function or just add loops were they're needed. The big loop option would just be a loop of callbacks that are added dynamically with an add function. adding a function would look like this setLoop(function(){ alert('hahaha! I\'m a really annoying loop that bugs you every tenth of a second'); }); setLoop would add the function to the monolithic loop. so is the is worth anything in performance or should I just stick to lots of little loops using setInterval?

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• Cloud Agnostic Architecture?

  - by Dave

  Hi, I'm doing some architecture work on a new solution which will initially run in Windows Azure. However I'd like the solution (or at least the architecture/design) to be Cloud Agnostic (to whatever extent is realistic). Has anyone done any work on this front or seen any good white papers/blog posts? Our highlevel architecture will consist of a payload being sent to a web service (WCF for instance), this will be dumped on a queue (for arguments sake) and a worker process will grab messages off this queue and proccess them. There will be a database of customer information which we'd ideally like to keep out of the cloud however there are obvious performance considerations. Keen to hear other's thoughts. Cheers Dave

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• Returning several COUNT results from one ASP SQL statement

  - by user89691

  Say I have a table like this: Field1 Field2 Field3 Field4 fred tom fred harry tom tom dick harry harry and I want to determine what proportion of it has been completed for each field. I can execute: SELECT COUNT (Field1) WHERE (Field1 <> '') AS Field1Count SELECT COUNT (Field2) WHERE (Field2 <> '') AS Field2Count SELECT COUNT (Field3) WHERE (Field3 <> '') AS Field3Count SELECT COUNT (Field4) WHERE (Field4 <> '') AS Field4Count Is it possible to roll up these separate SQL statements into one that will return the 4 results in one hit? Is there any performance advantage to doing so (given that the number of columns and rows may be quite large in practice)?

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• Tokenizer for full-text

  - by user72185

  This should be an ideal case of not re-inventing the wheel, but so far my search has been in vain. Instead of writing one myself, I would like to use an existing C++ tokenizer. The tokens are to be used in an index for full text searching. Performance is very important, I will parse many gigabytes of text. Edit: Please note that the tokens are to be used in a search index. Creating such tokens is not an exact science (afaik) and requires some heuristics. This has been done a thousand time before, and probably in a thousand different ways, but I can't even find one of them :) Any good pointers? Thanks!

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