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  • Retrieving snapshots of game statistics

    - by SatheeshJM
    What is a good architecture for storing game statistics, so that I can retrieve snapshots of it at various moments? Say I have a game, and the user's statistics initially are: { hours_played = 0, games_played = 0, no_of_times_killed = 0, } When the user purchases something for the first time from within the game, the stats are { hours_played = 10, games_played = 2, no_of_times_killed = 5, } And when he purchases something for the second time, the stats are { hours_played = 20, games_played = 4, no_of_times_killed = 10, } Let me name the events as "purchase1" and "purchase2" How do I model my statistics, so that at any point in the future, I will be able to retrieve the snapshot of the statistics at the time when "purchase1" was fired. Similarly for "purchase2" and any other event I will add. Hope that made sense..

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  • What does /dev/null mean in the shell?

    - by rishiag
    I've started learning bash scripting by using this guide: http://www.tldp.org/LDP/abs/abs-guide.pdf However I got stuck at the first script: cd /var/log cat /dev/null > messages cat /dev/null > wtmp echo "Log files cleaned up." What do lines 2 and 3 do in Ubuntu (I understand cat)? Is it only for other Linux distributions? After running this script as root, the output I get is Log files cleaned up. But /var/log still contains all the files.

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  • Database for survey

    - by zfm
    One of my job now is to design a database for a survey. Let's say we have a series of questions (web-based), in which one page contains one question. Not every person will be given the same questions, those are based on their previous answers and also randomness. I would like to know whether it is better to have database like this user question answer userX question1 answer1A userX question2 answer2C userX question5 answer5F userY question1 answer1B userY question3 answer3B userY question6 answer6D ... or user q1 q2 q3 q4 q5 q6 userX 1A 2C null null 5F null userY 1B null 3B null null 6D ... My idea here is, using the second approach seems better, however I would like to know whether updating the table is (much) slower than inserting a new row? Also with the first approach, I can omit having some null answers. The total questions given are fix, the client wont add any more question later on. So my question is, what will you do if you were me?

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  • Are there any specific workflows or design patterns that are commonly used to create large functional programming applications?

    - by Andrew
    I have been exploring Clojure for a while now, although I haven't used it on any nontrivial projects. Basically, I have just been getting comfortable with the syntax and some of the idioms. Coming from an OOP background, with Clojure being the first functional language that I have looked very much into, I'm naturally not as comfortable with the functional way of doing things. That said, are there any specific workflows or design patterns that are common with creating large functional applications? I'd really like to start using functional programming "for real", but I'm afraid that with my current lack of expertise, it would result in an epic fail. The "Gang of Four" is such a standard for OO programmers, but is there anything similar that is more directed at the functional paradigm? Most of the resources that I have found have great programming nuggets, but they don't step back to give a broader, more architectural look.

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  • installing ubuntu 12.04 along windows xp and windows 7

    - by Anand A J
    I have Windows XP installed on C drive and Windows 7 installed on F drive. I want to install Ubuntu 12.04 alongwith Windows (keeping both XP and 7) in drive G with out losing any data stored in the computer. I have a hard disk of 500 GB size with C (14.8 GB left),D,E,F, and G (15.7 GB left). I tried to install Ubuntu 12.04 from DVD and getting stuck at the time of selecting partitions .! How to select the device for boot loader installation? Will the installation of Ubuntu into G drive affects the data stored in the hard disk or in G drive especially? After installing Ubuntu can I use Windows XP and Windows 7? This is my first attempt to use Ubuntu. Can any body help me please?

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  • What the best way to wire up Entity Framework database context (model) to ViewModel in MVVM WPF?

    - by hal9k2
    As in the question above: What the best way to wire up Entity Framework database model (context) to viewModel in MVVM (WPF)? I am learning MVVM pattern in WPF, alot of examples shows how to implement model to viewModel, but models in that examples are just simple classes, I want to use MVVM together with entity framework model (base first approach). Whats the best way to wire model to viewModel. Thanks for answers. //ctor of ViewModel public ViewModel() { db = new PackageShipmentDBEntities(); // Entity Framework generated class ListaZBazy = new ObservableCollection<Pack>(db.Packs.Where(w => w.IsSent == false)); } This is my usual ctor of ViewModel, think there is a better way, I was reading about repository pattern, not sure if I can adapt this to WPF MVVM

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  • Very heavy .PDF file. How to handle it?

    - by Luigi
    I should print this file on paper, but it is heavy (2,3 MB) and the printing process is very slow. But this is not the whole problem. I should first create another .pdf file (grayscale) with four pages on each sheet. When I try to print this file as a .pdf file, the process of creation of the new file is even slower than the printing process, and the output file is much heavier than the original (hundreds of megabytes). How can I shrink the pdf file? Is there a way to create a printer friendly .pdf version of the file? Before you ask, I can't simply print it on pages. I must create this .pdf file with four pages on each sheet.

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  • Removing mdadm array and converting to regular disks while preserving data

    - by Jeffrey Kevin Pry
    I have a 6 disk (2TB each) mdadm RAID 5 volume created in Ubuntu 12.04 Server. However, I'm moving to a different solution and want to "unraid" my disks but keep the data. Only 50% is in use. From what I can surmise I basically have to do this recursively for each physical disk. Fail the disk Format the failed disk Move a portion of files to the new disk. Reshape the array Shrink the logical volume md0 This seems like a very time consuming process. Is there an easier way to do this (automatically perhaps) without buying new disks to temporarily hold the data? I am also aware that during this processing my RAID volume will be degraded and vulnerable the entire time. I am not too concerned about this and will be using battery backup and moving the most important files off first. Thank you for your help!

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  • Performance triage

    - by Dave
    Folks often ask me how to approach a suspected performance issue. My personal strategy is informed by the fact that I work on concurrency issues. (When you have a hammer everything looks like a nail, but I'll try to keep this general). A good starting point is to ask yourself if the observed performance matches your expectations. Expectations might be derived from known system performance limits, prototypes, and other software or environments that are comparable to your particular system-under-test. Some simple comparisons and microbenchmarks can be useful at this stage. It's also useful to write some very simple programs to validate some of the reported or expected system limits. Can that disk controller really tolerate and sustain 500 reads per second? To reduce the number of confounding factors it's better to try to answer that question with a very simple targeted program. And finally, nothing beats having familiarity with the technologies that underlying your particular layer. On the topic of confounding factors, as our technology stacks become deeper and less transparent, we often find our own technology working against us in some unexpected way to choke performance rather than simply running into some fundamental system limit. A good example is the warm-up time needed by just-in-time compilers in Java Virtual Machines. I won't delve too far into that particular hole except to say that it's rare to find good benchmarks and methodology for java code. Another example is power management on x86. Power management is great, but it can take a while for the CPUs to throttle up from low(er) frequencies to full throttle. And while I love "turbo" mode, it makes benchmarking applications with multiple threads a chore as you have to remember to turn it off and then back on otherwise short single-threaded runs may look abnormally fast compared to runs with higher thread counts. In general for performance characterization I disable turbo mode and fix the power governor at "performance" state. Another source of complexity is the scheduler, which I've discussed in prior blog entries. Lets say I have a running application and I want to better understand its behavior and performance. We'll presume it's warmed up, is under load, and is an execution mode representative of what we think the norm would be. It should be in steady-state, if a steady-state mode even exists. On Solaris the very first thing I'll do is take a set of "pstack" samples. Pstack briefly stops the process and walks each of the stacks, reporting symbolic information (if available) for each frame. For Java, pstack has been augmented to understand java frames, and even report inlining. A few pstack samples can provide powerful insight into what's actually going on inside the program. You'll be able to see calling patterns, which threads are blocked on what system calls or synchronization constructs, memory allocation, etc. If your code is CPU-bound then you'll get a good sense where the cycles are being spent. (I should caution that normal C/C++ inlining can diffuse an otherwise "hot" method into other methods. This is a rare instance where pstack sampling might not immediately point to the key problem). At this point you'll need to reconcile what you're seeing with pstack and your mental model of what you think the program should be doing. They're often rather different. And generally if there's a key performance issue, you'll spot it with a moderate number of samples. I'll also use OS-level observability tools to lock for the existence of bottlenecks where threads contend for locks; other situations where threads are blocked; and the distribution of threads over the system. On Solaris some good tools are mpstat and too a lesser degree, vmstat. Try running "mpstat -a 5" in one window while the application program runs concurrently. One key measure is the voluntary context switch rate "vctx" or "csw" which reflects threads descheduling themselves. It's also good to look at the user; system; and idle CPU percentages. This can give a broad but useful understanding if your threads are mostly parked or mostly running. For instance if your program makes heavy use of malloc/free, then it might be the case you're contending on the central malloc lock in the default allocator. In that case you'd see malloc calling lock in the stack traces, observe a high csw/vctx rate as threads block for the malloc lock, and your "usr" time would be less than expected. Solaris dtrace is a wonderful and invaluable performance tool as well, but in a sense you have to frame and articulate a meaningful and specific question to get a useful answer, so I tend not to use it for first-order screening of problems. It's also most effective for OS and software-level performance issues as opposed to HW-level issues. For that reason I recommend mpstat & pstack as my the 1st step in performance triage. If some other OS-level issue is evident then it's good to switch to dtrace to drill more deeply into the problem. Only after I've ruled out OS-level issues do I switch to using hardware performance counters to look for architectural impediments.

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  • Any way to set up a grid for a board game in cocos 2d?

    - by Scott
    My first idea was to create a 2d array for my columns and rows, but it seems like there should be a better, or possibly cleaner, way to achieve this. Each square on the grid is going to have a background image, probably a .png although I might just draw the images with a draw method. Basically, I want to be able to drag and drop images onto the individual grid squares. I've been searching for a solution and the closest thing I can find is the tiled map solution. That just seems like a little overkill for what I'm trying to accomplish. Also, I don't know if this helps but i need my grid to be 12 by 12 and take up the entire width of the iphone screen.

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  • Are two database trips reasonable for a login system?

    - by Randolph Potter
    I am designing a login system for a project, and have an issue about it requiring two trips to the database when a user logs in. User types in username and password Database is polled and password hash is retrieved for comparative purposes (first trip) Code tests hash against entered password (and salt), and if verified, resets the session ID New session ID and username are sent back to the database to write a row to the login table, and generate a login ID for that session. EDIT: I am using a random salt. Does this design make sense? Am I missing something? Is my concern about two trips unfounded? Comments and suggestions are welcome.

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  • New Thinking for Supply Chain Analytics. PLM for Process. And Untangling Services Complexity.

    - by David Hope-Ross
    The first edition of the quarterly Oracle Information InDepth Value Chain and Procurement Transformation newsletter has just been published. It’s a solid round-up of news and analysis from the fast-moving world of global supply chains and supply management.  As the title of this post implies, the latest edition covers a wide array of great topics. But the story on supply chain analytics from Endeca is especially interesting. Without giving away the ending, it explores new ways of thinking about the value of information and how to exploit it for supply chain improvement. If you enjoy this edition, think about opting-in via the subscription link. It is an easy way to keep up with the latest and greatest.

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  • What level/format of access should be given to a client to the issue tracking system?

    - by dukeofgaming
    So, I used to think that it would be a good idea to give the customer access to the issue tracking system, but now I've seen that it creates less than ideal situations, like: Customer judging progress solely on ticket count Developers denied to add issues to avoid customer thinking that there is less progress Customer appointing people on their side to add issues who don't always do a good job (lots of duplicate issues, insufficient information to reproduce, and other things that distract people from doing their real job) However, I think customers should have access to some indicators or proof that there is progress being done, as well as a right to report bugs. So, what would be the ideal solution to this situation?, specially, getting out of or improving the first situation described?

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  • Importance of having EDU backlinks

    - by maisdesign
    I've built a few links on 50 EDU / GOV websites. 1 of them has PR 8, 3 of them have PR 7, 8 of them PR6,7 of them PR5,12 of them PR4,8 of them PR3, 1 of them PR2, 6 of them PR1, 10 of them PR0. My website has PR3 and is on first page of Google/Yahoo/Bing for a few keywords that I like How long will it take to notice a difference in PR or domain authority? (Don't tell me that PR has no value now, I know it but it is a 'fashion' thing). So you say that DOMAIN Authority isn't an important factor?

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  • ati graphics always on

    - by naveen
    i use a lenovo y560 and has ubunto 12.04 and win 7 installed when i boot into ubunto i find that the ati car is always on which drains the battery and overheats the system is there any to switch off the ati graphics and use intel hd in ubuntu ati hd 5730 is the graphics card that i use and it has switchable graphics in it. in bios the only two options for video adapter is discrete and switchable after installing ati driver from amd website i am getting a commamd prompt as log in screen first error message comes as Your system is running in low-graphics mode with options to run in low graphics mode this time reconfigure exit all three options i am stuck i need to manually reboot the system

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  • Is there a good way to get pixel-perfect collision detection in XNA?

    - by ashes999
    Is there a well-known way (or perhaps reusable bit of code) for pixel-perfect collision detection in XNA? I assume this would also use polygons (boxes/triangles/circles) for a first-pass, quick-test for collisions, and if that test indicated a collision, it would then search for a per-pixel collision. This can be complicated, because we have to account for scale, rotation, and transparency. WARNING: If you're using the sample code from the link from the answer below, be aware that the scaling of the matrix is commented out for good reason. You don't need to uncomment it out to get scaling to work.

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  • Google Places seo?

    - by sam
    Im familiar with seo and getting higher google listings but for allot of services google has recently been making there search results (were applicable) much more location orientated.. for instance searching for a "accountant in london" or "accountancy firm london" will through return the first half of page 1 as google places listings, then under about 6 of these you will get your normal search results so somone who used to rank #1 on page 1 now will rank effectily #7. What i was wandering is that i cant see any reasons as to why the company that rank high in the places results get there, often they are not high up in the search results. Is there a way to optimise on or offsite to rise up the google places listings in your city ?

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  • Desktop interface crashes after software updates

    - by N.C. Weber
    Recently, after installing Ubuntu software updates on the evening of December 7th, 2012, my desktop interface crashes regularly leaving me with a command line screen with a long string of automated commands showing (I assume what goes on behind the pretty desktop). At first, I thought it was only crashing whenever I played DirectX games in WINE, but now it crashes if I open the native Firefox browser or if it's doing nothing at all but sitting there. Apport attempts to report the bugs after restart, but often they crash as well. I've done a SMART check on the hard drive, and everything report OK. No read errors, no bad sectors. I am using an Acer Extensa 4620Z Memory: 2.0 GiB Processor: Intel Pentium Dual CPU T2370 @ 1.73GHz x 2 GraphicsL: Intel 965GM x86/MMX/SSE2 OS: Ubuntu 12.10 32-bit Disk: 116.0 GB with 33.4 GB Available

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  • Sang Shin is back!

    - by arungupta
    Sang Shin is back at Oracle. He is well known for his wide range of Java tutorials at javapassion.com. As a former Sun evangelist, he helped GlassFish and Java EE adoption and continued to do even after his days at Sun. In his current role, he will help evangelize and drive adoption of the Java EE platform, GlassFish, and WebLogic server. You will see him online, speaking at conferences, blogging, and at our different social media channels. Say hello to him whenever you meet him. Here is what Sang had to say about his comeback: I AM BACK to where it all started. It sure felt like coming back home and it's good to see the first hand the spirit of innovation still is alive and well here in Oracle especially on Java front. Looking forward to be engaged with everyone in Java EE community with Passion again! Looking forward to working with Sang! You can ping him at @javapassion.

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  • Reversi/Othello early-game evaluation function

    - by Vladislav Il'ushin
    I've written my own Reversi player, based on the MiniMax algorithm, with Alpha-Beta pruning, but in the first 10 moves my evaluation function is too slow. I need a good early-game evaluation function. I'm trying to do it with this matrix (corresponding to the board) which determines how favourable that square is to have: { 30, -25, 10, 5, 5, 10, -25, 30,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 30, -25, 10, 5, 5, 10, -25, 30,},}; But it doesn't work well. Have you even written an early-game evaluation function for Reversi?

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  • Ubuntu gone out of order - Wont install any packages. What do I do?

    - by Aborted
    Lately, I've been getting some strange behaviour from Ubuntu. First and the most important is that it wont install updates. It gives a package installation error and it simply wont work. Earlier I tried to install TeamViewer via the Software Center, but got the same package error. I also feel like the connection speed is going slower than it should - don't know if this one is relevant to this case. What's wrong with my installation? How do I fix these package installation errors?

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  • wireless driver error after install

    - by James
    after following this command to update wifi drivers:1- Boot into Ubuntu 2- Open a terminal by pressing Ctrl+Alt+T 3- Type in the following (verbatim!) sudo apt-get update && sudo apt-get upgrade press Enter, the command will prompt for your password (the one you use to login into Ubuntu), type it and press Enter. Wait for it to finish updating your system. Now type: sudo apt-get remove bcmwl-kernel-source sudo apt-get install firmware-b43-installer Wait for the command to finish installing the driver, when done restart your computer. i get a message after the first command when installing has done saying not enough space so it aborts! what do i do to fix this

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  • My ASUS U32U with fresh Xubuntu install shows a black screen 50-80% of the startups

    - by Jona Ekenberg
    I have recently installed Ubuntu 12.10 with Xubuntu-package on my ASUS U32U notebook (Radeon HD 6320 GPU). The issue I have is that more often than not, after the GRUB-select screen I get a black screen, and three times total white lines (kind of) flashes very quickly (with maybe 5 seconds between each flash). I'm not even able to get to the login-screen (nor the Xubuntu loading screen). At first I thought it was simply me having installed something dumb or messed up some settings, but even after reformatting the partition and installing ubuntu again, the problem remains. Before I formatted it xfce4's window manager wouldn't start either, but it does now (when I am able to see anything). I can access the virual consoles (ctrl+alt+f1), but I can't see anything, but I've managed to shutdown the computer by using it (sudo shutdown -h now).

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  • Configuration of the network manager via DBus: how to set the ad hoc mode

    - by Andrea
    I have an hard nut to crack: a nice bottle of italian Chianti wine to the solver! :) To automatically configure Wifi, I first have to kill the network manager and than activate the wifi via the commandline: I do this all automatically in my application and works great. However... it is not the right way to do this. As the user has no network gui anymore to configure some other network access. A much better and transparent way would be to configure wifi directly via network manager over the DBus interface. I was able to configure it, but I wasn't able to set it to ad hoc mode... Searching the web for a while: a lot about configuration in general but nothing related to ad hoc mode. I think the only way to do figure that out is to look into the source code of the network manager...maybe someone already did it and he can answer.

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  • "Unknown Filesystem" error without CDROM

    - by Utku Tarhan
    I've got a problem with Ubuntu 12.04 LTS. At first I ran mount command on terminal. Then I restarted my computer. After that, when my computer opened there is writing this: error: unknown filesystem grub rescue I searched commands and I found ls command. I tried it and I got this: (hd0) (hd0,msdos5) (hd0,msdos1) My computer's DVD driver is broken and I tried to boot Ubuntu on USB but it doesn't worked. My computer's specs: PC Name: HP Presario F780ET Processor: AMD Turion 64 X2 Mobile Technology TL-60 Ram: 2GB Ubuntu Version: 12.04 LTS

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