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• Why do Java/C# edge out C++ as the recommended language to learn OOP on S.O?

  - by viksit

  I noticed after reading the answers/discussion to this question (What is the best language to learn OOP on?) - that more and more people are recommending C# or Java over C++ to learn OOP on. A simple term search on that answer page results in 10 hits for C++, 21 for C# and 27 for Java. Now, I understand that these 2 languages fix a lot of quirks and issues with C++, and looked up these resources that relate mostly to performance, JVM vs native implementation, systems focus vs applications, manual memory management vs automated et al. My question is - are there any fundamental differences in the OO capabilities of Java/C# vs C++? Or are the former recommended purely due to their generic ease of use/improvements over the latter? Thanks. PS, I'm aware of Java interface inheritance vs C++ multiple inheritance as a difference. I would consider that an implementational one rather than functional.

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• Reading files from an embedded ZIP archive

  - by aix

  I have a ZIP archive that's embedded inside a larger file. I know the archive's starting offset within the larger file and its length. Are there any Java libraries that would enable me to directly read the files contained within the archive? I am thinking along the lines of ZipFile.getInputStream(). Unfortunately, ZipFile doesn't work for this use case since its constructors require a standalone ZIP file. For performance reasons, I cannot copy the ZIP achive into a separate file before opening it. edit: Just to be clear, I do have random access to the file.

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• vector<vector<largeObject>> vs. vector<vector<largeObject>*> in c++

  - by Leif Andersen

  Obviously it will vary depending on the compiler you use, but I'm curious as to the performance issues when doing vector<vector<largeObject>> vs. vector<vector<largeObject>*>, especially in c++. In specific: let's say that you have the outer vector full, and you want to start inserting elements into first inner vector. How will that be stored in memory if the outer vector is just storing pointers, as apposed to storing the whole inner vector. Will the whole outer vector have to be moved to gain more space, or will the inner vector be moved (assuming that space wasn't pre-allocated), causing problems with the outer vector? Thank you

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• Separation of static and dynamic content in Java EE applications

  - by Dan

  We work with IBM products and we typically use IBM Http Servers (read Apache) as a reverse proxy for our application servers. For performance reasons we serve static content (.gif, .jpg, .css, .html etc.) from our http servers, to ease the burden a bit from the application server. So far, we have to distribute files to http server and configure it manually (writing custom scripts at best.) The problem is the effort needed to keep everything in synch, especially when you need to update the app. Does any Java EE product support this “out of the box”? Is there a way to have application server do this automatically, like in cluster configuration for example, where master node is in charge of distributing the application to other nodes and for keeping everything in synch.

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• What messaging technologies in windows-ce for guaranteed msg delivery?

  - by Aidanapword

  We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (I have not found any RabbitMQ clients for CE, by example) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too.

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• MSSQL choosing row (from group) with max value

  - by sriehl

  I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following. id | code | value id | code | value 13 | AA | 0.5 13 | AC | 2.0 13 | AB | 1.0 14 | AB | 1.5 14 | AA | 2.0 13 | AA | 0.5 15 | AB | 0.5 15 | AB | 3.0 15 | AD | 1.5 15 | AA | 1.0 I need to get a list of id's, with the code (sumed from both tables) with the largest value. 13 | AC 14 | AA 15 | AB There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year.

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• How can I dynamically inject code into event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• MySQL locking problem

  - by teehoo

  I have a simple setup of a set of writers and a set of readers working with a MySQL ISAM table. The writers are only inserting rows while the readers are only checking for new rows. OK, so I know that I don't need a lock in this situation, since I'm not modifying existing rows. However my Writers are accessing one more table that does need a lock. I piece of information seems irrelevant except for the following limitation stated in the MySQL documentation: A session that requires locks must acquire all the locks that it needs in a single LOCK TABLES statement. While the locks thus obtained are held, the session can access only the locked tables. For example, in the following sequence of statements, an error occurs for the attempt to access t2 because it was not locked in the LOCK TABLES statement: So to access the table I want to insert rows into, I NEED to lock it, which is causing me performance problems. Any suggestions of how to get around this?

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• MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

  - by Cory House

  MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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• Getting latest Subsonic builds

  - by Alex Yakunin

  I need the latest Subsonic build or build it by my own. Subsonic project web site shows the latest available version is Subsonic v3.0.0.3 released at July 15, 2009. Questions: Are there any later builds - e.g. maintained by community members? If so, how can I get the latest one? In worst case I'm ready to get the latest source code and try to build it by my own. Are there any instructions for this? Please note, that I'm not interested in almost 1 year old builds - I need a build based on the latest code for tests (LINQ, performance), ideally - compiled for .NET 4.0.

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• Measuring daemon CPU utilization over a portion of it's wall clock run time

  - by WhirlWind

  I am dealing with a network-related daemon: it takes data in, processes it, and spits it out. I would like to increase the performance of this daemon by profiling it and reducing it's CPU utilization. I can do this easily on Linux with gprof. However, I would also like to use something like "time" to measure it's total CPU utilization over a period of time. If possible, I would like to time it over a period that is less than its total run time: thus, I would like to start the daemon, wait awhile, generate CPU statistics, stop generating them, then stop the daemon at some later time. The "time" command would work well for me, but it seems to require that I start and stop the daemon as a child of time. Is there a way to measure CPU utilization for only a portion of the daemon's wall clock time?

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• What is the best Java numerical method package?

  - by Bob Cross

  I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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• Semantic stuff (RDF, OWL) on mobile phones - is it possible?

  - by Brian Schimmel

  I'm thinking about using semantic (web) technogies like RDF and OWL in an application on mobile devices. Currently I'm targeting android, but I'd also be interested in the possibilities on the iPhone and on J2ME. I would like to use a lib instead of implementing everything from scratch. I know that there are some libraries and frameworks like Jena, Redland, Protégé but they don't state on which platforms they are known to work. Having a dynamic object model and parsing from and to XML are must-haves for me. I'd also like to use reasoning, but I've been told it was rather computing-intensive, so that's only a nice-to-have. For all platforms mentioned, the question can be interpreted as Is it possible in theory (especially for J2ME I'm not sure) Are there libs that are known to work on those platforms? Is the performance on a mobile platform good enough for real world usage?

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• Good reasons why to not use XIB files?

  - by mystify

  Are there any good reasons why I should not use XIB / NIB files with an highly customized UI and extensive animations and super low memory footprint needs? As a beginner I started with XIB. Then I figured out I couldn't do just about everything in them. It started to get really hard to customize things the way I wanted them to be. So at the end, I threw all my XIBs away and did it all programmatically. So when someone asks me if XIB is good, I generally say: Yeah, if you want to make crappy boring interfaces and don't care too much about performance, go ahead. But what else could be a reason not to use XIB? Am I the only iPhone developer who prefers doing everything programmatically for this reasons?

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• How to reliably measure available memory in Linux?

  - by Alex B

  Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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• Asp .Net MVC Viewmodel should be class or struct?

  - by Jonas Everest

  Hey guys, I have just been thinking about the concept of view model object we create in asp.net MVC. Our purpose is to instantiate it and pass it from controller to view and view read it and display the data. Those view model are usually instantiated through constructor. We won't need to initialize the members, we may not need to redefine/override parameterless constructor and we don't need inheritance feature there. So, why don't we use struct type for our view model instead of class. It will enhance the performance.

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• Is is better to store serialized data or raw html in mysql?

  - by Yegor

  I de-normalized my database, since the application was crawling otherwise, and Im storing a list of categories for each item in the DB as a raw html version, and simply echoing it out in my design. Each category is actually a link, which is include a tag. Naturally, this is abit of a pain, especially if I want to change the look of how the category links are displayed, since I gotta update all the old cached entries. What if I were to store this data as a serialized array instead, and simply unserialize it, and then apply formatting to it in php. Would there be a significant performance decrease over simply echoing out the raw html?

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• Append in Dom taking more time in IE than Firefox or any other browser.

  - by user307635

  Hi , I m working on .net framework 3.0 visual studio 08 and Testing it in IE8 and other browsers. Whenever I m inserting new elements in DOM (ex. 300 divs at one time) than I m getting the performance very slow in IE . Why?. If its a javascript debugging which is taking time or what else. Is it really true that IE Dom Append takes much time than any other browser. Please help me , I m stuck badly.

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• Java vs Flash for webcam access

  - by Alfredo Palhares

  I will make a video chat website, but coming from PHP and Python for the web i have no experience with video steaming. What do you recommend? Java or Flash? What's more flexible ? I am thinking of even making a C++ server application for stream controlling with a PHP fronted. Since is going to be a high traffic website and performance is a must. Can you point to some direction? Any documentation? Framework?

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• WPF/.NET data access models - resource recommendations

  - by jasonk

  We're in the early design/prep phases of transferring/updating a rather large "legacy" 3 tier client-server app to a new version. We’re looking at doing WPF over Winforms as it appears to be the direction Microsoft is pushing development of the future and we’d like the maximize the life cycle/span of the apps. That said during the rewrite we’d like to make as many changes to our data access/presentation model to improve performance as much as possible up front as many. I’ve been doing some research along that vein but the vast majority of the resources I've found that discuss WPF focus only simple data tracking apps or focus on the very basics UI design/controls. The few items that even discuss data presentation are fairly elementary in depth. Are there any books/articles/recommended reading/other resources recommended for development related to large enterprise level business apps? Any “gotchas” that should/could be avoided? General advice to minimize the time underwater

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• Endianness manipulation - is there a C library for this?

  - by Malvineous

  Hi all, With the sort of programs I write (working with raw file data) I often need functions to convert between big and little endian. Usually I write these myself (which is covered by many other posts here) but I'm not that keen on doing this for a number of reasons - the main one being lack of testing. I don't really want to spend ages testing my code in a big endian emulator, and often just omit the code for big endian machines altogether. I also would rather make use of faster functions provided by various compilers, while still keeping my programs cross-platform. The only things I can find are socket calls like htons() but they require different #include files on each platform, and some GPL code like this, however that particular file, while comprehensive, seems to miss out on some of the high performance functions provided by some compilers. So, does anyone know of a library (ideally just a .h file) that is well tested and provides a standard set of functions for dealing with endianness across many compilers and platforms?

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• Maximizing the number of threads to fully utilize all available resources without hindering overall

  - by Matt

  Let's say I have to generate a bunch of result files, and I want to make it as fast as possible. Each result file is generated independently of any other result file; in fact, one could say that each result file is agnostic to every other result file. The resources used to generate each result file is also unique to each. How can I dynamically decide the optimal number of threads to run simultaneously in order to minimize the overall run time? Is my only option to write my own thread manager that watches performance counters and adjust accordingly or does there exists some solid classes that already accomplish this?

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• C# method generic params parameter bug?

  - by Mike M

  Hey, I appears to me as though there is a bug/inconsistency in the C# compiler. This works fine (first method gets called): public void SomeMethod(string message, object data); public void SomeMethod(string message, params object[] data); // .... SomeMethod("woohoo", item); Yet this causes "The call is ambiguous between the following methods" error: public void SomeMethod(string message, T data); public void SomeMethod(string message, params T[] data); // .... SomeMethod("woohoo", (T)item); I could just use the dump the first method entirely, but since this is a very performance sensitive library and the first method will be used about 75% of the time, I would rather not always wrap things in an array and instantiate an iterator to go over a foreach if there is only one item. Splitting into different named methods would be messy at best IMO. Thoughts?

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• Why do I get CA1811 when I call a private method from a public method in C++/CLI?

  - by brickner

  I've recently upgraded my project from Visual Studio 2008 to Visual Studio 2010. By enabling Code Analysis and building on Release, I'm getting warning CA1811: Avoid uncalled private code. I've managed to reduce the code to this: .h file: public ref class Foo { public: virtual System::String^ ToString() override; private: static System::String^ Bar(); }; .cpp file: String^ Foo::ToString() { return Bar(); } String^ Foo::Bar() { return "abc"; } The warning I get: CA1811 : Microsoft.Performance : 'Foo::Bar(void)' appears to have no upstream public or protected callers. It doesn't matter if Bar() is static or not. I've tried to reproduce it in C# but I can't. I can only reproduce it in C++/CLI. Why do I get this warning? Is this a Visual Studio 2010 bug?

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• How would MVVM be for games?

  - by Benny Jobigan

  Particularly for 2d games, and particularly silverlight/wpf games. If you think about it, you can divide a game object into its view (the graphic on the screen) and a view-model/model (the state, ai, and other data for the object). In silverlight, it seems common to make each object a user control, putting the model and view into a single object. I suppose the advantage of this is simplicity. But, perhaps it's less clean or has some disadvantages in terms of the underlying "game engine". What are your thoughts on this matter? What are some advantages and disadvantages of using the MVVM pattern for game development? How about performance? All thoughts are welcome.

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