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• Best choice for off-site backup: dd vs tar

  - by plok

  I have two 1TB single-partition hard disks configured as RAID1, of which I would like to make an off-site backup on a third disk, which I am still to buy. The idea is to store the backup at a relative's house, considerably far away from my place, in the hope that all the information will be safe in the case of a global thermonuclear apocalypse. Of course, this backup would be well encrypted. What I still have to decide is whether I am going to simply tar the entire partition or, instead, use dd to create an image of the disks. Is there any non-trivial difference between these two approaches that I could be overlooking? This off-site backup would be updated no more than two or three times a year, in the best of the cases, so performance should not be a factor to be pondered at all. What, and why, would you use if you were me? dd, tar, or a third option?

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• Is scala functional programming slower than traditional coding?

  - by Fred Haslam

  In one of my first attempts to create functional code, I ran into a performance issue. I started with a common task - multiply the elements of two arrays and sum up the results: var first:Array[Float] ... var second:Array[Float] ... var sum=0f; for(ix<-0 until first.length) sum += first(ix) * second(ix); Here is how I reformed the work: sum = first.zip(second).map{ case (a,b) => a*b }.reduceLeft(_+_) When I benchmarked the two approaches, the second method takes 40 times as long to complete! Why does the second method take so much longer? How can I reform the work to be both speed efficient and use functional programming style?

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• Create empty C# event handlers automatically

  - by TomA

  It is not possible to fire an event in C# that has no handlers attached to it. So before each call it is necessary to check if the event is null. if ( MyEvent != null ) { MyEvent( param1, param2 ); } I would like to keep my code as clean as possible and get rid of those null checks. I don't think it will affect performance very much, at least not in my case. MyEvent( param1, param2 ); Right now I solve this by adding an empty inline handler to each event manually. This is error prone, since I need to remember to do that etc. void Initialize() { MyEvent += new MyEvent( (p1,p2) => { } ); } Is there a way to generate empty handlers for all events of a given class automatically using reflection and some CLR magic?

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• What is the best platform/language for a 3D game in a web browser?

  - by CodeJustin.com

  I have enjoyed making 2D games in various langues (actionscript 3.0, java, python, others) but now I'm ready to move into 3D and to really get me amped up while learning 3D development I'm going to attempt to make a 3D multiplayer game (I already have server written in python). I'm looking for a platform that will run a 3D game well in the browser on low end computers with low end internet. What first came to mind was try Java or use flash/silver light with a 3D framework but I wanted to ask the good people of stackoverflow since performance is a big part of my needs and also good documentation is a plus since I'm just starting 3D development. (the programming language does not matter)

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• How should i draw text and shapes in wpf and C#?

  - by peterhu

  I want to do basic WPF graphics, i.e. rectangles, lines, circles and text. When should I use Drawing and when should I use a DrawingVisual? I have some code that uses Drawing and I render those to a DrawingImage and display that in an image control. Is this the right way? I could not see how to add text to a drawing. I had trouble positioning it too. Should I be rendering to a Canvas? I have some code that uses DrawingVisual and writes to a DrawingContext. That is like WinForms. Is this the recommended way? Do you have any high level advice on which APIs to use for basic graphics and labels? Will they options work on Silver Light and Desktop?

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• Designing entire webpages as SVG files

  - by user1311390

  Disclaimer I realize that given the absurdity of the title, this sounds like a troll. However, it's a genuine question. My background involves OpenGL / x86 assembly. I've recently started learning web programming. I really like SVG + CSS, and was wondering -- why do people not design entire webpages in SVG? Context SVG provides beautiful primitive: quadratic + cubic bezier curves; lines + filling -- all as vector graphics SVG provides text SVG provides affine transformations Questions Are there examples of people designing entire websites as a giant SVG file? If not, what the limitations? Are there performance hits when using SVG primitives as opposed to divs/tables?

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• Is there any disadvantage to putting API code into a JAR along with the classes?

  - by Adam Gent

  In Java if you package the source code (.java) files into the jar along with classes (.class) most IDE's like eclipse will show the javadoc comments for code completion. IIRC there are few open-source projects that do this like JMock. Lets say I have cleanly separated my API code from implementation code so that I have something like myproject-api.jar and myproject-impl.jar is there any reason why I should not put the source code in my myproject-api.jar ? Because of Performance? Size? Why don't other projects do this?

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• using arrays to get best memory alignment and cache use, is it necessary?

  - by Alberto Toglia

  I'm all about performance these days cause I'm developing my first game engine. I'm no c++ expert but after some research I discovered the importance of the cache and the memory alignment. Basically what I found is that it is recommended to have memory well aligned specially if you need to access them together, for example in a loop. Now, In my project I'm doing my Game Object Manager, and I was thinking to have an array of GameObjects references. meaning I would have the actual memory of my objects one after the other. static const size_t MaxNumberGameObjects = 20; GameObject mGameObjects[MaxNumberGameObjects]; But, as I will be having a list of components per object -Component based design- (Mesh, RigidBody, Transformation, etc), will I be gaining something with the array at all? Anyway, I have seen some people just using a simple std::map for storing game objects. So what do you guys think? Am I better off using a pure component model?

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• What is the best way to keep database data encrypted with user passwords?

  - by Dan Sosedoff

  Let's say an application has really specific data which belongs to a user, and nobody is supposed to see it except the owner. I use MySQL database with DataMapper ORM mapper. The application is written in Ruby on Sinatra. Application behavior: User signs up for an account. Creates username and password. Logs into his dashboard. Some fields in specific tables must be protected. Basically, I'm looking for auto-encryption for a model properties. Something like this: class Transaction include DataMapper::Resource property :id, Serial property :value, String, :length => 1024, :encrypted => true ... etc ... belongs_to :user end I assume that encryption/decryption on the fly will cause performance problems, but that's ok. At least if that works - I'm fine. Any ideas how to do this?

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• The case of the mysterious MySQL caching across restarts

  - by shanusmagnus

  I found a very slow MySQL query in my web app. The weird thing is that the query is only slow the first time it's executed, despite the fact that the query_cache is set to its default (query_cache_size 0) like so: mysql> show variables like 'query%'; +------------------------------+---------+ | Variable_name | Value | +------------------------------+---------+ | query_alloc_block_size | 8192 | | query_cache_limit | 1048576 | | query_cache_min_res_unit | 4096 | | query_cache_size | 0 | | query_cache_type | ON | | query_cache_wlock_invalidate | OFF | | query_prealloc_size | 8192 | +------------------------------+---------+ The even weirder thing is that this speedup persists even after the MySQL server has been stopped and restarted (I'm using OSX, and perform this restart using the system preferences pane.) The only way I can re-create the poor performance of the initial query is by rebooting the system. So my question is: how is this happening? Obviously some sort of caching at work, but where? And how does it persist across database restarts? This query is mediated through our web app, which comes via PHP/Apache, but there are no extra bells and whistles, and the curious caching also persists across Apache restarts. Help?

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• How to pass a reference to a string in JavaScript?

  - by ijjo

  Maybe a closure is my solution? Not exactly sure how to pull it off though. The code is set up like so: var globalVar = ''; var globalVar2 = ''; function func() { if (condition) func2(globalVar) else func2(globalVar2) } In func2() I cache some HTML in a main container into the appropriate global variable that I pass to it. Basically I have a main container that holds different pages depending on what tab they choose. For performance I want to cache the page into global vars so I need to know what tab is active to figure out which global var to assign the HTML to.

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• Alter top and bottom borders of Dojo/Dijit Dialog and ContentPane

  - by Joe Zitzelberger

  I have a Dojo/Dijit Dialog that contains a FORM. There is a top border between the title bar and the content, and a bottom border below the content. Both are about 19 or 20 pixels high and colored #eeeeee. I can't find these borders in the CSS anywhere -- actually, neither can the IE Developer Toolbar -- they just don't seem to exist as elements. I suspect that Dijit is adding these programatically. Is there any way to just remove these borders? I just want my content to consume all of the dialog area below the title bar. TIA

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• How to structure opening hours of a place? May-be there's even an ontology for it?

  - by Ago

  Does anyone know any ontology which specifies opening hours of places? For example, I have a museum, which has 2 seasons. For low season (season start and end is specified), it is opened 10.00 - 18.00 on weekdays and 10-16 on saturday (on sunday it's closed), for high season it's opened 10-20 on weekdays and 10-18 on weekend. If there is no ontology, may-be people have experience, how best to structure information like that? I'm describing information in RDF. But whatever comments are welcome (even if you have relational database which holds given data). Thanks

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• Response.Redirect exception

  - by Tedd Hansen

  Executing the line: Response.Redirect("Whateva.aspx", true); Results in: A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code The exception is because of the "true" part, telling it to end the current request immediately. Is this how it should be? If we consider: Exceptions are generally considered heavy, and many times the reason for ending the request early is to avoid processing the rest of the page. Exceptions show up in performance monitoring, so monitoring the solution will show a false number of exceptions. Is there an alternative way to achieve the same?

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• Capture IP packets on Dialup connection - Windows 7

  - by Assaf Levy

  Our product utilizes (the wonderful) Winpcap to capture ip packets from all devices with an IP address and analyze them in real time. Unfortunately, we discovered that it does NOT capture any packets on dialup (e.g. PPP) connections on Windows 7, and that there are no near-term plans for enabling this (1). So we need something else. Microsoft Network Monitor and Windows Packet Filter are two options that surfaced during a bit of googling, but before delving into research I wanted to ask the experienced: what are out options, given the following requirements: Capture all in/outbound IP packets on the machine. Complete background processing - no UI should be involved. Support Windows Vista / 7. Performance (user should not feel the difference). Thanks in advance.

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• How do you deal with the more mundane parts of programming tasks?

  - by Uri

  My experience as a developer is that many projects or tickets are a mix of a short and focused very interesting task (e.g., designing some API or a platform to solve something) and a lot of repetitive and mundane tasks that cannot be automated (such as certain refactorings to use the API or platform, implementation of certain tests, some GUI handling, etc). I believe that this is the nature of our profession, unless we are high-level architects or managements and can delegate this work. The only item in my personal arsenal when dealing with these tasks is to devote some of my attention to radio or audiobooks (preferably not in English as I find it hard to concentrate on two "streams" of English at the same time). I maintain sufficient attention to carry the task and don't lose concentration as fast. I'm wondering how others cope with these and maintain concentration.

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• Best keyboards for emacs?

  - by catphive

  For emacs users out there, what are your recommended keyboards? Bonus points for keyboards that: Have no capslock key. Instead, a control key in that position. Alt keys that are closer to the center, and easier to use with meta key combos. I find alt keys too far to the left to be a bit awkward to hit with my thumb in some key combos. Help ergonomically with emacs in other ways. I'm not a huge fan of model M style high and clacky keys. I instead prefer laptop style flat keys; however, I'm not disqualifying either category.

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• Spring 3.0 REST implementation or Jersey?

  - by hnilsen

  Hi, SO! I'm currently trying to figure out which implementation of JSR-311 I'm going to recommend further up the food chain. I've pretty much narrowed it down to two options - Spring 3.0 with it's native support for REST - or use Sun's own Jersey (Restlets might also be an option). To me it doesn't seem to be much of a difference in the actual syntax, but there might be issues with performance that I haven't figured out yet. The service is meant to replace some heavy-duty EJB's and make a RESTful Webservice instead. The load is expected to be rather high, up in the 100k users per day (max) range, but will be seriously load balanced. Thanks for all your insights.

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• Separate one-off code paths

  - by DeadMG

  I'm implementing an application with different code paths that shall be chosen once at startup and then fixed forevermore for that execution- for example, choosing D3D11 or D3D9 rendering path. Obviously I don't want to duplicate all my other code. Is run-time inheritance (no virtual inheritance) a fair solution? I don't want to waste a bunch of performance making virtual lookups when the type was fixed long ago. Not just that, but it makes me nervous that the functions can't be inlined and whether or not it affects RVO and NRVO and such. Am I just being over-concerned about this?

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• Where is Python support for PEM + RSA + DES3?

  - by jasonjs

  I need a Python library that supports PEM files and both RSA signing and DES3 encryption. pycrypto doesn't seem to support PEM, and its mechanism for loading existing keys is undocumented and cryptic. m2crypto doesn't seem to support DES/DES3, oddly. I've been running an openssl subprocess, but I'd rather have something built in and preferably fast. Does this exist? (Failing that, I hesitate to ask, but are there high-level enough C apis available for this that I could write a special-purpose extension without killing myself/introducing vulns?)

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• How to Get the Method/Function Call Trace for a Specific Run?

  - by JackWM

  Given a Java or JavaScript program, after its execution, print out a sequence of calls. The calls are in invocation order. E.g. main() { A(); } A() { B(); C(); } Then the call trace should be: main -> A() -> B() -> C() Is there any tool that can profile and output this kind of information? It seems this is common a need for debugging or performance tuning. I noticed that some profilers can do this, but I prefer a simpler/easy-to-use one. Thanks!

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• Java Web Server with Jetty - TCP Connections Taking Long

  - by daysleeper

  I have an application with fairly high traffic (20K req/min) running on the JVM with a Jetty servlet container on Ubuntu. Below is my Jetty configuration: 10 20 2000 2 When I analyze the network traffic, I realize that sometimes it is taking long to establish TCP connections on the port that Jetty is running. The long connections are varying between 3.0s and 9.0s. The port is configured to accept MAX number of TCP connections. Do you know what might be causing the delay in accepting connections? Thanks

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• Selecting a value from multiple dictionaries inside an enumeration

  - by johaanfaust

  If I have an enumeration of dictionaries IEnumerable<IDictionary<string, float>> enumeration can I perform a Linq query on it so that I can select by a value from each dictionary in the enumeration using the same key? I can do this in a loop: float f; foreach (var dictionary in enumeration) { if (dictionary.TryGetValue("some key", out f)) { Console.WriteLine(f); } } (The eventual plan is to compare the performance of the query verses the equivalent nested looping statements (the enumeration itself is formed from either another query or an equivalent set of loops).)

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• Which are the current/emerging desktop development technologies worth looking into?

  - by heeboir

  Greetings, With all the existing development towards web development and emerging technologies in that area, I'm left wondering; what is a state of the art way to implement desktop applications in this day and age? If you were to start a new application of considerable size from scratch what technology would you invest your efforts in (focusing on cross platform portability, decent performance and interoperability with existing standards)? I've looked into the Adobe Air platform which appears quite impressive but seems rather limited to support a large application. Would something like Java/SWT still be the sensible choice? Do things like GWT fit the bill? Thanks P.S. I'm leaving my question a bit open-ended in an effort to gather diverse answers. Surely this a subjective matter and there is no right and wrong answer.

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• Take advantage of multiple cores executing SQL statements

  - by willvv

  I have a small application that reads XML files and inserts the information on a SQL DB. There are ~ 300 000 files to import, each one with ~ 1000 records. I started the application on 20% of the files and it has been running for 18 hours now, I hope I can improve this time for the rest of the files. I'm not using a multi-thread approach, but since the computer I'm running the process on has 4 cores I was thinking on doing it to get some improvement on the performance (although I guess the main problem is the I/O and not only the processing). I was thinking on using the BeginExecutingNonQuery() method on the SqlCommand object I create for each insertion, but I don't know if I should limit the max amount of simultaneous threads (nor I know how to do it). What's your advice to get the best CPU utilization? Thanks

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