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  • "make" and "make install" never work

    - by Nirmik
    I have been trying it from a long time now and this time it got my nerves... The commands make and make install used to install a program from an extracted tar ball never work for some reason... The make command gives me the error- make: *** No targets specified and no makefile found. Stop. and the make install command gives me the error make: *** No rule to make target `install'. Stop. Why are these commands not executing? What should I do to solve this issue?

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  • How to Tweak the Low Battery Action On Your Windows 7 Laptop

    - by The Geek
    If you’ve got a netbook with really great battery life, you’ll probably still have loads of time left even with only 10% of the battery remaining. Here’s how to tweak the settings so it alerts you or goes into sleep mode at a more reasonable time. Note: obviously if you don’t have a great battery in your laptop, you should probably be careful with these settings or you might lose data. If anything, you’d be better off making the notifications happen sooner in that case Latest Features How-To Geek ETC The 20 Best How-To Geek Linux Articles of 2010 The 50 Best How-To Geek Windows Articles of 2010 The 20 Best How-To Geek Explainer Topics for 2010 How to Disable Caps Lock Key in Windows 7 or Vista How to Use the Avira Rescue CD to Clean Your Infected PC The Complete List of iPad Tips, Tricks, and Tutorials Classic Super Mario Brothers Theme for Chrome and Iron Experimental Firefox Builds Put Tabs on the Title Bar (Available for Download) Android Trojan Found in the Wild Chaos, Panic, and Disorder Wallpaper Enjoy Christmas Beyond the Holiday with Christmas Eve Crisis Parrotfish Extends the Number of Services Accessible in Twitter Previews

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  • Page load speeds effect on crawl rate

    - by Sam Pegler
    We've noticed a big drop in the total pages crawled per day on our site, we have no control over the crawl rate in google webmaster tools so it's possible this has been changed by google. However it's a fairly large site and I wouldn't of thought that the crawl rate would've been decreased. What we have noticed though is a sizeable increase in page load times, in my mind this would be the cause. Can anyone else confirm if the crawl rate is directly correlated to page load time? Seems logical, longer page load time, less pages crawled. Any decent documentation on this would be appreciated, I don't normally have any input on SEO so this is new to me.

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  • Don't Call it a Comeback

    - by Chris Haaker
    I received the email like most of you about Jeff and crew stepping down and selling the blog to another company. That it is a long time associate and friend of the team we have all grown to know and love, I feel much better about the move. Who cares, Chris, you haven't blogged religiously in ages! I know, and its a crime. Blame life, Twitter, my kids, laziness or whatever else you can think of. I always tell myself I am going to make a comeback - - "Don't call it a comeback - I been here for years." But after a few posts I seem to lose my steam. Its hard to explain, hell, I can't explain it. But we'll see what happens this time. Just don't call it a comeback.  2012 rMBP 15" Quad Core 2.33 GHz 16GB Memory 258GB SSDMarsEdit 3.5 (Please Microsoft Live Team - Make LiveWriter for OS X)

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  • Volume setting isn't remembered after restart/shutdown

    - by Iulian
    This is my first time here and I'm new to linux and also to Ubuntu. I've installed first version 11.10 and there was some problems with the unity dock and also the problem with the volume not being remembered after restart or shutdown. I'm using dualboot with Windows 7. Ubuntu was installed after windows. I have 2 sound cards. One is onboard, on the motherboard, and the other is external, an E-MU 0404 USB 2.0 sound card. The last one is my primary sound card and I've choosed it as default output sound card. I've upgraded to 12.04 hopeing that this was fiex but even in this version the OS doesn't keep the volume where it was last time. The big problem is that sometimes I forget about this problem and start music and it starts at full volume and soon I think I will die of heart attack. Is there a way to make it remember or at least to tell him to start at a specific volume not at 100%?

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  • CodePlex Daily Summary for Thursday, May 08, 2014

    CodePlex Daily Summary for Thursday, May 08, 2014Popular ReleasesOneNote Tagging Kit: OneNoteTaggingKit Add-In v2.3.5241.24721: Bugfix Release First time add-in registration problem fixed (issue 973 ). Was introduced by changing installer technology. Page tags retrieved from page meta element rather than outline to avoid round-trip encoding issues and avoid tags getting out of sync if someone edits the tags in the outline. Fixed issue with popup which showed an incorrect message for a short timeAST - a tool for exploring windows kernel: Ast-0.1-win8.1x86: Ast-0.1-win8.1x86Ghostscript.NET: Ghostscript.NET v.1.1.8.: 1.1.8. fixed incompatibility problem with 'gsapisetarg_encoding' function in Ghostscript releases prior to 9.10. (this function was introduced in 9.10 release) fixed older versions incompatibility problem with '-dMaxBitmap=1g' switch bugfix which in some cases turns on text antialiasing for Ghostscript 9.14 added better initialization checking 1.1.7. implemented Ghostscript native library verification with a friendly error message that will clear out the confusion when used native Ghosts...SimCityPak: SimCityPak 0.3.0.0: Contains several bugfixes, newly identified properties and some UI improvements. Main new features UI overhaul for the main index list: Icons for each different index, including icons for different property files Tooltips for all relevant fields Removed clutter Identified hundreds of additional properties (thanks to MaxisGuillaume) - this should make modding gameplay easierSeal Report: Seal Report 1.4: New Features: Report Designer: New option to convert a Report Source into a Repository Source. Report Designer: New contextual helper menus to select, remove, copy, prompt elements in a model. Web Server: New option to expand sub-folders displayed in the tree view. Web Server: Web Folder Description File can be a .cshtml file to display a MVC View. Views: additional CSS parameters for some DIVs. NVD3 Chart: Some default configuration values have been changed. Issues Addressed:16 ...Magick.NET: Magick.NET 6.8.9.002: Magick.NET linked with ImageMagick 6.8.9.0.VidCoder: 1.5.22 Beta: Added ability to burn SRT subtitles. Updated to HandBrake SVN 6169. Added checks to prevent VidCoder from running with a database version newer than it expects. Tooltips in the Advanced Video panel now trigger on the field labels as well as the fields themselves. Fixed updating preset/profile/tune/level settings on changing video encoder. This should resolve some problems with QSV encoding. Fixed tunes and profiles getting set to blank when switching between x264 and x265. Fixed co...NuGet: NuGet 2.8.2: We will be releasing a 2.8.2 version of our own NuGet packages and the NuGet.exe command-line tool. The 2.8.2 release will not include updated VS or WebMatrix extensions. NuGet.Server.Extensions.dll needs to be used alongside NuGet-Signed.exe to provide the NuGet.exe mirror functionality.SmartStore.NET - Free ASP.NET MVC Ecommerce Shopping Cart Solution: SmartStore.NET 2.0.2: SmartStore.NET 2.0.2 is primarily a maintenance release for version 2.0.0, which has been released on April 04 2014. It contains several improvements & important fixes. BugfixesIMPORTANT FIX: Memory leak leads to OutOfMemoryException in application after a while Installation fix: some varchar(MAX) columns get created as varchar(4000). Added a migration to fix the column specs. Installation fix: Setup fails with exception Value cannot be null. Parameter name: stream Bugfix for stock iss...Channel9's Absolute Beginner Series: Windows Phone 8.1: Entire source code for Windows Phone 8.1 Absolute Beginner Series.BIDS Helper: BIDS Helper 1.6.6: This BIDS Helper beta release brings support for SQL Server 2014 and SSDTBI for Visual Studio 2013. (Note that SSDTBI for Visual Studio 2013 is currently unavailable to download from Microsoft. We are releasing BIDS Helper support to help those who downloaded it before it became unavailable, and we will recheck BIDS Helper 2014 is compatible after SSDTBI becomes available to download again.) BIDS Helper 2014 Beta Limitations: SQL Server 2014 support for Biml is still in progress, so this bet...Windows Phone IsoStoreSpy (a cool WP8.1 + WP8 Isolated Storage Explorer): IsoStoreSpy WP8.1 3.0.0.0 (Win8 only): 3.0.0.0 + WP8.1 & WP8 device allowed + Local, Roaming or Temp directory Selector for WindowsRuntime apps + Version number in the title :)CS-Script for Notepad++ (C# intellisense and code execution): Release v1.0.24.0: ShortcutMapping panel now allows direct modification of the shortcuts. Custom updater dropped support for MSI installation but it still allows downloading of MSI http://www.csscript.net/npp/codeplex/non_msi_update.pngProDinner - ASP.NET MVC Sample (EF5, N-Tier, jQuery): 8.2: upgrade to mvc 5 upgrade to ASP.net MVC Awesome 4.0, EF 6.1, latest jcrop, Windsor Castle etc. ability to show/hide the dog using tinymce for the feedback page mobile friendly uiASP.net MVC Awesome - jQuery Ajax Helpers: 4.0: version 4.0 ========================== - added InitPopup, InitPopupForm helpers, open initialized popups using awe.open(name, params) - added Tag or Tags for all helpers, usable in mod code - added popup aweclose, aweresize events - popups have api accessible via .data('api'), with methods open, close and destroy - all popups have .awe-popup class - popups can be grouped using .Group(string), only 1 popup in the same group can exist at the same time - added awebeginload event for...SEToolbox: SEToolbox 01.028.008 Release 2: Fixes for drag-drop copying. Added ship joiner, to rejoin a broken ship! Installation of this version will replace older version.ScreenToGif: Release 1.0: What's new: • Small UI tweaks everywhere. • You can add Text, Subtitles and Title Frames. • Processing the gif now takes less time. • Languages: Spanish, Italian and Tamil added. • Single .exe multi language. • Takes less time to apply blur and pixelated efect. • Restart button. • Language picker. (If the user wants to select a diferent language than the system's) • "Encoding Finished" page with a link to open the file. • GreenScreen unchanged pixels to save kilobytes. • "Check for Updates" t...Touchmote: Touchmote 1.0 beta 11: Changes Support for multiple monitor setup Additional settings for analog sticks More reliable pairing Bug fixes and improvementsMicrosoft Script Analyzer: Microsoft Script Analyzer 1.1: The Script Analyzer scans your current PowerShell script code against some PowerShell best practice rules, and provide suggestions to improve the script quality and readability. By double-clicking the checking result, the relevant script code will be highlighted in the code editor. Script Analyzer result You can configure the Script Analyzer rules in the Settings window of Script Analyzer. Script Analyzer settings The current release includes 5 PowerShell best practice rules. Invoke-...Microsoft Script Browser: Script Browser 1.1: Script Browser for Windows PowerShell ISE was designed and developed in response to many IT Pros’ and MVPs’ feedback during the MVP Global Summit. It puts nearly 10K script examples at IT Pros fingertips when they write scripts to automate their IT tasks. Users can search, learn, download and manage scripts from within their scripting environment - PowerShell ISE - with just a few button clicks. It saves the time of switching back and forth between webpages and scripting environment, and also...New ProjectsAgenda do Estudante: Aplicativo para auxiliar estudantes no gerenciamento do tempo, disponível na WEB, buscando possuir ampla acessibilidade. Code Analysis Rule Collection: Contains a set of diagnostics, code fixes and refactorings built on the Microsoft .NET Compiler Platform "Roslyn".CRM User Diagnostics Tool: DiagnosticsDbWord: this tools use xml.sql generate daily report and weekly report from word. EasyWork: ADO.NET Entity Framework Common Service Locator Unity Unity Interception Extension MEF ASP.NET MVC jQWidgetsEjerciciosFer: Ultimate Summary re LocoGestionEvenement: ASP .NET applicationINNOVA: Sistema web-movil para disponiblidad...,.Internal: This is an internal project for personal usageLearnserve CORE - SCORM LMS: Learnserve CORE LMS is a comprehensive .NET SCORM LMS Module designed to extend DNN into a CMS/LMS that can deliver any online training.M2B Gestion Entretiens: Gestion des entretiensModern DevOps Tools: Modern DevOps Tools is based around building an tools that uses recommended practices that will work inside of your continuous delivery cycle.Monopoly NOHI: Monopoly for the NOHIORT MAY 2014 HOTELUCHO C# MVC3 EF5: Academic web project using MVC 3, Entity Framework 5. Hotel reservations management. User registration and room reservations.ProfSteeve: ProfSteeve is a teaching tool.Project issue resolution lists: wenti Registry Settings Export Library: The main purpose of this project is to enable the creation of .reg files from registry keys.Scroll++: Enables scrolling ui-elements without focusing them. SIGCBI: Sistema para Gestión de las áreas de Almacén, Administración y Ventas del Complejo Turístico Baños del Inca.SISPERRHH - WEB: Sistema de Gestión de RRHH.Trabajo Practico Laboratorio V: Trabajo Practico Laboratorio VTraining_MEF_MVC: Training MEF MVCTraining_MEF_SimpleCalculator: Simple Calculator MEFTraining_MVC_ExploringMVCParts: Training Exploring MVC PartsTres Punto Cinco: Tres Punto CincoUI Exception Handler: UI Exception Handler is a simple library that provides error windows for unexpected .Net application exceptions.Widjet_jQueryUI_CustomLineSelector: Custom line selector

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  • Windows 7: Search indexing is stuck

    - by Ricket
    When I open Indexing Options, it says: 4,317 items indexed Indexing in progress. Search results might not be complete during this time. It's stuck at 4,317 though; no more items have been indexed. Worst of all, SearchIndexer.exe is taking up 100% CPU (well, 50%, but I have a dual core CPU; it's taking up all processing power it can). It is not causing hard drive activity though. I tried clicking "Troubleshoot search and indexing" at the bottom of the Indexing Options window, but it couldn't find any problem. I've also tried the repair registry key that several websites suggest; I change HKLM\SOFTWARE\Microsoft\Windows Search SetupCompletedSuccessfully to 0 and restarted the computer, and it apparently repaired because it flipped back to 1, but the same problem continues to occur. It's reducing the battery life of my laptop and making it really hot so that my fans are running all the time. I've had to disable the Windows Search service. How can I fix this? Do I need to just flat-out reformat my computer? Update: I've tried rebuilding a couple times. There's nothing unusual about the locations I have to index, and I don't have any downloads in progress or anything like that. I don't see any reason why it stopped, and I noticed it much too late to do a system restore. At this point, I'm hoping someone will offer up some secret answer that will fix the problem, thus the bounty. Another update: I tried starting the service again, just to let it try yet again. It seemed okay at first (Indexing Options showed it operating at reduced speed due to user activity, and the number of files was going up). A while later I checked, and the service had stopped. Event viewer revealed some errors like this: Log Name: Application Source: Application Error Date: 2/1/2010 7:34:23 PM Event ID: 1000 Task Category: (100) Level: Error Keywords: Classic User: N/A Computer: ricky-win7 Description: Faulting application name: SearchIndexer.exe, version: 7.0.7600.16385, time stamp: 0x4a5bcdd0 Faulting module name: NLSData0007.dll, version: 6.1.7600.16385, time stamp: 0x4a5bda88 Exception code: 0xc0000005 Fault offset: 0x002141ba Faulting process id: 0x13a0 Faulting application start time: 0x01caa39f2a70ec02 Faulting application path: C:\Windows\system32\SearchIndexer.exe Faulting module path: C:\Windows\System32\NLSData0007.dll Report Id: b4f7a7ae-0f92-11df-87fc-e5d65d8794c2 Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="Application Error" /> <EventID Qualifiers="0">1000</EventID> <Level>2</Level> <Task>100</Task> <Keywords>0x80000000000000</Keywords> <TimeCreated SystemTime="2010-02-02T00:34:23.000000000Z" /> <EventRecordID>10689</EventRecordID> <Channel>Application</Channel> <Computer>ricky-win7</Computer> <Security /> </System> <EventData> <Data>SearchIndexer.exe</Data> <Data>7.0.7600.16385</Data> <Data>4a5bcdd0</Data> <Data>NLSData0007.dll</Data> <Data>6.1.7600.16385</Data> <Data>4a5bda88</Data> <Data>c0000005</Data> <Data>002141ba</Data> <Data>13a0</Data> <Data>01caa39f2a70ec02</Data> <Data>C:\Windows\system32\SearchIndexer.exe</Data> <Data>C:\Windows\System32\NLSData0007.dll</Data> <Data>b4f7a7ae-0f92-11df-87fc-e5d65d8794c2</Data> </EventData> </Event> If you are having the same error and arrived here from a Google search, please comment or add an answer detailing your progress on this, if any...

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  • GDD-BR 2010 [1C] Google Web Tookit: What it is, How it Works and Deeper Dives

    GDD-BR 2010 [1C] Google Web Tookit: What it is, How it Works and Deeper Dives Speaker: Chris Ramsdale Track: Cloud Computing Time slot: C [12:05 - 12:50] Room: 1 Level: 151 If you're like the rest of us, at some point in your web app development you've wondered if there was an easier solution. One that includes built-in debuggers, code refactoring, reliable syntax highlighting, etc. After all, why should the server-side and desktop programmers get all of the good tools? The good news is that with Google Web Toolkit (GWT) you do have access to these tools. And in this session, Chris Ramsdale will get you up and running with GWT, including what it is, how it works, and deeper dives into generators, native Javascript interop, and compiler optimizations. From: GoogleDevelopers Views: 1 0 ratings Time: 35:02 More in Science & Technology

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  • Is it worth it to learn some programming before college?

    - by Howlgram
    I'm in my last year of highschool and I am very interested in programming, the thing is I don't know if it could be worth it to start learning programming now, im afraid that when I get to college they might just teach all I might have learned in a few classes making a waste the time spent on learning that before college. Right now I'm on my last year of highschool and I know absolutely nothing about programming. There are other similar questions where people answer saying it is good to learn beforehand, but I doubt their situation might be like mine, maybe they had much more time to learn programming (as if they were not on their last year of highschool) before college so they could learn some serious skills, besides they say they already know at least the basics about a language, instead, I know nothing and I have no idea how much could I learn this year. If it wasn't clear I want to study computer's science

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  • How to write efficient code in spite of heavy deadlines

    - by gladysbixly
    Hi all, I am working in an environment wherein we have many projects with strict deadlines on deliverables. We even talk directly to the clients so getting the jobs done and fast is a must. My issue is that i'd always write code for the first solution that comes to my mind, which of course I thought as best at that moment. It always ends up ugly though and i'd later realize that there are better ways to do it but can't afford to change due to time restrictions. Are there any tips by which I could make my code efficient yet deliver on time?

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  • JS closures - Passing a function to a child, how should the shared object be accessed

    - by slicedtoad
    I have a design and am wondering what the appropriate way to access variables is. I'll demonstrate with this example since I can't seem to describe it better than the title. Term is an object representing a bunch of time data (a repeating duration of time defined by a bunch of attributes) Term has some print functionality but does not implement the print functions itself, rather they are passed in as anonymous functions by the parent. This would be similar to how shaders can be passed to a renderer rather than defined by the renderer. A container (let's call it Box) has a Schedule object that can understand and use Term objects. Box creates Term objects and passes them to Schedule as required. Box also defines the print functions stored in Term. A print function usually takes an argument and uses it to return a string based on that argument and Term's internal data. Sometime the print function could also use data stored in Schedule, though. I'm calling this data shared. So, the question is, what is the best way to access this shared data. I have a lot of options since JS has closures and I'm not familiar enough to know if I should be using them or avoiding them in this case. Options: Create a local "reference" (term used lightly) to the shared data (data is not a primitive) when defining the print function by accessing the shared data through Schedule from Box. Example: var schedule = function(){ var sched = Schedule(); var t1 = Term( function(x){ // Term.print() return (x + sched.data).format(); }); }; Bind it to Term explicitly. (Pass it in Term's constructor or something). Or bind it in Sched after Box passes it. And then access it as an attribute of Term. Pass it in at the same time x is passed to the print function, (from sched). This is the most familiar way for my but it doesn't feel right given JS's closure ability. Do something weird like bind some context and arguments to print. I'm hoping the correct answer isn't purely subjective. If it is, then I guess the answer is just "do whatever works". But I feel like there are some significant differences between the approaches that could have a large impact when stretched beyond my small example.

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  • Deploying Data-Tier Applications of SQL Server 2008 R2

    SQL Server 2008 R2 Data-Tier Applications make database development, deployment and management much easier. When you create and build a Data Tier Application, it creates a single, self-contained unit of deployment called a DAC package. Arshad Ali shows you how to deploy the created DAC package and discusses the different methods of deployment. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Which Large File System Format to use for USB Flash drive compatible with Ubuntu/Mac/Windows?

    - by wajiw
    I've had this problem for a long time and can't find a solution. I switch between the 3 OSes all the time and use a 1TB USB Drive to do so. I can't seem to find a format that is compatible across all systems that handles large files (at least 8-9 GB). Does anyone have a solution for this? Recently I've tried exFat but that messes up the filesystem when trying to read on windows after adding files from Ubuntu (using the fuse driver). The OSes currently I'm using are Windows Vista/7, Mac OS X (10.6.5) and Ubuntu 10.10

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  • Moving from XNA/C# to DirectX/C++ quite confused

    - by misiMe
    I made some game with XNA/C# for Windows Phone and Windows 8, since XNA is dead and Visual studio doesn't support it (I have to target Windows Phone 7.1 to build with XNA), I want to start learning something more "consistent in time" and improve my skills. I'm a little confused about the possibilities, because C++/DirectX alone seems difficult, so I found some high-level classes to help: DirectX Toolkit Cocos2D My questions are: What will happen when they will "die" like XNA? Is C++'s approces more "professional" than C#/XNA and why? Is C++'s approces more "portable"? Is C++'s approces more resistant in terms of time? Is there any consideration about DirectX TK and Cocos2D in terms of performance? I ask that because I found that every Game software house in my country looks for skilled C++ programmers.

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  • USB Drive Warm Boot Issue. Cold boot = Perfect. Warm boot = "No boot sector found on USB device"

    - by Dan
    I'm experiencing a boot/reboot quirk similar to, yet somewhat different from others posted here. I have two Western Digital "Passport" external USB2 drives (160GB and 320GB) with Ubuntu 11.10 installed. The BIOS on my laptop is set to boot USB drives before the internal drive, and it works well. Either drive will cold-boot Ubuntu 11.10 perfectly. However, at times the computer must be restarted (warm boot) to have software updates or other changes take effect. When I warm-boot the computer, the computer goes through its normal shutdown/restart, then the usual BIOS tests, at which time the USB drive is selected momentarily (as normal), and that's when the trouble starts. I get a "No boot sector found on USB device", and the computer proceeds to boot Windows from the internal drive. If I press F12 early during the restart sequence (allows manual selection of the boot sequence), USB is still shown before the internal drive on the sequence list (as it should be). If I highlight "USB" and press ENTER, I still get a "No boot sector..." error message, but the external USB drive then proceeds to boot Ubuntu normally. I have a third external USB drive (Western Digital 160 GB Media Center) that cold-boots and warm-boots perfectly, so I know everything in the computer is set up properly. It also tells me Ubuntu is set up correctly on the drives, as all three drives were done identically, and at the same time. I've tried formatting the Passport drives NTFS and FAT32, but it didn't change anything. If I power-down the computer, then start it up again, it will boot Ubuntu from either of the Passport drives perfectly - every time. It's as if during a warm boot the Passport drives are somehow looking for the boot loader in the wrong location on the drive - yet either drives works when booting from a cold start. Not a show-stopper .. but frustrating. Computer is a Dell XPS M1530, A12 BIOS (latest), but I don't think the computer plays into the issue because one of the three drives works at all times. It's only the two WD Passport models at issue here. Thanks!

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  • Of transactions and Mongo

    - by Nuri Halperin
    Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

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  • What constitutes proper use of threads in programming?

    - by Smith
    I am tired of hearing people recommend that you should use only one thread per process, while many programs use up to 100 per process! take for example some common programs vb.net ide uses about 25 thread when not debugging System uses about 100 chrome uses about 19 Avira uses more than about 50 Any time I post a thread related question, I am reminded almost every time that I should not use more that one thread per process, and all the programs I mention above are ruining on my system with a single processor. What constitutes proper use of threads in programming? Please make general comment, but I'd prefer .NET framework thanks EDIT changed processor to process

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  • Ubuntu on USB does not boot on MacBook

    - by Sean H
    Ubuntu is installed on a 32 gigabyte flash-drive and it successfully booted every time up until I partitioned my hard-drive and installed Windows as a secondary boot (for programming reasons). Now every time I attempt to boot the Ubuntu flash-drive it boots into Windows XP. The same goes for partitions, I partitioned my hard-drive and installed Ubuntu and it only booted Windows XP. I am on a MacBook 6,1 with Mac OS X 10.6.8, 2 partitions, and I am using ReFit as my boot-loader. EDIT: I had Ubuntu working fine from FLASH DRIVE and at one point as a partition. I later uninstalled Ubuntu from my hard-drive and installed Windows. I then had to re-image my computer for certain reasons and I installed windows. Now when I attempt to boot anything other than Windows or OS X it boots into windows. Ubuntu was never on my hard drive while Ubuntu was on it. The flash-drive has been its own thing and has the boot-loader installed to it and loads from ReFit but boots into windows.

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  • Where can I find accessible bug/issue databases with complete revision history

    - by namenlos
    I'm performing some research and analysis on bug/issue tracking databases and more specifically on how programmers and teams of programmers actually interact with them. What I'm looking for involves understanding how those databases change over time. So what I don't need for example: is a database of all the bugs of some open source project as the bugs exist today. What I do need is a complete set of revision history for every issue/bug in the database. This would enable me to pick a specific datetime and say here were the list of all the issues/bugs that existed at that moment in time. Anyway know of some publicly accessible issue/bug databases that expose this revision data? Ideally, the revision would look something like this (shown for a single bug, with two revisions) ISSUEID PRI SEV ASSIGNEDTO MODIFIEDON VALIDUNTIL 1 2 2 mel apr-1-2010:5pm apr-1-2010:6pm 1 2 3 steve apr-1-2010:6pm NULL

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  • How do I improve my logic in general and programming in particular?

    - by Dinesh Venkata
    I'm good with understanding technology and implementing it. At least that is what I feel. But it seems that when I come across experienced programmers they point out that my logic is weak. I feel that I would need some time with real programming to improve it. But nobody is ready to give that time to me. I'm just about starting my carer and it often feels disheartening to hear this. I want know how can I improve my logic and also does this sort of thing happens to others too?

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