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  • Can I expect a performance gain from removing this JOIN?

    - by makeee
    I have a "items" table with 1 million rows and a "users" table with 20,000 rows. When I select from the "items" table I do a join on the "users" table (items.user_id = user.id), so that I can grab the "username" from the users table. I'm considering adding a username column to the items table and removing the join. Can I expect a decent performance increase from this? It's already quite fast, but it would be nice to decrease my load (which is pretty high). The downside is that if the user changes their username, items will still reflect their old username, but this is okay with me if I can expect a decent performance increase. I'm asking stackoverflow because benchmarks aren't telling me too much. Both queries finish very quickly. Regardless, I'm wondering if removing the join would lighten load on the database to any significant degree.

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  • LBA48 in Linux SCSI ATA Passthrough

    - by Ben Englert
    I am writing a custom disk monitoring/diagnostics app which, among other things, needs to do stuff to SATA disks behind a SAS PCI card under Linux. So far I am following this guide as well as the example code in sg_utils to pass ATA taskfiles through the SCSI layer. Seems to be working okay. However, in both cases, the CDB data structure (pointed to by the cmdp member of the sg_io argument to the ioctl) has only one unsigned char worth of space for the number of sectors. If you look at the ata_taskfile structure in linux\ata.h you'll see that it has an "nsect" and a "hob_nsect" field - high order bits for the sector count, to support LBA48. It turns out that in my application I need LBA48 support. So, anyone know how to set up an sg_io_hdr structure with an LBA48 sector count?

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  • Performance of Managed C++ Vs UnManaged/native C++

    - by bsobaid
    I am writing a very high performance application that handles and processes hundreds of events every millisecond. Is Unmanaged C++ faster than managed c++? and why? Managed C++ deals with CLR instead of OS and CLR takes care of memory management, which simplifies the code and is probably also more efficient than code written by "a programmer" in unmanaged C++? or there is some other reason? When using managed, how can one then avoid dynamic memory allocation, which causes a performance hit, if it is all transparent to the programmer and handled by CLR? So coming back to my question, Is managed C++ more efficient in terms of speed than unmanaged C++ and why?

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  • What lessons can you learn from software maintanence?

    - by Vasil Remeniuk
    Hello everyone, In the perfect world, all the software developers would work with the cutting edge technologies, creating systems from the scratch. In the real life, almost all of us have to maintain software from time to time (unlucky ones do it on a regular basis). Personally I first 2 years of my career was fixing bugs in the company that no longer exists (it has been taken up by Oracle). And probably the biggest lesson I've learned that time - despite of the pressure, always try to get as much information about the domain as possible (even if it's irrelevant to fixing a specific bug or adding a feature) - abstract domain knowledge doesn't lose value as fast as knowledge about trendy frameworks or methodologies. What lessons have you learned from maintenance?

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  • "SQL Server does not exist or access denied." upon VB.Net Deployment

    - by JasonMHirst
    Have built a small VB.Net app in VS2010. The connection string to the SQL Server is as follows: <connectionStrings> <add name="IWSR_DataDownloadWizard.My.MySettings.sqlConnection" connectionString="Provider=SQLOLEDB.1;Data Source=SQLServer;Integrated Security=SSPI;Initial Catalog=IWSROL" providerName="System.Data.OleDb" /> </connectionStrings> Within the VS2010 environment AND on my machine, the connection works perfectly, however when I deploy to clients I get an error message of: [DBNETLIB][ConnectionOpen (Connect()).]SQL Server does not exist or access denied. I've tried to search the net for solutions, have seen a few instances of people saying to NOT use the Server Name but the IP Address instead (this doesn't work) and some saying to remove the "Provider=SQLOLEDB.1", again this doesn't work. Can anyone suggest a solution please? Further information: Development System is Windows7 using VS2010 Deployment systems are a combination of Windows XP, Windows 2000 and Windows 7 SQL Server is SQL2000 (soon to be SQL2005). TIA

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  • Screening (multi)collinearity in a reggresion model

    - by aL3xa
    I hope that this one is not going to be "ask-and-answer" question... here goes: (multi)collinearity refers to extremely high correlations between predictors in the regression model. How to cure them... well, sometimes you don't need to "cure" collinearity, since it doesn't affect regression model itself, but interpretation of an effect of individual predictors. One way to spot collinearity is to put each predictor as a dependent variable, and other predictors as independent variables, determine R2, and if it's larger than .9 (or .95), we can consider predictor redundant. This is one "method"... what about other approaches? Some of them are time consuming, like excluding predictors from model and watching for b-coefficient changes - they should be noticeably different. Of course, we must always bare in mind specific context/goal of analysis... Sometimes, only remedy is to repeat a research, but right now, I'm interested in various ways of screening redundant predictors when (multi)collinearity occurs in a regression model.

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  • mystified by qr.Q(): what is an orthonormal matrix in "compact" form?

    - by gappy
    R has a qr() function, which performs QR decomposition using either LINPACK or LAPACK (in my experience, the latter is 5% faster). The main object returned is a matrix "qr" that contains in the upper triangular matrix R (i.e. R=qr[upper.tri(qr)]). So far so good. The lower triangular part of qr contains Q "in compact form". One can extract Q from the qr decomposition by using qr.Q(). I would like to find the inverse of qr.Q(). In other word, I do have Q and R, and would like to put them in a "qr" object. R is trivial but Q is not. The goal is to apply to it qr.solve(), which is much faster than solve() on large systems.

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  • How to have tortoisesvn Always freeze svn:externals for tags

    - by dnndeveloper
    Is this possible with tortoiseSVN?: Always freeze svn:externals for tags the scenario is our trunk will always use the 'head' revision for externals, however when we create 'tags' we would like for them to have a revision set for externals to properly 'freeze' them at a specific point in time. Thanks! Update Thanks to everyone for your feedback/info. Since I could not find anything that would completely meet our needs (tried smartsvn and svncopy.pl) I made a console app that so far has passed all our test cases. A high level overview: The app takes a repository URL then looks for all externals and adds the last commit revision for them - I do a "svn info" and get the "commit revision". The app works with both folder and single file externals. Here is the source code and complete setup files: http://svnxf.codeplex.com/

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  • Curious: Could LLVM be used for Infocom z-machine code, and if so how? (in general)

    - by jonhendry2
    Forgive me if this is a silly question, but I'm wondering if/how LLVM could be used to obtain a higher performance Z-Machine VM for interactive fiction. (If it could be used, I'm just looking for some high-level ideas or suggestions, not a detailed solution.) It might seem odd to desire higher performance for a circa-1978 technology, but apparently Z-Machine games produced by the modern Inform 7 IDE can have performance issues due to the huge number of rules that need to be evaluated with each turn. Thanks! FYI: The Z-machine architecture was reverse-engineered by Graham Nelson and is documented at http://www.inform-fiction.org/zmachine/standards/z1point0/overview.html

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  • Set the path for the location of media files in program

    - by Zaheer Boovaji
    I have made a Java Swing Desktop application in Netbeans which can play media files I have put the videos in my workspace resources location and in my java program I am calling those media files using an URL which is something like this: C:/users/Dell/My Documents /NetBeansProjects/Media/src/resources/ MediaFiles/ddd.mpg This works well when I run in my IDE and also i have made Jar for this it works well on my computer but the problem is when i copy this jar file on my friends system the interface is coming but when I click a button to play a media file it says: C:/users/Dell/MyDocuments/NetBeansProjects/Media/src/resources/ MediaFiles/ddd.mpg does not exist So, please provide me a solution of how to set the default path so that when I run a jar file on other systems it should play the media file location I am passing as in my program. How to set the path for the location of media files in program? Update The videos are in the jar file.

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  • Django admin page dropdowns

    - by zen
    I am building a high school team application using Django. Here is my working models file: class Directory(models.Model): school = models.CharField(max_length=60) website = models.URLField() district = models.SmallIntegerField() conference = models.ForeignKey(Conference) class Conference(models.Model): conference_name = models.CharField(max_length=50) url = models.URLField() class Meta: ordering = ['conference_name'] When I open my admin pages and go to edit a school's conference the drop down looks like this: <select> <option value="1">Conference Object</option> <option value="2">Conference Object</option> <select> How do I replace "Conference Object" with the conference_name?

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  • Crystal Reports and WMF image

    - by Eve
    I have a problem with inserting a vector graphics (WMF) into report (Crystal Reports v10.5 from Visual Studio 2008). The image is static, inserted by choosing "Insert Picture" during report design in VS. The problem is that it displays differently (size and aspect ratio) on machines with different operating systems and screen resolutions. Converting to bitmap isn't possible beacause loss of the quality of print isn't acceptable. I thought about dynamic loading of the image, but in this version of CR. I don't see a possibility to set dynamic graphic location in picture properties. Is there any way to solve this problem?

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  • Is code clearness killing application performance?

    - by Jorge Córdoba
    As today's code is getting more complex by the minute, code needs to be designed to be maintainable - meaning easy to read, and easy to understand. That being said, I can't help but remember the programs that ran a couple of years ago such as Winamp or some games in which you needed a high performance program because your 486 100 Mhz wouldn't play mp3s with that beautiful mp3 player which consumed all of your CPU cycles. Now I run Media Player (or whatever), start playing an mp3 and it eats up a 25-30% of one of my four cores. Come on!! If a 486 can do it, how can the playback take up so much processor to do the same? I'm a developer myself, and I always used to advise: keep your code simple, don't prematurely optimize for performance. It seems that we've gone from "trying to get it to use the least amount of CPU as possible" to "if it doesn't take too much CPU is all right". So, do you think we are killing performance by ignoring optimizations?

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  • Good book(s) for MMORPG design & implementation?

    - by mawg
    I am a long time professional C/C++ programmer (mostly embedded systems) and a hobbyist windows & php hacker. Can anyone recommend a book(s) specifically aimed at designing and (hopefully) implementing an MMORPG? I don't need general how to design or how to code books. Maybe a really good generic games book, but I am not interested in 1st person shooters, I want to know what it takes to implement an MMORPG. Good books, maybe also good URLs. Thanks just searching eBay and Amazon threw up a whole slew of books. Amazon's customer reviews give me an idea of how good they are, and the overview tells me what areas they cover

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  • Agile - When does it work well, and when doesn't it?

    - by Randy Minder
    Our team is debating whether we want to become Agile or not. None of us are really fluent in Agile. I'd like some thoughts on when Agile works well, and when it doesn't? To give a little background, we are a small group of developers, six in total. We have far more work that we can handle. Our priorities change often. What is a high priority today, may not be tomorrow. We have many applications to create and maintain. If you need more information to answer this, please feel free to ask. Thanks.

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  • How is the ">" operator implemented (on 32 bit integers)?

    - by Ron Klein
    Let's say that the environment is x86. How do compilers compile the "" operator on 32 bit integers. Logically, I mean. Without any knowledge of Assembly. Let's say that the high level language code is: int32 x, y; x = 123; y = 456; bool z; z = x > y; What does the compiler do for evaluating the expression x > y? Does it perform something like (assuming that x and y are positive integers): w = sign_of(x - y); if (w == 0) // expression is 'false' else if (w == 1) // expression is 'true' else // expression is 'false' Is there any reference for such information?

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  • What Database to distribute as part of a C# app backend

    - by jez
    I am planning on writing and commercialising a C# app which will store data in an underlying database I use MySQL on my environment for my own development and this is what I would have used to write the application for myself (no need to use FK - MyISAM engine would be fine). I am concerned about how easy it will be to distribute the app together with the database engine. Would using MySQL allow me for easy packaging of the app for a "one-click" install on the client side? (ie I do not want them to have to install MySQL by themselves) and also is it feasible from a licensing point of view? Are there other Database systems which would make the process more straight-forward

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  • Tool for response time analysis on JBoss server?

    - by Ariel Vardi
    I am running a pretty high traffic cluster of JBoss servers serving REST requests and I am interested in tools reading the access logs in Tomcat format (with %D parameter) to provide a detailed analysis of the response time on a per-call basis. Ideally this tool would generate a chart showing the progression of the response time throughout the day, hour per hour, then a weekly view with averages on the day, and monthly with average on the weeks (CACTI style). I've looked for such tools and couldn't find anything. Is any of you guys aware of something close to that before I start writing my own? I haven't looked into CACTI extensions yet, but that be an option?

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  • How do you design a database to allow fast multicolumn searching?

    - by Fletcher Moore
    I am creating a real estate search from RETS data, but this is a general question. When you have a variety of columns that you would like the user to be able to filter their search result by, how do you optimize this? For example, http://www.charlestonrealestateguide.com/listings.php has 16 or so optional filters. Granted, he only has up to 11,000 entries (I have the same data), but I don't imagine the search is performed with just a giant WHERE AND AND AND ... clause. Or is this typically accomplished with one giant multicolumn index? Newegg, Amazon, and countless others also have cool & fast filtering systems for large amounts of data. How do they do it? And is there a database optimization reason for the tendency to provide ranges instead of empty inputs, or is that merely for user convenience?

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  • Is there a standard format string in ASP.NET to convert 1/2/3/... to 1st/2nd/3rd...?

    - by Dr. Monkey
    I have an integer in an Access database, which is being displayed in ASP.NET. The integer represents the position achieved by a competitor in a sporting event (1st, 2nd, 3rd, etc.), and I'd like to display it with a standard suffix like 'st', 'nd', 'rd' as appropriate, rather than just a naked number. An important limitation is that this is for an assignment which specifies that no VB or C# code be written (in fact it instructs code behind files to be deleted entirely). Ideally I'd like to use a standard format string if available, otherwise perhaps a custom string (I haven't worked with format strings much, and this isn't high enough priority to dedicate significant time to*, but I am very curious about whether there's a standard string for this). (* The assignment is due tonight, and I've learned the hard way that I can't afford to spend time on things that don't get the marks, even if they irk me significantly.)

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  • Empty or "flush" a file descriptor without read()?

    - by Teddy
    (Note: This is not a question of how to flush a write(). This is the other end of it, so to speak.) Is it possible to empty a file descriptor that has data to be read in it without having to read() it? You might not be interested in the data, and reading it all would therefore waste space and cycles you might have better uses for. If it is not possible in POSIX, do any operating systems have any non-portable ways to do this? UPDATE: Please note that I'm talking about file descriptors, not streams.

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  • VitrtualStringTree. How to Drag'n'Drop to ROOT level?

    - by Alexandr
    A have a tree: ROOT - VirtualStringTree(You don't see it, TVirtualStringTree.RootNode) - My Root Node 1 - My Root Node 2 - - Second node 1 - - Second node 2 - - Second node 3 - My Root Node 3 I can Drag'n'Drop "My Root Node 3" to any visible node, but I can't return it to defaut position, to the root level of tree. I try that: //Part of code from OnDragDrop Event of VirtualStringTree if (Sender.DropTargetNode = Sender.RootNode) then begin for i := 0 to high(Nodes) do begin LinksTree.MoveTo(Nodes[i], Sender.DropTargetNode, Attachmode, False); end; end; I places mouse to nowhere, but nothing happens. In DragOver I accepted drop to root if DropTarget is VST.RootNode. Anybody knows, how to drop node to VST.RootNode if I drag mouse to empty space of component?

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  • Programming language for fast calculations with big integers

    - by sub
    I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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  • Anyone Know a Great Sparse One Dimensional Array Library in Python?

    - by TheJacobTaylor
    I am working on an algorithm in Python that uses arrays heavily. The arrays are typically sparse and are read from and written to constantly. I am currently using relatively large native arrays and the performance is good but the memory usage is high (as expected). I would like to be able to have the array implementation not waste space for values that are not used and allow an index offset other than zero. As an example, if my numbers start at 1,000,000 I would like to be able to index my array starting at 1,000,000 and not be required to waste memory with a million unused values. Array reads and writes needs to be fast. Expanding into new territory can be a small delay but reads and writes should be O(1) if possible. Does anybody know of a library that can do it? Thanks!

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  • Call a JavaScript function in a Google Chrome window from a vb.net program

    - by user1464827
    I am having a real problem with this. I want to know if it is possible to run/call a javascript function in a Google Chrome web browser window from a VB.net application. The scenario is that i want to monitor the pc activity (which i know how to) and then if a certain event is met (for example, high ram usage) then it calls a JavaScript function in a Google Chrome web browser window so the website is updated. Sort of like a bridge. The only bit it need to know is the vb.net code for how to access a chrome window and invoke a javascript function if its possible. I assume i will need to use process handlers? Any help is appreciated.

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