Search Results

Search found 5638 results on 226 pages for 'scheduling algorithm'.

Page 174/226 | < Previous Page | 170 171 172 173 174 175 176 177 178 179 180 181  | Next Page >

  • Python Web Applications: What is the way and the method to handle Registrations, Login-Logouts and Cookies? [on hold]

    - by Phil
    I am working on a simple Python web application for learning purposes. I have chosen a very minimalistic and simple framework. I have done a significant amount of research but I couldn't find a source clearly explaining what I need, which is as follows: I would like to learn more about: User registration User Log-ins User Log-outs User auto-logins I have successfully handled items 1 and 3 due to their simple nature. However, I am confused with item 2 (log-ins) and item 4 (auto-logins). When a user enters username and password, and after hashing with salts and matching it in the DB; What information should I store in the cookies in order to keep the user logged in during the session? Do I keep username+password but encrypt them? Both or just password? Do I keep username and a generated key matching their password? If I want the user to be able to auto-login (when they leave and come back to the web page), what information then is kept in the cookies? I don't want to use modules or libraries that handle these things automatically. I want to learn basics and why something is the way it is. I would also like to point out that I do not mind reading anything you might offer on the topic that explains hows and whys. Possibly with algorithm diagrams to show the process. Some information: I know about setting headers, cookies, encryption (up to some level, obviously not an expert!), request objects, SQLAlchemy etc. I don't want any data kept in a single web application server's store. I want multiple app-servers to be handle a user, and whatever needs to be kept on the server to be done with a Postgres/MySQL via SQLAlchemy (I think, this is called stateless?) Thank you.

    Read the article

  • What is a Coding Dojo?

    - by huwyss
    Recently i found out that there is a thing called "coding dojo". The point behind it is that software developers want to have a space to learn new stuff like processes, methods, coding details, languages, and whatnot in an environment without stress. Just for fun. No competition. No results required. No deadlines.Some days ago I joined the Zurich coding dojo. We were three programmers with different backgrounds.We gave ourselves the task to develop a method that takes an input value and returns its prime factors. We did pair programming and every few minutes we switched positions. We used test driven development. The chosen programming language was Ruby.I haven't really done TDD before. It was pretty interesting to see the algorithm develop following the testcases.We started with the first test input=1 then developed the most simple productive program that passed this very first test. Then we added the next test input=2 and implemented the productive code. We kept adding tests and made sure all tests are passed until we had the general solution.When we improved the performance of our code we saw the value of the tests we wrote before. Of course our first performance improvement broke several tests.It was a very interesting experience to see how other developers think and how they work. I will participate at the dojo again and can warmly recommend it to anyone. There are  coding dojos all over the world.Have fun!

    Read the article

  • Asynchrony in C# 5 (Part II)

    - by javarg
    This article is a continuation of the series of asynchronous features included in the new Async CTP preview for next versions of C# and VB. Check out Part I for more information. So, let’s continue with TPL Dataflow: Asynchronous functions TPL Dataflow Task based asynchronous Pattern Part II: TPL Dataflow Definition (by quote of Async CTP doc): “TPL Dataflow (TDF) is a new .NET library for building concurrent applications. It promotes actor/agent-oriented designs through primitives for in-process message passing, dataflow, and pipelining. TDF builds upon the APIs and scheduling infrastructure provided by the Task Parallel Library (TPL) in .NET 4, and integrates with the language support for asynchrony provided by C#, Visual Basic, and F#.” This means: data manipulation processed asynchronously. “TPL Dataflow is focused on providing building blocks for message passing and parallelizing CPU- and I/O-intensive applications”. Data manipulation is another hot area when designing asynchronous and parallel applications: how do you sync data access in a parallel environment? how do you avoid concurrency issues? how do you notify when data is available? how do you control how much data is waiting to be consumed? etc.  Dataflow Blocks TDF provides data and action processing blocks. Imagine having preconfigured data processing pipelines to choose from, depending on the type of behavior you want. The most basic block is the BufferBlock<T>, which provides an storage for some kind of data (instances of <T>). So, let’s review data processing blocks available. Blocks a categorized into three groups: Buffering Blocks Executor Blocks Joining Blocks Think of them as electronic circuitry components :).. 1. BufferBlock<T>: it is a FIFO (First in First Out) queue. You can Post data to it and then Receive it synchronously or asynchronously. It synchronizes data consumption for only one receiver at a time (you can have many receivers but only one will actually process it). 2. BroadcastBlock<T>: same FIFO queue for messages (instances of <T>) but link the receiving event to all consumers (it makes the data available for consumption to N number of consumers). The developer can provide a function to make a copy of the data if necessary. 3. WriteOnceBlock<T>: it stores only one value and once it’s been set, it can never be replaced or overwritten again (immutable after being set). As with BroadcastBlock<T>, all consumers can obtain a copy of the value. 4. ActionBlock<TInput>: this executor block allows us to define an operation to be executed when posting data to the queue. Thus, we must pass in a delegate/lambda when creating the block. Posting data will result in an execution of the delegate for each data in the queue. You could also specify how many parallel executions to allow (degree of parallelism). 5. TransformBlock<TInput, TOutput>: this is an executor block designed to transform each input, that is way it defines an output parameter. It ensures messages are processed and delivered in order. 6. TransformManyBlock<TInput, TOutput>: similar to TransformBlock but produces one or more outputs from each input. 7. BatchBlock<T>: combines N single items into one batch item (it buffers and batches inputs). 8. JoinBlock<T1, T2, …>: it generates tuples from all inputs (it aggregates inputs). Inputs could be of any type you want (T1, T2, etc.). 9. BatchJoinBlock<T1, T2, …>: aggregates tuples of collections. It generates collections for each type of input and then creates a tuple to contain each collection (Tuple<IList<T1>, IList<T2>>). Next time I will show some examples of usage for each TDF block. * Images taken from Microsoft’s Async CTP documentation.

    Read the article

  • How do I get 5.1 surround sound working on an Acer Aspire 5738ZG?

    - by kbargais_LV
    I got a problem with sound. I tried everything but no results. :( I got 3 sound ports. my daemon: # This file is part of PulseAudio. # # PulseAudio is free software; you can redistribute it and/or modify # it under the terms of the GNU Lesser General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # PulseAudio is distributed in the hope that it will be useful, but # WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU # General Public License for more details. # # You should have received a copy of the GNU Lesser General Public License # along with PulseAudio; if not, write to the Free Software # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 # USA. ## Configuration file for the PulseAudio daemon. See pulse-daemon.conf(5) for ## more information. Default values are commented out. Use either ; or # for ## commenting. ; daemonize = no ; fail = yes ; allow-module-loading = yes ; allow-exit = yes ; use-pid-file = yes ; system-instance = no ; local-server-type = user ; enable-shm = yes ; shm-size-bytes = 0 # setting this 0 will use the system-default, usually 64 MiB ; lock-memory = no ; cpu-limit = no ; high-priority = yes ; nice-level = -11 ; realtime-scheduling = yes ; realtime-priority = 5 ; exit-idle-time = 20 ; scache-idle-time = 20 ; dl-search-path = (depends on architecture) ; load-default-script-file = yes ; default-script-file = /etc/pulse/default.pa ; log-target = auto ; log-level = notice ; log-meta = no ; log-time = no ; log-backtrace = 0 resample-method = speex-float-1 ; enable-remixing = yes ; enable-lfe-remixing = no flat-volumes = no ; rlimit-fsize = -1 ; rlimit-data = -1 ; rlimit-stack = -1 ; rlimit-core = -1 ; rlimit-as = -1 ; rlimit-rss = -1 ; rlimit-nproc = -1 ; rlimit-nofile = 256 ; rlimit-memlock = -1 ; rlimit-locks = -1 ; rlimit-sigpending = -1 ; rlimit-msgqueue = -1 ; rlimit-nice = 31 ; rlimit-rtprio = 9 ; rlimit-rttime = 1000000 ; default-sample-format = s16le ; default-sample-rate = 44100 ; default-sample-channels = 6 ; default-channel-map = front-left,front-right default-fragments = 8 default-fragment-size-msec = 10 ; enable-deferred-volume = yes ; deferred-volume-safety-margin-usec = 8000 ; deferred-volume-extra-delay-usec = 0

    Read the article

  • Efficient path-finding in free space

    - by DeadMG
    I've got a game situated in space, and I'd like to issue movement orders, which requires pathfinding. Now, it's my understanding that A* and such mostly apply to trees, and not empty space which does not have pathfinding nodes. I have some obstacles, which are currently expressed as fixed AABBs- that is, there is no unbounded "terrain" obstacle. In addition, I expect most obstacles to be reasonably approximable as cubes or spheres. So I've been thinking of applying a much simpler pathfinding algorithm- that is, simply cast a ray from the current position to the target position, and then I can get a list of obstacles using spatial partitioning relatively quickly. What I'm not so sure about is how to determine the part where the ordered unit manoeuvres around the obstacles. What I've been thinking so far is that I will simply use potential fields- that is, all units will feel a strong repulsive force away from each other and a moderate force towards the desired point. This also has the advantage that to issue group orders, I can simply order a mid-level force towards another entity. But this obviously won't achieve the optimal solution. Will potential fields achieve a reasonable approximation given my parameters, or do I need another solution?

    Read the article

  • Beginners guide to developing optimization software

    - by Florenc
    I am novice in "serious" programming i.e. applications that deal with real-life applications and software projects that go beyond school assignments. My interests include optimization, operations research, algorithms and lately i discovered how much I do like software design/development/engineering. I have already developed some simple desktop applications for some "famous" problems like TSP using heuristc approaches, a VRP solver (in progress) and so on. While developing this kind of software I actually used basic concepts taught at school such as object-orientation analysis and design. But, I found these courses rather elementary and quite boring (for my expectations). So I decided to go a little further and start developing "real" software (and this is where I realized how important and interesting software engineering/design is.) Now, here's my issue: I can not find a "study guide" for developing software of this kind. Currently, there are numerous resources out there (books, websites, tutorials) in designing and developing complex IS, web applications, smartphone apps but I can't find a book for example entitled "optimization software development". Definetly, someone could claim that "design patterns apply to software in general" but that's not my point. My point is that I could simply use my imagination for "simple" implementations, but what happens, when my imagination can not go further? In other words I'm looking for a guide/path to bridge the gap between: Mathematics-Algorithm Design-Software Engineering-Optimization-Software development

    Read the article

  • Ubuntu-Java Installation-Topcoder-“Java not found”

    - by hakuna121
    I realized that this might be the dumbest question here, but being a total beginner as I am, I really couldn't figure it out after trying all kinds of instructions I could found on the web. Specs: Ubuntu 13.04; What I intended to do: check out the Algorithm Competition section, by clicking the second-to-left tab,located on the top-left of the page: http://community.topcoder.com/tc What I got: a pop-up saying Java not found! Java could not be automatically detected on your machine. This page will attempt to automatically install Java and Java Web Start. If the download and installation does not occur automatically, click the link below to go to the Sun website where you can download the latest version of Java. What I did: I followed instructions on this Ubuntu Documentation page: https://help.ubuntu.com/community/Java and installed OpenJDK(Java Runtime Environment/Browser plugin/SDK) through Ubuntu Software Center. Then I rebooted the system, tried the page again. But I still got the java not found pop-up described above. Question: What's missing the get this working? Thank you!

    Read the article

  • How does the new google maps make buildings and cityscapes 3D?

    - by Aerovistae
    Anyone who's seen the new Google maps has no doubt taken note of the incredible amount of three-dimensional detail in select American cities such as Boston, New York, Chicago, and San Francisco. They've even modeled the trees, bridges and some of the boats in the harbor! Minor architectural details are present. It's crazy. Looking at it up close, I've found there's a rectangular area around each of those cities, and anything within them is 3Dified, but it cuts off hard and fast at the edge, even if it's in the middle of a building. The edge of the rectangle is where the 3D stops. This leads me to think it's being done algorithmically (which would make sense, given the scale of the project, how many trees and buildings and details there are), and yet I can't imagine how that's possible. How could an algorithm model all these things without extensive data on their shapes and contours? How could it model the individual wires of a bridge, or the statues in a park? It must be done by hand, and yet how could it be for so much detail! Does anyone have any insight on this?

    Read the article

  • BoundingSpheres move when they should not

    - by NDraskovic
    I have a XNA 4.0 project in which I load a file that contains type and coordinates of items I need to draw to the screen. Also I need to check if one particular type (the only movable one) is passing in front or trough other items. This is the code I use to load the configuration: if (ks.IsKeyDown(Microsoft.Xna.Framework.Input.Keys.L)) { this.GraphicsDevice.Clear(Color.CornflowerBlue); Otvaranje.ShowDialog(); try { using (StreamReader sr = new StreamReader(Otvaranje.FileName)) { String linija; while ((linija = sr.ReadLine()) != null) { red = linija.Split(','); model = red[0]; x = red[1]; y = red[2]; z = red[3]; elementi.Add(Convert.ToInt32(model)); podatci.Add(new Vector3(Convert.ToSingle(x), Convert.ToSingle(y), Convert.ToSingle(z))); sfere.Add(new BoundingSphere(new Vector3(Convert.ToSingle(x), Convert.ToSingle(y), Convert.ToSingle(z)), 1f)); } } } catch (Exception ex) { Window.Title = ex.ToString(); } } The "Otvaranje" is an OpenFileDialog object, "elementi" is a List (determines the type of item that would be drawn), podatci is a List (determines the location where the items will be drawn) and sfere is a List. Now I solved the picking algorithm (checking for ray and bounding sphere intersection) and it works fine, but the collision detection does not. I noticed, while using picking, that BoundingSphere's move even though the objects that they correspond to do not. The movable object is drawn to the world1 Matrix, and the static objects are drawn into the world2 Matrix (world1 and world2 have the same values, I just separated them so that the static elements would not move when the movable one does). The problem is that when I move the item I want, all boundingSpheres move accordingly. How can I move only the boundingSphere that corresponds to that particular item, and leave the rest where they are?

    Read the article

  • Effective and simple matching for 2 unequal small-scale point sets

    - by Pavlo Dyban
    I need to match two sets of 3D points, however the number of points in each set can be different. It seems that most algorithms are designed to align images and trimmed to work with hundreds of thousands of points. My case are 50 to 150 points in each of the two sets. So far I have acquainted myself with Iterative Closest Point and Procrustes Matching algorithms. Implementing Procrustes algorithms seems like a total overkill for this small quantity. ICP has many implementations, but I haven't found any readily implemented version accounting for the so-called "outliers" - points without a matching pair. Besides the implementation expense, algorithms like Fractional and Sparse ICP use some statistics information to cancel points that are considered outliers. For series with 50 to 150 points statistic measures are often biased or statistic significance criteria are not met. I know of Assignment Problem in linear optimization, but it is not suitable for cases with unequal sets of points. Are there other, small-scale algorithms that solve the problem of matching 2 point sets? I am looking for algorithm names, scientific papers or C++ implementations. I need some hints to know where to start my search.

    Read the article

  • What sort of data should be sent for mouse-based movement in a multiplayer game?

    - by Daniel
    I'm new to the Multiplayer Rodeo here so please bear with me... I am just getting started and I'm trying to figure out how to deal with movement. I've looked at the question Best way to implement mouse-based movement in MMOG which gives me a pretty good idea, but I'm still struggling with what kind of data should be sent to the server. If a player is on position [x:0, y:0] and I click with the mouse on [x:40, y:40] to start movement, what information should I send to the server? Should I calculate the position based on velocity on client side and just send the expected location? Or should I send current location and velocity and direction? When the server is updating the clients on the players' whereabouts, should the position be sent only, and the clients expected to interpolate/predict movement, or can the direction sent from the client (instead of just coordinates) be used. My concern(or confusion) is regarding the ping/lag frequency of data update and use of a predictive algorithm, as I'd like the movement to be smooth even with a high latency, and prevent ability to cheat(though that's not the top priority).

    Read the article

  • Influence Maps for Pathfinding?

    - by james
    I'm taking the plunge and am getting into game dev, it's been going well but I've got stuck on a problem. I have a maze that is 100x100 with 0,1 to indicate if its a path or a wall. Within the maze I have 300 or so enemies and a player. The outcome I'm looking for is all the enemies work their way towards the player position. Originally I did this using an A* path finding algorithm but with 300 enemies it was taking forever to path find each one individually. After some research I found that an influence map / collaborative diffusion would be the best way to go. But I'm having a real hard time working out how this is actually done. Firstly.. How do you create a influence map? From what I understand each of my walls with have a scent of 0 so that makes them impassable.. then basically a radial effect from my player position to each other cell (So my player starts at 100 and then going outwards from that each other cell will be reduced value) Is that correct? If so,.. How would you do that (Math magic?) My next problem is if that is correct how would my "enemies" stop from getting stuck if they have gone down the wrong way? As say if my player was standing on the otherside of a wall if the enemy is just looking for larger numbers wont it keep getting stuck? I'm doing this in JavaScript so performance is key. Thanks for any help! EDIT: Or if anyones got a better solution? I've been reading about navmeshs, steering pathing, pre calculating all paths on load etc etc

    Read the article

  • Recommended formats to store bitmaps in memory?

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

    Read the article

  • How can I determine the first visible tile in an isometric perspective?

    - by alekop
    I am trying to render the visible portion of a diamond-shaped isometric map. The "world" coordinate system is a 2D Cartesian system, with the coordinates increasing diagonally (in terms of the view coordinate system) along the axes. The "view" coordinates are simply mouse offsets relative to the upper left corner of the view. My rendering algorithm works by drawing diagonal spans, starting from the upper right corner of the view and moving diagonally to the right and down, advancing to the next row when it reaches the right view edge. When the rendering loop reaches the lower left corner, it stops. There are functions to convert a point from view coordinates to world coordinates and then to map coordinates. Everything works when rendering from tile 0,0, but as the view scrolls around the rendering needs to start from a different tile. I can't figure out how to determine which tile is closest to the upper right corner. At the moment I am simply converting the coordinates of the upper right corner to map coordinates. This works as long as the view origin (upper right corner) is inside the world, but when approaching the edges of the map the starting tile coordinate obviously become invalid. I guess this boils down to asking "how can I find the intersection between the world X axis and the view X axis?"

    Read the article

  • Maintaining C/C++/Java skills as a web developer

    - by wwwuser
    When I was in college I learned how to program in C, C++, and Java. Currently, I'm a web developer using front end and back end technologies (HTML/CSS/JS, PHP, MYSQL). While the sorting algorithms and OOP concepts that I learned in college can be applied to web development, I'm looking for ways to keep up my knowledge of all languages. I enjoy programming in C-Style (C/C++/Java) languages and front-end/back-end technologies. Unfortunately, there aren't many options to use C-style languages to build websites. However, I would like to keep up my knowledge and skills in the languages I learned in college as I know they will continue to help me with my growth. What resources are available to keep challenging myself in C-style languages that are relevant to web development? Would contract work for C-style languages be beneficial? Are there sites that offer algorithm challenges? Any help is appreciated. I'm also interested in how others that have asked themselves this have solved this problem.

    Read the article

  • What Is The Formula for the 3 of 9 Bar Code Alphabet?

    - by Chris Moschini
    Background: 3 of 9 Barcode Alphabet A simple syntax for 3 of 9 bar codes What is the formula behind the alphabet and digits in a 3 of 9 bar code? For example, ASCII has a relatively clear arrangement. Numbers start at 33, capitals at 65, lowercase at 97. From these starting points you can infer the ASCII code for any number or letter. The start point for each range is also a multiple of 32 + 1. Bar codes seem random and lacking sequence. If we use the syntax from the second link, this is the first six characters in 3 of 9: A 100-01 B 010-01 C 110-00 D 001-01 E 101-00 F 011-00 I see no pattern here; what is it? I'm as much interested in the designer's intended pattern behind these as I am in someone devising an algorithm of their own that can give you the above code for a given character based on its sequence. I struggled with where to put this question; is it history, computer science, information science? I chose Programmers because a StackExchange search had the most barcode hits here, and because I wanted to specifically relate it to ASCII to explain what sort of formula/explanation I'm looking for.

    Read the article

  • Where did I write that code ?

    - by Tarun Arora
    Every been in that situation when you desperately need to find that code you checked into TFS a few days back but just can’t remember what team project, what branch, what solution or what file you checked it into. Well you are not alone… Only if there was a way to efficiently search for files and text with in TFS. It is possible… You need to get your hands on Agent Ransack… This is a stand a lone tool that does not integrate with TFS but gives you the capability to search through text files effortlessly. Agent Ransack searches through files, text or otherwise, fast and efficiently. When searching the contents of files for code, or other text, Agent Ransack displays the text found so you can quickly browse the results without having to separately open each file! Agent Ransack is free for both Personal and Commercial use and can be Download from here.   Set the Look In directory of the Ransack search tool to your TFS Workspace and type the text you would like to scan for, you can limit the search by narrowing down the filter path or the name of the file. Found text is shown with highlighted keywords so you don't need to waste time opening each file looking for the right information.         The regular expression wizard helps you build regular expressions for complex pattern matching searches         You even have the option of searching by modified, created or last accessed date          Export your results to a file for importing into other apps or for sharing with others          Agent Ransack also provides search support for popular Office formats including Office 2007 and OpenOffice Next time you are looking for that illusive line of code whether it is a method declaration, function call, or algorithm that you checked into TFS, use Agent Ransack for a quick search.

    Read the article

  • Why is quicksort better than other sorting algorithms in practice?

    - by Raphael
    This is a repost of a question on cs.SE by Janoma. Full credits and spoils to him or cs.SE. In a standard algorithms course we are taught that quicksort is O(n log n) on average and O(n²) in the worst case. At the same time, other sorting algorithms are studied which are O(n log n) in the worst case (like mergesort and heapsort), and even linear time in the best case (like bubblesort) but with some additional needs of memory. After a quick glance at some more running times it is natural to say that quicksort should not be as efficient as others. Also, consider that students learn in basic programming courses that recursion is not really good in general because it could use too much memory, etc. Therefore (and even though this is not a real argument), this gives the idea that quicksort might not be really good because it is a recursive algorithm. Why, then, does quicksort outperform other sorting algorithms in practice? Does it have to do with the structure of real-world data? Does it have to do with the way memory works in computers? I know that some memories are way faster than others, but I don't know if that's the real reason for this counter-intuitive performance (when compared to theoretical estimates).

    Read the article

  • How do I decide what type of programmer I want to be?

    - by Pearsonartphoto
    I've been working at my current work for some time, and I'm considering a bit of a change of careers. I'm trying to decide what it is exactly that I want to do, and I'm really just not sure. I'm not wanting a solution for my particular case, but what I'd like to know are some generalities of things I can look for. Here are some positions that I'm considering, and what my definitions are (I'm probably calling them something other than what is standard, but hopefully this will do for now). I'm looking for quizzes, articles, explanations, or anything that can help me figure this out. Manager - Managing programmers in some sense, mostly in making sure they are kept working. Coder - A person who is told to make a program do XYZ, and makes it do that. Doesn't have to model anything, or come up with formulas. Algorithm Designer - A person who comes up with a way to make software do something, but doesn't necessarily code that program, at least, not in it's final form. QA - A person who tests code for bugs, preferably with the code in hand. Architect - This person figures out how all of the pieces fit together, is a technical manager of sorts. Maintainer - This person takes someone else's existing code, and makes sure it is fixed when issues arise. Also of some note is figuring out what industry I want to work in. Feel free to add any of your own categories.

    Read the article

  • How to calculate new velocities between resting objects (AABB) after accelerations?

    - by Tiedye
    lately I have been trying to create a 2D platformer engine in C++ with Direct2D. The problem I am currently having is getting objects that are resting against each other to interact correctly after accelerations like gravity have been applied to them. Right now I can detect collisions and respond to them correctly (I think) and when objects collide they remember what other objects they're resting against so objects can be pushed by other objects (note that there is no bounce in any collisions so when objects collide they are guaranteed to become resting until something else happens). Every time the simulation advances, the acceleration for objects is applied to their velocities (for example vx += ax * t, where t is time elapsed since last advancement). After these accelerations are applied, I want to check if any objects that are resting against each other are moving at different speeds than their counterparts (as different objects can have different accelerations) and depending on that difference either unlink the two objects so they are no longer resting, or even out their velocities so they are moving at the same speed once again. I am having trouble creating an algorithm that can do this across many resting objects. Here's a diagram to help explain my problem

    Read the article

  • Finding maximum number of congruent numbers

    - by Stefan Czarnecki
    Let's say we have a multiset (set with possible duplicates) of integers. We would like to find the size of the largest subset of the multiset such that all numbers in the subset are congruent to each other modulo some m 1. For example: 1 4 7 7 8 10 for m = 2 the subsets are: (1, 7, 7) and (4, 8, 10), both having size 3. for m = 3 the subsets are: (1, 4, 7, 7, 10) and (8), the larger set of size 5. for m = 4 the subsets are: (1), (4, 8), (7, 7), (10), the largest set of size 2. At this moment it is evident that the best answer is 5 for m = 3. Given m we can find the size of the largest subset in linear time. Because the answer is always equal or larger than half of the size of the set, it is enough to check for values of m upto median of the set. Also I noticed it is necessary to check for only prime values of m. However if values in the set are large the algorithm is still rather slow. Does anyone have any ideas how to improve it?

    Read the article

  • Polygon is rotating too fast

    - by Manderin87
    I am going to be using a polygon collision detection method to test when objects collide. I am attempting to rotate a polygon to match the sprites rotation. However, the polygon is rotating too fast, much faster than the sprite is. I feel its a timing issue, but the sprite rotates like it is supposed to. Can anyone look at my code and tell me what could be causing this issue? public void rotate(float x0, float y0, double angle) { for(Point point : mPoints) { float x = (float) (x0 + (point.x - x0) * Math.cos(Utilities.toRadians(angle)) - (point.y - y0) * Math.sin(Utilities.toRadians(angle))); float y = (float) (y0 + (point.x - x0) * Math.sin(Utilities.toRadians(angle)) + (point.y - y0) * Math.cos(Utilities.toRadians(angle))); point.x = x; point.y = y; } } This algorithm works when done singly, but once I plug it into the update method the rotation is too fast. The Points used are: P1 608, 368 P2 640, 464 P3 672, 400 Origin x0 is: 640 400 The angle goes from 0 to 360 as the sprite rotates. When the codes executes the triangle looks like a star because its moving so fast. The rotation is done in the sprites update method. The rotation method just increases the sprites degree by .5 when it executes. public void update() { if(isActive()) { rotate(); mBounding.rotate(mPosition.x, mPosition.y, mDegree); } }

    Read the article

  • How do 2D physics engines solve the problem of resolving collisions along tiled walls/floors in non-grid-based worlds?

    - by ssb
    I've been working on implementing my SAT algorithm which has been coming along well, but I've found that I'm at a wall when it comes to its actual use. There are plenty of questions regarding this issue on this site, but most of them either have no clear, good answer or have a solution based on checking grid positions. To restate the problem that I and many others are having, if you have a tiled surface, like a wall or a floor, consisting of several smaller component rectangles, and you traverse along them with another rectangle with force being applied into that structure, there are cases where the object gets caught on a false collision on an edge that faces the inside of the shape. I have spent a lot of time thinking about how I could possibly solve this without having to resort to a grid-based system, and I realized that physics engines do this properly. What I want to know is how they do this. What do physics engines do beyond basic SAT that allows this kind of proper collision resolution in complex environments? I've been looking through the source code to Box2D trying to find out how they do it but it's not quite as easy as looking at a Collision() method. I think I'm not good enough at physics to know what they're doing mathematically and not good enough at programming to know what they're doing programmatically. This is what I aim to fix.

    Read the article

  • OpenGL : sluggish performance in extracting texture from GPU

    - by Cyan
    I'm currently working on an algorithm which creates a texture within a render buffer. The operations are pretty complex, but for the GPU this is a simple task, done very quickly. The problem is that, after creating the texture, i would like to save it. This requires to extract it from GPU memory. For this operation, i'm using glGetTexImage(). It works, but the performance is sluggish. No, i mean even slower than that. For example, an 8MB texture (uncompressed) requires 3 seconds (yes, seconds) to be extracted. That's mind puzzling. I'm almost wondering if my graphic card is connected by a serial link... Well, anyway, i've looked around, and found some people complaining about the same, but no working solution so far. The most promising advise was to "extract data in the native format of the GPU". Which i've tried and tried, but failed so far. Edit : by moving the call to glGetTexImage() in a different place, the speed has been a bit improved for the most dramatic samples : looking again at the 8MB texture, it knows requires 500ms, instead of 3sec. It's better, but still much too slow. Smaller texture sizes were not affected by the change (typical timing remained into the 60-80ms range). Using glFinish() didn't help either. Note that, if i call glFinish() (without glGetTexImage), i'm getting a fixed 16ms result, whatever the texture size or complexity. It really looks like the timing for a frame at 60fps. The timing is measured for the full rendering + saving sequence. The call to glGetTexImage() alone does not really matter. That being said, it is this call which changes the performance. And yes, of course, as stated at the beginning, the texture is "created into the GPU", hence the need to save it.

    Read the article

  • Algorithms for Data Redundancy and Failover for distributed storage system?

    - by kennetham
    I'm building a distributed storage system that works with different storage sizes. For instance, my storage devices have sizes of 50GB, 70GB, 150GB, 250GB, 1000GB, 5 storage systems in one system. My application will store any files to the storage system. Question: How can I build a distributed storage with the idea of data redundancy and fail-over to store documents, videos, any type of files at the same time ensuring that should one of any storage devices fail, there would be another copy of these files on another storage device. However, the concern is, 50GB of storage can only store this maximum number of files as compared to 70GB, 150GB etc. With one storage in mind, bringing 5 storage systems like a cloud storage, is there any logical way to distribute or store the files through my application? How do I ensure data redundancy through different storage sizes? Is there any algorithm to collate multiple blob files into a single file archive? What is the best solution for one cloud storage with multiple different storage sizes? I open this topic with the objective of discussing the best way to implement this idea, assuming simplicity, what are the issues of this implementation, performance measurements and discussion of the limitations.

    Read the article

< Previous Page | 170 171 172 173 174 175 176 177 178 179 180 181  | Next Page >