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• Package system broken - E: Sub-process /usr/bin/dpkg returned an error code (1)

  - by delha

  After installing some packages and libraries I have an error on Package Manager, I can't run any update because it says: "The package system is broken If you are using third party repositories then disable them, since they are a common source of problems. Now run the following command in a terminal: apt-get install -f " I've tried to do what it says and it returns me: jara@jara-Aspire-5738:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required: libcaca-dev libopencv2.3-bin nite-dev python-bluez ps-engine libslang2-dev python-sphinx ros-electric-geometry-tutorials ros-electric-geometry-visualization python-matplotlib libzzip-dev ros-electric-orocos-kinematics-dynamics ros-electric-physics-ode libbluetooth-dev libaudiofile-dev libassimp2 libnetpbm10-dev ros-electric-laser-pipeline python-epydoc ros-electric-geometry-experimental libasound2-dev evtest python-matplotlib-data libyaml-dev ros-electric-bullet ros-electric-executive-smach ros-electric-documentation libgl2ps0 libncurses5-dev ros-electric-robot-model texlive-fonts-recommended python-lxml libwxgtk2.8-dev daemontools libxxf86vm-dev libqhull-dev libavahi-client-dev ros-electric-geometry libgl2ps-dev libcurl4-openssl-dev assimp-dev libusb-1.0-0-dev libopencv2.3 ros-electric-diagnostics-monitors libsdl1.2-dev libjs-underscore libsdl-image1.2 tipa libusb-dev libtinfo-dev python-tz python-sip libfltk1.1 libesd0 libfreeimage-dev ros-electric-visualization x11proto-xf86vidmode-dev python-docutils libvtk5.6 ros-electric-assimp x11proto-scrnsaver-dev libnetcdf-dev libidn11-dev libeigen3-dev joystick libhdf5-serial-1.8.4 ros-electric-joystick-drivers texlive-fonts-recommended-doc esound-common libesd0-dev tcl8.5-dev ros-electric-multimaster-experimental ros-electric-rx libaudio-dev ros-electric-ros-tutorials libwxbase2.8-dev ros-electric-visualization-common python-sip-dev ros-electric-visualization-tutorials libfltk1.1-dev libpulse-dev libnetpbm10 python-markupsafe openni-dev tk8.5-dev wx2.8-headers freeglut3-dev libavahi-common-dev python-roman python-jinja2 ros-electric-robot-model-visualization libxss-dev libqhull5 libaa1-dev ros-electric-eigen freeglut3 ros-electric-executive-smach-visualization ros-electric-common-tutorials ros-electric-robot-model-tutorials libnetcdf6 libjs-sphinxdoc python-pyparsing libaudiofile0 Use 'apt-get autoremove' to remove them. The following extra packages will be installed: libcv-dev The following NEW packages will be installed libcv-dev 0 upgraded, 1 newly installed, 0 to remove and 4 not upgraded. 2 not fully installed or removed. Need to get 0 B/3,114 kB of archives. After this operation, 11.1 MB of additional disk space will be used. Do you want to continue [Y/n]? y (Reading database ... 261801 files and directories currently installed.) Unpacking libcv-dev (from .../libcv-dev_2.1.0-7build1_amd64.deb) ... dpkg: error processing /var/cache/apt/archives/libcv-dev_2.1.0-7build1_amd64.deb (-- unpack): trying to overwrite '/usr/bin/opencv_haartraining', which is also in package libopencv2.3-bin 2.3.1+svn6514+branch23-12~oneiric dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/libcv-dev_2.1.0-7build1_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) I've tried everything people recommend on internet like: sudo apt-get clean sudo apt-get autoremove sudo apt-get update sudo apt-get upgrade sudo apt-get -f install Also I've tried to install the synaptic manager but it doesn't let me install anything.. As you can see nothing works so I'm desperate! I'm using ubuntu 11.10, 64 bits Thanks!!

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• Cocos2d: Changing b2Body x val every frame causes jitter

  - by Joey Green

  So, I have a jumping mechanism similar to what you would see in doodle jump where character jumps and you use the accelerometer to make character change direction left or right. I have a player object with position and a box2d b2Body with position. I'm changing the player X position via the accelerometer and the Y position according to box2d. pseudocode for this is like so -----accelerometer acceleration------ player.position = new X -----world update--------- physicsWorld-step() //this will get me the new Y according to the physics similation //so we keep the bodys Y value but change x to new X according to accelerometer data playerPhysicsBody.position = new pos(player.position.x, keepYval) player.position = playerPhysicsBody.position Now this is simplifying my code, but I'm doing the position conversion back and forth via mult or divide by PTM_. Well, I'm getting a weird jitter effect after I get big jump in acceleration data. So, my questions are: 1) Is this the right approach to have the accelerometer control the x pos and box2d control the y pos and just sync everthing up every frame? 2) Is there some issue with updating a b2body x position every frame? 3) Any idea what might be creating this jitter effect? I've collecting some data while running the game. Pre-body is before I set the x value on the b2Body in my update method after I world-step(). Post of course is afterwards. As you can see there is definitively a pattern. 012-06-19 08:14:13.118 Game[1073:707] pre-body pos 5.518720~24.362963 2012-06-19 08:14:13.120 Game[1073:707] post-body pos 5.060156~24.362963 2012-06-19 08:14:13.131 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.133 Game[1073:707] delta 0.016669 2012-06-19 08:14:13.135 Game[1073:707] pre-body pos 5.060156~24.689455 2012-06-19 08:14:13.137 Game[1073:707] post-body pos 5.502138~24.689455 2012-06-19 08:14:13.148 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.150 Game[1073:707] delta 0.016667 2012-06-19 08:14:13.151 Game[1073:707] pre-body pos 5.502138~25.006948 2012-06-19 08:14:13.153 Game[1073:707] post-body pos 5.043575~25.006948 2012-06-19 08:14:13.165 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.167 Game[1073:707] delta 0.016644 2012-06-19 08:14:13.169 Game[1073:707] pre-body pos 5.043575~25.315441 2012-06-19 08:14:13.170 Game[1073:707] post-body pos 5.485580~25.315441 2012-06-19 08:14:13.180 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.182 Game[1073:707] delta 0.016895 2012-06-19 08:14:13.185 Game[1073:707] pre-body pos 5.485580~25.614935 2012-06-19 08:14:13.188 Game[1073:707] post-body pos 5.026768~25.614935 2012-06-19 08:14:13.198 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.199 Game[1073:707] delta 0.016454 2012-06-19 08:14:13.207 Game[1073:707] pre-body pos 5.026768~25.905428 2012-06-19 08:14:13.211 Game[1073:707] post-body pos 5.469213~25.905428 2012-06-19 08:14:13.217 Game[1073:707] acceleration x -0.137421 2012-06-19 08:14:13.223 Game[1073:707] player velocity x: -65.022644 2012-06-19 08:14:13.229 Game[1073:707] delta 0.016603

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• Space partitioning when everything is moving

  - by Roy T.

  Background Together with a friend I'm working on a 2D game that is set in space. To make it as immersive and interactive as possible we want there to be thousands of objects freely floating around, some clustered together, others adrift in empty space. Challenge To unburden the rendering and physics engine we need to implement some sort of spatial partitioning. There are two challenges we have to overcome. The first challenge is that everything is moving so reconstructing/updating the data structure has to be extremely cheap since it will have to be done every frame. The second challenge is the distribution of objects, as said before there might be clusters of objects together and vast bits of empty space and to make it even worse there is no boundary to space. Existing technologies I've looked at existing techniques like BSP-Trees, QuadTrees, kd-Trees and even R-Trees but as far as I can tell these data structures aren't a perfect fit since updating a lot of objects that have moved to other cells is relatively expensive. What I've tried I made the decision that I need a data structure that is more geared toward rapid insertion/update than on giving back the least amount of possible hits given a query. For that purpose I made the cells implicit so each object, given it's position, can calculate in which cell(s) it should be. Then I use a HashMap that maps cell-coordinates to an ArrayList (the contents of the cell). This works fairly well since there is no memory lost on 'empty' cells and its easy to calculate which cells to inspect. However creating all those ArrayLists (worst case N) is expensive and so is growing the HashMap a lot of times (although that is slightly mitigated by giving it a large initial capacity). Problem OK so this works but still isn't very fast. Now I can try to micro-optimize the JAVA code. However I'm not expecting too much of that since the profiler tells me that most time is spent in creating all those objects that I use to store the cells. I'm hoping that there are some other tricks/algorithms out there that make this a lot faster so here is what my ideal data structure looks like: The number one priority is fast updating/reconstructing of the entire data structure Its less important to finely divide the objects into equally sized bins, we can draw a few extra objects and do a few extra collision checks if that means that updating is a little bit faster Memory is not really important (PC game)

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• Career Advice: finding challenging work in software and web development

  - by dianovich

  Having left my physics degree early, I started out in the realm of web design / front end web development and was able to get work quite quickly. I moved on to spend a chunk of my time on servers and gained experience with frameworks like Wordpress and Drupal, then the likes of Codeigniter and CakePHP and became comfortable in Debian-based and RHEL/CentOS environments. I ventured in to iOS development and published a couple of native apps to the app store too! I have started to spend a good deal of my time writing Python and have invested a little time in Django. The problem is, I still spend a fair chunk of my time doing more front end web development (writing markup and CSS for site themes, design-lead JavaScript, small applications for which application architecture and software engineering are relatively unimportant or too time consuming to invest in) in my job. What I want to do is really exercise the systematic/logical portion of my brain and tackle challenging problems on a daily basis. I want to have to care about big-oh running times, modularity in software, DRY, performance tuning and development methodologies. I want to work for a firm whose clients say: "Yes, these things are important to us and we'll pay you to get them right." But it is difficult: I have no formal training and am potentially becoming a jack of all trades. Not that being a jack of many trades is necessarily a bad thing, but the scope of work I find myself involved in is far too broad. And, there are only so many hours in a day outside of work! My question is: where do I go from here? I am starting to work on a few open source projects and have started to publish content to my blog. But this isn't likely to make it past the recruitment consultants and HR departments of many-a-firm. And I do not, for example, work in a team that practices agile methodologies, so how do I get work in such a team to gain experience? While I have been responsible for implementing version control and some solid working practices into our current environment, there is only so far I can go in this context. What would convince you that i'm worth taking a risk? What would convince you that i'll have caught up the other guys in your employ in next to no time?

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• Game Review: God of Light

  Luckily I came across this title at a very early stage. If I remember correctly, I took notice of God of Light on Twitter right on the weekend it has been published on the Play Store. "Sit back and become immersed into the world of God of Light, the game that rethinks the physics puzzle genre with its unique environment exploration gameplay, amazing graphics and exclusive soundtrack created by electronic music icon UNKLE. Join cute game mascot, Shiny, on his way to saving the universe from the impending darkness. Play through a variety of exciting game worlds and dozens of levels with mind-blowing puzzles. Your goal is to explore game levels, seek for game objects that reflect, split, combine, paint, bend and teleport rays of light energy to activate the Sources of Life and bring light back to the universe." Mastering the various reflection items in God of Light is very easy to learn and new elements are introduced during the game. Amazing puzzle game Here's the initial review I posted on the Play Store: "Great change in puzzles Fantastic and refreshing concept of puzzle solving. The effects and the music match very well, putting the player in the right mood to game. Get enlightened and grow your skills until you are a true God of Light." And it remains true, even after completing the first realm completely. Similar to Quell it took me only a couple of hours during the evening to complete all levels in the available three realms, unfortunately. God of Light currently consists of 75 levels, well it's 25 in each realm to be precise, and the challenges are increasing. Compared to the iOS version from the AppStore, God of Light is available for free on Android - at least the first realm (25 levels). Unlocking the other two remaining realms is done through an in-app purchase. The visual appearance, the sound effects and the background music provided by UNKLE makes God of Light a superb package for any puzzle gamer. Whether it is simply reflecting light over multiple mirrors, or later on bending the rays of light with black holes, or using prisms to either split, enforce, or colourise your beam, God of Light is great fun and offers a good amount of joy. Check out the following screenshots for some impressions. God of Light: Astonishing graphics and visual appeal throughout the game God of Light - Introduction to the game during the first levels. New light items are introduced at each stage during the game play God of Light: Increasing complexity and puzzle fun Hopefully, Playmous is going to provide more astonishing looking realms and interesting gimmicks in future versions. Play Store: God of Light Also, check out the latest game updates on the official web site of Playmous

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• Smooth animation when using fixed time step

  - by sythical

  I'm trying to implement the game loop where the physics is independent from rendering but my animation isn't as smooth as I would like it to be and it seems to periodically jump. Here is my code: // alpha is used for interpolation double alpha = 0, counter_old_time = 0; double accumulator = 0, delta_time = 0, current_time = 0, previous_time = 0; unsigned frame_counter = 0, current_fps = 0; const unsigned physics_rate = 40, max_step_count = 5; const double step_duration = 1.0 / 40.0, accumulator_max = step_duration * 5; // information about the circ;e (position and velocity) int old_pos_x = 100, new_pos_x = 100, render_pos_x = 100, velocity_x = 60; previous_time = al_get_time(); while(true) { current_time = al_get_time(); delta_time = current_time - previous_time; previous_time = current_time; accumulator += delta_time; if(accumulator > accumulator_max) { accumulator = accumulator_max; } while(accumulator >= step_duration) { if(new_pos_x > 1330) velocity_x = -15; else if(new_pos_x < 70) velocity_x = 15; old_pos_x = new_pos_x; new_pos_x += velocity_x; accumulator -= step_duration; } alpha = accumulator / static_cast<double>(step_duration); render_pos_x = old_pos_x + (new_pos_x - old_pos_x) * alpha; al_clear_to_color(al_map_rgb(20, 20, 40)); // clears the screen al_draw_textf(font, al_map_rgb(255, 255, 255), 20, 20, 0, "current_fps: %i", current_fps); // print fps al_draw_filled_circle(render_pos_x, 400, 15, al_map_rgb(255, 255, 255)); // draw circle // I've added this to test how the program will behave when rendering takes // considerably longer than updating the game. al_rest(0.008); al_flip_display(); // swaps the buffers frame_counter++; if(al_get_time() - counter_old_time >= 1) { current_fps = frame_counter; frame_counter = 0; counter_old_time = al_get_time(); } } I have added a pause during the rendering part because I wanted to see how the code would behave when a lot of rendering is involved. Removing it makes the animation smooth but then I'll have to make sure that I don't let the frame rate drop too much and that doesn't seem like a good solution. I've been trying to fix this for a week and have had no luck so I'd be very grateful if someone can read through my code. Thank you! Edit: I added the following code to work out the actual velocity (pixels per second) of the ball each time the ball is rendered and surprisingly it's not constant so I'm guessing that's the issue. I'm not sure why it's not constant. alpha = accumulator / static_cast<double>(step_duration); render_pos_x = old_pos_x + (new_pos_x - old_pos_x) * alpha; cout << (render_pos_x - old_render_pos) / delta_time << endl; old_render_pos = render_pos_x;

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• How do I import my first sprites?

  - by steven_desu

  Continuing from this question (new question - now unrelated) So I have a thorough background in programming already (algorithms, math, logic, graphing problems, etc.) however I've never attempted to code a game before. In fact, I've never had anything more than minimal input from a user during the execution of a program. Generally input was given from a file or passed through console, all necessary functions were performed, then the program terminated with an output. I decided to try and get in on the world of game development. From several posts I've seen around gamedev.stackexchange.com XNA seems to be a favorite, and it was recommended to me when I asked where to start. I've downloaded and installed Visual Studio 2010 along with the XNA Framework and now I can't seem to get moving in the right direction. I started out looking on Google for "xna game studio tutorial", "xna game development beginners", "my first xna game", etc. I found lots of crap. The official "Introduction to Game Studio 4.0" gave me this (plus my own train of thought happily pasted on top thanks to MSPaint): http://tinypic.com/r/2w1sgvq/7 The "Get Additional Help" link (my best guess, since there was no "Continue" or "Next" link) lead me to this page: http://tinypic.com/r/2qa0dgx/7 I tried every page. The forum was the only thing that seemed helpful, however searching for "beginner", "newbie", "getting started", "first project", and similar on the forums turned up many threads with specific questions that are a bit above my level ("beginner to collision detection", for instance) Disappointed I returned to the XNA Game Studio home page. Surely their own website would have some introduction, tutorial, or at least a useful link to a community. EVERYTHING on their website was about coding Windows Phone 7.... Everything. http://tinypic.com/r/10eit8i/7 http://tinypic.com/r/120m9gl/7 Giving up on any official documentation after a while, I went back to Google. I managed to locate www.xnadevelopment.com. The website is built around XNA Game Studio 3.0, but how different can 3.0 be from 4.0?.... Apparently different enough. http://tinypic.com/r/5d8mk9/7 http://tinypic.com/r/25hflli/7 Figuring that this was the correct folder, I right-clicked.... http://tinypic.com/r/24o94yu/7 Hmm... maybe by "Add Content Reference" they mean "Add a reference to an existing file (content)"? Let's try it (after all- it's my only option) http://tinypic.com/r/2417eqt/7 At this point I gave up. I'm back. My original goal in my last question was to create a keyboard-navigable 3D world (no physics necessary, no logic or real game necessary). After my recent failures my goal has been revised. I want to display an image on the screen. Hopefully in time I'll be able to move it with the keyboard.

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• Suggestions for getting an open source electron beam tracking code going

  - by Boaz

  I work in the field of accelerator physics and synchrotron radiation. High energy electrons circulating in large rings of magnets produce x-rays that are used for a variety of different kinds of science. Running and improving these facilities requires controlling and modelling the electron beam as it circulates in the ring. A code to model this basically requires trackers to follow the electrons through the elements (something called a symplectic integrator), and then the computation of different parameters associated with this motion. The problem with these codes is that every facility has there own. In principle the code is not so complex. And as a modelling project, one might think it has some general interest. Who doesn't want to be able to create a track in space out of magnets and watch the electrons circulate? There is a Matlab based code to do this called Accelerator Toolbox, but the creator of the code is no longer in the field. I put the code in Sourceforge under the name atcollab. The basic resource is in C- it is the set of symplectic integrators. These are available in the atcollab code here. It has been useful to put the code on Sourceforge in order to exchange code, but the community of users is quite small and most are too busy to put that much time into collaboration. So in terms of really improving the code, I don't think it has been so successful. Any piece of this picture could be recreated without that much difficulty, but overall it is a bit complex, and because each lab has their own installation with lots of add-on Matlab code, people find it hard to really work together and share code. Somehow I think we need to involve a wider community in our development, or just use some standard tools. But for that, I suppose it needs to be of some general interest. I think symplectic integrators may have some general interest. And the part about a plug-in architecture to build up the ring ought to fit other patterns. Or the other option is to just accept that this is not a problem of general interest, and work harder within our small community. Suggestions, or anecdotes of analogous experience would be appreciated.

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• Register Game Object Components in Game Subsystems? (Component-based Game Object design)

  - by topright

  I'm creating a component-based game object system. Some tips: GameObject is simply a list of Components. There are GameSubsystems. For example, rendering, physics etc. Each GameSubsystem contains pointers to some of Components. GameSubsystem is a very powerful and flexible abstraction: it represents any slice (or aspect) of the game world. There is a need in a mechanism of registering Components in GameSubsystems (when GameObject is created and composed). There are 4 approaches: 1: Chain of responsibility pattern. Every Component is offered to every GameSubsystem. GameSubsystem makes a decision which Components to register (and how to organize them). For example, GameSubsystemRender can register Renderable Components. pro. Components know nothing about how they are used. Low coupling. A. We can add new GameSubsystem. For example, let's add GameSubsystemTitles that registers all ComponentTitle and guarantees that every title is unique and provides interface to quering objects by title. Of course, ComponentTitle should not be rewrited or inherited in this case. B. We can reorganize existing GameSubsystems. For example, GameSubsystemAudio, GameSubsystemRender, GameSubsystemParticleEmmiter can be merged into GameSubsystemSpatial (to place all audio, emmiter, render Components in the same hierarchy and use parent-relative transforms). con. Every-to-every check. Very innefficient. con. Subsystems know about Components. 2: Each Subsystem searches for Components of specific types. pro. Better performance than in Approach 1. con. Subsystems still know about Components. 3: Component registers itself in GameSubsystem(s). We know at compile-time that there is a GameSubsystemRenderer, so let's ComponentImageRender will call something like GameSubsystemRenderer::register(ComponentRenderBase*). pro. Performance. No unnecessary checks as in Approach 1. con. Components are badly coupled with GameSubsystems. 4: Mediator pattern. GameState (that contains GameSubsystems) can implement registerComponent(Component*). pro. Components and GameSubystems know nothing about each other. con. In C++ it would look like ugly and slow typeid-switch. Questions: Which approach is better and mostly used in component-based design? What Practice says? Any suggestions about implementation of Approach 4? Thank you.

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• What are some good realistic programming related movies (docu-dramas, documentaries, accurate fiction, etc)?

  - by EpsilonVector

  A while ago I asked this question and the result was this. Following the response I got in the meta question I'm re-asking the question with new guidelines to focus it on the direction I wanted it to have originally. ================================================================== The guidelines are as follows: by "programming related" I mean movies from which we can learn about stuff like the development process, or history of software/computers, or programming culture. In other words, they must be grounded in the industry. No tangential stuff. Good entries answer as many of the following criteria as possible: Teach you about the history of the industry, or the development process, or teach you about important industry related topics (software patents for example) Are based on real life events, companies, people, practices, and they are the main focus of the movie After watching them, you feel like you understand or know something about the programmers' world that you didn't before (or you can see how someone could have such a response). You can point to it and say "this faithfully represents the industry/programmer culture at some point in time". This might be something you would show laymen to explain to them what "your people" are like and what is it that you do. Examples for good entries include: Pirates of Silicon Valley- the story of how Microsoft and Apple started the industry. Revolution OS- The story of Linux's rise to fame, and a pretty good cover of the Free Software/Open Source world. Aardvark'd: 12 Weeks with Geeks- development process. Examples for bad entries: Movies who's sole relevance is that they can be appreciated by programmers. The point of this question is not to be "what are some good movies" with "for a programmer" appended to it. Just because the writers got a few computer jokes right in itself doesn't make it about the industry. Movies where there's a computer related element, but are not about the industry. For example, 24 (the TV series). It's a product of the information age but it isn't actually about it. Another example is movies where there's a really cool programmer character, but are overall about something completely different. Likewise, The Big Bang Theory is not about physics, even though they have a cool physicist as a character. Science fiction, even if it draws ideas from computers. For example, the Matrix trilogy. Movies that you can't point to them and say: this is a faithful representation of our world (at some point in time). If you can't do that then it doesn't mirror the industry. Keep it one entry per answer so that the voting could sort the entries out.

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• design a model for a system of dependent variables

  - by dbaseman

  I'm dealing with a modeling system (financial) that has dozens of variables. Some of the variables are independent, and function as inputs to the system; most of them are calculated from other variables (independent and calculated) in the system. What I'm looking for is a clean, elegant way to: define the function of each dependent variable in the system trigger a re-calculation, whenever a variable changes, of the variables that depend on it A naive way to do this would be to write a single class that implements INotifyPropertyChanged, and uses a massive case statement that lists out all the variable names x1, x2, ... xn on which others depend, and, whenever a variable xi changes, triggers a recalculation of each of that variable's dependencies. I feel that this naive approach is flawed, and that there must be a cleaner way. I started down the path of defining a CalculationManager<TModel> class, which would be used (in a simple example) something like as follows: public class Model : INotifyPropertyChanged { private CalculationManager<Model> _calculationManager = new CalculationManager<Model>(); // each setter triggers a "PropertyChanged" event public double? Height { get; set; } public double? Weight { get; set; } public double? BMI { get; set; } public Model() { _calculationManager.DefineDependency<double?>( forProperty: model => model.BMI, usingCalculation: (height, weight) => weight / Math.Pow(height, 2), withInputs: model => model.Height, model.Weight); } // INotifyPropertyChanged implementation here } I won't reproduce CalculationManager<TModel> here, but the basic idea is that it sets up a dependency map, listens for PropertyChanged events, and updates dependent properties as needed. I still feel that I'm missing something major here, and that this isn't the right approach: the (mis)use of INotifyPropertyChanged seems to me like a code smell the withInputs parameter is defined as params Expression<Func<TModel, T>>[] args, which means that the argument list of usingCalculation is not checked at compile time the argument list (weight, height) is redundantly defined in both usingCalculation and withInputs I am sure that this kind of system of dependent variables must be common in computational mathematics, physics, finance, and other fields. Does someone know of an established set of ideas that deal with what I'm grasping at here? Would this be a suitable application for a functional language like F#? Edit More context: The model currently exists in an Excel spreadsheet, and is being migrated to a C# application. It is run on-demand, and the variables can be modified by the user from the application's UI. Its purpose is to retrieve variables that the business is interested in, given current inputs from the markets, and model parameters set by the business.

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• Why does creating dynamic bodies in JBox2D freeze my app?

  - by Amplify91

  My game hangs/freezes when I create dynamic bullet objects with Box2D and I don't know why. I am making a game where the main character can shoot bullets by the user tapping on the screen. Each touch event spawns a new FireProjectileEvent that is handled properly by an event queue. So I know my problem is not trying to create a new body while the box2d world is locked. My bullets are then created and managed by an object pool class like this: public Projectile getProjectile(){ for(int i=0;i<mProjectiles.size();i++){ if(!mProjectiles.get(i).isActive){ return mProjectiles.get(i); } } return mSpriteFactory.createProjectile(); } mSpriteFactory.createProjectile() leads to the physics component of the Projectile class creating its box2d body. I have narrowed the issue down to this method and it looks like this: public void create(World world, float x, float y, Vec2 vertices[], boolean dynamic){ BodyDef bodyDef = new BodyDef(); if(dynamic){ bodyDef.type = BodyType.DYNAMIC; }else{ bodyDef.type = BodyType.STATIC; } bodyDef.position.set(x, y); mBody = world.createBody(bodyDef); PolygonShape dynamicBox = new PolygonShape(); dynamicBox.set(vertices, vertices.length); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = dynamicBox; fixtureDef.density = 1.0f; fixtureDef.friction = 0.0f; mBody.createFixture(fixtureDef); mBody.setFixedRotation(true); } If the dynamic parameter is set to true my game freezes before crashing, but if it is false, it will create a projectile exactly how I want it just doesn't function properly (because a projectile is not a static object). Why does my program fail when I try to create a dynamic object at runtime but not when I create a static one? I have other dynamic objects (like my main character) that work fine. Any help would be greatly appreciated. This is a screenshot of a method profile I did: Especially notable is number 8. I'm just still unsure what I'm doing wrong. Other notes: I am using JBox2D 2.1.2.2. (Upgraded from 2.1.2.1 to try to fix this problem) When the application freezes, if I hit the back button, it appears to move my game backwards by one update tick. Very strange.

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• How to interview a natural scientist for a dev position?

  - by Silas

  I already did some interviews for my company, mostly computer scientists for dev positions but also some testers and project managers. Now I have to fill a vacancy in our research group within the R&D department (side note: “research” means that we try to solve problems in our professional domain/market niche using software in research projects together with universities, other companies, research centres and end user organisations. It’s not computer science research; we’re not going to solve the P=NP problem). Now we invited a guy holding an MSc in chemistry (with a lot of physics in his CV, too), who never had any computer science lesson. I already talked with him about half an hour at a local university’s career days and there’s no doubt the guy is smart. Also his marks are excellent and he graduated with distinction. For his BSc he needed to teach himself programming in Mathematica and told me believably that he liked programming a lot. Also he solved some physical chemistry problem that I probably don’t understand using his own software, implemented in Mathematica, for his MSc thesis. It includes a GUI and a notable size of 8,000 LoC. He seems to be very attracted by what we’re doing in our research group and to be honest it’s quite difficult for an SME like us to get good people. I also am very interested in hiring him since he could assist me in writing project proposals, reports, doing presentations and so on. He would probably fit to our team, too. The only question left is: How can I check if he will get the programming skills he needs to do software implementation in our projects since this will be a significant part of the job? Of course I will ask him what it is, that is fascinating him about programming. I’ll also ask how he proceeded to write his natural science software and how he structured it. I’ll ask about how he managed to obtain the skills and information about software development he needed. But is there something more I could ask? Something more concrete perhaps? Should I ask him to explain his Mathematica solution? To be clear: I’m not looking for knowledge in a particular language or technology stack. We’re a .NET shop in product development but I want to have a free choice for our research projects. So I’m interested in the meta-competence being able to learn whatever is actually needed. I hope this question is answerable and not open-ended since I really like to know if there is a default way to check for the ability to get further programming skills on the job. If something is not clear to you please give me some comments and let me improve my question.

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• Top down space game control problem

  - by Phil

  As the title suggests I'm developing a top down space game. I'm not looking to use newtonian physics with the player controlled ship. I'm trying to achieve a control scheme somewhat similar to that of FlatSpace 2 (awesome game). I can't figure out how to achieve this feeling with keyboard controls as opposed to mouse controls though. Any suggestions? I'm using Unity3d and C# or javaScript (unityScript or whatever is the correct term) works fine if you want to drop some code examples. Edit: Of course I should describe FlatSpace 2's control scheme, sorry. You hold the mouse button down and move the mouse in the direction you want the ship to move in. But it's not the controls I don't know how to do but rather the feeling of a mix of driving a car and flying an aircraft. It's really well made. Youtube link: FlatSpace2 on iPhone I'm not developing an iPhone game but the video shows the principle of the movement style. Edit 2 As there seems to be a slight interest, I'll post the version of the code I've used to continue. It works good enough. Sometimes good enough is sufficient! using UnityEngine; using System.Collections; public class ShipMovement : MonoBehaviour { public float directionModifier; float shipRotationAngle; public float shipRotationSpeed = 0; public double thrustModifier; public double accelerationModifier; public double shipBaseAcceleration = 0; public Vector2 directionVector; public Vector2 accelerationVector = new Vector2(0,0); public Vector2 frictionVector = new Vector2(0,0); public int shipFriction = 0; public Vector2 shipSpeedVector; public Vector2 shipPositionVector; public Vector2 speedCap = new Vector2(0,0); void Update() { directionModifier = -Input.GetAxis("Horizontal"); shipRotationAngle += ( shipRotationSpeed * directionModifier ) * Time.deltaTime; thrustModifier = Input.GetAxis("Vertical"); accelerationModifier = ( ( shipBaseAcceleration * thrustModifier ) ) * Time.deltaTime; directionVector = new Vector2( Mathf.Cos(shipRotationAngle ), Mathf.Sin(shipRotationAngle) ); //accelerationVector = Vector2(directionVector.x * System.Convert.ToDouble(accelerationModifier), directionVector.y * System.Convert.ToDouble(accelerationModifier)); accelerationVector.x = directionVector.x * (float)accelerationModifier; accelerationVector.y = directionVector.y * (float)accelerationModifier; // Set friction based on how "floaty" controls you want shipSpeedVector.x *= 0.9f; //Use a variable here shipSpeedVector.y *= 0.9f; //<-- as well shipSpeedVector += accelerationVector; shipPositionVector += shipSpeedVector; gameObject.transform.position = new Vector3(shipPositionVector.x, 0, shipPositionVector.y); } }

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• Glm Vector Transformations [duplicate]

  - by Reanimation

  This question already has an answer here: Car-like Physics - Basic Maths to Simulate Steering 2 answers I have a cube rendered on the screen which represents a car (or similar). Using Projection/Model matrices and Glm I am able to move it back and fourth along the axes and rotate it left or right. I'm having trouble with the vector mathematics to make the cube move forwards no matter which direction it's current orientation is. (ie. if I would like, if it's rotated right 30degrees, when it's move forwards, it travels along the 30degree angle on a new axes). I hope I've explained that correctly. This is what I've managed to do so far in terms of using glm to move the cube: glm::vec3 vel; //velocity vector void renderMovingCube(){ glUseProgram(movingCubeShader.handle()); GLuint matrixLoc4MovingCube = glGetUniformLocation(movingCubeShader.handle(), "ProjectionMatrix"); glUniformMatrix4fv(matrixLoc4MovingCube, 1, GL_FALSE, &ProjectionMatrix[0][0]); glm::mat4 viewMatrixMovingCube; viewMatrixMovingCube = glm::lookAt(camOrigin, camLookingAt, camNormalXYZ); vel.x = cos(rotX); vel.y=sin(rotX); vel*=moveCube; //move cube ModelViewMatrix = glm::translate(viewMatrixMovingCube,globalPos*vel); //bring ground and cube to bottom of screen ModelViewMatrix = glm::translate(ModelViewMatrix, glm::vec3(0,-48,0)); ModelViewMatrix = glm::rotate(ModelViewMatrix, rotX, glm::vec3(0,1,0)); //manually turn glUniformMatrix4fv(glGetUniformLocation(movingCubeShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader movingCube.render(); //draw glUseProgram(0); } keyboard input: void keyboard() { char BACKWARD = keys['S']; char FORWARD = keys['W']; char ROT_LEFT = keys['A']; char ROT_RIGHT = keys['D']; if (FORWARD) //W - move forwards { globalPos += vel; //globalPos.z -= moveCube; BACKWARD = false; } if (BACKWARD)//S - move backwards { globalPos.z += moveCube; FORWARD = false; } if (ROT_LEFT)//A - turn left { rotX +=0.01f; ROT_LEFT = false; } if (ROT_RIGHT)//D - turn right { rotX -=0.01f; ROT_RIGHT = false; } Where am I going wrong with my vectors? I would like change the direction of the cube (which it does) but then move forwards in that direction.

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• Why are MVC & TDD not employed more in game architecture?

  - by secoif

  I will preface this by saying I haven't looked a huge amount of game source, nor built much in the way of games. But coming from trying to employ 'enterprise' coding practices in web apps, looking at game source code seriously hurts my head: "What is this view logic doing in with business logic? this needs refactoring... so does this, refactor, refactorrr" This worries me as I'm about to start a game project, and I'm not sure whether trying to mvc/tdd the dev process is going to hinder us or help us, as I don't see many game examples that use this or much push for better architectural practices it in the community. The following is an extract from a great article on prototyping games, though to me it seemed exactly the attitude many game devs seem to use when writing production game code: Mistake #4: Building a system, not a game ...if you ever find yourself working on something that isn’t directly moving your forward, stop right there. As programmers, we have a tendency to try to generalize our code, and make it elegant and be able to handle every situation. We find that an itch terribly hard not scratch, but we need to learn how. It took me many years to realize that it’s not about the code, it’s about the game you ship in the end. Don’t write an elegant game component system, skip the editor completely and hardwire the state in code, avoid the data-driven, self-parsing, XML craziness, and just code the damned thing. ... Just get stuff on the screen as quickly as you can. And don’t ever, ever, use the argument “if we take some extra time and do this the right way, we can reuse it in the game”. EVER. is it because games are (mostly) visually oriented so it makes sense that the code will be weighted heavily in the view, thus any benefits from moving stuff out to models/controllers, is fairly minimal, so why bother? I've heard the argument that MVC introduces a performance overhead, but this seems to me to be a premature optimisation, and that there'd more important performance issues to tackle before you worry about MVC overheads (eg render pipeline, AI algorithms, datastructure traversal, etc). Same thing regarding TDD. It's not often I see games employing test cases, but perhaps this is due to the design issues above (mixed view/business) and the fact that it's difficult to test visual components, or components that rely on probablistic results (eg operate within physics simulations). Perhaps I'm just looking at the wrong source code, but why do we not see more of these 'enterprise' practices employed in game design? Are games really so different in their requirements, or is a people/culture issue (ie game devs come from a different background and thus have different coding habits)?

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• Android Array Lag?

  - by Mike

  I am making a platform game for Android. It is sort of a tile based game. I added bullets and enemies with AI and a bunch of tile types. I created a simple map with no Enemies. Everything was running well and smooth until I shot a bunch of bullets randomly everywhere. A couple of hundreds of bullets later, the FPS lowered. I made a test to find out if the bullets were the problem so I made another simple map with just a tile to stand on and left it for a while. Minutes later, I played around with it a bit to check if the FPS changed and it didnt. I reloaded the same map and shot a lot of bullets. Minutes later, the FPS was visibly lower even after the number of bullets were zero. Points to note: Programmed FPS is 30 Tested on a Samsung Galaxy Y and Samsung Galaxy W Any tile, enemy, bullet that is off screen is not drawn to prevent lag Bullets collide with Tiles (if they dont collide with in 450 frames, they are removed from the array) I used List bullets = new ListArray(); I used bullets.add(new Bullet(x, y, params...)); I used for(...){ if(...){ bullets.remove(i); } } Code for bullet: private void drawBullets(Canvas canvas) { for (int i = 0; i < bullets.size(); i++) { Bullet b = bullets.get(i); b.update(canvas); //updates physics if (b.t > blm) { //if the bullet is past its expiry bullets.remove(i); i--; } else { if (svx((b.x)) > 0 && svx(b.x) < width && svy((b.y)) > 0 && svy(b.y) < height) { // if bullet is not off screen b.draw(canvas); // draw the bullet } } } } I tried searching for solutions and references but I have no luck. I'm guessing that the lag has something to do with the Array and the Bullets or Classes that I've loaded? I'm not sure! Someone please help! Thanks in advance! :)

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• When attaching AI to a vehicle should I define all steps or try Line of Sight?

  - by ThorDivDev

  This problem is related to an intersection simulation I am building for university. I will try to make it as general as possible. I am trying to assign AI to a vehicle using the JMonkeyEngine platform. AIGama_JmonkeyEngine explains that if you wish to create a car that follows a path you can define the path in steps. If there was no physics attached whatsoever then all you need to do is define the x,y,z values of where you want the object to appear in all subsequent steps. I am attaching the vehicleControl that implements jBullet. In this case the author mentions that I would need to define the steering and accelerating behaviors at each step. I was trying to use ghost controls that represented waypoints and when on colliding the car would decide what to do next like stopping at a red light. This didn't work so well. Car doesn't face right. public void update(float tpf) { Vector3f currentPos = aiVehicle.getPhysicsLocation(); Vector3f baseforwardVector = currentPos.clone(); Vector3f forwardVector; Vector3f subsVector; if (currentState == ObjectState.Running) { aiVehicle.accelerate(-800); } else if (currentState == ObjectState.Seeking) { baseforwardVector = baseforwardVector.normalize(); forwardVector = aiVehicle.getForwardVector(baseforwardVector); subsVector = pointToSeek.subtract(currentPos.clone()); System.out.printf("baseforwardVector: %f, %f, %f\n", baseforwardVector.x, baseforwardVector.y, baseforwardVector.z); System.out.printf("subsVector: %f, %f, %f\n", subsVector.x, subsVector.y, subsVector.z); System.out.printf("ForwardVector: %f, %f, %f\n", forwardVector.x, forwardVector.y, forwardVector.z); if (pointToSeek != null && pointToSeek.x + 3 >= currentPos.x && pointToSeek.x - 3 <= currentPos.x) { aiVehicle.steer(0.0f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x > currentPos.x) { aiVehicle.steer(-0.5f); aiVehicle.accelerate(-40); } else if (pointToSeek != null && pointToSeek.x < currentPos.x) { aiVehicle.steer(0.5f); aiVehicle.accelerate(-40); } } else if (currentState == ObjectState.Stopped) { aiVehicle.accelerate(0); aiVehicle.brake(40); } }

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• How to synchronize the ball in a network pong game?

  - by Thaars

  I’m developing a multiplayer network pong game, my first game ever. The current state is, I’ve running the physic engine with the same configurations on the server and the clients. The own paddle movement is predicted and get just confirmed by the authoritative server. Is a difference detected between them, I correct the position at the client by interpolation. The opponent paddle is also interpolated 200ms to 100ms in the past, because the server is broadcasting snapshots every 100ms to each client. So far it works very well, but now I have to simulate the ball and have a problem to understanding the procedure. I’ve read Valve’s (and many other) articles about fast-paced multiplayer several times and understood their approach. Maybe I can compare my ball with their bullets, but their advantage is, the bullets are not visible. When I have to display the ball, and see my paddle in the present, the opponent in the past and the server is somewhere between it, how can I synchronize the ball over all instances and ensure, that it got ever hit by the paddle even if the paddle is fast moving? Currently my ball’s position is simply set by a server update, so it can happen, that the ball bounces back, even if the paddle is some pixel away (because of a delayed server position). Until now I’ve got no synced clock over all instances. I’m sending a client step index with each update to the server. If the server did his job, he sends the snapshot with the last step index of each client back to the clients. Now I’m looking for the stored position at the returned step index and compare them. Do I need a common clock to sync the ball? EDIT: I've tried to sync a common clock for the server and all clients with a timestamp. But I think it's better to use an own stepping instead of a timestamp (so I don't need to calculate with the ping and so on - and the timestamp will never be exact). The physics are running 60 times per second and now I use this for keeping them synchronized. Is that a good way? When the ball gets calculated by each client, the angle after bouncing can differ because of the different position of the paddles (the opponent is 200ms in the past). When the server is sending his ball position, velocity and angle (because he knows the position of each paddle and is authoritative), the ball could be in a very different position because of the different angles after bouncing (because the clients receive the server data after 100ms). How is it possible to interpolate such a huge difference? I posted this question some days ago at stackoverflow, but got no answer yet. Maybe this is the better place for this question.

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• Where can I ask questions that aren't IT questions?

  - by Adam Davis

  Thank you for your confidence in our abilities But have you read this? FAQ We get a lot of interesting technical questions on here, but Server Fault is meant to be first and foremost a resource for system administrators and IT professionals. In other words, Server Fault isn't meant to cater to every computer problem - just those that only exist in or can best be solved in the IT and sysadmin domain Yes, someone here might be able to help you, but you'll find that other forums more focused on your topic can give you a much better answer than a bunch of IT professionals. It's likely that your question will be downvoted, closed, and in some cases marked "offensive." It's not that we hate you, it's just that we like to keep our corn pops separate from our cocoa puffs. In that vein, here are a bunch of other forums where you can get help: (This list contains the top two forums for each category as voted for below.) Programming Stackoverflow Consumer Level Computer Hardware Ars Technica OpenForum Tom's Hardware Forums Computer Software Anandtech Forum Web Design/Hosting/CMS SitePoint Forums Web Hosting Talk Math, Science, Engineering Physics Forums PlanetMath Other/General Ask Metafilter Google Search Mahalo Answers Check out the answers below for even more suggestions! What forums can people go to to ask the questions that are off topic here? Please list only ONE forum per answer so votes can bring the best forums to the top. Return to FAQ Index

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• My IIS server won't serve SSL sites to some browsers

  - by sbleon

  (Update: This is now cross-posted at http://stackoverflow.com/questions/3355000. This is the more appropriate forum, but StackOverflow gets a lot more traffic.) I've got an IIS 6.0 server that won't serve pages over SSL to some browsers. In Webkit-based browsers on OS X 10.6, I can't load pages at all. In MSIE 8 on Windows XP SP3, I can load pages, but it will sometimes hang downloading images or sending POSTs. Working: Firefox 3.6 (OS X + Windows) Chrome (Windows) Partially Working: MSIE 8 (works sometimes, but hangs up, especially on POSTs) Not Working: Chrome 5 (OS X) Safari 5 (OS X) Mobile Safari (iOS 4) On OS X (the easiest platform for me to test on), Chrome and Firefox both negotiate the same TLS Cipher, but Chrome hangs on or after the post-negotiation handshake. Chrome packet capture (via ssldump): 1 1 0.0485 (0.0485) C>S Handshake ClientHello Version 3.1 cipher suites Unknown value 0xc00a Unknown value 0xc009 Unknown value 0xc007 Unknown value 0xc008 Unknown value 0xc013 Unknown value 0xc014 Unknown value 0xc011 Unknown value 0xc012 Unknown value 0xc004 Unknown value 0xc005 Unknown value 0xc002 Unknown value 0xc003 Unknown value 0xc00e Unknown value 0xc00f Unknown value 0xc00c Unknown value 0xc00d Unknown value 0x2f TLS_RSA_WITH_RC4_128_SHA TLS_RSA_WITH_RC4_128_MD5 Unknown value 0x35 TLS_RSA_WITH_3DES_EDE_CBC_SHA Unknown value 0x32 Unknown value 0x33 Unknown value 0x38 Unknown value 0x39 TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA compression methods NULL 1 2 0.3106 (0.2620) S>C Handshake ServerHello Version 3.1 session_id[32]= bb 0e 00 00 7a 7e 07 50 5e 78 48 cf 43 5a f7 4d d2 ed 72 8f ff 1d 9e 74 66 74 03 b3 bb 92 8d eb cipherSuite TLS_RSA_WITH_RC4_128_MD5 compressionMethod NULL Certificate ServerHelloDone 1 3 0.3196 (0.0090) C>S Handshake ClientKeyExchange 1 4 0.3197 (0.0000) C>S ChangeCipherSpec 1 5 0.3197 (0.0000) C>S Handshake [hang, no more data transmitted] Firefox packet capture: 1 1 0.0485 (0.0485) C>S Handshake ClientHello Version 3.1 resume [32]= 14 03 00 00 4e 28 de aa da 7a 25 87 25 32 f3 a7 ae 4c 2d a0 e4 57 cc dd d7 0e d7 82 19 f7 8f b9 cipher suites Unknown value 0xff Unknown value 0xc00a Unknown value 0xc014 Unknown value 0x88 Unknown value 0x87 Unknown value 0x39 Unknown value 0x38 Unknown value 0xc00f Unknown value 0xc005 Unknown value 0x84 Unknown value 0x35 Unknown value 0xc007 Unknown value 0xc009 Unknown value 0xc011 Unknown value 0xc013 Unknown value 0x45 Unknown value 0x44 Unknown value 0x33 Unknown value 0x32 Unknown value 0xc00c Unknown value 0xc00e Unknown value 0xc002 Unknown value 0xc004 Unknown value 0x96 Unknown value 0x41 TLS_RSA_WITH_RC4_128_MD5 TLS_RSA_WITH_RC4_128_SHA Unknown value 0x2f Unknown value 0xc008 Unknown value 0xc012 TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA Unknown value 0xc00d Unknown value 0xc003 Unknown value 0xfeff TLS_RSA_WITH_3DES_EDE_CBC_SHA compression methods NULL 1 2 0.0983 (0.0497) S>C Handshake ServerHello Version 3.1 session_id[32]= 14 03 00 00 4e 28 de aa da 7a 25 87 25 32 f3 a7 ae 4c 2d a0 e4 57 cc dd d7 0e d7 82 19 f7 8f b9 cipherSuite TLS_RSA_WITH_RC4_128_MD5 compressionMethod NULL 1 3 0.0983 (0.0000) S>C ChangeCipherSpec 1 4 0.0983 (0.0000) S>C Handshake 1 5 0.1019 (0.0035) C>S ChangeCipherSpec 1 6 0.1019 (0.0000) C>S Handshake 1 7 0.1019 (0.0000) C>S application_data 1 8 0.2460 (0.1440) S>C application_data 1 9 0.3108 (0.0648) S>C application_data 1 10 0.3650 (0.0542) S>C application_data 1 11 0.4188 (0.0537) S>C application_data 1 12 0.4580 (0.0392) S>C application_data 1 13 0.4831 (0.0251) S>C application_data [etc] Update: Here's a Wireshark capture from the server end. What's going on with those two much-delayed RST packets? Is that just IIS terminating what it perceives as a non-responsive connection? 19 10.129450 67.249.xxx.xxx 10.100.xxx.xx TCP 50653 > https [SYN] Seq=0 Win=65535 Len=0 MSS=1460 WS=3 TSV=699250189 TSER=0 20 10.129517 10.100.xxx.xx 67.249.xxx.xxx TCP https > 50653 [SYN, ACK] Seq=0 Ack=1 Win=16384 Len=0 MSS=1460 WS=0 TSV=0 TSER=0 21 10.168596 67.249.xxx.xxx 10.100.xxx.xx TCP 50653 > https [ACK] Seq=1 Ack=1 Win=524280 Len=0 TSV=699250189 TSER=0 22 10.172950 67.249.xxx.xxx 10.100.xxx.xx TLSv1 Client Hello 23 10.173267 10.100.xxx.xx 67.249.xxx.xxx TCP [TCP segment of a reassembled PDU] 24 10.173297 10.100.xxx.xx 67.249.xxx.xxx TCP [TCP segment of a reassembled PDU] 25 10.385180 67.249.xxx.xxx 10.100.xxx.xx TCP 50653 > https [ACK] Seq=148 Ack=2897 Win=524280 Len=0 TSV=699250191 TSER=163006 26 10.385235 10.100.xxx.xx 67.249.xxx.xxx TLSv1 Server Hello, Certificate, Server Hello Done 27 10.424682 67.249.xxx.xxx 10.100.xxx.xx TCP 50653 > https [ACK] Seq=148 Ack=4215 Win=524280 Len=0 TSV=699250192 TSER=163008 28 10.435245 67.249.xxx.xxx 10.100.xxx.xx TLSv1 Client Key Exchange 29 10.438522 67.249.xxx.xxx 10.100.xxx.xx TLSv1 Change Cipher Spec 30 10.438553 10.100.xxx.xx 67.249.xxx.xxx TCP https > 50653 [ACK] Seq=4215 Ack=421 Win=65115 Len=0 TSV=163008 TSER=699250192 31 10.449036 67.249.xxx.xxx 10.100.xxx.xx TLSv1 Encrypted Handshake Message 32 10.580652 10.100.xxx.xx 67.249.xxx.xxx TCP https > 50653 [ACK] Seq=4215 Ack=458 Win=65078 Len=0 TSV=163010 TSER=699250192 7312 57.315338 10.100.xxx.xx 67.249.xxx.xxx TCP https > 50644 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0 19531 142.316425 10.100.xxx.xx 67.249.xxx.xxx TCP https > 50653 [RST, ACK] Seq=4215 Ack=458 Win=0 Len=0

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• /dev/sda1 not a subset of /dev/sda?

  - by Guillaume Brunerie

  Hi, the first entry of my partition table is: $ sudo hexdump -Cv -n 16 -s 446 /dev/sda 000001be 80 01 01 00 83 fe ff ff 3f 00 00 00 81 1c 20 03 |........?..... .| (-Cv describe the output format, -n 16 asks for 16 bytes and -s 446 skips the first 446 bytes) You can see that my first partition is a primary Linux partition and that this partition begin at sector 63 (see for example here for the structure of the partition table). I would then expect that except for the first 63 sectors and the other partitions, /dev/sda1 and /dev/sda are exactly the same. But this is not the case, the sector #2 of /dev/sda1 is not exactly the same as the sector #65 of /dev/sda (but they are very similar, only 16 bytes are different): $ sudo hexdump -Cv -n 512 -s 65b /dev/sda 00008200 00 20 19 00 90 03 64 00 2d 00 05 00 5a 2f 56 00 |. ....d.-...Z/V.| 00008210 b6 b1 16 00 00 00 00 00 02 00 00 00 02 00 00 00 |................| 00008220 00 80 00 00 00 80 00 00 00 20 00 00 d8 38 ee 4c |......... ...8.L| 00008230 9a 01 ef 4c 05 00 24 00 53 ef 01 00 01 00 00 00 |...L..$.S.......| 00008240 59 23 e9 4c 00 4e ed 00 00 00 00 00 01 00 00 00 |Y#.L.N..........| 00008250 00 00 00 00 0b 00 00 00 00 01 00 00 3c 00 00 00 |............<...| 00008260 42 02 00 00 7b 00 00 00 85 23 eb f2 71 67 44 f5 |B...{....#..qgD.| 00008270 bb 8f 6f f2 3a 59 ff 4d 55 62 75 6e 74 75 00 00 |..o.:Y.MUbuntu..| 00008280 00 00 00 00 00 00 00 00 2f 75 62 75 6e 74 75 00 |......../ubuntu.| 00008290 d8 3c df 5d 00 88 ff ff 52 d0 ef 1d 00 00 00 00 |.<.]....R.......| 000082a0 c0 40 51 b6 00 88 ff ff 00 4e c8 bb 00 88 ff ff |[email protected]......| 000082b0 c0 f6 86 b8 00 88 ff ff 30 2e 0d a0 ff ff ff ff |........0.......| 000082c0 38 3d df 5d 00 88 ff ff 00 00 00 00 00 00 fe 03 |8=.]............| 000082d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000082e0 08 00 00 00 00 00 00 00 00 00 00 00 8a 53 d3 0e |.............S..| 000082f0 7c 7a 43 e4 8b fb ca e0 72 b7 fa c8 01 01 00 00 ||zC.....r.......| 00008300 00 00 00 00 00 00 00 00 16 4c 47 4b 0a f3 03 00 |.........LGK....| 00008310 04 00 00 00 00 00 00 00 00 00 00 00 fe 7f 00 00 |................| 00008320 24 b7 0c 00 fe 7f 00 00 01 00 00 00 22 37 0d 00 |$..........."7..| 00008330 ff 7f 00 00 01 00 00 00 23 37 0d 00 00 00 00 00 |........#7......| 00008340 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 |................| 00008350 00 00 00 00 00 00 00 00 00 00 00 00 1c 00 1c 00 |................| 00008360 01 00 00 00 e9 7f 00 00 00 00 00 00 00 00 00 00 |................| 00008370 00 00 00 00 04 00 00 00 9f 7d bb 00 00 00 00 00 |.........}......| 00008380 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00008390 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000083a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000083b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000083c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000083d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000083e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000083f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| versus $ sudo hexdump -Cv -n 512 -s 2b /dev/sda1 00000400 00 20 19 00 90 03 64 00 2d 00 05 00 5a 2f 56 00 |. ....d.-...Z/V.| 00000410 b6 b1 16 00 00 00 00 00 02 00 00 00 02 00 00 00 |................| 00000420 00 80 00 00 00 80 00 00 00 20 00 00 df 76 ef 4c |......... ...v.L| 00000430 df 76 ef 4c 06 00 24 00 53 ef 01 00 01 00 00 00 |.v.L..$.S.......| 00000440 59 23 e9 4c 00 4e ed 00 00 00 00 00 01 00 00 00 |Y#.L.N..........| 00000450 00 00 00 00 0b 00 00 00 00 01 00 00 3c 00 00 00 |............<...| 00000460 46 02 00 00 7b 00 00 00 85 23 eb f2 71 67 44 f5 |F...{....#..qgD.| 00000470 bb 8f 6f f2 3a 59 ff 4d 55 62 75 6e 74 75 00 00 |..o.:Y.MUbuntu..| 00000480 00 00 00 00 00 00 00 00 2f 75 62 75 6e 74 75 00 |......../ubuntu.| 00000490 d8 3c df 5d 00 88 ff ff 52 d0 ef 1d 00 00 00 00 |.<.]....R.......| 000004a0 c0 40 51 b6 00 88 ff ff 00 4e c8 bb 00 88 ff ff |[email protected]......| 000004b0 c0 f6 86 b8 00 88 ff ff 30 2e 0d a0 ff ff ff ff |........0.......| 000004c0 38 3d df 5d 00 88 ff ff 00 00 00 00 00 00 fe 03 |8=.]............| 000004d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000004e0 08 00 00 00 00 00 00 00 00 00 00 00 8a 53 d3 0e |.............S..| 000004f0 7c 7a 43 e4 8b fb ca e0 72 b7 fa c8 01 01 00 00 ||zC.....r.......| 00000500 00 00 00 00 00 00 00 00 16 4c 47 4b 0a f3 03 00 |.........LGK....| 00000510 04 00 00 00 00 00 00 00 00 00 00 00 fe 7f 00 00 |................| 00000520 24 b7 0c 00 fe 7f 00 00 01 00 00 00 22 37 0d 00 |$..........."7..| 00000530 ff 7f 00 00 01 00 00 00 23 37 0d 00 00 00 00 00 |........#7......| 00000540 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 08 |................| 00000550 00 00 00 00 00 00 00 00 00 00 00 00 1c 00 1c 00 |................| 00000560 01 00 00 00 e9 7f 00 00 00 00 00 00 00 00 00 00 |................| 00000570 00 00 00 00 04 00 00 00 a3 7d bb 00 00 00 00 00 |.........}......| 00000580 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00000590 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000005a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000005b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000005c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000005d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000005e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000005f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| For example in the third line, there is a 8.L in the first hexdump and v.L in the second. Why are there differences?

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• Saving ink when printing?

  - by Walkerneo

  I need a map of the SMC campus, but I'm really sick of running out of ink after printing one thing and then having to pay ridiculous sums of money to buy more ink. The map is here: http://www.smc.edu/campusmap/images/SMC-2D-Map_12-Clr_9-10_crop.jpg I would print in black and white, but I'm wondering if there are any chrome or photoshop extensions, or even websites that transform the image into something more ink-conservative. For example, I don't need the buildings to be a solid color, or the roads to be gray, so it would be a tremendous waste of ink to print it as is. Anyone know anything like I'm talking about?

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• The physical working paradigm of a signal passing on wire.

  - by smwikipedia

  Hi, This may be more a question of physics, so pardon me if there's any inconvenience. When I study computer networks, I often read something like this in order to represent a signal, we place some voltage on one end of the wire and the other end will detect the voltage and thus the signal. So I am wondering how a signal exactly passes through wire? Here's my current understanding based on my formal knowledge about electronics: First we need a close circuit to constrain/hold the electronic field. When we place a voltage at somewhere A of the circuit, electronic field will start to build up within the circuit medium, this process should be as fast as light speed. And as the electronic field is being built up, the electrons within the circuit medium are moved, and thus electronic current occurs, and once the electronic current is strong enough to be detected at somewhere else B on the complete circuit, then B knows about what has happend at A and thus communication between A and B is achieved. The above is only talking about the process of sending a single voltage through wire. If there's a bitstream and we need to send a series of voltages, I am not sure which of the following is true: The 2nd voltage should only be sent from A after the 1st voltage has been detected at B, the time interval is time needed to stimulate the electronic field in the medium and form a detectable electronic current at B. Several different voltages could be sent on wire one by one, different electronic current values will exists along the wire simutaneously and arrive at B successively. I hope I made myself clear and someone else has ever pondered this question. (I tag this question with network cause I don't know if there's a better option.) Thanks, Sam

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• Disable DirectDraw, but still have Direct3D?

  - by GodsBoss

  I have a Windows XP SP3 machine, with up-to-date patches. It has DirectX 9.0c, version number 4.09.00.0904. Can I disable DirectDraw, but have Direct3D still active? I read the Wikipedia articles about DirectDraw and Direct3D, but do not know if I understand them correctly: That is, it contains many commands for 3D rendering; however, since version 8, Direct3D has superseded the old DirectDraw framework and also taken responsibility for the rendering of 2D graphics. Does that mean DirectDraw is now a part of Direct3D? Because I cannot disable DirectDraw without disabling Direct3D, but it works the other way around.

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