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• Determine if a decimal can be stored as int32

  - by anchandra

  I am doing some custom serializing, and in order to save some space, i want to serialize the decimals as int, if possible value wise. Performance is a concern, since i am dealing with a high volume of data. The current method i use is: if ((value > Int32.MinValue) && (value < Int32.MaxValue) && ((valueAsInt = Decimal.ToInt32(value)) == value)) { return true; } Can this be improved?

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• When does it make sense to use a map?

  - by kiwicptn

  I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category and put up an example. Property values (like a bean) age -> 30 sex -> male loc -> calgary Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1

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• OpenGL and layouts

  - by Hnefi

  I'm using OpenGL to render a game view in my android application. The game is turn based and I wish to add some buttons to the interface. I'd prefer to use standard Android widgets, structured in an XML-generated layout (or, if I have to, a hardcoded layout) and put the OpenGL view in its own window as part of that layout. So in regards to this, I have 3 questions: 1: Is such a thing possible? I've done a few half-hearted tries, but have had no luck so far. 2: Is such a thing advisable? Does it carry a significant performance penalty, for example, over using OpenGL-based homebrew widgetry? 3: Is it possible to pass particular arguments to instances created in XML layouts? For example, my current OpenGL view has three arguments in its constructor; is it somehow possible for me to invoke that particular constructor with particular parameters when it's part of a layout?

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• Emulating a transaction-safe SEQUENCE in MySQL

  - by Michael Pliskin

  We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance (meaning minimizing locks and deadlocks) We don't care if some of the values won't be used, i.e. gaps in sequence are ok. There is an easy way to archieve that by creating a separate InnoDB table with a counter, however this means it will take part in transaction and will introduce locks and waiting. I am thinking to try a MyISAM table with manual locks, any other ideas or best practices?

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• Detecting and reloading updated application parameters at runtime

  - by VeeKayBee

  I am working on an ASP.NET web application(using .NET 4.5 and C#).The application deals with lot of units (for measuring like KG,Litre,KM etc). So based on the selected unit we have to implement some allowed range.This values can be configured without much effort. We identified two solutions for this Keeping a configuration xml. Suppose the values in xml, does it requires an iisreset or any other thing which can take the site down for some time, if we are changing the xml file to change some validation. Keeping in Db, then use SQL dependency caching. So an update to DB can reflect the caching values.SO i believe if we change the values, it will update the cache. How much complex is this and does it effect the performance ? It will be great helpful, if we have some other method to achieve this. Thanks in advance.

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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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• 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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• 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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• What factors could cause the scalability issue on a 10-core CPU?

  - by JackWM

  I am tuning the performance of parallel Java programs. And want to check the impacts from the Architecture. I'm look into the Intel 10-core CPU, Intel(R) Xeon(R) CPU E7-L8867. I found my program only scales up to 5 cores. What could be the causes? I'm considering the Architecture effects. e.g. memory contention? More specifically, Are the 10 cores symmetric to each other? How many memory controllers does it have?

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• On Memory Allocation and C++

  - by Arpan

  And I quote from MSDN http://msdn.microsoft.com/en-us/library/aa366533(VS.85).aspx: The malloc function has the disadvantage of being run-time dependent. The new operator has the disadvantage of being compiler dependent and language dependent. Now the questions folks: a) What do we mean that malloc is run-time dependent? What kind of dynamic memory allocation functions can be independent of run-time? This statement sounds real strange. b) new is language dependent? Of course it should be right? Are HeapAlloc, LocalAlloc etc language independent? c) From a pure performance perspective are the MSVC provided routines preferable? Arpan

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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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• storing huge amount of records into classic asp cache object is SLOW

  - by aspm

  we have some nasty legacy asp that is performing like a dog and i narrowed it down to because we are trying to store 15K+ records into the application cache object. but that's not the killer. before it stores it, it converts the ADO stream to XML then stores it. this conversion of the huge record set to XML spikes the CPU and causes all kinds of havoc on users when it's happening. and unfortunately we do this XML conversion to read the cache a lot, causing site wide performance problems. i don't have the resources to convert everything to .net. so that's out. but i need to obviously use caching, but int his case the caching is hurting instead of helping. is there a more effecient way to store this data instead of doing this xml conversion to/from every time we read/update the cache?

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• Php getting too many connections error from MySQL

  - by uzioriluzan

  Hello everyone, I am using MySQL and PHP with 2 application servers and 1 database server. With the increase of the number of users (around 1000 by now), I'm getting the following error : SQLSTATE[08004] [1040] Too many connections The parameter "max_connections" is set to "1000" in my.cnf and "mysql.max_persistent" is set to -1 in php.ini. There are at most 1500 apache processes running at a time since the "MaxClients" apache parameter is equal to 750 and we have 2 application servers. Should I raise the "max_connections" to 1500 as indicated in here? Or should I set "mysql.max_persistent" to 750 (we use PDO with persistent connections for performance reasons since the database server is not the same as the application servers)? Or should I try something else? Thanks in advance!

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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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• 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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• Available options for hosting FTP server in .NET application

  - by duane

  I need to implement an FTP service inside my .NET application (running as a Windows Service) and have not had much luck finding good/current source code or vendors. Ideally it needs to be able to respond to the basic FTP Protocol and accept the data stream from an upload via a stream, enabling me to process the data as it is being received (think on the fly hashing). I need to be able to integrate it into my service because it will stack on top of our current code base with an existing custom TCP/IP communication protocol. I don't want to write (and then spend time debugging and performance testing) my own protocol, or implementation. I have already found plenty of ftp client implementations, I just need an acceptable server solution.

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• config.cache_classes = true in production mode has problems in IE

  - by techno_log

  Hi Dears, In my rails app. I am using link_to_function to bring an ajax tabs in one page.Everything works fine in Moazilla and other browsers. But in IE the tabs are not loading only when the server is started in production mode(doesn't matter whether its webrick or mongrel). In development mode everything is fine. So I figured out that the issue was with one line config.cache_classes = true in app/config/environments/production.rb when i changed the above code to config.cache_classes = false everything works fine. So I assume caching causes problem in rails. When I Googled about this I found many have the issues with caching. So my question is 1) is there any other fix for this? 2) Does this fix (config.cache_classes = false) causes any performance issues. If then how to overcome that? Any comments and suggestions are welcome. Techno_log

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• Rewriting .each() loop as for loop to optimize, how to replicate $(this).attr()

  - by John B

  I running into some performance issues with a jquery script i wrote when running in ie so I'm going through it trying to optimize any way possible. Apparently using for loops is way faster than using the jQuery .each method. This has led me to a question regarding the equivalent of $(this) inside a for loop. I'm simplifying what I'm doing in my loop down to just using an attr() function as it gets across my main underlying question. Im doing this with each(simplified) var existing = $('#existing'); existing.each(function(){ console.log($(this).attr('id')); }); And I've tried rewriting it as a for loop as such: var existing = $('#existing'); for(var i = 0;i < existing.length;i++) { console.log(existing[i].attr('id')); } Its throwing an error saying: Uncaught TypeError: Object #<HTMLDivElement> has no method 'attr' Thanks.

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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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• Rails: getting logic to run at end of request, regardless of filter chain aborts?

  - by JSW

  Is there a reliable mechanism discussed in rails documentation for calling a function at the end of the request, regardless of filter chain aborts? It's not after filters, because after filters don't get called if any prior filter redirected or rendered. For context, I'm trying to put some structured profiling/reporting information into the app log at the end of every request. This information is collected throughought the request lifetime via instance variables wrapped in custom controller accessors, and dumped at the end in a JSON blob for use by a post-processing script. My end goal is to generate reports about my application's logical query distribution (things that depend on controller logic, not just request URIs and parameters), performance profile (time spent in specific DB queries or blocked on webservices), failure rates (including invalid incoming requests that get rejected by before_filter validation rules), and a slew of other things that cannot really be parsed from the basic information in the application and apache logs. At a higher level, is there a different "rails way" that solves my app profiling goal?

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• when to use StringBuilder in java

  - by kostja

  It is supposed to be generally preferable to use a StringBuilder for String concatenation in Java. Is it always the case? What i mean is : Is the overhead of creating a StringBuilder object, calling the append() method and finally toString() smaller then concatenating existing Strings with + for 2 Strings already or is it only advisable for more Strings? If there is such a threshold, what does it depend on (the String length i suppose, but in which way)? And finally - would you trade the readability and conciseness of the + concatenation for the performance of the StringBuilder in smaller cases like 2, 3, 4 Strings?

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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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• 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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• 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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• Is both approach same ?

  - by Harikrishna

  I have one datatable which is not bindided and records are coming from the file by parsing it in the datatable dynamically every time. Now there is three columns in the datatable Marks1,Marks2 and FinalMarks. And their types is decimal. Now for making addition of columns Marks1 and Marks2 's records and store it into FinalMarks column,For that what I do is : datatableResult.Columns["FinalMarks"].Expression="Marks1+Marks2"; It's works properly. It can be done in other way also is foreach (DataRow r in datatableResult.Rows) { r["FinalMarks"]=Convert.ToDecimal(r["Marks1"])+Convert.ToDecimal(r["Marks2"]); } Now I don't know that which is the best way to do this means performance wise. Is first approach same as second approach in background means is both approach same or what?

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