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• Which is the best API/Library to use when accessing a WebCam in .Net?

  - by Doctor Jones

  Which is the best API to use when accessing a WebCam in .Net? (I know they can be webcam specific, I am willing to buy a new webcam if it means better results). I want to write a desktop application that will take video from a webcam and store it in MPEG4 formats (DivX, Xvid, etc...). I would also like to access bitmap stills from the device so I can do image comparison between frames. I have tried various libraries, and none have really been a great fit (some have performance issues (very inconsistent framerates), some have image quality limitations, some just crash out for seemingly no reason. I want to get high quality video (as high as I can get) and a decent framerate. My webcam is more than up to the job and I was hoping that there would be a nice Managed .Net library around that would help my cause. Are webcam APIs all just incredibly bad?

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• PostgreSQL: How to index all foreign keys?

  - by biggusjimmus

  I am working with a large PostgreSQL database, and I are trying to tune it to get more performance. Our queries and updates seem to be doing a lot of lookups using foreign keys. What I would like is a relatively simple way to add Indexes to all of our foreign keys without having to go through every table (~140) and doing it manually. In researching this, I've come to find that there is no way to have Postgres do this for you automatically (like MySQL does), but I would be happy to hear otherwise there, too.

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• Objective C: Why is this code leaking?

  - by Johnny Grass

  I'm trying to implement a method similar to what mytunescontroller uses to check if it has been added to the app's login items. This code compiles without warnings but if I run the leaks performance tool I get the following leaks: Leaked Object # Address Size Responsible Library Responsible Frame NSURL 7 < multiple > 448 LaunchServices LSSharedFileListItemGetFSRef NSCFString 6 < multiple > 432 LaunchServices LSSharedFileListItemGetFSRef Here is the responsible culprit: - (BOOL)isAppStartingOnLogin { LSSharedFileListRef loginListRef = LSSharedFileListCreate(NULL, kLSSharedFileListSessionLoginItems, NULL); if (loginListRef) { NSArray *loginItemsArray = (NSArray *)LSSharedFileListCopySnapshot(loginListRef, NULL); NSURL *itemURL; for (id itemRef in loginItemsArray) { if (LSSharedFileListItemResolve((LSSharedFileListItemRef)itemRef, 0, (CFURLRef *) &itemURL, NULL) == noErr) { if ([[itemURL path] hasPrefix:[[NSBundle mainBundle] bundlePath]]) { [loginItemsArray release]; CFRelease(loginListRef); return YES; } } } [loginItemsArray release]; CFRelease(loginListRef); } return NO; }

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• Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?

  - by Jay

  I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance. Is there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design/create my database, and then have Django reverse engineer the models file?

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• code-style: Is inline initialization of JS objects ok?

  - by michael

  I often find myself using inline initialization (see example below), especially in a switch statement when I don't know which case loop will hit. I find it easier to read than if statements. But is this good practice or will it incur side-effects or a performance hit? for (var i in array) { var o = o ? o : {}; // init object if it doesn't exist o[array[i]] = 1; // add key-values } Is there a good website to go to get coding style tips?

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• [Symfony] Admin generator and i18n

  - by David

  I have read lots of questions about i18n, but I haven't found any about performance. I have a simple backend app listing the contents of an ads table. These ads have a category, that is translated in some languages (it's defined as i18n in the Doctrine schema). So, when I add a "table_method" in my generator.yml to include de Category table, it reduces the number of queries, but there are yet some of them referencing i18n translation tables. So, if I add the category Translation table to the query, it reduces even more the queries BUT it increases the processing time considerably. Why this time penalty? Just because of the translation table? And why isn't the filter using this method to avoid so many translation queries as well? I mean, if I want to filter by category, it is making one query per category to include the translation table. Why??

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• Cheap shared windows hosting

  - by Elangovan

  Hi I have recently purchased a domain from go daddy, now I am looking for a cheap windows hosting. Following are my requirements Shared Windows hosting Should be cheap in price Should have at least one SQL server Db and one mysql db. Should support atleast asp.net 3.5 and php Will be good if it has support for asp.net mvc (no problem even if it is not available also) Should be able to install third party blog sites. Bandwidth, total space and performance are not very important. Silverlight is also an added advantage (no problem even if it is not available also). There should be no advertisement or banner added by the hosting company in the site.

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• Running multiple jvms for different applications in same machine

  - by Rajesh

  We are getting frequent out of memory errors in our dev. machines We are running webshpere, eclipse, soap UI and maven in it. Our server gets down due to this "out of memory errors" when we restart our applications in websphere 2/3 times, We already increased the virtual memory setting in wesphere to 1GB. So what i did was copied the jre we use in eclipse and maven folders so that each of these uses individual jvms. But the performance of websphere is same. 2/3 restarts and out of memory errors. Is there any may of making eclipse and maven use different jvms other than websphere's?

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• How to receive HTTP messages using Socket

  - by Poma

  I'm using Socket class for my web client. I can't use HttpWebRequest since it doesn't support socks proxies. So I have to parse headers and handle chunked encoding by myself. The most difficult thing is to determine length of content so I have to read it byte-by-byte. First I have to use ReadByte() to find last header ("\r\n\r\n" combination), then read chunk's size etc. But this approach has very poor performance. Can you suggest better solution? Maybe some open source examples or libraries that handle http request through sockets (not very big and complicated though, I'm a noob)

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• Hit Testing with CALayer using the alpha properties of the CALayer contents.

  - by Charliehorse

  I'm writing a game for Mac using Cocoa. I'm currently implementing hit testing and have founds that CALayer offers hit testing, but does not seem to implement the alpha properties. As I have at times many CALayers stacked on top of each other, I really need to find a way to determine what the user actually meant to click on. I'm thinking if I could somehow get an array that contains pointers to all of the CALayers that contain the click point, I could filter through them some how. However the only way I've got so far to create the array is: NSMutableArray* anArrayOfLayers = [NSMutableArray array]; for (CALayer* aLayer in mapLayer.sublayers) { if ([aLayer containsPoint:mouseCoord]) [anArrayOfLayers addObject:aLayer]; } Then sort the array by the CALayer's z-values then go through checking if the pixel at location is alpha or not. However, between the sort and the alpha check this seems to be an incredible performance hog. (How would you even check the alpha?) Is there any way to do this?

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• ImageView source scaling done right. How?

  - by Aleksey Malevaniy

  Scope Image bitmap have to be shown as imageView.setImageBitmap(bitmap) and scaled to fit UI. This could be done via: bitmap = Bitmap.createScaledBitmap(bitmap, newWidth, newHeight, true); xml's ImageView attributes such as android:layout_width="newWidth" android:layout_height="newHeight" android:adjustViewBounds="true" android:scaleType="fitCenter" Problem Which way is better for performance? I prefer xml 'cause this is UI specific problem and I prefer to use xmls for UI definition. Also we set width/height values in dp, it means we have the same UI for different screens. Thanks!

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• dotTrace cant create deploy folder on Windows Azure Web Sites (WAWS)

  - by Orhan Maden

  I get the error message 'Can't create deploy folder.' when I try to profile a remote websites on WAWS. Actions taken: Downloaded and installed the dotTrace Profiler 5.5 from the JetBrains website Downloaded the dotTrace.Performance.Remote version 5.5.0 from Nuget Published the website to WAWS via Visual Studio 2013 Started the dotTrace application as Administrator Connected to the remote _https://subdomain.azurwebsites.net/AgentService.asmx. See image: http://1drv.ms/1nF5Cyh Selected the w3wp process and pressed Run Got the error message 'Can't create deploy folder'. See image: http://1drv.ms/U5h35A I'm running dotTrace in trial mode at the moment. Swift help is much appreciated. Orhan

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• How does Core Data determine if an NSObjects data can be dropped?

  - by Kevin

  In the app I am working on now I was storing about 500 images in Core Data. I have since pulled those images out and store them in the file system now, but in the process I found that the app would crash on the device if I had an array of 500 objects with image data in them. An array with 500 object ids with the image data in those objects worked fine. The 500 objects without the image data also worked fine. I found that I got the best performance with both an array of object ids and image data stored on the filesystem instead of in core data. The conclusion I came to was that if I had an object in an array that told Core Data I was "using" that object and Core Data would hold on to the data. Is this correct?

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• Is it really wrong to version documents using CouchDB's behaviour?

  - by Tomas Sedovic

  This is one of those "I know I shouldn't do this but it's oh so convenient." questions. Sorry about that. I plan to use CouchDB for storing a bunch of documents and keeping their entire revision history. CouchDB does the versioning automatically, but it is strongly discouraged for programmer's use: "You cannot rely on document revisions for any other purpose than concurrency control." From what I've found on the CouchDB wiki, the versions can get deleted either during compaction or during replication. As far as I can tell, Compaction must always be triggered manually and Replication occurs only when there's more than one database server. The question is: if I won't run compaction and will use only single database instance for my documents, can I just use CouchDB's document versioning and expect it to work? What other problems I might run into? E.g. does not running compaction hurt the performance or consume significantly more disk space (than if I did handle the versioning manually)?

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• Generate a commutative hash based on three sets of numbers?

  - by DarkAmgine

  I need to generate a commutative hash based on three sets of "score" structs. Each score has a "start", an "end" and a "number". Both start and end are usually huge numbers (8-9 digits) but number is just from 1 to 4. I need them to be commutative so the order does not matter. I'm using XOR at the moment but it seems to be giving bad results. Since I'm working with large large datasets, I'd prefer a performance-friendly solution. Any suggestions? Thanks =] public static int getCustomHash(cnvRegion c1, cnvRegion c2, cnvRegion c3) { int part1 = (c1.startLocation * c2.startLocation * c3.startLocation); int part2 = (c1.endLocation * c2.endLocation * c3.endLocation); int part3 = (c1.copyNumber + c2.copyNumber + c3.copyNumber)*23735160; return part1 ^ part2 ^ part3; }

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• How to I count key collisions when using boost::unordered_map?

  - by Nikhil

  I have a data structure with 15 unsigned longs, I have defined a hash function using hash_combine as follows: friend std::size_t hash_value(const TUPLE15& given) { std::size_t seed = 0; boost::hash_combine(seed, val1); boost::hash_combine(seed, val2); ... return seed; } I insert a large number of values into a boost::unordered_map but the performance is not good enough. Probably, I could do better with an alternative hashing function. To confirm this, I need to check how many collisions I am getting. How do I do this?

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• Conceptually, how does replay work in a game?

  - by SnOrfus

  I was kind of curious as to how replay might be implemented in a game. Initially, I thought that there would be just a command list of every player/ai action that was taken in the game, and it then 're-plays' the game and lets the engine render as usual. However, I have looked at replays in FPS/RTS games, and upon careful inspection even things like the particles and graphical/audible glitches are consistent (and those glitches are generally *in*consistent). So How does this happen. In fixed camera angle games I though it might just write every frame of the whole scene to a stream that gets stored and then just replays the stream back, but that doesn't seem like enough for games that allow you to pause and move the camera around. You'd have to store the locations of everything in the scene at all points in time (No?). So for things like particles, that's a lot of data to push which seems like a significant draw on the game's performance whilst playing.

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• Detect numbers and process them ?

  - by Madhup

  Hi, I am trying to detect the numbers written on a grid and then process them using the iPhone camera. What i have found till yet are some good examples like: http://blog.damiles.com/?p=93 http://cmgresearch.blogspot.com/2010/01/augmented-reality-on-iphone-how-to_01.html Although I am able to draw the numbers on the overlay view to a good extent but still not able to detect what these numbers are. What I don't wanna do is to go through the whole AI process: training the system, providing the system whole set of values and then process them, because this is so much troublesome for me as well for the performance of my application. So guys having any idea or work arround for this please help. Thanks, Madhup

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• What FIX implementation do you recommend for use with .NET

  - by Ajaxx

  I am reviewing implementation choices for FIX when using .NET. A few obvious choices come to mind, but I want to know if there are other options, better choices or if we've made the same decision as a lot of you. QuickFIX - Stable, C++ implementation - so you've got unmanaged code to interop with. FIX4NET - C# implementation - seems to have some gaps in its implementation. DIY - Chime in here if you've made your own FIX engine Let me throw in some caveats here. I'm not looking for sub 100 microsecond processing. Performance is a requirement, but not so much that it's driving my decisions. A solid product that is stable, performs well and is flexible enough to deal with vendor specific dialects is the sweet spot. The more we can do in .NET the better.

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• iPhone. How to intercept system dialogs?

  - by Sjakelien

  My app offers the user the opportunity to put an event in his native calendar. For that, I refer to an online webcal:// URL. Since the underlying .ics file is quite big (containing quite a few events), it sometimes (also depending on the network performance)takes a while before the "Do you want to subscribe"-dialog sequence kicks in. I would like to give the user some feedback in the mean time, like a spinner, or a changing graphic, for him to know that something is going to happen. Question: how does my app know, that the "Do you want to subscribe"-dialog has been shown, and that the user has chosen either a Cancel of OK button in that dialog, so I can stop the spinner?

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• Best method of Zend Framework caching

  - by iamthejeff

  I have a blog built using Zend Framework, which I realize might be a bit overkill for a blog alone, but I am planning on adding other features in the future. Nevertheless, I've noticed pages could be a little speedier. I've done a basic caching method that basically captures everything in index.php (Core frontend and File backend), which works great, but unfortunately it also prevents dynamic page contents from updating (messages like "this was posted 5 minutes ago", etc) until the cache period expires. So my question is what would be the best method of caching to improve performance? I am doing fairly basic queries which are mostly simple selects, not many joins or anything fancy (using Zend_Db_Table), and even on a small database page loads are a little sluggish. Is it worth it to cache queries or should I focus my time elsewhere?

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• How to synchronize static method in java.

  - by Summer_More_More_Tea

  Hi there: I come up with this question when implementing singleton pattern in Java. Even though the example listed blow is not my real code, yet very similar to the original one. public class ConnectionFactory{ private static ConnectionFactory instance; public static synchronized ConnectionFactory getInstance(){ if( instance == null ){ instance = new ConnectionFactory(); } return instance; } private ConnectionFactory(){ // private constructor implementation } } Because I'm not quite sure about the behavior of a static synchronized method, I get some suggestion from google -- do not have (or as less as possible) multiple static synchronized methods in the same class. I guess when implementing static synchronized method, a lock belongs to Class object is used so that multiple static synchronized methods may degrade performance of the system. Am I right? or JVM use other mechanism to implement static synchronized method? What's the best practice if I have to implement multiple static synchronized methods in a class? Thank you all! Kind regards!

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• asynchronous calls in asp.net

  - by lockedscope

  in this sample, two threads created; a worker thread created by BeginInvoke and an I/O completion thread created by SendAsync method. but another author in his UnsafeQueueNativeOverlapped example, don't recommend this. i want to use SendAsync or ...Async in an asp.net page and i want to use PageAsyncTask. however, its BeginEventHandler requires AsyncResult to be returned which SendAsync does not return. afaik, event based async pattern is the most recommended way so how could we call SendAsync or any ...Async methods without creating two threads and hurting the performance?

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• Android: Custom Clock widget Service work-around?

  - by Anthony Forloney

  I was interested in developing a clock widget for the homescreen and upon reading Home Screen Widgets tutorial, is there a pre-existing Service I could reference for updating the current time rather than re-inventing the wheel? I have currently Retro Clock on my android phone and noticed that when I click it, it pops up the Alarm Clock settings, but with the default Google Analog Clock widget, upon click does nothing. Is that because the Retro Clock widget implements the Alarm Clock service? If so, how can I go about referencing that service? Or do I have this all wrong and misunderstood? Any help is appreciated. EDIT: I believe implementing the service to update the clock would drain the battery life tremendously, any ideas on a work around or help shed some light on any performance issues with using Service?

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• SSIS - Connection Management Within a Loop

  - by Rob Bowman

  Hi I have the following SSIS package: The problem is that within the Foreach loop a connection is opened and closed for each iteration. On running SQL Profiler I see a series of: Audit Login RPC:Completed Audit Lout The duration for the login and the RPC that actually does the work is minimal. However, the duration for the logout is significant, running into several seconds each. This causes the JOB to run very slowly - taking many hours. I get the same problem when running either on a test server or stand-alone laptop. Could anyone please suggest how I may change the package to improve performance? Also, I have noticed that when running the package from Visual Studio, it looks as though it continues to run with the component blocks going amber then green but actually all the processing has been completed and SQL profiler has dropped silent? Thanks, Rob.

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