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  • How do I find the closest points(thereby forming a polygon) enclosing a particular point?(see image)

    - by nilspin
    I am working with a game engine, and my task is to add code for simulating fracture of rigid meshes. Right now I'm only working on breaking a cube. I am using Voronoi's algorithm to make a (realistic)fractured shard and I am using the half-plane method to generate a voronoi cell. Now the way I do this is for every seed point, I make planes that are perpendicular bisector planes(the straight black lines in the image) with rest of the seed points and I calculate the intersections of all these planes to give me distinct points(all the orange dots). I've gotten this far. Out of all these calculated intersection points, I only need the ones that are closest and enclosing the seed point(the points encircled in red) and I need to discard all the rest. Information that I have : 1) Plane equations of all planes(defined by normalized normal vectors and their distance from origin) 2) Points of intersection(that I've calculated) Can anybody help me find out how I can find the points encircled in red? Thanks.

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  • Linear feedback shift register?

    - by Mattia Gobbi
    Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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  • Writing a factory for classes that have required arguments

    - by Kyle Adams
    I understand the concept of factory pattern such that you give it something it spits out something of the same template back so if I gave a factory class apple, I expect to get many apples back with out having to instantiate a new apple ever time. what if that apple has a required argument of seed, or multiple required arguments of seed, step and leaf? how do you use factory pattern here? that is how do I use factory pattern to instantiate this: $apple = new Apple($seed, $stem, $leaf);

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  • Ruby on Rails 2.3.5: Populating my prod and devel database with data (migration or fixture?)

    - by randombits
    I need to populate my production database app with data in particular tables. This is before anyone ever even touches the application. This data would also be required in development mode as it's required for testing against. Fixtures are normally the way to go for testing data, but what's the "best practice" for Ruby on Rails to ship this data to the live database also upon db creation? ultimately this is a two part question I suppose. 1) What's the best way to load test data into my database for development, this will be roughly 1,000 items. Is it through a migration or through fixtures? The reason this is a different answer than the question below is that in development, there's certain fields in the tables that I'd like to make random. In production, these fields would all start with the same value of 0. 2) What's the best way to bootstrap a production db with live data I need in it, is this also through a migration or fixture? I think the answer is to seed as described here: http://lptf.blogspot.com/2009/09/seed-data-in-rails-234.html but I need a way to seed for development and seed for production. Also, why bother using Fixtures if seeding is available? When does one seed and when does one use fixtures?

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  • passing in javascript values into iframe tag

    - by Cedar Jensen
    What's the best way to pass in the value held in a javascript variable into an iframe call on the same html page? I'm trying to improve my site's page response times by moving ad serving javascript code (the typical document.write('<script type="text/javascript" src="..") into a separate iframe. (Based on this posting) The request to the ad server typically require a seed variable declared once per site and incremented each time page is loaded by the client. What I want to do is pass in the seed variable into the document invoked by my iframe section. The seed variable is initialized in the 'head' tag of my main html document: <head> <script type="text/javascript"> <!-- custom_seed=1; //--> </script> </head> Later in the html document, I make the request through an iframe which returns the html necessary to invoke the ad server. <body> <!-- a bunch of html to display the page --> <iframe src="somepage.html" width="100%" height="100%"> <p>No support for iframe</p> </iframe> </body> The html returned in the 'somepage.html' has a script used to call the ad server and needs to use the earlier declared seed variable as a parameter: <script type="text/javascript"> document.write('<script type="text/javascript" src="http://ad.server.net/...seed='+ custom_seed +'?"></script>'); custom_seed++; </script> What's a good way to achieve this?

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  • C++ Greatest Number Verification

    - by Daniel
    Hey guys, I was assigned to create a program that creates n arrays composed by 10 random integers. The the program should sum all the integers and display the result. After, it has to verify which of the sums is the greatest and it has to display that array and the result. Im having troubles getting it done and would like to get some help! Thanks once again. Here is my code so far: #include <iostream> #include <iomanip> #include <cmath> using namespace std; double random(unsigned int &seed); unsigned int seed = 5; void generateData(int set[10]); int sumData(int set[10]); void checkData(int sumResult, int arrayNumber); int main (int argc, char * const argv[]) { int arrayNumber, sumResult; int set[10]; do { cout << "Number of Arrays to Compare: " << endl; cin >> arrayNumber; } while (arrayNumber < 0); for (int i = 0; i < arrayNumber; ++i) { generateData(set); sumResult = sumData(set); cout << "Sum --> " << sumResult << endl; checkData(sumResult, arrayNumber); } return 0; } double random(unsigned int &seed) { const int MODULUS = 15749; const int MULTIPLIER = 69069; const int INCREMENT = 1; seed = ((MULTIPLIER * seed) + INCREMENT) % MODULUS; return double(seed) / double(MODULUS); } void generateData(int set[10]) { for (int i = 0; i < 10; ++i) { set[i] = int (5 + 6 * random(seed)); cout << set[i] << " || "; } } int sumData(int set[10]) { int sumTotal = 0; for (int i = 0; i < 10; ++i) sumTotal = sumTotal + set[i]; return sumTotal; } void checkData(int sumResult, int arrayNumber) { int largerNumber; int tempSet[2]; for (int i = 0; i < arrayNumber; ++i) { if (sumResult > largerNumber) { tempSet[i] = sumResult; } } }

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  • How to I count key collisions when using boost::unordered_map?

    - by Nikhil
    I have a data structure with 15 unsigned longs, I have defined a hash function using hash_combine as follows: friend std::size_t hash_value(const TUPLE15& given) { std::size_t seed = 0; boost::hash_combine(seed, val1); boost::hash_combine(seed, val2); ... return seed; } I insert a large number of values into a boost::unordered_map but the performance is not good enough. Probably, I could do better with an alternative hashing function. To confirm this, I need to check how many collisions I am getting. How do I do this?

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  • Capistrano asks for SSH password when deploying from local machine to server

    - by GhostRider
    When I try to ssh to a server, I'm able to do it as my id_rsa.pub key is added to the authorized keys in the server. Now when I try to deploy my code via Capistrano to the server from my local project folder, the server asks for a password. I'm unable to understand what could be the issue if I'm able to ssh and unable to deploy to the same server. $ cap deploy:setup "no seed data" triggering start callbacks for `deploy:setup' * 13:42:18 == Currently executing `multistage:ensure' *** Defaulting to `development' * 13:42:18 == Currently executing `development' * 13:42:18 == Currently executing `deploy:setup' triggering before callbacks for `deploy:setup' * 13:42:18 == Currently executing `db:configure_mongoid' * executing "mkdir -p /home/deploy/apps/development/flyingbird/shared/config" servers: ["dev1.noob.com", "176.9.24.217"] Password: Cap script: # gem install capistrano capistrano-ext capistrano_colors begin; require 'capistrano_colors'; rescue LoadError; end require "bundler/capistrano" # RVM bootstrap # $:.unshift(File.expand_path('./lib', ENV['rvm_path'])) require 'rvm/capistrano' set :rvm_ruby_string, 'ruby-1.9.2-p290' set :rvm_type, :user # or :user # Application setup default_run_options[:pty] = true # allow pseudo-terminals ssh_options[:forward_agent] = true # forward SSH keys (this will use your SSH key to get the code from git repository) ssh_options[:port] = 22 set :ip, "dev1.noob.com" set :application, "flyingbird" set :repository, "repo-path" set :scm, :git set :branch, fetch(:branch, "master") set :deploy_via, :remote_cache set :rails_env, "production" set :use_sudo, false set :scm_username, "user" set :user, "user1" set(:database_username) { application } set(:production_database) { application + "_production" } set(:staging_database) { application + "_staging" } set(:development_database) { application + "_development" } role :web, ip # Your HTTP server, Apache/etc role :app, ip # This may be the same as your `Web` server role :db, ip, :primary => true # This is where Rails migrations will run # Use multi-staging require "capistrano/ext/multistage" set :stages, ["development", "staging", "production"] set :default_stage, rails_env before "deploy:setup", "db:configure_mongoid" # Uncomment if you use any of these databases after "deploy:update_code", "db:symlink_mongoid" after "deploy:update_code", "uploads:configure_shared" after "uploads:configure_shared", "uploads:symlink" after 'deploy:update_code', 'bundler:symlink_bundled_gems' after 'deploy:update_code', 'bundler:install' after "deploy:update_code", "rvm:trust_rvmrc" # Use this to update crontab if you use 'whenever' gem # after "deploy:symlink", "deploy:update_crontab" if ARGV.include?("seed_data") after "deploy", "db:seed" else p "no seed data" end #Custom tasks to handle resque and redis restart before "deploy", "deploy:stop_workers" after "deploy", "deploy:restart_redis" after "deploy", "deploy:start_workers" after "deploy", "deploy:cleanup" 'Create symlink for public uploads' namespace :uploads do task :symlink do run <<-CMD rm -rf #{release_path}/public/uploads && mkdir -p #{release_path}/public && ln -nfs #{shared_path}/public/uploads #{release_path}/public/uploads CMD end task :configure_shared do run "mkdir -p #{shared_path}/public" run "mkdir -p #{shared_path}/public/uploads" end end namespace :rvm do desc 'Trust rvmrc file' task :trust_rvmrc do run "rvm rvmrc trust #{current_release}" end end namespace :db do desc "Create mongoid.yml in shared path" task :configure_mongoid do db_config = <<-EOF defaults: &defaults host: localhost production: <<: *defaults database: #{production_database} staging: <<: *defaults database: #{staging_database} EOF run "mkdir -p #{shared_path}/config" put db_config, "#{shared_path}/config/mongoid.yml" end desc "Make symlink for mongoid.yml" task :symlink_mongoid do run "ln -nfs #{shared_path}/config/mongoid.yml #{release_path}/config/mongoid.yml" end desc "Fill the database with seed data" task :seed do run "cd #{current_path}; RAILS_ENV=#{default_stage} bundle exec rake db:seed" end end namespace :bundler do desc "Symlink bundled gems on each release" task :symlink_bundled_gems, :roles => :app do run "mkdir -p #{shared_path}/bundled_gems" run "ln -nfs #{shared_path}/bundled_gems #{release_path}/vendor/bundle" end desc "Install bundled gems " task :install, :roles => :app do run "cd #{release_path} && bundle install --deployment" end end namespace :deploy do task :start, :roles => :app do run "touch #{current_path}/tmp/restart.txt" end desc "Restart the app" task :restart, :roles => :app do run "touch #{current_path}/tmp/restart.txt" end desc "Start the workers" task :stop_workers do run "cd #{current_path}; RAILS_ENV=#{default_stage} bundle exec rake resque:stop_workers" end desc "Restart Redis server" task :restart_redis do "/etc/init.d/redis-server restart" end desc "Start the workers" task :start_workers do run "cd #{current_path}; RAILS_ENV=#{default_stage} bundle exec rake resque:start_workers" end end

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  • Scriptable BitTorrent clients?

    - by James McMahon
    In an effort further automate all the little computer house keeping tasks that can waste my time I am looking into BitTorrent clients that have the ability to script common tasks. I've done some Googling and it looks like Transmission might have some of said such capabilities, but there site wasn't very clear on the details. Things I am looking to do; Prioritize and label torrents based on trackers Set seed length based on trackers and filesize Set additional seed time when a torrent's seed time expires based on a number of factors, like time spent seeding, remaining disk space and ratio. Move torrents to appropriate places post seeding based on labels and tracker Basically, while I could Python or Bash script things like moving torrents around and other simple actions, I need away to talk to the client to figure out things like the torrent seed time, tracker, labels, filesize, etc. Is there any client out there that would allow me to all or a subset these actions? I have access to Linux, Mac and Windows and am not tied to any particular torrent client. I am a programmer so I have no problems writing scripts, but examples of torrent scripting would also be helpful.

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  • Best Method For Evaluating Existing Software or New Software

    How many of us have been faced with having to decide on an off-the-self or a custom built component, application, or solution to integrate in to an existing system or to be the core foundation of a new system? What is the best method for evaluating existing software or new software still in the design phase? One of the industry preferred methodologies to use is the Active Reviews for Intermediate Designs (ARID) evaluation process.  ARID is a hybrid mixture of the Active Design Review (ADR) methodology and the Architectural Tradeoff Analysis Method (ATAM). So what is ARID? ARD’s main goal is to ensure quality, detailed designs in software. One way in which it does this is by empowering reviewers by assigning generic open ended survey questions. This approach attempts to remove the possibility for allowing the standard answers such as “Yes” or “No”. The ADR process ignores the “Yes”/”No” questions due to the fact that they can be leading based on how the question is asked. Additionally these questions tend to receive less thought in comparison to more open ended questions. Common Active Design Review Questions What possible exceptions can occur in this component, application, or solution? How should exceptions be handled in this component, application, or solution? Where should exceptions be handled in this component, application, or solution? How should the component, application, or solution flow based on the design? What is the maximum execution time for every component, application, or solution? What environments can this component, application, or solution? What data dependencies does this component, application, or solution have? What kind of data does this component, application, or solution require? Ok, now I know what ARID is, how can I apply? Let’s imagine that your organization is going to purchase an off-the-shelf (OTS) solution for its customer-relationship management software. What process would we use to ensure that the correct purchase is made? If we use ARID, then we will have a series of 9 steps broken up by 2 phases in order to ensure that the correct OTS solution is purchases. Phase 1 Identify the Reviewers Prepare the Design Briefing Prepare the Seed Scenarios Prepare the Materials When identifying reviewers for a design it is preferred that they be pulled from a candidate pool comprised of developers that are going to implement the design. The believe is that developers actually implementing the design will have more a vested interest in ensuring that the design is correct prior to the start of code. Design debriefing consist of a summary of the design, examples of the design solving real world examples put in to use and should be no longer than two hours typically. The primary goal of this briefing is to adequately summarize the design so that the review members could actually implement the design. In the example of purchasing an OTS product I would attempt to review my briefing prior to its distribution with the review facilitator to ensure that nothing was excluded that should have not been. This practice will also allow me to test the length of the briefing to ensure that can be delivered in an appropriate about of time. Seed Scenarios are designed to illustrate conceptualized scenarios when applied with a set of sample data. These scenarios can then be used by the reviewers in the actual evaluation of the software, All materials needed for the evaluation should be prepared ahead of time so that they can be reviewed prior to and during the meeting. Materials Included: Presentation Seed Scenarios Review Agenda Phase 2 Present ARID Present Design Brainstorm and prioritize scenarios Apply scenarios Summarize Prior to the start of any ARID review meeting the Facilitator should define the remaining steps of ARID so that all the participants know exactly what they are doing prior to the start of the review process. Once the ARID rules have been laid out, then the lead designer presents an overview of the design which typically takes about two hours. During this time no questions about the design or rational are allowed to be asked by the review panel as a standard, but they are written down for use latter in the process. After the presentation the list of compiled questions is then summarized and sent back to the lead designer as areas that need to be addressed further. In the example of purchasing an OTS product issues could arise regarding security, the implementation needed or even if this is this the correct product to solve the needed solution. After the Design presentation a brainstorming and prioritize scenarios process begins by reducing the seed scenarios down to just the highest priority scenarios.  These will then be used to test the design for suitability. Once the selected scenarios have been defined the reviewers apply the examples provided in the presentation to the scenarios. The intended output of this process is to provide code or pseudo code that makes use of the examples provided while solving the selected seed scenarios. As a standard rule, the designers of the systems are not allowed to help the review board unless they all become stuck. When this occurs it is documented and along with the reason why the designer needed to help the review panel back on track. Once all of the scenarios have been completed the review facilitator reviews with the group issues that arise during the process. Then the reviewers will be polled as to efficacy of the review experience. References: Clements, Paul., Kazman, Rick., Klien, Mark. (2002). Evaluating Software Architectures: Methods and Case Studies Indianapolis, IN: Addison-Wesley

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  • How to have desktop icons constantly highlighted?

    - by Jim Seed
    In Windows 7 when I set the desktop color, it actually sets the color of text in desktop icons. So if I have a black wallpaper, I need to set it to white so icon text will be visible. If I want to have a multi-colored wallpaper then this causes a problem, as icon text won't be readable over areas where color is the same as the set desktop color. Is there a way to have icons constantly highlighted to avoid this?

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  • ubiquity automatic install stops at keyboard layout chooser

    - by badgerhill
    i am trying to automate an ubuntu (12.04.1 64bit) installation using ubiquity & preseed on a desktop live cd. it almost works fine. i edited the txt.cfg and added label unattended menu label ^Unattended installation kernel /casper/vmlinuz append file=/cdrom/preseed/custom.seed boot=casper initrd=/casper/initrd.lz quiet splash noprompt -- this is my custom.seed file the problem is that, the installer shows the keyboard layout chooser and i have to click next. the correct language & keyboard layout (german) are already preselected. what am i missing, or what's wrong in my custom.seed file, to automate the next click? thomas

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  • ubiquity automatic install stops at keyboard layout chooser

    - by badgerhill
    I am trying to automate an Ubuntu (12.04.1 64bit) installation using ubiquity & preseed on a desktop live cd. It almost works fine. I edited the txt.cfg and added label unattended menu label ^Unattended installation kernel /casper/vmlinuz append file=/cdrom/preseed/custom.seed boot=casper initrd=/casper/initrd.lz quiet splash noprompt -- This is my custom.seed file The problem is that the installer shows the keyboard layout chooser and I have to click next. The correct language & keyboard layout (german) are already preselected. What am I missing, or what's wrong in my custom.seed file, to automate the next click?

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  • GSL Uniform Random Number Generator

    - by Jamaia
    I want to use GSL's uniform random number generator. On their website, they include this sample code: #include <stdio.h> #include <gsl/gsl_rng.h> int main (void) { const gsl_rng_type * T; gsl_rng * r; int i, n = 10; gsl_rng_env_setup(); T = gsl_rng_default; r = gsl_rng_alloc (T); for (i = 0; i < n; i++) { double u = gsl_rng_uniform (r); printf ("%.5f\n", u); } gsl_rng_free (r); return 0; } However, this does not rely on any seed and so, the same random numbers will be produced each time. They also specify the following: The generator itself can be changed using the environment variable GSL_RNG_TYPE. Here is the output of the program using a seed value of 123 and the multiple-recursive generator mrg, $ GSL_RNG_SEED=123 GSL_RNG_TYPE=mrg ./a.out But I don't understand how to implement this. Any ideas as to what modifications I can make to the above code to incorporate the seed?

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  • Why does my performance slow to a crawl I move methods into a base class?

    - by Juliet
    I'm writing different implementations of immutable binary trees in C#, and I wanted my trees to inherit some common methods from a base class. However, I find. I have lots of binary tree data structures to implement, and I wanted move some common methods into in a base binary tree class. Unfortunately, classes which derive from the base class are abysmally slow. Non-derived classes perform adequately. Here are two nearly identical implementations of an AVL tree to demonstrate: AvlTree: http://pastebin.com/V4WWUAyT DerivedAvlTree: http://pastebin.com/PussQDmN The two trees have the exact same code, but I've moved the DerivedAvlTree.Insert method in base class. Here's a test app: using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using Juliet.Collections.Immutable; namespace ConsoleApplication1 { class Program { const int VALUE_COUNT = 5000; static void Main(string[] args) { var avlTreeTimes = TimeIt(TestAvlTree); var derivedAvlTreeTimes = TimeIt(TestDerivedAvlTree); Console.WriteLine("avlTreeTimes: {0}, derivedAvlTreeTimes: {1}", avlTreeTimes, derivedAvlTreeTimes); } static double TimeIt(Func<int, int> f) { var seeds = new int[] { 314159265, 271828183, 231406926, 141421356, 161803399, 266514414, 15485867, 122949829, 198491329, 42 }; var times = new List<double>(); foreach (int seed in seeds) { var sw = Stopwatch.StartNew(); f(seed); sw.Stop(); times.Add(sw.Elapsed.TotalMilliseconds); } // throwing away top and bottom results times.Sort(); times.RemoveAt(0); times.RemoveAt(times.Count - 1); return times.Average(); } static int TestAvlTree(int seed) { var rnd = new System.Random(seed); var avlTree = AvlTree<double>.Create((x, y) => x.CompareTo(y)); for (int i = 0; i < VALUE_COUNT; i++) { avlTree = avlTree.Insert(rnd.NextDouble()); } return avlTree.Count; } static int TestDerivedAvlTree(int seed) { var rnd = new System.Random(seed); var avlTree2 = DerivedAvlTree<double>.Create((x, y) => x.CompareTo(y)); for (int i = 0; i < VALUE_COUNT; i++) { avlTree2 = avlTree2.Insert(rnd.NextDouble()); } return avlTree2.Count; } } } AvlTree: inserts 5000 items in 121 ms DerivedAvlTree: inserts 5000 items in 2182 ms My profiler indicates that the program spends an inordinate amount of time in BaseBinaryTree.Insert. Anyone whose interested can see the EQATEC log file I've created with the code above (you'll need EQATEC profiler to make sense of file). I really want to use a common base class for all of my binary trees, but I can't do that if performance will suffer. What causes my DerivedAvlTree to perform so badly, and what can I do to fix it?

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  • BadPaddingException in Android encrypt

    - by DarthRoman
    Hi everyone, I am making an Android application, and I want to encrypt a String before sending it to a DataBase, and encrytpion is correct. The problem is when I am going to decrypt the String, because I get a BadPaddingException and I have no idea where the problem is. Here is the code: public final static String HEX = "36A52C8FB7DF9A3F"; public static String encrypt(String seed, String cleartext) throws Exception { byte[] rawKey = getRawKey(seed.getBytes()); byte[] result = encrypt(rawKey, cleartext.getBytes()); return toHex(result); } public static String decrypt(String seed, String encrypted) throws Exception { byte[] rawKey = getRawKey(seed.getBytes()); byte[] enc = toByte(encrypted); byte[] result = decrypt(rawKey, enc); return new String(result); } public static String toHex(String txt) { return toHex(txt.getBytes()); } public static String fromHex(String hex) { return new String(toByte(hex)); } public static byte[] toByte(String hexString) { int len = hexString.length()/2; byte[] result = new byte[len]; for (int i = 0; i < len; i++) result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue(); return result; } public static String toHex(byte[] buf) { if (buf == null) return ""; StringBuffer result = new StringBuffer(2*buf.length); for (int i = 0; i < buf.length; i++) { appendHex(result, buf[i]); } return result.toString(); } private static byte[] getRawKey(byte[] seed) throws Exception { KeyGenerator kgen = KeyGenerator.getInstance("AES"); SecureRandom sr = SecureRandom.getInstance("SHA1PRNG"); sr.setSeed(seed); kgen.init(128, sr); // 192 and 256 bits may not be available SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); return raw; } private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception { SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); byte[] encrypted = cipher.doFinal(clear); return encrypted; } private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception { SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.DECRYPT_MODE, skeySpec); byte[] decrypted = cipher.doFinal(encrypted); return decrypted; } private static void appendHex(StringBuffer sb, byte b) { sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f)); } I encrypt and decrypt with this code: String encrypted = encrypt(HEX, "some text"); String decrypted = decrypt(HEX, encrypted); Can anyone help me please? Thank you very much!!

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  • Randomised objects are assigning themselves to more than one array location

    - by Thaddeus Aid
    this.size = 9; this.populationSize = 10; Random rand = new Random(); Integer[][] easy1 = new Integer[size][size]; easy1 = this.initializeEasy1(easy1); this.sudokuArray = new Sudoku[this.populationSize]; for (int i = 0; i < this.sudokuArray.length; i++){ long seed = rand.nextLong(); System.out.println("" + seed); this.sudokuArray[i] = new Sudoku(easy1, this.size, seed); } I am building an evolutionary sudoku solver and I am having a problem where the last Sudoku object is overwriting all the other objects in the array. Where in the code did I mess up? /edit here is the constructor of the class public Sudoku(Integer[][] givensGrid, int s, long seed){ this.size = s; this.givens = givensGrid; this.grid = this.givens.clone(); Random rand = new Random(seed); System.out.println("Random " + rand.nextInt()); // step though each row of the grid for (int i = 0; i < size; i++){ ArrayList<Integer> numbers = new ArrayList<Integer>(); numbers = this.makeNumbers(numbers); // step through each column to find the givens and remove from numbers for (int j = 0; j < size; j++){ if (this.grid[i][j] != 0){ numbers.remove(this.grid[i][j]); } } // go back through the row and assign the numbers randomly for (int j = 0; j < size; j++){ if (this.grid[i][j] == 0){ int r = rand.nextInt(numbers.size()); this.grid[i][j] = numbers.get(r); numbers.remove(r); } } } System.out.println("============="); System.out.println(this.toString()); }

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  • whether rand_r is real thread safe?

    - by terry
    Well, rand_r function is supposed to be a thread safe function. However, by its implementation, I cannot believe it could make itself not change by other threads. Suppose that two threads will invoke rand_r in the same time with the same variable seed. So read-write race will occur. The code rand_r implemented by glibc is listed below. Anybody knows why rand_r is called thread safe? int rand_r (unsigned int *seed) { unsigned int next = *seed; int result; next *= 1103515245; next += 12345; result = (unsigned int) (next / 65536) % 2048; next *= 1103515245; next += 12345; result <<= 10; result ^= (unsigned int) (next / 65536) % 1024; next *= 1103515245; next += 12345; result <<= 10; result ^= (unsigned int) (next / 65536) % 1024; *seed = next; return result; }

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  • Sending an int array through Winsocks

    - by seed
    I'm trying to send an int array through Winsocks. I might be wrong, but I'm pretty sure only a char* is supported so I'm kind of stuck on how to do this properly. There are also problems with little/big edian, so what would be a good way to do this? I've already asked a question of converting int array to char but it was recommended to start a new thread on this in the networking section instead.

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  • iPhone SDK in C++?

    - by seed
    This might be a really silly question, but is the iPhone SDK available in C++? Since I heard C++ is an officially supported language, is their any SDK avaliable for it?

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  • create a random sequence, skip to any part of the sequence

    - by Michael Xu
    Hi everyone, In Linux. There is an srand() function, where you supply a seed and it will guarantee the same sequence of pseudorandom numbers in subsequent calls to the random() function afterwards. Lets say, I want to store this pseudo random sequence by remembering this seed value. Furthermore, let's say I want the 100 thousandth number in this pseudo random sequence later. One way, would be to supply the seed number using srand(), and then calling random() 100 thousand times, and remembering this number. Is there a better way of skipping all 99,999 other numbers in the pseudo random list and directly getting the 100 thousandth number in the list. thanks, m

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  • Arbitrary-precision random numbers in C: generation for Monte Carlo simulation without atmospheric n

    - by Yktula
    I know that there are other questions similar to this one, however the following question pertains to arbitrary-precision random number generation in C for use in Monte Carlo simulation. How can we generate good quality arbitrary-precision random numbers in C, when atmospheric noise isn't always available, without relying on disk i/o or network access that would create bottlenecks? libgmp is capable of generating random numbers, but, like other implementations of pseudo-random number generators, it requires a seed. As the manual mentions, "the system time is quite easy to guess, so if unpredictability is required then it should definitely not be the only source for the seed value." Is there a portable/ported library for generating random numbers, or seeds for random numbers? The libgmp also mentions that "On some systems there's a special device /dev/random which provides random data better suited for use as a seed." However, /dev/random and /dev/urandom can only be used on *nix systems.

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  • is there a such thing as a randomly accessible pseudo-random number generator? (preferably open-sour

    - by lucid
    first off, is there a such thing as a random access random number generator, where you could not only sequentially generate random numbers as we're all used to, assuming rand100() always generates a value from 0-100: for (int i=0;i<5;i++) print rand100() output: 14 75 36 22 67 but also randomly access any random value like: rand100(0) would output 14 as long as you didn't change the seed rand100(3) would always output 22 rand100(4) would always output 67 and so on... I've actually found an open-source generator algorithm that does this, but you cannot change the seed. I know that pseudorandomness is a complex field; I wouldn't know how to alter it to add that functionality. Is there a seedable random access random number generator, preferably open source? or is there a better term for this I can google for more information? if not, part 2 of my question would be, is there any reliably random open source conventional seedable pseudorandom number generator so I could port it to multiple platforms/languages while retaining a consistent sequence of values for each platform for any given seed?

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  • how to generate uncorrelated random numbers in repeated calls in parallel?

    - by user1446948
    I want to write a function which will be repeatedly called by other functions many times. Inside this function it is supposed to generate a lot of random numbers and this part will be treated in parallel. If only for one run, the seed can be chosen differently for each thread, so that the random numbers will be uncorrelated. However, if this function will be called the 2nd time, it seems that the random numbers will repeat unless the seed will be again changed during the later calls. So my question is, is there a good way to generate the random numbers or reset the seed so that the random numbers generated by repeated calls to this function and also by different threads are really random? Thank you.

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