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• External hard drive not recognized

  - by sr71

  Installed Ubuntu 10.10 on a hard drive by itself (no windows). All updates are up to date. Everything`works fine except when I plug in a 320 gig Toshiba external hard drive....it is not recognized. When I plug in an 8 gig flash drive it is recognized no problem. What do I mean by "not recognized"? I mean: how do you know it was not recognized. You can check the command "cat /proc/partitions" in a terminal with and without the hdd attached. If you see some difference, it's ok. If the difference is something like "sda1" (sd+letter+number) then you have partition on it, maybe it can't be handled in Ubuntu (no filesystem on it or so). If there is only "sda" in the difference for example (sd+letter, but no number after it) then the drive itself is detected, just no partition is created on it. Also you can check out the messages of the kernel, with the "dmesg" command in the terminal. If there is no disk/partition/anything in /proc/partitions, there can be an USB level problem, you can issue command "lsusb" as it was suggested before my answer. It's really matter of what do you mean about "not recognized". @Marco Ceppi @Oli @Pitto By "not recognized" I meant that when I plug in a 8 gig flash drive an icon immediately appears on the desktop imdicating that there is a flash drive plugged in and I can click on it and view the files on the flash drive. It also shows up on the "Nautilus" default file manager. When I plug in the 320 gig Toshiba external hard drive, I get no indication on the desktop or the file manager (thus "not recogized"). When I run the command cat/proc/partitions/ I get an error message Could not open location 'file:///home/bob/cat/proc/partitions' with or without the external hard drive installed. With the dmeg command I get about 10 pages of info with no mention of disk/partition/anything in /proc/partitions. When I run lsusb command I get the following: bob@bob-desktop:~$ lsusb Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 003: ID 04b3:3003 IBM Corp. Rapid Access III Keyboard Bus 003 Device 002: ID 04b3:3004 IBM Corp. Media Access Pro Keyboard Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

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• Using HBase or Cassandra for a token server

  - by crippy

  I've been trying to figure out how to use HBase/Cassandra for a token system we're re-implementing. I can probably squeeze quite a lot more from MySQL, but it just seems it has come to clinging on to the wrong tool for the task just because we know it well. Eventually will hit a wall (like happened to us in other areas). Naturally I started looking into possible NoSQL solutions. The prominent ones (at least in terms of buzz) are HBase and Cassandra. The story is more or less like this: A user can send a gift other users. Each gift has a list of recipients or is public in which case limited by number or expiration date For each gift sent we generate some token that uniquely identifies that gift. For each gift we track the list of potential recipients and their current status relating to that gift (accepted, declinded etc). A user can request to see all his currently pending gifts A can request a list of users he has sent a gift to today (used to limit number of gifts sent) Required the ability to "dump" or "ignore" expired gifts (x day old gifts are considered expired) There are some other requirements but I believe the above covers the essentials. How would I go and model that using HBase or Cassandra? Well, the wall was performance. A few 10s of millions of records per day over 2 tables kept for 2 weeks (wish I could have kept it for more but there was no way). The response times kept getting slower and slower until eventually we had to start cutting down number of days we kept data. Caching helps here but it's not an ideal solution since a big part of the ops are updates. Also, as I hinted in my original post. We use MySQL extensively. We know exactly what it can and can't do both in naive implementations followed by native partitioning and finally by horizontally sharding our dataset on the application level to reside on multiple DB nodes. It can be done, but that's not really what I'm trying to get from this. I asked a very specific question about designing a solution using a NoSQL solution since it's very hard to find examples for designs out there. Brainlag, not trying to come off as rude. I actually appreciate it a lot that you are the only one who even bothered to respond. but I see it over and over again. People ask questions and others assume they have no idea what they're talking about and give an irrelevant answer. Ignore RDBMS please. The question is about nosql.

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• No network connectivity (not wired or wireless) - RT5390

  - by Ben Udy

  I am starting to think I simply need to accept a small loss and sell my new ASUS K73E. Because I really don't enjoy computing when I have to deal with Windough$ and this windows 7 64 bit on my new ASUS is even worse than the old machines with XP. I have written to ASUS and they simply say "We don't support Linux" and while Ralink's website says they do support Linux I can't get anyone to tell me what model Ralink card might be in my machine. Is anyone out there who might be able to give me some useful advice???? Here is the answer to command lspci nn && lsusb && lsmod && rfkill list all: di,snd_seq snd 54244 16 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device uvcvideo 57374 0 videodev 34361 1 uvcvideo v4l1_compat 13251 2 uvcvideo,videodev soundcore 6620 1 snd snd_page_alloc 7076 2 snd_hda_intel,snd_pcm psmouse 63677 0 serio_raw 3978 0 lp 7028 0 parport 32635 2 ppdev,lp fbcon 35102 71 tileblit 1999 1 fbcon font 7557 1 fbcon bitblit 4707 1 fbcon softcursor 1189 1 bitblit video 17375 0 output 1871 1 video vga16fb 11385 1 vgastate 8961 1 vga16fb ahci 32360 2 di,snd_seq snd 54244 16 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device uvcvideo 57374 0 videodev 34361 1 uvcvideo v4l1_compat 13251 2 uvcvideo,videodev soundcore 6620 1 snd snd_page_alloc 7076 2 snd_hda_intel,snd_pcm psmouse 63677 0 serio_raw 3978 0 lp 7028 0 parport 32635 2 ppdev,lp fbcon 35102 71 tileblit 1999 1 fbcon font 7557 1 fbcon bitblit 4707 1 fbcon softcursor 1189 1 bitblit video 17375 0 output 1871 1 video vga16fb 11385 1 vgastate 8961 1 vga16fb ahci 32360 2 Edit #2 lspci 00:00.0 Host bridge: Intel Corporation Device 0104 (rev 09) 00:02.0 VGA compatible controller: Intel Corporation Device 0116 (rev 09) 00:16.0 Communication controller: Intel Corporation Cougar Point HECI Controller #1 (rev 04) 00:1a.0 USB Controller: Intel Corporation Cougar Point USB Enhanced Host Controller #2 (rev 05) 00:1b.0 Audio device: Intel Corporation Cougar Point High Definition Audio Controller (rev 05) 00:1c.0 PCI bridge: Intel Corporation Cougar Point PCI Express Root Port 1 (rev b5) 00:1c.1 PCI bridge: Intel Corporation Cougar Point PCI Express Root Port 2 (rev b5) 00:1c.5 PCI bridge: Intel Corporation Cougar Point PCI Express Root Port 6 (rev b5) 00:1d.0 USB Controller: Intel Corporation Cougar Point USB Enhanced Host Controller #1 (rev 05) 00:1f.0 ISA bridge: Intel Corporation Device 1c49 (rev 05) 00:1f.2 SATA controller: Intel Corporation Cougar Point 6 port SATA AHCI Controller (rev 05) 00:1f.3 SMBus: Intel Corporation Cougar Point SMBus Controller (rev 05) 02:00.0 Network controller: RaLink Device 5390 03:00.0 Ethernet controller: Atheros Communications Device 1083 (rev c0) lsusb Bus 002 Device 002: ID 8087:0024 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 13d3:5710 IMC Networks Bus 001 Device 002: ID 8087:0024 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Thanks for the suggestion because this gave me a model for Ralink RT5390. I have now gone to Ralink.com and downloaded (via Windows 7) the driver package (it is a bz2 file). I hope I can figure out how to install it. And FYI - I was not able to run su (not authorized?) and dmidecode didn't exist (probably needs to be downloaded BUT no internet yet in Ubuntu)

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• What are the differences between abstract classes, interfaces, and when to use them

  - by user66662

  Recently I have started to wrap my head around OOP, and I am now to the point where the more I read about the differences between Abstract classes and Interfaces the more confused I become. So far, neither can be instantiated. Interfaces are more or less structural blueprints that determine the skeleton and abstracts are different by being able to partially develop code. I would like to learn more about these through my specific situation. Here is a link to my first question if you would like a little more background information: What is a good design model for my new class? Here are two classes I created: class Ad { $title; $description $price; function get_data($website){ } function validate_price(){ } } class calendar_event { $title; $description $start_date; function get_data($website){ //guts } function validate_dates(){ //guts } } So, as you can see these classes are almost identical. Not shown here, but there are other functions, like get_zip(), save_to_database() that are common across my classes. I have also added other classes Cars and Pets which have all the common methods and of course properties specific to those objects (mileage, weight, for example). Now I have violated the DRY principle and I am managing and changing the same code across multiple files. I intend on having more classes like boats, horses, or whatever. So is this where I would use an interface or abstract class? From what I understand about abstract classes I would use a super class as a template with all of the common elements built into the abstract class, and then add only the items specifically needed in future classes. For example: abstract class content { $title; $description function get_data($website){ } function common_function2() { } function common_function3() { } } class calendar_event extends content { $start_date; function validate_dates(){ } } Or would I use an interface and, because these are so similar, create a structure that each of the subclasses are forced to use for integrity reasons, and leave it up to the end developer who fleshes out that class to be responsible for each of the details of even the common functions. my thinking there is that some 'common' functions may need to be tweaked in the future for the needs of their specific class. Despite all that above, if you believe I am misunderstanding the what and why of abstracts and interfaces altogether, by all means let a valid answer to be stop thinking in this direction and suggest the proper way to move forward! Thanks!

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• Our Favorite Highlights from OpenWorld 2012

  - by Kathy.Miedema

  By Kathy Miedema and Misha Vaughan, Oracle Applications User Experience The Oracle Applications User Experience (UX) team’s activities around OpenWorld expand every year, but this year we certainly raised the bar.   Members of our team helped deliver three, separate, all-day training events in the week prior to OpenWorld. Our Fusion User Experience Advocates (FXA) and Applications UX Sales Ambassadors (SAMBA) have all-new material around the Oracle user experience to deliver at conferences in the coming year - Fusion Applications design patterns, mobile design patterns, and the new face of Fusion. We also delivered a hands-on workshop sharing user experience tools for our customers that is designed to answer this question: "If I have no UX staff, what do I do?" We also spent the weeks just before OpenWorld preparing to talk about the new face of Fusion Applications, a greatly simplified entry experience into Fusion Applications for self-service users, CRM users, and IT managers who want to change the look and feel quickly. Special thanks to Oracle ACE Director Floyd Teter for the first mention of our project.Jeremy Ashley, VP, Oracle Applications User Experience Customers may have seen one of the many OpenWorld session demos of the new face of Fusion, which will be available with Fusion Applications soon. It was shown in sessions by Oracle's Chris Leone, Anthony Lye, and our own Vice President, Jeremy Ashley, among others.   Leone reinforced the importance of user experience as one of three main design principles for Fusion Applications, emphasizing that Fusion was designed from the beginning to be intelligent, social, and mobile. User experience highlights of the new face of Fusion, he said, included the need for "zero training," and he called the experience "easy to use." He added that deploying it for HCM self-service would be effortless.  Customers take part in a usability lab tour during OpenWorld 2012. Customers also may have seen the new face of Fusion on the demogrounds or during one of our teams' chartered lab tours at the end of the week. We tested other new designs at our on-site lab in the Intercontinental Hotel, next to Moscone West. Applications User Experience team members show eye-tracking and mobile demos at OOW. We were also excited to kick off new branches of the Oracle Usability Advisory Board, which now has groups in Latin America and the Middle East, in addition to North America and EMEA.   And we were pleasantly surprised by the interest in one of our latest research projects, Oracle Voice, which is designed to enable faster data input for on-the-go users. We offer a big thank-you to the Nuance demopod for sharing the demo with OpenWorld attendees.  For more information on our program and products like the new face of Fusion, please comment below. 

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• 2D Animation Smoothness - Delta time vs. Kinematics

  - by viperld002

  I'm animating a sprite in 2D with key frames of rotation and xy-positions. I've recently had a discussion with someone saying that when the device (happens to be an iPad using cocos2D) hits a performance bump due to whatever else the user may be doing, lag will arise and that the best way to fight it is to not use actual positions, but velocities, accelerations and torques with kinematics. His message is to evaluate the positions and rotations from these speeds at the current point in time. I've never experienced a situation where I've heard of using kinematics to stem lag in 2D animations and am not sure of how effective it could be. Also, it seems to be overkill. The application is not networked so it's all running on a local device. The desired effect is that the animation always plays as closely as it can to the target frame rate. Wouldn't the technique suffer the same problems as just using the time since the last frame or a fixed time step since the kinematics would also require some time value to perform the calculation? What techniques could you suggest to best achieve the desired effect? EDIT 1 Thank you for your responses, they are very illuminating. I want to clarify my question before choosing an answer however, to make sure that this post really serves it's purpose. I have a sprite of a ball, and a text file with 3 arrays worth of information (rotation,translations x, translations y) with each unit of information existing as a key frame to be stepped through (0 to 49 and back to 0 to replay it again). I have this playing by interpolating from the current key frame to the next, every n-units of time. The animation is visibly correct when compared to a video I was given of it, and it is smooth because of the interpolations between the key frames. This is the existing state of the project. There are no physics simulated, only a static animation of a ball moving in a way an artist specifically designed. Should I, instead of rotation in degrees and translations by positions in space, derive velocities, accelerations and torques to express this static animation as a function of time? As in, position now = foo(time now), where foo uses kinematics.

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• Ubuntu 10.10 not recognizing external hard drive

  - by sr71

  Installed Ubuntu 10.10 on a hard drive by itself (no windows). All updates are up to date. Everything`works fine except when I plug in a 320 gig Toshiba external hard drive....it is not recognized. When I plug in an 8 gig flash drive it is recognized no problem. What do I mean by "not recognized"? I mean: how do you know it was not recognized. You can check the command "cat /proc/partitions" in a terminal with and without the hdd attached. If you see some difference, it's ok. If the difference is something like "sda1" (sd+letter+number) then you have partition on it, maybe it can't be handled in Ubuntu (no filesystem on it or so). If there is only "sda" in the difference for example (sd+letter, but no number after it) then the drive itself is detected, just no partition is created on it. Also you can check out the messages of the kernel, with the "dmesg" command in the terminal. If there is no disk/partition/anything in /proc/partitions, there can be an USB level problem, you can issue command "lsusb" as it was suggested before my answer. It's really matter of what do you mean about "not recognized". @Marco Ceppi @Oli @Pitto By "not recognized" I meant that when I plug in a 8 gig flash drive an icon immediately appears on the desktop imdicating that there is a flash drive plugged in and I can click on it and view the files on the flash drive. It also shows up on the "Nautilus" default file manager. When I plug in the 320 gig Toshiba external hard drive, I get no indication on the desktop or the file manager (thus "not recogized"). When I run the command "cat/proc/partitions/" I get an error message Could not open location 'file:///home/bob/cat/proc/partitions' with or without the external hard drive installed. With the "dmeg" command I get about 10 pages of info with no mention of disk/partition/anything in /proc/partitions. When I run "lsub" command I get the following: bob@bob-desktop:~$ lsusb Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 003: ID 04b3:3003 IBM Corp. Rapid Access III Keyboard Bus 003 Device 002: ID 04b3:3004 IBM Corp. Media Access Pro Keyboard Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub bob@bob-desktop:~$

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• Motivating yourself to actually write the code after you've designed something

  - by dpb

  Does it happen only to me or is this familiar to you too? It's like this: You have to create something; a module, a feature, an entire application... whatever. It is something interesting that you have never done before, it is challenging. So you start to think how you are going to do it. You draw some sketches. You write some prototypes to test your ideas. You are putting different pieces together to get the complete view. You finally end up with a design that you like, something that is simple, clear to everybody, easy maintainable... you name it. You covered every base, you thought of everything. You know that you are going to have this class and that file and that database schema. Configure this here, adapt this other thingy there etc. But now, after everything is settled, you have to sit down and actually write the code for it. And is not challenging anymore.... Been there, done that! Writing the code now is just "formalities" and makes it look like re-iterating what you've just finished. At my previous job I sometimes got away with it because someone else did the coding based on my specifications, but at my new gig I'm in charge of the entire process so I have to do this too ('cause I get payed to do it). But I have a pet project I'm working on at home, after work and there is just me and no one is paying me to do it. I do the creative work and then when time comes to write it down I just don't feel like it (lets browse the web a little, see what's new on P.SE, on SO etc). I just want to move to the next challenging thing, and then to the next, and the next... Does this happen to you too? How do you deal with it? How do you convince yourself to go in and write the freaking code? I'll take any answer.

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• How are you coping with Ubuntu's Unity app launcher? (It auto-hides, can't minimize apps)

  - by Bad Learner

  [Firstly, let me tell you that this cannot be subjective in anyway, as I think at least Ubuntu beginners will have these questions boggling in their mind; and yes, this is a question that has a definite answer - - so, I am completely within the rules.] Okay, coming to the point, I see that Ubuntu uses Unity since v10.xx (netbook edition?) and carried the same to v11.04 & v11.10. As someone who's stuck to Windows for all these years, it's somewhat difficult to cope with Ubuntu's Unity, for the following reasons: [1] The Unity app launcher (to the screen's left) auto-hides when a window is maximized. [2]- And once launched, apps cannot be minimized by clicking the app's icon in the launcher. I have to go to the top-left of the screen and click the "_" button. I do know I can fix these issues by installing some configuration tool. But the thing is, if that's how it's meant to work, Canonical/Ubuntu would have designed it that way. But they didn't. Why? w.r.t above points [1], [2]: [1] EDITED: So, does it mean, it's good to work without maximizing the windows? Because if I maximize the window, the app launcher hides. And I need to hover the mouse to the left of the screen, wait a bit (even if it's a sec or even less, I can still feel the lag), and then click on the next app icon in the launcher to switch to it. I do know, I can use Alt+TAB to switch, but I am not sure which window comes next. This, I feel, isn't productive. Also, this makes me feel, Ubuntu is designed for large screens (it's nice on my 1920x1080p screen), because I can have two windows side-by-side or something like that on a large screen. This is not possible on smaller screens. [2]- Being able to minimize an application's window by clicking on its icon in the launcher (just like it works on Windows & probably elsewhere) would have been great, rather than having to go to the top-left and clicking the _ (minimize) button which brings up the app launcher itself (from hiding) most of the time. It's too tiring to have these small issues in the UI. I really would like to know how you are coping with these issues the way they are?

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• Oracle Customer Success Forum - Batesville - Oracle Sales Cloud - June 24th, 5pm CET

  - by Richard Lefebvre

  Batesville uses Oracle Sales Cloud to create a common platform and standardize processes for business transformation across field sales and telesales. Using real-time KPI dashboards, they are measuring their business success with consistency across their sales reps.We are pleased to invite you to a discussion with Batesville on industry trends, why sales automation is important, reasons for choosing Oracle Sales Cloud, and the vendor evaluation process. Please click on the register button to confirm your attendance by 5:00 p.m. Pacific Time on June 23, 2014.Speakers: Diane Kinker, Director CRM Program Chris Haven, Senior Director Product Management, Oracle (Moderator) Organization Profile:Batesville (www.Batesville.com), a wholly owned subsidiary of Hillenbrand, Inc. (NYSE:HI), is the leader in the North American death care industry. For more than 125 years, Batesville has been dedicated to helping families honor the lives of those they love®. Batesville’s innovation has changed the face of funeral service, from advancements in manufacturing and quality to patented features and memorialization offerings, technology and web-based solutions, and profit-enhancing merchandising systems and room displays. Our history of manufacturing excellence, product innovation, superior customer service and reliable delivery has helped Batesville become – and remain – a market leader. Event Description:In this informal reference call, you will have the opportunity to hear Batesville discuss industry trends, why sales automation is important, the decision making process for choosing Oracle Sales Cloud, and the vendor evaluation process. The call will open with a brief overview, followed by discussion, and an open question and answer session. Please allow one hour for the call.Why Oracle:Batesville looked to transform its sales automation processes. Oracle Sales Cloud met these needs and Batesville’s requirements for: Standardized end-to-end Sales Processes including Sales Performance Management (territory management, quota management and incentive compensation) Mobile capabilities with integration to Microsoft Outlook and Smartphones Creation of the WIG Dashboard (Wildly Important Goal) using reporting and analytics Click the Register Now button to confirm your attendance for this informative event. Registration will close at 5:00 p.m. Pacific Time on June 23, 2014.After you register your information will be forwarded through an Approval Process. Once your registration request has been validated against the invitation database, you will receive an email confirmation with your registration details as long as there is availability. Please be advised that Batesville will revise the registrants list and may dismiss registrations as they see fit. Register Now!

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• Fixing a NoClassDefFoundError

  - by Chris Okyen

  I have some code: package ftc; import java.util.Scanner; public class Fer_To_Cel { public static void main(String[] argv) { // Scanner object to get the temp in degrees Farenheit Scanner keyboard = new Scanner(System.in); boolean isInt = true; // temporarily put as true in case the user enters a valid int the first time int degreesF = 0; // initialy set to 0 do { try { // Input the temperature text. System.out.print("\nPlease enter a temperature (integer number, no fractional part) in degrees Farenheit: "); degreesF = Integer.parseInt(keyboard.next()); // Get user input and Assign the far. temperature variable, which is casted from String to int. } // Let the user know in a user friendly notice that the value entered wasnt an int ( give int value range ) , and then give error log catch(java.lang.Exception e) { System.out.println("Sorry but you entered a non-int value ( needs to be between ( including ) -2,147,483,648 and 2,147,483,647 ).. \n"); e.printStackTrace(); isInt = false; } } while(!isInt); System.out.println(""); // print a new line. final int degreesC = (5*(degreesF-32)/9); // convert the degrees from F to C and store the resulting expression in degreesC // Print out a newline, then print what X degrees F is in Celcius. System.out.println("\n" + degreesF + " degrees Farenheit is " + degreesC + " degrees Celcius"); } } And The following error: C:\Program Files\Java\jdk1.7.0_06\bin>java Fer_To_Cel Exception in thread "main" java.lang.NoClassDefFoundError: Fer_To_Cel (wrong name: ftc/Fer_To_Cel) at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:791) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14 at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:423) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:356) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:480) The code compiled without compile errors, but presented errors during execution. Which leads me to two questions. I know Errors can be termed Compiler, Runtime and Logic Errors, but the NoClassDefFoundError inherits java.lang.LinkageError. Does that make it a Linker error, being niether of the three types of errors I listed, If I am right this is the answer. For someone else who obtains the singular .java file and compiles it, would this be the only way to solve this problem? Or can I (should I ) do/have done something to fix this problem? Basically, based on a basis of programming, is this a fault of me as the writer? Could this be done once on, my half and be distributed and not needed be done again?

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• Best way to implement a simple bullet trajectory

  - by AirieFenix

  I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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• How can I get my ATI / AMD drivers to work with any kernel above 3.2.0.x?

  - by TorakTu

  How can I get my ATI / AMD drivers to work with any kernel above 3.2.0.x ? WHAT DID WORK Installed original AMD64 version of Ubuntu 12.04 ISO image. Burned DVD and installed which shown kernel 3.2.0-23 to begin with. Got 5.1 surround sound working. Got ATI ( Now its AMD ) video drivers installed for my Radeon HD R6870 Video card from AMD's website. fglrxinfo came up and reported as normal. THE PROBLEM Kernel 3.2.0.x kept locking up so I tried higher kernel versions. But ATI / AMD Drivers do not install on any kernel Above 3.2.0.x WHAT I HAVE TRIED I have gone over this tutorial many times ( https://help.ubuntu.com/community/BinaryDriverHowto/ATI ) and it doesn't work on ANY kernel except 3.2.0.x. The problems I am having here are that the ATI / AMD drivers working for the 12.04 Precise with kernel 3.2.0-23 and 24, But the computer kept locking up. Although all my games would work, the lock ups were random and were constant. So I looked all over the web for 3 days trying to find an answer and the lock up issue was said to just update the kernel. So I did. Have tried many kernels. All of them .. no lock ups. BUT the Restricted AMD drivers from the AMD website will not install. And none of the OpenSource AMD drivers have EVER installed no matter what Kernel or version I tried. EXAMPLE OUTPUT OF 3D TYPE OF ERRORS Javax.media.opengl.GLException: glXGetConfig failed: error code GLX_NO_EXTENSION at com.sun.opengl.impl.x11.X11GLDrawableFactory.glXGetConfig(X11GLDrawableFactory.java:651) at com.sun.opengl.impl.x11.X11GLDrawableFactory.xvi2GLCapabilities(X11GLDrawableFactory.java:350) at com.sun.opengl.impl.x11.X11GLDrawableFactory.chooseGraphicsConfiguration(X11GLDrawableFactory.java:174) at javax.media.opengl.GLCanvas.chooseGraphicsConfiguration(GLCanvas.java:520) at javax.media.opengl.GLCanvas.<init>(GLCanvas.java:131) at haven.HavenPanel.<init>(HavenPanel.java:68) at haven.HavenPanel.<init>(HavenPanel.java:78) at haven.MainFrame.<init>(MainFrame.java:182) at haven.MainFrame.main2(MainFrame.java:306) at haven.MainFrame.access$100(MainFrame.java:34) at haven.MainFrame$7.run(MainFrame.java:360) at java.lang.Thread.run(Thread.java:722) And of course this is what fglrxinfo shows : X Error of failed request: BadRequest (invalid request code or no such operation) Major opcode of failed request: 139 (ATIFGLEXTENSION) Minor opcode of failed request: 66 () Serial number of failed request: 13 Current serial number in output stream: 13 EDIT : I forgot to mention that I DID look at this post over the last few days and it did not help.

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• MatheMagics - Guess My Age Method 1

  - by PointsToShare

  © 2011 By: Dov Trietsch. All rights reserved MatheMagic – Guess My Age – Method 1 The Mathemagician stands on the stage and asks an adult to do the following: ·         Do the next few steps on your calculator, or the calculator in your phone, or even on a piece of paper. ·         Do it silently! Don’t tell me the results until I ask for them directly ·         Compute a single digit multiple of 9 – any one of 9, 18, 27, … all the way to 81, will do. ·         Now multiply your age by 10 ·         Subtract the 9 multiple from this number. ·         Tell me the result. Notice that I don’t know which multiple of 9 you subtracted from 10 times your age. I will nonetheless immediately tell you what your age is. How do I do this? Let’s do the algebra. 10X – 9Y = 10X – 10Y + Y = 10(X – Y) + Y Now remember, you asked an adult, so his/her age is a two digit number (maybe even 3 digits), thus reducing it by the single digit multiplied by nine is still positive – the lowest is can be is 100 – 81 which yields 19. Now make two numbers out of the result. The last digit and the number before it. This number is X – Y or the age minus the single digit you selected. The last digit is this very single digit. This is always so regardless of the digit you selected. So… Add tis digit to the other number and you get back the age! Q.E.D Example: I am 76 years old and here is what happens when I do the steps 76 x 10 = 760 760 – 18 = 742 made of 74 and 2. My age is 74 + 2 760 – 81 = 679 made of 67 and 9. My age is 67 + 9 A note to the socially aware mathemagician – it is safer to do it with a man. The chances of a veracious answer are much, much higher! The trick may be accomplished on any 2 or 3 digit number, not just one’s age, but if you want to know your date’s age, it’s a good way to elicit it. That’s All Folks PS for more Ageless “Age” mathemagics go to www.mgsltns.com/games.htm and also here: http://geekswithblogs.net/PointsToShare/archive/2011/11/15/mathemagics---guess-my-age---method-2.aspx

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• Building SANE from git-source produce backend missmatch on 12.04 even if built locally

  - by deinonychusaur

  It seems to me that with Ubuntu Precise Pangolin it is all but easy to do a proper install of SANE from source (git-repo). I've found other scanning issues trying to find an answer to this, where the output people posted seems to indicate they suffer the same issue (unknowingly). If I run on a fresh install of Ubuntu 12.04 with compiled SANE source from the git I get: $ scanimage -V scanimage (sane-backends) 1.0.24git; backend version 1.0.22 (I basically followed the instructions on http://ubuntuportal.com/2012/02/how-to-get-an-canon-canoscan-lide-100-scanner-to-work-in-ubuntu-11-10linux-mint-12.html since I didn't find any other information making sure that sane was not installed prior to installation.) My primary interest is the epson2-backend. In 1.0.22 it offers the wrong TPU settings for Epson V700 (TPU2-mode wasn't supported in 1.0.22, and the scanner is useless to me if I don't have the TPU2-support). Since if I ask it to enter transparency mode, it shows 1.0.22 behaviour, it implies that the epson2-backend comes from 1.0.22 and not 1.0.24 even though I just built it. If I install SANE with prefix to a local folder and run that version of scanimage it still produces the mismatch. However, on another computer where I installed a custom 1.0.22 build of SANE prior to upgrading to Ubuntu 12.04, I can build and install the same SANE-git locally and have it correctly match backends: $ ./SANE/bin/scanimage -V scanimage (sane-backends) 1.0.24git; backend version 1.0.24 $ scanimage -V scanimage (sane-backends) 1.0.22; backend version 1.0.22 On this computer the 1.0.24 works correctly in finding TPU2 on Epson V700. So what am I missing/doing wrong? (And I want to replace 1.0.22 with 1.0.24 for the whole system, the local build was just debugging.) Any help would be much appreciated. Edit 1: Just tried compiling SANE using this instruction on Ubuntu 10.04 and it worked like a charm. However, when I upgraded to 12.04 (really would like to run 12.04), SANE was downgraded to 1.0.22. When trying the same set of instructions on 12.04 I was still out of luck -- the backend missmatch was there again (and I do have libusb-dev installed) Edit 2: I updated to Ubuntu 12.10 which now has the 1.0.23 SANE drivers. I haven't dared trying to compile from source on 12.10 since 1.0.23 is good enough for me. This is just a work-around and I would still like to know what's up with Ubuntu 12.04.

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• Breakout ball collision detection, bouncing against the walls [solved]

  - by Sri Harsha Chilakapati

  I'm currently trying to program a breakout game to distribute it as an example game for my own game engine. http://game-engine-for-java.googlecode.com/ But the problem here is that I can't get the bouncing condition working properly. Here's what I'm using. public void collision(GObject other){ if (other instanceof Bat || other instanceof Block){ bounce(); } else if (other instanceof Stone){ other.destroy(); bounce(); } //Breakout.HIT.play(); } And here's by bounce() method public void bounce(){ boolean left = false; boolean right = false; boolean up = false; boolean down = false; if (dx < 0) { left = true; } else if (dx > 0) { right = true; } if (dy < 0) { up = true; } else if (dy > 0) { down = true; } if (left && up) { dx = -dx; } if (left && down) { dy = -dy; } if (right && up) { dx = -dx; } if (right && down) { dy = -dy; } } The ball bounces the bat and blocks but when the block is on top of the ball, it won't bounce and moves upwards out of the game. What I'm missing? Is there anything to implement? Please help me.. Thanks EDIT: Have changed the bounce method. public void bounce(GObject other){ //System.out.println("y : " + getY() + " other.y + other.height - 2 : " + (other.getY() + other.getHeight() - 2)); if (getX()+getWidth()>other.getX()+2){ setHorizontalDirection(Direction.DIRECTION_RIGHT); } else if (getX()<(other.getX()+other.getWidth()-2)){ setHorizontalDirection(Direction.DIRECTION_LEFT); } if (getY()+getHeight()>other.getY()+2){ setVerticalDirection(Direction.DIRECTION_UP); } else if (getY()<(other.getY()+other.getHeight()-2)){ setVerticalDirection(Direction.DIRECTION_DOWN); } } EDIT: Solved now. See the changed method in my answer.

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• Need help on a problemset in a programming contest

  - by topher

  I've attended a local programming contest on my country. The name of the contest is "ACM-ICPC Indonesia National Contest 2013". The contest has ended on 2013-10-13 15:00:00 (GMT +7) and I am still curious about one of the problems. You can find the original version of the problem here. Brief Problem Explanation: There are a set of "jobs" (tasks) that should be performed on several "servers" (computers). Each job should be executed strictly from start time Si to end time Ei Each server can only perform one task at a time. (The complicated thing goes here) It takes some time for a server to switch from one job to another. If a server finishes job Jx, then to start job Jy it will need an intermission time Tx,y after job Jx completes. This is the time required by the server to clean up job Jx and load job Jy. In other word, job Jy can be run after job Jx if and only if Ex + Tx,y = Sy. The problem is to compute the minimum number of servers needed to do all jobs. Example: For example, let there be 3 jobs S(1) = 3 and E(1) = 6 S(2) = 10 and E(2) = 15 S(3) = 16 and E(3) = 20 T(1,2) = 2, T(1,3) = 5 T(2,1) = 0, T(2,3) = 3 T(3,1) = 0, T(3,2) = 0 In this example, we need 2 servers: Server 1: J(1), J(2) Server 2: J(3) Sample Input: Short explanation: The first 3 is the number of test cases, following by number of jobs (the second 3 means that there are 3 jobs for case 1), then followed by Ei and Si, then the T matrix (sized equal with number of jobs). 3 3 3 6 10 15 16 20 0 2 5 0 0 3 0 0 0 4 8 10 4 7 12 15 1 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 8 10 4 7 12 15 1 4 0 50 50 50 50 0 50 50 50 50 0 50 50 50 50 0 Sample Output: Case #1: 2 Case #2: 1 Case #3: 4 Personal Comments: The time required can be represented as a graph matrix, so I'm supposing this as a directed acyclic graph problem. Methods I tried so far is brute force and greedy, but got Wrong Answer. (Unfortunately I don't have my code anymore) Could probably solved by dynamic programming too, but I'm not sure. I really have no clear idea on how to solve this problem. So a simple hint or insight will be very helpful to me.

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• What Counts for a DBA: Passion

  - by drsql

  One of my first questions, when interviewing for a DBA/Programmer position, is always: “Why do you want this job?” The answers I receive range from cheesy hyperbole (“I want to enhance your services with my vast knowledge”) to deadpan realism (“I have N kids who all have a hole in the front of their face where food goes"). Both answers are fine in their own way, at least displaying some self-confidence, humour and honesty, but once in a while, I'll hear the answer that is music to me ears... “I LOVE DATABASES!” Whenever I hear it, my nerves tingle in hopeful anticipation; have I found someone for whom working with database isn't just a job, but a passion? Inevitably, I'm often disappointed. What initially seemed like passion turns out to be rather shallow enthusiasm; the person is enthusiastic about working with databases in the same way he or she might be about eating a bag of Cajun spiced kettle chips; enjoyable, but not something to think about too deeply or take too seriously. Enthusiasm comes, and enthusiasm goes. I've seen countless technical forum users burst onto the scene in a blaze of frantic question-answering, only to fade away within days, never to be heard from again. Passion, however, is more of a longstanding commitment. The biographies of the great technologists and authors of the recent past are full of the sort of passion and engrossment that lead a person to write a novel non-stop for a fortnight with no sleep and only dog food to eat (Philip K. Dick), or refuse to leave the works of the first tunnel under the Thames, even though it was flooded (Brunel). In a similar (though more modest) way, my passion for working with databases has led me to acts that might cause someone for whom it was "just a job" to roll their eyes in disbelief. Most evenings you're more likely to find me reading a database book than watching TV. I've spent hundreds of hours of my spare time writing blogs and articles (some of which are only read by tens of people); I've spent hundreds of dollars travelling to conferences, paying my own flight and hotel expenses, so that I can share a little of what I know, and mix with some like-minded people. And I know I'm far from alone in this, in the SQL Server community. Passion isn't everything, of course, and it isn't always accompanied by any great skill, but in almost every case, that skill can be cultivated over time. If you are doing what you are passionate about, work turns into more than just a way to feed your kids; it becomes your hobby, entertainment, and preoccupation. And it is this passion that gives a DBA the obsessive stubbornness, the refusal to be beaten by even the most difficult problem, which is often so crucial. A final word of warning though: passion without limits can turn weird. Never let it get in the way of your wife, kids, bills, or personal hygiene.

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• Will you share your SQL Server configuration?

  - by Bill Graziano

  I regularly visit client sites and review their SQL Server configurations.  I come across all kinds of strange settings.  I’ve been thinking about a way to aggregate people’s configurations and see what’s common and what’s unique.  I used to do that with polls on SQLTeam.com.  I think we can find out more interesting things if we look at combinations of settings in relation to size and volume. I’ve been working on an application for another project that is similar.  It will be fairly easy to use that code for this.  I can have something up and running in a few days – if people are interested in it.  I admit that I often come up with ideas that just don’t make sense.  This may be one of them.  One of your biggest concerns has be how secure your data is.  My solution is not to store anything identifying.  The instance name and database names can both be “anonymized” and I don’t store the machine name or IP address or anything to do with logins. Some of the questions I’m curious about are: At what size database does the Enterprise Edition become prevalent? Given the total size of the databases how much RAM is common? How many people have multiple data files?  At what size does that become prevalent? How common is database mirroring?  Replication?  Log shipping? How common is full recovery mode?  At what data size does it become prevalent? I think those are all questions that are easy to answer -- with the right data.  The big question is whether or not people will share their SQL Server configurations.  I understand that organizations in regulated or high security environments can’t participate.  But I think that leaves many, many people that can.  Are you willing to share your configuration and learn about others?  I have a simple sign up form here.  It’s actually a mailing list signup that also captures your edition, number of servers and largest database.  The list will only be used for this project.  Is your SQL Server is configured correctly?  Do you wonder what the next step is as your data grows?  Take a second and sign up.

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• Many sources of movement in an entity system

  - by Sticky

  I'm fairly new to the idea of entity systems, having read a bunch of stuff (most usefully, this great blog and this answer). Though I'm having a little trouble understanding how something as simple as being able to manipualate the position of an object by an undefined number of sources. That is, I have my entity, which has a position component. I then have some event in the game which tells this entity to move a given distance, in a given time. These events can happen at any time, and will have different values for position and time. The result is that they'd be compounded together. In a traditional OO solution, I'd have some sort of MoveBy class, that contains the distance/time, and an array of those inside my game object class. Each frame, I'd iterate through all the MoveBy, and apply it to the position. If a MoveBy has reached its finish time, remove it from the array. With the entity system, I'm a little confused as how I should replicate this sort of behavior. If there were just one of these at a time, instead of being able to compound them together, it'd be fairly straightforward (I believe) and look something like this: PositionComponent containing x, y MoveByComponent containing x, y, time Entity which has both a PositionComponent and a MoveByComponent MoveBySystem that looks for an entity with both these components, and adds the value of MoveByComponent to the PositionComponent. When the time is reached, it removes the component from that entity. I'm a bit confused as to how I'd do the same thing with many move by's. My initial thoughts are that I would have: PositionComponent, MoveByComponent the same as above MoveByCollectionComponent which contains an array of MoveByComponents MoveByCollectionSystem that looks for an entity with a PositionComponent and a MoveByCollectionComponent, iterating through the MoveByComponents inside it, applying/removing as necessary. I guess this is a more general problem, of having many of the same component, and wanting a corresponding system to act on each one. My entities contain their components inside a hash of component type - component, so strictly have only 1 component of a particular type per entity. Is this the right way to be looking at this? Should an entity only ever have one component of a given type at all times?

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• Proven Approach to Financial Progress Using Modern Best Practice

  - by Oracle Accelerate for Midsize Companies

  Normal 0 false false false EN-US X-NONE X-NONE by Larry Simcox, Sr. Director, Oracle Midsize Programs Top performing organizations generate 25 percent higher profit margins and grow at twice the rate of their competitors. How do they do it? Recently, Dr. Stephen G. Timme, President of FinListics Solutions and Adjunct Professor at the Georgia Institute of Technology, joined me on a webcast to answer that question. I've know Dr. Timme since my days at G-log when we worked together to help customers determine the ROI of transportation management solutions. We were also joined by Steve Cox, Vice President of Oracle Midsize Programs, who recently published an Oracle E-book, "Modern Best Practice Explained". In this webcast, Cox provides his perspective on how best performing companies are moving from best practice to modern best practice.  Watch the webcast replay and you'll learn about the easy to follow, top down approach to: Identify processes that should be targeted for improvement Leverage a modern best practice maturity model to start a path to progress Link financial performance gaps to operational KPIs Improve cash flow by benchmarking key financial metrics Develop intelligent estimates of achievable cash flow benefits Click HERE to watch a replay of the webcast. You might also be interested in the following: Video: Modern Best Practices Defined  AppCast: Modern Best Practices for Growing Companies Looking for more news and information about Oracle Solutions for Midsize Companies? Read the latest Oracle for Midsize Companies Newsletter Sign-up to receive the latest communications from Oracle’s industry leaders and experts Larry Simcox Senior Director, Oracle Midsize Programs responsible for supporting and creating marketing content ,communications, sales and partner program support for Oracle's go to market activities for midsize companies. I have over 17 years experience helping customers identify the value and ROI from their IT investment. I live in Charlotte NC with my family and my dog Dingo. The views expressed here are my own, and not necessarily those of Oracle. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

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• Why does my ID3DXSprite appear to be incorrectly scaled?

  - by Bjoern

  I am using D3D9 for rendering some simple things (a movie) as the backmost layer, then on top of that some text messages, and now wanted to add some buttons to that. Before adding the buttons everything seemed to have worked fine, and I was using a ID3DXSprite for the text as well (ID3DXFont), now I am loading some graphics for the buttons, but they seem to be scaled to something like 1.2 times their original size. In my test window I centered the graphic, but it being too big it just doesnt fit well, for example the client area is 640x360, the graphic is 440, so I expect 100 pixel on left and right, left side is fine [I took screenshot and "counted" the pixels in photoshop], but on the right there is only about 20 pixels) My rendering code is very simple (I am omitting error checks, et cetera, for brevity) // initially viewport was set to width/height of client area // clear device m_d3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET|D3DCLEAR_STENCIL|D3DCLEAR_ZBUFFER, D3DCOLOR_ARGB(0,0,0,0), 1.0f, 0 ); // begin scene m_d3dDevice->BeginScene(); // render movie surface (just two triangles to which the movie is rendered) m_d3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE,false); m_d3dDevice->SetSamplerState( 0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR ); // bilinear filtering m_d3dDevice->SetSamplerState( 0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR ); // bilinear filtering m_d3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE ); m_d3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG2, D3DTA_DIFFUSE ); //Ignored m_d3dDevice->SetTextureStageState( 0, D3DTSS_COLOROP, D3DTOP_SELECTARG1 ); m_d3dDevice->SetTexture( 0, m_movieTexture ); m_d3dDevice->SetStreamSource(0, m_displayPlaneVertexBuffer, 0, sizeof(Vertex)); m_d3dDevice->SetFVF(Vertex::FVF_Flags); m_d3dDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2); // render sprites m_sprite->Begin(D3DXSPRITE_ALPHABLEND | D3DXSPRITE_SORT_TEXTURE | D3DXSPRITE_DO_NOT_ADDREF_TEXTURE); // text drop shadow m_font->DrawText( m_playerSprite, m_currentMessage.c_str(), m_currentMessage.size(), &m_playerFontRectDropShadow, DT_RIGHT|DT_TOP|DT_NOCLIP, m_playerFontColorDropShadow ); // text m_font->DrawText( m_playerSprite, m_currentMessage.c_str(), m_currentMessage.size(), &m_playerFontRect, DT_RIGHT|DT_TOP|DT_NOCLIP, m_playerFontColorMessage ) ); // control object m_sprite->Draw( m_texture, 0, 0, &m_vecPos, 0xFFFFFFFF ); // draws a few objects like this m_sprite->End() // end scene m_d3dDevice->EndScene(); What did I forget to do here? Except for the control objects (play button, pause button etc which are placed on a "panel" which is about 440 pixels wide) everything seems fine, the objects are positioned where I expect them, but just too big. By the way I loaded the images using D3DXCreateTextureFromFileEx (resizing wnidow, and reacting to lost device, etc, works fine too). For experimenting, I added some code to take an identity matrix and scale is down on the x/y axis to 0.75f, which then gave me the expected result for the controls (but also made the text smaller and out of position), but I don't know why I would need to scale anything. My rendering code is so simple, I just wanted to draw my 2D objects 1;1 the size they came from the file... I am really very inexperienced in D3D, so the answer might be very simple...

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• Oh no! My padding's invalid!

  - by Simon Cooper

  Recently, I've been doing some work involving cryptography, and encountered the standard .NET CryptographicException: 'Padding is invalid and cannot be removed.' Searching on StackOverflow produces 57 questions concerning this exception; it's a very common problem encountered. So I decided to have a closer look. To test this, I created a simple project that decrypts and encrypts a byte array: // create some random data byte[] data = new byte[100]; new Random().NextBytes(data); // use the Rijndael symmetric algorithm RijndaelManaged rij = new RijndaelManaged(); byte[] encrypted; // encrypt the data using a CryptoStream using (var encryptor = rij.CreateEncryptor()) using (MemoryStream encryptedStream = new MemoryStream()) using (CryptoStream crypto = new CryptoStream( encryptedStream, encryptor, CryptoStreamMode.Write)) { crypto.Write(data, 0, data.Length); encrypted = encryptedStream.ToArray(); } byte[] decrypted; // and decrypt it again using (var decryptor = rij.CreateDecryptor()) using (CryptoStream crypto = new CryptoStream( new MemoryStream(encrypted), decryptor, CryptoStreamMode.Read)) { byte[] decrypted = new byte[data.Length]; crypto.Read(decrypted, 0, decrypted.Length); } Sure enough, I got exactly the same CryptographicException when trying to decrypt the data even in this simple example. Well, I'm obviously missing something, if I can't even get this single method right! What does the exception message actually mean? What am I missing? Well, after playing around a bit, I discovered the problem was fixed by changing the encryption step to this: // encrypt the data using a CryptoStream using (var encryptor = rij.CreateEncryptor()) using (MemoryStream encryptedStream = new MemoryStream()) { using (CryptoStream crypto = new CryptoStream( encryptedStream, encryptor, CryptoStreamMode.Write)) { crypto.Write(data, 0, data.Length); } encrypted = encryptedStream.ToArray(); } Aaaah, so that's what the problem was. The CryptoStream wasn't flushing all it's data to the MemoryStream before it was being read, and closing the stream causes it to flush everything to the backing stream. But why does this cause an error in padding? Cryptographic padding All symmetric encryption algorithms (of which Rijndael is one) operates on fixed block sizes. For Rijndael, the default block size is 16 bytes. This means the input needs to be a multiple of 16 bytes long. If it isn't, then the input is padded to 16 bytes using one of the padding modes. This is only done to the final block of data to be encrypted. CryptoStream has a special method to flush this final block of data - FlushFinalBlock. Calling Stream.Flush() does not flush the final block, as you might expect. Only by closing the stream or explicitly calling FlushFinalBlock is the final block, with any padding, encrypted and written to the backing stream. Without this call, the encrypted data is 16 bytes shorter than it should be. If this final block wasn't written, then the decryption gets to the final 16 bytes of the encrypted data and tries to decrypt it as the final block with padding. The end bytes don't match the padding scheme it's been told to use, therefore it throws an exception stating what is wrong - what the decryptor expects to be padding actually isn't, and so can't be removed from the stream. So, as well as closing the stream before reading the result, an alternative fix to my encryption code is the following: // encrypt the data using a CryptoStream using (var encryptor = rij.CreateEncryptor()) using (MemoryStream encryptedStream = new MemoryStream()) using (CryptoStream crypto = new CryptoStream( encryptedStream, encryptor, CryptoStreamMode.Write)) { crypto.Write(data, 0, data.Length); // explicitly flush the final block of data crypto.FlushFinalBlock(); encrypted = encryptedStream.ToArray(); } Conclusion So, if your padding is invalid, make sure that you close or call FlushFinalBlock on any CryptoStream performing encryption before you access the encrypted data. Flush isn't enough. Only then will the final block be present in the encrypted data, allowing it to be decrypted successfully.

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• Help with Strategy-game AI

  - by f20k

  Hi, I am developing a strategy-game AI (think: Final Fantasy Tactics), and I am having trouble coming up for the design of the AI. My main problem is determining which is the optimal thing for it to do. First let me describe the priority of what action I would like the AI to take: Kill nearest player unit Fulfill primary directive (kill all player units, kill target unit, survive for x turns) Heal ally unit / cast buffer Now the AI can do the following in its turn: Move - {Attack / Ability / Item} (either attack or ability or item) {Attack / Ability / Item} - Move Move closer (if targets not in range) {Attack / Ability / Item} (if move not available) Notes Abilities have various ranges / effects / costs / effects. Each ai unit has maybe 5-10 abilities to choose from. The AI will prioritize killing over safety unless its directive is to survive for x turns. It also doesn't care about ability cost much. While a player may want to save a big spell for later, the AI will most likely use it asap. Movement is on a (hex) grid num of player units: 3-6 num of ai units: 3-7 or more. Probably max 10. AI and player take turns controlling ONE unit, instead of all at the same time. Platform is Android (if program doesnt respond after some time, there will be a popup saying to Force Quit or Wait - which looks really bad!). Now comes the questions: The best ability to use would obviously be the one that hits the most targets for the most damage. But since each ability has different ranges, I won't know if they are in range without exploring each possible place I can move to. One solution would be to go through each possible places to move to, determine the optimal attack at that location - which gives me a list of optimal moves for each location. Then choose the optimal out of the list and execute it. But this will take a lot of CPU time. Is there a better solution? My current idea is to move as close as possible towards the closest, largest group of people, and determine the optimal attack/ability from there. I think this would be a lot less work for the CPU and still allow for wide-range attacks. Its sub-optimal but the AI will still seem 'smart'. Other notes/questions: Am I over-thinking/over-complicating it? Better solution? I am open to all sorts of suggestions I have taken a look at the spell-casting question, but it doesn't take into account the movement - so perhaps use that algo for each possible move location? The top answer mentioned it wasn't great for area-of-effect and group fights - so maybe requires more tweaking? Please, if you mention a graph/tree, let me know basically how to use it. E.g. Node means ability, level corresponds to damage, then search for the deepest node.

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• Big-name School for Undergrad Students

  - by itaiferber

  As a soon-to-be graduating high school senior in the U.S., I'm going to be facing a tough decision in a few months: which college should I go to? Will it be worth it to go to Cornell or Stanford or Carnegie Mellon (assuming I get in, of course) to get a big-name computer science degree, internships, and connections with professors, while taking on massive debt; or am I better off going to SUNY Binghamton (probably the best state school in New York) and still get a pretty decent education while saving myself from over a hundred-thousand dollars worth of debt? Yes, I know questions like this has been asked before (namely here and here), but please bear with me because I haven't found an answer that fits my particular situation. I've read the two linked questions above in depth, but they haven't answered what I want to know: Yes, I understand that going to a big-name college can potentially get me connected with some wonderful professors and leaders in the field, but on average, how does that translate financially? I mean, will good connections pay off so well that I'd be easily getting rid of over a hundred-thousand dollars of debt? And how does the fact that I can get a fifth-years master's degree at Carnegie Mellon play into the equation? Will the higher degree right off the bat help me get a better-paying job just out of college, or will the extra year only put me further into debt? Not having to go to graduate school to get a comparable degree will, of course, be a great financial relief, but will getting it so early give it any greater worth? And if I go to SUNY Binghamton, which is far lesser-known than what I've considered (although if there are any alumni out there who want to share their experience, I would greatly appreciate it), would I be closing off doors that would potentially offset my short-term economic gain with long-term benefits? Essentially, is the short-term benefit overweighed by a potential long-term loss? The answers to these questions all tie in to my final college decision (again, permitting I make it to these schools), so I hope that asking the skilled and knowledgeable people of the field will help me make the right choice (if there is such a thing). Also, please note: I'm in a rather peculiar situation where I can't pay for college without taking out a bunch of loans, but will be getting little to no financial aid (likely federal or otherwise). I don't want to elaborate on this too much (so take it at face value), but this is mainly the reason I'm asking the question. Thanks a lot! It means a lot to me.

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