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• Nice name for `decorator' class?

  - by Lajos Nagy

  I would like to separate the API I'm working on into two sections: 'bare-bones' and 'cushy'. The idea is that all method calls in the 'cushy' section could be expressed in terms of the ones in the 'bare-bones' section, that is, they would only serve as convenience methods for the quick-and-dirty. The reason I would like to do this is that very often when people are beginning to use an API for the first time, they are not interested in details and performance: they just want to get it working. Anybody tried anything similar before? I'm particularly interested in naming conventions and organizing the code.

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• F# currying efficiency?

  - by Eamon Nerbonne

  I have a function that looks as follows: let isInSet setElems normalize p = normalize p |> (Set.ofList setElems).Contains This function can be used to quickly check whether an element is semantically part of some set; for example, to check if a file path belongs to an html file: let getLowerExtension p = (Path.GetExtension p).ToLowerInvariant() let isHtmlPath = isInSet [".htm"; ".html"; ".xhtml"] getLowerExtension However, when I use a function such as the above, performance is poor since evaluation of the function body as written in "isInSet" seems to be delayed until all parameters are known - in particular, invariant bits such as (Set.ofList setElems).Contains are reevaluated each execution of isHtmlPath. How can best I maintain F#'s succint, readable nature while still getting the more efficient behavior in which the set construction is preevaluated. The above is just an example; I'm looking for a general pattern that avoids bogging me down in implementation details - where possible I'd like to avoid being distracted by details such as the implementation's execution order since that's usually not important to me and kind of undermines a major selling point of functional programming.

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• com.sun.management.OperatingSystemMXBean use in an OSGi bundle

  - by Paul Whelan

  I have some legacy code that was used to monitor my applications cpu,memory etc that I want to convert to a bundle. Now when i start this bundle its complaining Missing Constraint: Import-Package: com.sun.management; version="0.0.0" I had used the OperatingSystemMXBean to get access to stats on the JVM. My question is can I use this class inside an OSGI container and if so how? Or should I use some other way to monitor my application. I was making an RMI call to the application from a web frontend to get the nodes performance figures pre OSGi.

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• Java Concurrency: CAS vs Locking

  - by Hugo Walker

  Im currently reading the Book Java Concurrency in Practice. In the Chapter 15 they are speaking about the Nonblocking algorithms and the compare-and-swap (CAS) Method. It is written that the CAS perform much better than the Locking Methods. I want to ask the people which already worked with both of this concepts and would like to hear when you are preferring which of these concept? Is it really so much faster? Personally for me the usage of Locks is much clearer and easier to understand and maybe even better to maintain. (Please correct me if I am wrong). Should we really focus creating our concurrent code related on CAS than Locks to get a better performance boost or is sustainability a higher thing? I know there is maybe not a strict rule, when to use what. But I just would like to hear some opinions, experiences with the new concept of CAS.

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• Service broker with SqlNotificationRequest

  - by user171523

  I am in the process of evaluating a Service Broker with SQL noticiation for my project. My requirements is User places a order from System A and it will update Order Table. As soon as order is place i need to notify the System B. I have done a quick POC with Trigger , Service Broker and SQLNotificaiton ADO.NET. It is working as i expected. What i would like to know the group A) What are the best practices i need to follow for this? B) What are disadvantages with the above approach if any? C) Are there any disadvantes of using the Triggers? If so what are those for above approach? The order table will get order from System A like 1000 to 1500 every day. I also would like to know the performance of above approach.

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• NameValueCollection vs Dictionary<string,string>

  - by frankadelic

  Any reason I should use Dictionary<string,string instead of NameValueCollection? (in C# / .NET Framework) Option 1, using NameValueCollection: //enter values: NameValueCollection nvc = new NameValueCollection() { {"key1", "value1"}, {"key2", "value2"}, {"key3", "value3"} }; // retrieve values: foreach(string key in nvc.AllKeys) { string value = nvc[key]; // do something } Option 2, using Dictionary<string,string... //enter values: Dictionary<string, string> dict = new Dictionary<string, string>() { {"key1", "value1"}, {"key2", "value2"}, {"key3", "value3"} }; // retrieve values: foreach (KeyValuePair<string, string> kvp in dict) { string key = kvp.Key; string val = kvp.Value; // do something } For these use cases, is there any advantage to use one versus the other? Any difference in performance, memory use, sort order, etc.?

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• Long-running transactions structured approach

  - by disown

  I'm looking for a structured approach to long-running (hours or more) transactions. As mentioned here, these type of interactions are usually handled by optimistic locking and manual merge strategies. It would be very handy to have some more structured approach to this type of problem using standard transactions. Various long-running interactions such as user registration, order confirmation etc. all have transaction-like semantics, and it is both error-prone and tedious to invent your own fragile manual roll-back and/or time-out/clean-up strategies. Taking a RDBMS as an example, I realize that it would be a major performance cost associated with keeping all the transactions open. As an alternative, I could imagine having a database supporting two isolation levels/strategies simultaneously, one for short-running and one for long-running conversations. Long-running conversations could then for instance have more strict limitations on data access to facilitate them taking more time (read-only semantics on some data, optimistic locking semantics etc). Are there any solutions which could do something similar?

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• Is there any killer application for Ontology/semantics/OWL/RDF yet?

  - by narnirajesh

  Hi Guys, I got interested in semantic technologies after reading a lot of books, blogs and articles on the net saying that it would make data machine-understandable, allow intelligent agents make great reasoning, automated & dynamic service composition etc.. I am still reading the same stuff from 2 years. The number of articles/blogs/semantic-conferences have increased considerably. But I am still unable to see any killer-application. Why is it so? Or is there some application/product (commercial/open-source) already existing, which actually is doing all that being boasted of? To put it more precisely, is there any product that leverages semantic technologies (esp RDF/OWL/SPARQL) and is delivering functionality/performance/maintainability, which would not have been possible with the existing (no-semantic) technologies? Some product that is completely dependent on semantic technologies and really adds value to the customers and generating revenues?

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• Concatenate boost::dynamic_bitset or std::bitset

  - by MOnsDaR

  Hey, what is the best way to concatenate 2 bitsets? For example i've got boost::dynamic_bitset<> test1( std::string("1111") ); boost::dynamic_bitset<> test2( std::string("00") ); they should be concatenated into a thrid Bitset test3 which then holds 111100 Solutions should use boost::dynamic_bitset. If the solution works with std::bitset, it would be nice too. There should be a focus on performance when concatenating the bits.

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• PyPy -- How can it possible beat CPython?

  - by Vulcan Eager

  From the Google Open Source Blog: PyPy is a reimplementation of Python in Python, using advanced techniques to try to attain better performance than CPython. Many years of hard work have finally paid off. Our speed results often beat CPython, ranging from being slightly slower, to speedups of up to 2x on real application code, to speedups of up to 10x on small benchmarks. How is this possible? Which Python implementation was used to implement PyPy? CPython? And what are the chances of a PyPyPy or PyPyPyPy beating their score? (On a related note... why would anyone try something like this?)

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• MongoMapper and bson_ext problem

  - by Fossmo

  I can't get MongoMapper to work with my Rails app. I get this error message: **Notice: C extension not loaded. This is required for optimum MongoDB Ruby driver performance. You can install the extension as follows: gem install bson_ext If you continue to receive this message after installing, make sure that the bson_ext gem is in your load path and that the bson_ext and mongo gems are of the same version. I have installed DevKit and installed the gem: gem install bson_ext --no-rdoc --no-ri (result: bson_ext-1.0.1 installed) I'm running on Windows 7. The Rails version is 2.3.7. I used the RubyInstaller when installing. Can anyone point me in the right direction?

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• grammar parser lexer antlr letteral

  - by BB

  What's the difference between this grammar: ... if_statement : 'if' condition 'then' statement 'else' statement 'end_if'; ... and this: ... if_statement : IF condition THEN statement ELSE statement END_IF; ... IF : 'if'; THEN: 'then'; ELSE: 'else'; END_IF: 'end_if'; .... ? If there is any difference, as this impacts on performance ... Thanks

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• SQL Server, temporary tables with truncate vs table variable with delete

  - by Richard

  I have a stored procedure inside which I create a temporary table that typically contains between 1 and 10 rows. This table is truncated and filled many times during the stored procedure. It is truncated as this is faster than delete. Do I get any performance increase by replacing this temporary table with a table variable when I suffer a penalty for using delete (truncate does not work on table variables) Whilst table variables are mainly in memory and are generally faster than temp tables do I loose any benefit by having to delete rather than truncate?

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• Language/tech specific books which improve vendor-neutral development skills

  - by dotnetdev

  If I ask what the following books have in common: "Accelerated C# 2010, C# in Depth, Pro C# 2008", the answer would be that they would help me to improve my understanding of C# and secondly, my general coding skills. What language-specific/tech-specific books (like those named above) would teach me a great deal about general programming techniques and good habits? I'm thinking Java books would be very good for me (I code in C# primarily), as both these languages are similar and so I am sure that specialist books on Java threading, performance tuning, etc, can be applied to C# (not all 100% content of a Java book). Thanks

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• Quick question regarding CSS sprites and memory usage

  - by Andy E

  Well, it's more to do with images and memory in general. If I use the same image multiple times on a page, will each image be consolidated in memory? Or will each image use a seperate amount of memory? I'm concerned about this because I'm building a skinning system for a Windows Desktop Gadget, and I'm looking at spriting the images in the default skin so that I can keep the file system looking clean. At the same time I want to try and keep the memory footprint to a minimum. If I end up with a single file containing 100 images and re-use that image 100 times across the gadget I don't want to have performance issues. Cheers.

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• Style: Dot notation vs. message notation in Objective-C 2.0

  - by groundhog

  In Objective-C 2.0 we got the "dot" notation for properties. I've seen various back and forths about the merits of dot notation vs. message notation. To keep the responses untainted I'm not going to respond either way in the question. What is your thought about dot notation vs. message notation for property accessing? Please try to keep it focused on Objective-C - my one bias I'll put forth is that Objective-C is Objective-C, so your preference that it be like Java or JavaScript aren't valid. Valid commentary is to do with technical issues (operation ordering, cast precedence, performance, etc), clarity (structure vs. object nature, both pro and con!), succinctness, etc. Note, I'm of the school of rigorous quality and readability in code having worked on huge projects where code convention and quality is paramount (the write once read a thousand times paradigm).

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• spring.net application scope repository object on loadbalanced application

  - by Bert Vandamme

  Hi, We have an application running on a loadbalanced environment, let say webserver A and B. The loadbalancing is on the HTTP level, so the loadbalancer directs each user request to one of both webservers. The scope of the repositories in the application is managed by the spring.net container, and the application relies on data that can be cached by the repository (performance reasons). In this case we can never be sure that the cached data in the repositories on both webservers is the same. Is there mechanism in spring.net that can manage this kind problem? Or is there another common approach for this kind of thing? Any ideas? Thx, Bert

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• Vsync in Flex/Flash/AS3?

  - by oshyshko

  I work on a 2D shooter game with lots of moving objects on the screen (bullets etc). I use BitmapData.copyPixels(...) to render entire screen to a buffer:BitmapData. Then I "copyPixels" from "buffer" to screen:BitmapData. The framerate is 60. private var bitmap:Bitmap = new Bitmap(); private var buffer:Bitmap = new Bitmap(); private function start():void { addChild(bitmap); } private function onEnterFrame():void { // render into "buffer" // copy "buffer" -> "bitmap" } The problem is that the sprites are tearing apart: some part of a sprite got shifted horizontally. It looks like a PC game with VSYNC turned off. Did anyone solve this problem? UPDATE: the question is not about performance, but about getting rid of screen tearing. [!] UPDATE: I've created another question and here you may try both implementations: using Flash way or BitmapData+copyPixels()

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• PageMethods security

  - by TenaciousImpy

  Hi, I'm trying to 'AJAX-ify' my site in order to improve the UI experience. In terms of performance, I'm also trying to get rid of the UpdatePanel. I've come across a great article over at Encosia showing a way of posting using PageMethods. My question is, how secure are page methods in a production environment? Being public, can anyone create a JSON script to POST directly to the server, or are there cross-domain checks taking place? My PageMethods would also write the data into the database (after filtering). I'm using Forms Authentication in my pages and, on page load, it redirects unauthenticated users to the login page. Would the Page Methods on this page also need to check authentication if the user POSTs directly to the method, or is that authentication inherited for the entire page? (Essentially, does the entire page cycle occur even if a user has managed to post only to the PageMethod)? Thanks

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• Handler invocation speed: Objective-C vs virtual functions

  - by Kerido

  I heard that calling a handler (delegate, etc.) in Objective-C can be even faster than calling a virtual function in C++. Is it really correct? If so, how can that be? AFAIK, virtual functions are not that slow to call. At least, this is my understanding of what happens when a virtual function is called: Compute the index of the function pointer location in vtbl. Obtain the pointer to vtbl. Dereference the pointer and obtain the beginning of the array of function pointers. Offset (in pointer scale) the beginning of the array with the index value obtained on step 1. Issue a call instruction. Unfortunately, I don't know Objective-C so it's hard for me to compare performance. But at least, the mechanism of a virtual function call doesn't look that slow, right? How can something other than static function call be faster?

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• Can I draw Qt objects directly to Win32 DC (Device Context)?

  - by Kevin

  I can draw Qt objects to an QImage and then draw the image to HDC or CDC. This may hurt our application's performance. It would be great if I can draw Qt objects directly to Win32 HDC or MFC CDC. I expect that there is a class, say QWin32Image for clear, then I can use it in this way: QWin32Image image(hdc, 100, 100, Format_ARGB32_Premultiplied); QPainter painter(&image); painter.drawText(....); Is it possible for my thought? Or is there a better way to do that?

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• Java Prepared Statement arguments!

  - by Epitaph

  I am planning to replace repeatedly executed Statement objects with PreparedStatement objects to improve performance. I am using arguments like the MySQL function now(), and string variables. Most of the PreparedStatement queries I have seen contained constant values (like 10, and strings like "New York") as arguments used for the "?" in the queries. How would I go about using functions like now(), and variables as arguments? Is it necessary to use the "?"s in the queries instead of actual values? I am quite confounded.

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• A control that contains multiple duplicate properties causing deadlock issues on IIS

  - by heads5150

  I am trying to work out if the above case is true for our site. I've been told by my hosting provider that this fix (http://support.microsoft.com/kb/974165) has to applied to our server due to performance issues. It basically describes an issues where UI code like: <asp:gridview id="GridView1" runat="server" ... PageSize="100" PagerSettings-Mode="Numeric" PagerStyle-BorderStyle="None" PagerStyle-BorderColor="Navy" PagerStyle-HorizontalAlign="Right" PagerSettings-PageButtonCount="2" PagerSettings-Position="Bottom"> <PagerStyle HorizontalAlign="Left" BorderColor="Navy" BorderStyle="None"></PagerStyle> ... <PagerSettings PageButtonCount="2"></PagerSettings> ... </asp:gridview> causing the following warning on the server "ISAPI 'C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll' reported itself as unhealthy for the following reason: 'Deadlock detected'." Does anybody know of a way that I can detect this issue in the build process or the debugger? Any help would be much appreciate.

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• Can I do video communication with silverlight 4.0?

  - by tom greene

  With silverlight 4.0, it is possible to show a live video of the user on the screen: Here is the code VideoBrush videoBrush = new VideoBrush(); CaptureSource captureSource = new CaptureSource { VideoCaptureDevice = CaptureDeviceConfiguration.GetAvailableVideoCaptureDevices().First() }; bool b = CaptureDeviceConfiguration.RequestDeviceAccess(); videoBrush.SetSource(captureSource); captureSource.Start(); myrect.Fill = videoBrush; However, I am looking at a way to show the video to someone else - seeing oneself on screen is not that interesting. Is it possible? Do I need my own server? Can I use clowd services to do the communication? Are there performance issues?

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• Best practices for combining Lucene.NET and a relational database?

  - by FlySwat

  I'm working on a project where I will have a LOT of data, and it will be searchable by several forms that are very efficiently expressed as SQL Queries, but it also needs to be searched via natural language processing. My plan is to build an index using Lucene for this form of search. My question is that if I do this, and perform a search, Lucene will then return the ID's of matching documents in the index, I then have to lookup these entities from the relational database. This could be done in two ways (That I can think of so far): N amount of queries (Horrible) Pass all the ID's to a stored procedure at once (Perhaps as a comma delimited parameter). This has the downside of being limited to the max parameter size, and the slow performance of a UDF to split the string into a temporary table. I'm almost tempted to mirror everything into lucenes index, so that I can periodicly generate the index from the backing store, but only need to access it for the frontend. Advice?

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