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• How should we deal with multiple transaction-report requests?

  - by Mithir

  We are developing a system for the retail market which one of it's features will enable clients(actually consumer clubs) to go through all transactions made by end-clients. One of the ways to get this information will be via an API. The idea is that there will be requests for reports with a start date and an end date, and a response will have all the transactions between those dates. We are worry that some reports may be very large, and that some clients will repeatedly request for reports, in this case the DB and CPU will be very overloaded. The same server that will service those requests, also takes care the the actual retail transactions (received by proprietary devices) and a Web application. We are not sure about how to limit the report requests from the API so that it won't affect the system too much. So, how should we deal with this scenario? any thoughts? EDIT: just to make clear: When I mentioned proprietary devices I meant "On-Location" devices which are used during sales with end-clients, this means that these requests shouldn't get delayed, and this is the main concern.

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• Ubuntu 10.04 hung on unattended apt-get upgrade?

  - by hafichuk

  I'm looking into why our ubuntu web server hung this morning and see that there was some package upgrades a few hours prior to the problem. I was able to ssh into the system and get a snapshot from top: top - 08:13:54 up 210 days, 8:25, 2 users, load average: 433.30, 422.40, 375.70 Tasks: 1192 total, 381 running, 810 sleeping, 0 stopped, 1 zombie Cpu(s): 0.5%us, 6.1%sy, 0.0%ni, 93.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 49549772k total, 48518392k used, 1031380k free, 960152k buffers Swap: 11595768k total, 279368k used, 11316400k free, 39355664k cached This is a 16 processor system, so I would typically expect a load in the low teens. I tried to restart apache, which didn't work, and subsequently had to do a hard reboot to get it working again (which it is). One thing I found was that the server did an unattended package update. Is it possible that upgrading php or curl (which our web sites use) might have caused apache to stop responding? Here is the snip from the unattended-upgrades.log from this morning: 2012-09-18 06:48:30,076 INFO Initial blacklisted packages: 2012-09-18 06:48:30,076 INFO Starting unattended upgrades script 2012-09-18 06:48:30,077 INFO Allowed origins are: ["['Ubuntu', 'lucid-security']"] 2012-09-18 06:49:37,017 INFO Packages that are upgraded: gnupg-curl php5-dev linux-server dhcp3-common linux-libc-dev php5-curl gpgv gnupg linux-headers-server linux-image-server php5 php5-mysql php-pear php5-cli php5-common libapache2-mod-php5 dhcp3-client 2012-09-18 06:49:37,018 INFO Writing dpkg log to '/var/log/unattended-upgrades/unattended-upgrades-dpkg_2012-09-18_06:49:37.017909.log'

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• How to squeeze the maximum performance out of Unity and GNOME 3?

  - by melvincv

  I see that I do not get good performance with the new Unity desktop, but I should say that Unity has improved a lot since the last edition Ubuntu 11.10. How to squeeze the maximum performance out of 1. Unity 2. GNOME 3 My system specs: -Processors- Intel(R) Pentium(R) Dual CPU E2180 @ 2.00GHz -Memory- Total Memory : 2049996 kB -PCI Devices- Host bridge : Intel Corporation 82G33/G31/P35/P31 Express DRAM Controller (rev 10) PCI bridge : Intel Corporation 82G33/G31/P35/P31 Express PCI Express Root Port (rev 10) (prog-if 00 [Normal decode]) VGA compatible controller : Intel Corporation 82G33/G31 Express Integrated Graphics Controller (rev 10) (prog-if 00 [VGA controller]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #1 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #2 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #3 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB UHCI Controller #4 (rev 01) (prog-if 00 [UHCI]) USB controller : Intel Corporation N10/ICH 7 Family USB2 EHCI Controller (rev 01) (prog-if 20 [EHCI]) PCI bridge : Intel Corporation 82801 PCI Bridge (rev e1) (prog-if 01 [Subtractive decode]) ISA bridge : Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge (rev 01) IDE interface : Intel Corporation 82801G (ICH7 Family) IDE Controller (rev 01) (prog-if 8a [Master SecP PriP]) IDE interface : Intel Corporation N10/ICH7 Family SATA Controller [IDE mode] (rev 01) (prog-if 8f [Master SecP SecO PriP PriO]) SMBus : Intel Corporation N10/ICH 7 Family SMBus Controller (rev 01) Ethernet controller : Intel Corporation PRO/100 VE Network Connection (rev 01)

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• How to determine if a 3D voxel-based room is sealed, efficiently

  - by NigelMan1010

  I've been having some issues with efficiently determining if large rooms are sealed in a voxel-based 3D rooms. I'm at a point where I have tried my hardest to solve the problem without asking for help, but not tried enough to give up, so I'm asking for help. To clarify, sealed being that there are no holes in the room. There are oxygen sealers, which check if the room is sealed, and seal depending on the oxygen input level. Right now, this is how I'm doing it: Starting at the block above the sealer tile (the vent is on the sealer's top face), recursively loop through in all 6 adjacent directions If the adjacent tile is a full, non-vacuum tile, continue through the loop If the adjacent tile is not full, or is a vacuum tile, check if it's adjacent blocks are, recursively. Each time a tile is checked, decrement a counter If the count hits zero, if the last block is adjacent to a vacuum tile, return that the area is unsealed If the count hits zero and the last block is not a vacuum tile, or the recursive loop ends (no vacuum tiles left) before the counter is zero, the area is sealed If the area is not sealed, run the loop again with some changes: Checking adjacent blocks for "breathable air" tile instead of a vacuum tile Instead of using a decrementing counter, continue until no adjacent "breathable air" tiles are found. Once loop is finished, set each checked block to a vacuum tile. Here's the code I'm using: http://pastebin.com/NimyKncC The problem: I'm running this check every 3 seconds, sometimes a sealer will have to loop through hundreds of blocks, and a large world with many oxygen sealers, these multiple recursive loops every few seconds can be very hard on the CPU. I was wondering if anyone with more experience with optimization can give me a hand, or at least point me in the right direction. Thanks a bunch.

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• PDFtk Password Protection Help

  - by Dave W.

  I am using Ubuntu 11.10 and am looking for a solution to password protect a bunch of pdf files in a directory in batch. I came across PDFtk and it looks like it might do what I need, but I've reviewed the command line PDFtk examples and can't figure out if there is a way to do it in batch without having to individually specify the output file name for every file. I'm hoping a command-line guru can take a look at the PDFtk syntax and tell me if there is some trick / command that will allow me to password protect a directory of pdf files (e.g., *.pdf) and overwrite the existing files using the same name, or consistently rename the individual output files without having to specify each output name individually. Here's a link to the PDFtk command line examples page: http://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/ Thanks for your help. I think I've answered my own question. Here's a bash script that appears to do the trick. I'd welcome help evaluating why the code I've commented out doesn't work... #!/bin/bash # Created by Dave, 2012-02-23 # This script uses PDFtk to password protect every PDF file # in the directory specified. The script creates a directory named "protected_[DATE]" # to hold the password protected version of the files. # # I'm using the "user_pw" parameter, # which means no one will be able to open or view the file without # the password. # # PDFtk must be installed for this script to work. # # Usage: ./protect_with_pdftk.bsh [FILE(S)] # [FILE(S)] can use wildcard expansion (e.g., *.pdf) # This part isn't working.... ignore. The goal is to avoid errors if the # directory to be created already exists by only attempting to create # it if it doesn't exists # #TARGET_DIR="protected_$(date +%F)" #if [ -d "$TARGET_DIR" ] #then #echo # echo "$TARGET_DIR directory exists!" #else #echo # echo "$TARGET_DIR directory does not exist!" #fi # mkdir protected_$(date +%F) for i in *pdf ; do pdftk "$i" output "./protected_$(date +%F)/$i" user_pw [PASSWORD]; done echo "Complete. Output is in the directory: ./protected_$(date +%F)"

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• Ask the Readers: How Do You Monitor Your Computer?

  - by Jason Fitzpatrick

  Beneath the shiny case of your computer and GUI of your operating system there’s a lot–CPU utilization, memory access, and disk space consumption to name a few things–you can keep an eye on. How do you keep an eye on resource utilization and more on your computer? Image available as wallpaper here. Whether you’re carefully managing a small pool of RAM, making sure your abundant apps don’t bog down your processor, or you just like having an intimate view of what’s going on in the guts of your computer, we want to hear all about the tools you use to do it. How and why do you monitor your computer? From disk use to case temps, any kind of monitoring is fair game. Sound off in the comments with the how and why of your monitoring arrangement and then be sure to stop back in on Friday for the What You Said roundup to see what tricks and tools your fellow readers are using to keep an eye on their hardware. HTG Explains: How Antivirus Software Works HTG Explains: Why Deleted Files Can Be Recovered and How You Can Prevent It HTG Explains: What Are the Sys Rq, Scroll Lock, and Pause/Break Keys on My Keyboard?

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• How-To Geek is Hiring a Geeky Writer – Here Are the Details

  - by The Geek

  Think you have the perfect combination of geek knowledge and writing skills? We’re looking for an experienced writer to join our team, and here are all the details. We need a new writer to cover topics surrounding Windows 7 or 8, home networking, home routers, security, media, troubleshooting, mobile devices, and many similar topics. We are not looking for writers that focus solely on Linux or tech news writers. Please apply if you have the following qualities: You must be a geek at heart. You must be able to put in plenty of time, work, and dedication. If you’re too busy already, don’t apply. You must be able to write articles that are easy to understand. You must be creative. You must generate ideas for articles on your own, and take suggestions like a pro. You must be at least 18 years old. You must have solid English writing skills. You must be able to write tips, how-to articles, explainers, guides, instructional articles, etc. Again, we are not looking for tech news writers. Here’s a couple of our previous articles so you can get an idea of what we’re looking for in terms of quality and content. Please make sure to look through these before you decide to apply. How-to Article: Make Your Own Windows 8 Start Button with Zero Memory Usage Explainer: HTG Explains: When Do You Need to Update Your Drivers? Explainer: HTG Explains: Why Do Hard Drives Show the Wrong Capacity in Windows? How-To Article: How to Factory Reset Your Android Phone or Tablet When It Won’t Boot How to Fix a Stuck Pixel on an LCD Monitor How to Factory Reset Your Android Phone or Tablet When It Won’t Boot Our Geek Trivia App for Windows 8 is Now Available Everywhere

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• Problems syncing photos and strange effects of uploaded files from other devices

  - by Daniel

  I have a Galaxy Spica (GT-i5700) Android v2.1, rooted with Leshak dev 7 #123. But never mind the root info, the problem would be the same unrooted. The photos from this phone is stored in "sdcard/images", nevertheless the phone also creates a "sdcard/DCIM" but only stores some thumbnails there. Problem nr 1: U1 only reads the DCIM-folder for automatic photo-upload. So photos stored in this phone is not uploaded. If I move photos to "DCIM" folder, U1 recognises the photos and start uploading them. Possible solution: Could there be an option in the settings, to set preferred photo folder? Problem nr 2: Out of 74 pictures, 12 did not get uploaded. Pressing "Retry failed transfers" in Settings does nothing. Pressing the files where status is "Upload failed, tap to retry" only changes the status to "Uploading..." but nothing gets uploaded. If I upload another file to U1, it is uploaded directly without any problem. It has nothing to do with file size, 1,1 MB files has been uploaded fine whilst some failed are 0,8 MB. Problem nr 3: The photos from DCIM are in my case uploaded to a folder called "Pictures - GT-I5700" in U1. If I log in to the homepage and from there upload another photo in "Pictures - GT-I5700", it shows up in U1 on my phone fine. But when I tap it, U1 downloads the photo to "sdcard/U1/Pictures - GT-I5700". If it sync photos from "sdcard/DCIM" to a specific folder, why not also download files to the same folder from which it is synced? After a while of usage, syncing and uploading files from different clients it would be a mishmash of folders and places files are stored and considering that I see no use of U1 at all. Another question: If my SD card in some way breaks down/some folders cannot be read/card temporarly changed and U1 is running, does U1 consider that as files deleted and also delete from the cloud?

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• Click buttons on the mouse stopped working in 12.10

  - by Kushal

  everything was great for a couple weeks after the upgrade, and then all of a sudden, the click buttons on my trackpad (as well as any other USB mouse I would hook up) stopped working. The pointer moves fine, but the clicks don't work. Sometimes the left click doesn't work but right click does, and then some times, neither works. I noticed this would begin when I would accidentally drag some text in a web browser (you know how when you try to move your pointer through the trackpad, but you accidentally tap down and it starts to drag whatever text you've selected on the window), and then you're done. The clicks won't work after that. They would work upon rebooting or logging off and back on, but then after a few minutes of usage, things would go back to being broken again. It happened a LOT when I was trying to play Scrabble on Facebook. I've raised a bug for this, but I haven't heard back anything on it. Here's the bug report: https://bugs.launchpad.net/bugs/1077805 Since the system was unusable this way, I had to remove it and install another OS based on 12.04. Has anyone else faced this issue or does someone know what to do to fix it? I'd go back to vanilla Ubuntu in a heartbeat if this issue can be fixed.

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• How to store bitmaps in memory?

  - by Geotarget

  I'm working with general purpose image rendering, and high-performance image processing, and so I need to know how to store bitmaps in-memory. (24bpp/32bpp, compressed/raw, etc) I'm not working with 3D graphics or DirectX / OpenGL rendering and so I don't need to use graphics card compatible bitmap formats. My questions: What is the "usual" or "normal" way to store bitmaps in memory? (in C++ engines/projects?) How to store bitmaps for high-performance algorithms, such that read/write times are the fastest? (fixed array? with/without padding? 24-bpp or 32-bpp?) How to store bitmaps for applications handling a lot of bitmap data, to minimize memory usage? (JPEG? or a faster [de]compression algorithm?) Some possible methods: Use a fixed packed 24-bpp or 32-bpp int[] array and simply access pixels using pointer access, all pixels are allocated in one continuous memory chunk (could be 1-10 MB) Use a form of "sparse" data storage so each line of the bitmap is allocated separately, reusing more memory and requiring smaller contiguous memory segments Store bitmaps in its compressed form (PNG, JPG, GIF, etc) and unpack only when its needed, reducing the amount of memory used. Delete the unpacked data if its not used for 10 secs.

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• Why would video stutter on HDMI but not on DVI?

  - by CorvT

  I've got a system running Ubuntu 12.04 with an i3 2120T CPU/GPU. When I play video through mplayer, I notice when I'm hooked up to a screen via HDMI there is a small stutter (1-2 frames) every few seconds. I don't see this happening when I connect via DVI on the same screen. Resolution and refresh rate are same for both HDMI and DVI, so I'm not sure where else the problem could be coming from. I've also tried two different screens, and different cables. I see the stutter with either HDMI-HDMI cables, or DVI-HDMI cable with DVI from the PC and HDMI into the screen. I don't see the stutter with DVI-DVI cables, or when I use HDMI-DVI cables with HDMI from the PC to DVI into the screen. I've also tried using an AMD 5XXX series card with the open source radeon driver, and saw the same problem. I then tried an nVidia GeForce 210 card with the closed source driver, and the stutter went away. To me this smells like a driver/mesa/glx issue (since the problem went away with the nvidia card/driver), but I have no idea how to track this down.

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• Are short abbreviated method/function names that don't use full words bad practice or a matter of style?

  - by Alb

  Is there nowadays any case for brevity over clarity with method names? Tonight I came across the Python method repr() which seems like a bad name for a method to me. It's not an English word. It apparently is an abbreviation of 'representation' and even if you can deduce that, it still doesn't tell you what the method does. A good method name is subjective to a certain degree, but I had assumed that modern best practices agreed that names should be at least full words and descriptive enough to reveal enough about the method that you would easily find one when looking for it. Method names made from words help let your code read like English. repr() seems to have no advantages as a name other than being short and IDE auto-complete makes this a non-issue. An additional reason given in an answer is that python names are brief so that you can do many things on one line. Surely the better way is to just extract the many things to their own function, and repeat until lines are not too long. Are these just a hangover from the unix way of doing things? Commands with names like ls, rm, ps and du (if you could call those names) were hard to find and hard to remember. I know that the everyday usage of commands such as these is different than methods in code so the matter of whether those are bad names is a different matter.

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• How to proceed when a bug in open source libraries is suspected?

  - by Suma

  We are using some open source libraries in our projects. Sometimes there are some issues found in some of them (most likely library bugs, but it may also be a wrong usage from our side, especially when sometimes documentation is not exactly 100 % complete). As the libraries are often quite complex, debugging them to pinpoint the source of the problem is sometimes quite hard. Can you help me to summarize what other options are there and how to exactly proceed with them? I have just recently hit some strange problems when using TCMalloc (Google scalable memory allocator) on Windows, so I would most welcome answers which would apply to this particular library, but more general answers are good as well. 1) Ask the maintainer/owner of the project for assistance. How can this be done? 2) Hire someone to identify and fix the issue. How to do this? How can I find someone with enough expertise in some particular library? ... any other options?

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• Ubuntu running like mud, system hangs and looks like its running at 3FPS

  - by user240803

  the system specks: AMD XP 3200+ 1GB DDR 333 RAM 160 GB HD IDE NVIDIA FX 5500 AGP Video Card Compaq Presario sr1230nx the system takes forever to boot and when it does it runs like total mud, reminds me of an overloaded system that has too many windows open or something... fresh install tried soo many thing like new memory (it had 512 stick) a new video card (onboard 8mb sis sounded like the problem, but wasn't... has gotten a little faster now but not by much) tried to disable all the things on the motherboard that could be, with no help... this machine runs windows XP, 7, and 8 JUST FINE!!! I mean for a single core CPU WIN8 runs AWESOME!!! BUT I already have a Gaming Desktop that has Windows 8 pro I want a Linux machine to get some time in and learn a few things... I want Ubuntu because of the Software center so I can install things I want until I am familiar with the command line.. I've worked on Computers since I was 12 I remember some of the DOS commands but I guess these are a little different... anyway any ideas? Ive also tried both drivers for the NVIDA card and that didn't help either... its not the card since it did this with both the NVIDA card and the SIS onboard... it also does this on live mode with the USB so I don't think its the HardDrive... I'm running out of options of hardware to try... I know this version of Linux works cuz Ive booted it on other machines and it ran great... what is with this Compaq? here is a vid of exactly what its doing... let me know if you need anything else I am right by the comptuer tonight so ask anything... http://youtu.be/-P-XNo81098

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• Advisor Webcast: Oracle Payments Funds Disbursement Analyzer

  - by SamanthaF-Oracle

  Have you registered for the Oracle Payments Funds Disbursement Analyzer Advisor Webcast in June? Don't delay! This one-hour session is recommended for technical and functional users of the Oracle Payments product who would like an introduction to Oracle Payment Funds Disbursement Analyzer. The session will highlight how to use the Payments Funds Disbursement Analyzer to identify and troubleshoot issues with Payment Process Request (PPR) and other Payments related processes/setups. TOPICS WILL INCLUDE: Overview of Oracle Payments Funds Disbursement Analyzer How to install and run Proactive usage of the Analyzer Using the Analyzer to troubleshoot When?  Wednesday, June 25, 2014 11:00 am, Eastern Daylight Time (New York, GMT-04:00) Wednesday, June 25, 2014 8:00 am, Pacific Daylight Time (San Francisco, GMT-07:00) Wednesday, June 25, 2014 4:00 pm, GMT Summer Time (London, GMT+01:00) Wednesday, June 25, 2014 8:30 pm, India Time (Mumbai, GMT+05:30) A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services. See Doc ID 1671948.1 for further details and to register your interest.

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• What to do when 'dpkg --configure -a' fails with too many errors?

  - by rudivonstaden

  During an upgrade from lucid (10.04) to precise (12.04), the X session froze, and I have been trying to recover the upgrade to get a stable system. I have performed the following steps: Used ssh to log in to the stalled system over the network. Checked the contents of the /var/log/dist-upgrade directory. There was no activity on main.log, apt.log or term.log. top showed that process 'precise' was using about 3% CPU, but I could find no evidence that the upgrade process was still doing anything. 'dpkg' did not show up in top, but it came up with pgrep dpkg | xargs ps Killed the 'dpkg' and 'precise' processes Tried to recover the upgrade by running sudo fuser -vki /var/lib/dpkg/lock;sudo dpkg --configure -a. This was partially successful (some packages were configured), but failed with the message Processing was halted because there were too many errors. I ran the same command a few times, and each time some packages were configured but others failed. Tried running sudo apt-get -f install. It fails with similar errors to dpkg. The current situation is that dpkg --configure -a and sudo apt-get -f install fails with two kinds of error: Dependency issues, e.g.: dpkg: dependency problems prevent configuration of cifs-utils: cifs-utils depends on samba-common; however: Package samba-common is not configured yet. dpkg: error processing cifs-utils (--configure): dependency problems - leaving unconfigured Resource conflict, e.g.: debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable Additionally, it seems there's reference to potential boot problems, so I'm not keen to reboot without fixing the install first: dpkg: too many errors, stopping Processing triggers for initramfs-tools ... update-initramfs: Generating /boot/initrd.img-3.2.0-25-generic cryptsetup: WARNING: failed to detect canonical device of /dev/sda1 cryptsetup: WARNING: could not determine root device from /etc/fstab So my question is, how to get a working install when dpkg --configure -a fails?

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• Hosting and scaling of a facebook application on cloud?

  - by DhruvPathak

  We would be building a facebook application in django(Python), but still not sure of where to host it economically,and with a good provision to scale in case the app gets viral. Some details about the app: i) Would be HTML based like a website,using django as a framework. ii) 100K is the number of expected pageviews in a day,if the app is viral. iii) The users will not generate any media content,only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment,cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost ? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. ( Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management ? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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• Correct architecture for running and stopping complex tasks in the background

  - by Phonon

  I'm having trouble working out the correct architecture for the following task. I have a GUI in Windows Forms that contains a ListBox, listing certain architectural layouts. One an item in this list is selected, a custom Control displays an interactive visualization of the selected layout. Drawing of this interactive diagram is a CPU-intensive task, and can take up to a second on my machine. The kind of functionality I'm trying to achieve is that if a user wants to quickly scroll through the layouts in the ListBox (say, holding down the down arrow key), I don't want my computer to sit there thinking about how to draw the layout before it allows the user to do anything else. The obvious answer is, of course, to run the layout calculations in a separate thread. But how do I make that thread return a whole control? How do I make sure I'm not running two layout calculations at once? I'm fairly new to this complex GUI business. So the real question is what is the right architecture to implement something like this? This seems like something people do all the time, but finding any suggestions on how to do it properly is really difficult.

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• Making efficeint voxel engines using "chunks"

  - by Wardy

  Concept I'm currently looking in to how voxel engines work with a view to possibly making one myself. I see a lot of stuff like this ... https://sites.google.com/site/letsmakeavoxelengine/home/chunks ... which talks about how to go about reducing the draw calls. What I can't seem to understand is how it actually saves draw call counts on the basis of the logic being something like this ... Without chunks foreach voxel in myvoxels DrawIfVisible() With Chunks foreach chunk in mychunks DrawIfVisible() which then does ... foreach voxel in myvoxels DrawIfVisible() So surely you saved nothing ?!?! You still make a draw call for each visible voxel do you not? A visible voxel needs a draw call in either scenario. The only real saving I can see is that the logic that evaluates a chunk will be able to determine if a large number of voxels are visible or not effectively saving a bit of "is this chunk visible" cpu time. But it's the draw calls that interest me ... The fewer of those, the faster the application. EDIT: In case it makes any difference I will probably be using XNA (DX not OpenGL) for my engine so don't consider my choice of example in the link above my choice of technology. But this question is such that I doubt it would matter.

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• Etiquette when asking questions in an IRC channel

  - by Zarkonnen

  Many larger OSS projects maintain IRC channels to discuss their usage or development. When I get stuck on using a project, having tried and failed to find information on the web, one of the ways I try to figure out what to do is to go into the IRC channel and ask. But my questions are invariably completely ignored by the people in the channel. If there was silence when I entered, there will still be silence. If there is an ongoing conversation, it carries on unperturbed. I leave the channel open for a few hours, hoping that maybe someone will eventually engage me, but nothing happens. So I worry that I'm being rude in some way I don't understand, or breaking some unspoken rule and being ignored for it. I try to make my questions polite, to the point, and grammatical, and try to indicate that I've tried the obvious solutions and why they didn't work. I understand that I'm obviously a complete stranger to the people on the channel, but I'm not sure how to fix this. Should I just lurk in the channel, saying nothing, for a week? That seems absurd too. A typical message I send might be "Hello all - I've been trying to get Foo to work, but I keep on getting a BarException. I tried resetting the Quux, but this doesn't seem to do anything. Does anyone have a suggestion on what I could try?"

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• Is chroot the right choice for my use case?

  - by Anthony

  Backstory: I am working on setting up a MineCraft server and want to allow admins to have ssh access to the MineCraft server console and appropriate mc server files, but not the whole system. The console provided by the minecraft server is only available to the user that launched the process. In addition, the admins will need terminal access to some basic cli tools such as wget, cp, mv, rm, and a text editor. Plan: I have already setup the ssh aspect of things, requiring pre-shared keys and whatnot. Setup a jailed environment in which all user activity will be contained. Setup user accounts. - The first user account will be the minecraft user. The minecraft user will start the MC server in a multiuser screen session and allow the other admins to attach to it. - Subsequent users should have their own /home directory for normal usage. Setup acl for the appropriate files to allow each user to edit the mc server files. No one will be doing system updates, nor will anyone be installing any programs, so I'll be the only user with sudo. The Issues: I don't want the ssh users to have access to the whole system. Users will still need to use wget or curl to update the mc server files. Is chroot the right tool for this use case, or is there something more appropriate for the job? I have no experience setting up a chroot environment and have found several tools to aid in this process. Jailkit seems to be the most robust, but it's not in the standard repos.

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• Questioning one of the arguments for dependency injection: Why is creating an object graph hard?

  - by oberlies

  Dependency injection frameworks like Google Guice give the following motivation for their usage (source): To construct an object, you first build its dependencies. But to build each dependency, you need its dependencies, and so on. So when you build an object, you really need to build an object graph. Building object graphs by hand is labour intensive (...) and makes testing difficult. But I don't buy this argument: Even without dependency injection, I can write classes which are both easy to instantiate and convenient to test. E.g. the example from the Guice motivation page could be rewritten in the following way: class BillingService { private final CreditCardProcessor processor; private final TransactionLog transactionLog; // constructor for tests, taking all collaborators as parameters BillingService(CreditCardProcessor processor, TransactionLog transactionLog) { this.processor = processor; this.transactionLog = transactionLog; } // constructor for production, calling the (productive) constructors of the collaborators public BillingService() { this(new PaypalCreditCardProcessor(), new DatabaseTransactionLog()); } public Receipt chargeOrder(PizzaOrder order, CreditCard creditCard) { ... } } So there may be other arguments for dependency injection (which are out of scope for this question!), but easy creation of testable object graphs is not one of them, is it?

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• Can't connect to Wireless Network - Ubuntu 12.04 LTS & Sabrent A111N USB Dongle

  - by Ohgodwhy

  I've been trying to connect to this network for quite some time. I can't directly connect to the router with a Wire, but can access the Router with other wireless devices without any issues. I had previously tried several other Wifi nic's but none of them would load properly. Today, i went and bought a new (supported) Sabrent A111N USB Dongle, which said explicitly that it works with Linux 2.4 +. I popped the Dongle in, and low-and-behold it immediately said that there were Available Wireless Connections. I selected my connection and tried to connect, but it just loops constantly while saying Wireless Disconnected then attempts to connect again over and over. ifconfig and iwconfig both show my device in a ready and working state. However, iwlist wlan0 scan says that there are no results found. I don't get it... At one point, I could see the CPU in the DHCP client list under the router, but it doesn't fully make the connection (something about a timeout?). Any help would be appreciated. Bus 001 Device 002: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN

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• What's wrong with cplusplus.com?

  - by Kerrek SB

  This is perhaps not a perfectly suitable forum for this question, but let me give it a shot, at the risk of being moved away. There are several references for the C++ standard library, including the invaluable ISO standard, MSDN, IBM, cppreference, and cplusplus. Personally, when writing C++ I need a reference that has quick random access, short load times and usage examples, and I've been finding cplusplus.com pretty useful. However, I've been hearing negative opinions about that website frequently here on SO, so I would like to get specific: What are the errors, misconceptions or bad pieces of advice given by cplusplus.com? What are the risks of using it to make coding decisions? Let me add this point: I want to be able to answer questions here on SO with accurate quotes of the standard, and thus I would like to post immediately-usable links, and cplusplus.com would have been my choice site were it not for this issue. Update: There have been many great responses, and I have seriously changed my view on cplusplus.com. I'd like to list a few choice results here; feel free to suggest more (and keep posting answers). As of June 29, 2011: Incorrect description of some algorithms (e.g. remove). Information about the behaviour of functions is sometimes incorrect (atoi), fails to mention special cases (strncpy), or omits vital information (iterator invalidation). Examples contain deprecated code (#include style). Inexact terminology is doing a disservice to learners and the general community ("STL", "compiler" vs "toolchain"). Incorrect and misleading description of the typeid keyword.

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• Buffer System For Items

  - by Ohmages

  I am going to reference this image of what I want to accomplish in JavaScript. This is the Diablo buffer system. This question may be a bit advanced (or possibly not even allowed). But I was wondering how you might go about implementing this type of system in a JavaScript game. Currently to implement such a system in JavaScript escapes me, and I am turning to SO to get some suggestions, ideas, and hopefully some insight in how I could accomplish this without being to costly on the CPU. Some thoughts of mine for implementing such a system would be to: Create DIVS within a DIV that hold each position of the inventory Go through each item you own in a container and see which DIV it belongs to Make said item images the DIVs image This type of system might possibly work if ALL items were 1x1, but for this example its not going to work out. I am at a complete lost of ideas how to even accomplish this. Although, maybe rendering directly to the canvas and checking mouse cords could work, there would more than likely be A HUGE annoyance when checking if other items are overlapping each other (meaning you cant place the item down, and possibly switching item with the cursor item ). That said, what am I left with? Do I need to makeshift my own hack system with messy code, or is there some source out there (that I don't know about) that has replicated this type of system in their own game. I would be very grateful to get some replies on how you might go about doing this, and will accept answers that can logically explain how you might implement such a system (code is not required). P.S. Id like to use pure JavaScript, and nothing else (even though it might be "reinventing the wheel", I also like to learn).

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