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  • c++ generate a good random seed for psudo random number generators

    - by posop
    I am trying to generate a good random seed for a psudo-random number generator. I thought I'd get the expert's opinions. let me know if this is a bad way of doing it or if there are much better ways. #include <iostream> #include <cstdlib> #include <fstream> #include <ctime> unsigned int good_seed() { unsigned int random_seed, random_seed_a, random_seed_b; std::ifstream file ("/dev/random", std::ios::binary); if (file.is_open()) { char * memblock; int size = sizeof(int); memblock = new char [size]; file.read (memblock, size); file.close(); random_seed_a = int(memblock); delete[] memblock; }// end if else { random_seed_a = 0; } random_seed_b = std::time(0); random_seed = random_seed_a xor random_seed_b; return random_seed; } // end good_seed()

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  • Server side random selection of players

    - by Ron
    Assuming I have a simple client-server game, where the server picks random players on a very frequent base, I was wondering what is the best way to select a random player (According to the following constraints): Solution must be high performance and highly scalable Random spread should be relatively even (meaning if I have 3 players and pick 99 times, they will all be picked 33 times more or less) Should only pick players who were active in the past X days (optional, but a big bonus) The actual DB or data model used to store players isn't an issue here, as we'll select the technology in accordance to our needs. However, high performance and scalability is (at the moment we have over 60,000 unique daily active players, and we plan on growing even more). Thanks!

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  • Make objects slide across the screen in random positions

    - by user3475907
    I want to make an object appear randomly at the right hand side of the screen and then slide across the screen and disapear at the left hand side. I am working with libgdx. I have this bit of code but it makes items fall from the top down. Please help. public EntityManager(int amount, OrthoCamera camera) { player = new Player(new Vector2(15, 230), new Vector2(0, 0), this, camera); for (int i = 0; i < amount; i++) { float x = MathUtils.random(0, MainGame.HEIGHT - TextureManager.ENEMY.getHeight()); float y = MathUtils.random(MainGame.WIDTH, MainGame.WIDTH * 10); float speed = MathUtils.random(2, 10); addEntity(new Enemy(new Vector2(x, y), new Vector2(-0, -speed))); }

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  • Is Unity's Random seeded automatically?

    - by Lohoris
    I seem to recall Unity's Random is automatically seeded; checking the documentation it doesn't say it outright, but a certain interpretation of their words might seem to imply it. The seed is normally set from some arbitrary value like the system clock before the random number functions are used. This prevents the same run of values from occurring each time a game is played and thus avoids predictable gameplay. However, it is sometimes useful to produce the same run of pseudo-random values on demand by setting the seed yourself. (emphasis added)

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  • .NET: will Random.Random operate differently inside a static method

    - by Craig Johnston
    I am having difficulty with the following code which is inside a static method of a non-static class. int iRand; int rand; rand = new Random((int)DateTime.Now.Ticks); iRand = rand.Next(50000); The iRand number, along with some other values, are being inserted into a new row of an Access MDB table via OLEDB. The iRand number is being inserted into a field that is part of the primary key, and the insert attempt is throwing the following exception even though the iRand number is supposed to be random: System.Data.OleDb.OleDbException: The changes you requested to the table were not successful because they would create duplicate values in the index, primary key, or relationship. Change the data in the field or fields that contain duplicate data, remove the index, or redefine the index to permit duplicate entries and try again. Could the fact the method is static be making the iRand number stay the same, for some reason?

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  • generate random opacity number using math random

    - by TechyDude
    I am trying to generate a random number for the css opacity. This is what I tried so far. CSS .test{ position : absolute; width : 15px; height : 15px; border-radius:15px; background-color : black; }? Script $(function() { for (var i = 0; i < 300; i++) { $("<div>", { class: "test", css: { opacity: randomOpacity } }).appendTo("body"); } function randomOpacity() { var opac = 0; opac = Math.random() < 1; console.log(opac); } randomize(); });? The Fiddle

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  • Random number generation

    - by Chandan Shetty SP
    I am using below code to generate random numbers in range... int randomNumberWithinRange(int min,int max) { int snowSize = 0; do { snowSize = rand()%max; } while( snowSize < min || snowSize > max ); return snowSize; } for(int i = 0; i < 10 ; i++) NSlog("@"%d",\t", randomNumberWithinRange(1,100)); If I quit my application and restart, same set of numbers are generated. How to generate different set of random numbers for every launching.

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  • Using system time directly to get random numbers

    - by Richard Mar.
    I had to return a random element from an array so I came up with this placeholder: return codes[(int) (System.currentTimeMillis() % codes.length - 1)]; Now than I think of it, I'm tempted to use it in real code. The Random() seeder uses system time as seed in most languages anyway, so why not use that time directly? As a bonus, I'm free from the worry of non-random lower bits of many RNGs. It this hack coming back to bite me? (The language is Java if that's relevant.)

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  • Random enemy placement on a 2d grid

    - by Robb
    I want to place my items and enemies randomly (or as randomly as possible). At the moment I use XNA's Random class to generate a number between 800 for X and 600 for Y. It feels like enemies spawn more towards the top of the map than in the middle or bottom. I do not seed the generator, maybe that is something to consider. Are there other techniques described that can improve random enemy placement on a 2d grid?

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  • Biased Random Number Generator

    - by cmptrer
    I am looking for a random number generator that can be biased. For instance, say I want a random number between 1-5, with the probability being: 1: Comes up 20% of the time 2: Comes up 10% of the time 3: Comes up 40% of the time 4: Comes up 25% of the time 5: Comes up 5% of the time Is there anything in the standard library, or other libraries out there that would do this? Alternatively, is there an efficient way to do this myself?

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  • Getting N random numbers that the sum is M

    - by marionmaiden
    Hello I want to get N random numbers that the sum of them is a value. For example, let's suppose I want 5 random numbers that their sum is 1 Then, a valid possibility is: 0.2 0.2 0.2 0.2 0.2 Other possibility is: 0.8 0.1 0.03 0.03 0.04 And so on. I need this for the creation of the matrix of belongings of the Fuzzy C-means.

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  • Random World Generation

    - by Alex Larsen
    I'm making a game like minecraft (although a different idea) but I need a random world generator for a 1024 block wide and 256 block tall map. Basically so far I have a multidimensional array for each layer of blocks (a total of 262,114 blocks). This is the code I have now: Block[,] BlocksInMap = new Block[1024, 256]; public bool IsWorldGenerated = false; Random r = new Random(); private void RunThread() { for (int BH = 0; BH <= 256; BH++) { for (int BW = 0; BW <= 1024; BW++) { Block b = new Block(); if (BH >= 192) { } BlocksInMap[BW, BH] = b; } } IsWorldGenerated = true; } public void GenWorld() { new Thread(new ThreadStart(RunThread)).Start(); } I want to make tunnels and water but the way blocks are set is like this: Block MyBlock = new Block(); MyBlock.BlockType = Block.BlockTypes.Air; How would I manage to connect blocks so the land is not a bunch of floating dirt and stone?

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  • SQLAuthority News – Random Thoughts and Random Ideas

    - by pinaldave
    There are days when I keep on wondering about SQL, and even my life overall. Today is Saturday so I decided to write about SQL Server. Just like any other mornings, I woke up at 5 and opened my blog editor. I usually do not open Twitter or Facebook when I am planning to focus on my work, as they are little distractions for me. But today I opened my Twitter account and came across a very interesting quote from a friend: ‘Can I expect you to be different today?’ Well, I think it was very powerful quote for me to read first thing on a new day. This quote froze me for a while and made me think, “Do I really want to write about an SQL Server tip, or something different?”  After a little thinking, I’ve realized that for today I would go on and write something different. I am going to write about a few of the ideas and thoughts I had yesterday. After writing all these, I realized that if I am thinking so much in a day, and if I write a blog post of my random musing of the week or month, it can be so long (and boring). Here are some of my random thoughts I’d like to share with you: When the airplane lands, why does everybody get up and try to rush out when their luggage would be coming probably 20-30 minutes later? I really do not like this question when it was asked to me: “SQL Server is not using optimal index which I just created – how can I force it?” I am not going elaborate on this statement but you are allowed to in the comment section. Why do some people wish Good Morning even when they meet us after 4 PM? Can I optimize a query so much that it gives me a result before I execute it? Is it corruption when someone does their personal household work at office? The lane where I drive is always the slowest lane. Why waste time on correcting others when there are a lot of pending improvements for ourselves? If I have to get Tattoo, which SQL Server Execution Plan symbol should I get? Why do I reach office so early that the coffee machine is yet running its daily cleaning job? Why does every laptop have a ‘Page Up’ key at different locations on the keyboard? While I like color movies, I really appreciate black and white photographs. I do not appreciate statements like, “If I receive your books in PDF, I will spread it to many people to give you much greater exposure. So would you please send them to me ASAP?” Do not tell me, “Why does the database grow back after shrinking it every day?” I suggest you use “Search this blog” for the explanation. Petrol prices are currently at INR 74. I hope the rate remains there. Let me ask you the same question which started my day today:  “Can I expect you to be different today?” Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Python: Random is barely random at all?

    - by orokusaki
    I did this to test the randomness of randint: >>> from random import randint >>> >>> uniques = [] >>> for i in range(4500): # You can see I optimistic. ... x = randint(500, 5000) ... if x in uniques: ... raise Exception('We duped ' + str(x) + ' at iteration number ' + str(i)) ... uniques.append(x) ... Traceback (most recent call last): File "(stdin)", line 4, in (module) Exception: 'We duped 4061 at iteration number 67 I tried about 10 times more and the best result I got was 121 iterations before a repeater. Is this the best sort of result you can get from the standard library?

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  • Probability Random Number Generator

    - by Excl
    Let's say I'm writing a simple luck game - each player presses Enter and the game assign him a random number between 1-6. Just like a cube. At the end of the game, the player with the highest number wins. Now, let's say I'm a cheater. I want to write the game so player #1 (which will be me) has a probability of 90% to get six, and 2% to get each of the rest numbers (1, 2, 3, 4, 5). So, how can I generate a number random, and set the probability for each number? Thanks.

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  • Use of qsrand, random method that is not random

    - by Andy M
    Hey everyone, I'm having a strange problem here, and I can't manage to find a good explanation to it, so I thought of asking you guys : Consider the following method : int MathUtility::randomize(int Min, int Max) { qsrand(QTime::currentTime().msec()); if (Min > Max) { int Temp = Min; Min = Max; Max = Temp; } return ((rand()%(Max-Min+1))+Min); } I won't explain you gurus what this method actually does, I'll instead explain my problem : I realised that when I call this method in a loop, sometimes, I get the same random number over and over again... For example, this snippet... for(int i=0; i<10; ++i) { int Index = MathUtility::randomize(0, 1000); qDebug() << Index; } ...will produce something like : 567 567 567 567...etc... I realised too, that if I don't call qsrand everytime, but only once during my application's lifetime, it's working perfectly... My question : Why ?

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  • Difference Procedural Generation and Random Generation

    - by U-No-Poo
    Today, I got into an argument about the term "procedural generation". My point was that its different from "classic" random generation in the way that procedural is based on a more mathematical, fractal based, algorithm leading to a more "realistic" distribution and the usual randomness of most languages are based on a pseudo-random-number generator, leading to an "unrealistic", in a way, ugly, distribution. This discussion was made with a heightmap in mind. The discussion left me somehow unconvinced about my own arguments though, so, is there more to it? Or am I the one who is, in fact, simply wrong?

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  • Random number generation algorithm for human brains?

    - by Magnus Wolffelt
    Are you aware of, or have you devised, any practical, simple-to-learn "in-head" algorithms that let humans generate (somewhat "true") random numbers? By "in-head" I mean.. preferrably without any external tools or devices. Also, a high output (many random numbers per minute) is desirable. Asked this on SO but it didn't get much interest. Maybe this is better suited for programmers.. :) I'm genuinely curious about anything that people might have come up with on this problem.

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  • Random Cache Expiry

    - by mahemoff
    I've been experimenting with random cache expiry times to avoid situations where an individual request forces multiple things to update at once. For example, a web page might include five different components. If each is set to time out in 30 minutes, the user will have a long wait time every 30 minutes. So instead, you set them all to a random time between 15 and 45 minutes to make it likely at most only one component will reload for any given page load. I'm trying to find any research or guidelines on this topic, e.g. optimal variance parameters. I do recall seeing one article about how Google (?) uses this technique, but can't locate it, and there doesn't seem to be much written about the topic.

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  • VB.NET - Removing a number from a random number generator

    - by Alex
    I am trying to create a lottery simulator. The lottery has 6 numbers, the number generated must be between 1 - 49 and cannot be in the next number generated. I have tried using the OR function but I'm not entirely sure if I am using it properly. Any help would be great. Thanks. Public Class Form1 Private Sub cmdRun_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdRun.Click 'Creates a new Random class in VB.NET Dim RandomClass As New Random() '#################################### Dim RandomNumber1 As Integer RandomNumber1 = RandomClass.Next(1, 49) 'Displays first number generated txtFirst.Text = (RandomNumber1) '#################################### Dim RandomNumber2 As Integer RandomNumber2 = RandomClass.Next(1, 49) If RandomNumber2 = RandomNumber1 Then RandomNumber2 = RandomClass.Next(1, 49) End If 'Displays second number generated txtSecond.Text = (RandomNumber2) '#################################### Dim RandomNumber3 As Integer RandomNumber3 = RandomClass.Next(1, 49) If RandomNumber3 = RandomNumber2 Or RandomNumber2 Then RandomNumber3 = RandomClass.Next(1, 49) End If 'Displays third number generated txtThird.Text = (RandomNumber3) '#################################### Dim RandomNumber4 As Integer RandomNumber4 = RandomClass.Next(1, 49) If RandomNumber4 = RandomNumber3 Or RandomNumber2 Or RandomNumber1 Then RandomNumber4 = RandomClass.Next(1, 49) End If 'Displays fourth number generated txtFourth.Text = (RandomNumber4) '#################################### Dim RandomNumber5 As Integer RandomNumber5 = RandomClass.Next(1, 49) If RandomNumber5 = RandomNumber4 Or RandomNumber3 Or RandomNumber2 Or RandomNumber1 Then RandomNumber5 = RandomClass.Next(1, 49) End If 'Displays fifth number generated txtFifth.Text = (RandomNumber5) '#################################### Dim RandomNumber6 As Integer RandomNumber6 = RandomClass.Next(1, 49) If RandomNumber6 = RandomNumber5, RandomNumber4, RandomNumber3, RandomNumber2, RandomNumber1 Then RandomNumber6 = RandomClass.Next(1, 49) End If 'Displays sixth number generated txtSixth.Text = (RandomNumber6) End Sub

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  • C++ random number from a set

    - by user69514
    Is it possible to print a random number in C++ from a set of numbers with ONE SINGLE statement? let's say the set is 2, 5, 22, 55, 332 i looked up rand, but I double it's possible to do in a single statement

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  • How do I produce "enjoyably" random, as opposed to pseudo-random?

    - by Hilton Campbell
    I'm making a game which presents a number of different kinds of puzzles in sequence. I choose each puzzle with a pseudorandom number. For each puzzle, there are a number of variations. I choose the variation with another pseudorandom number. And so on. The thing is, while this produces near-true randomness, this isn't what the player really wants. The player typically wants what they perceive to be and identify as random, but only if it doesn't tend to repeat puzzles. So, not really random. Just unpredictable. Giving it some thought, I can imagine hacky ways of doing it. For example, temporarily eliminating the most recent N choices from the set of possibilities when selecting a new choice. Or assigning every choice an equal probability, reducing a choice's probability to zero on selection, and then increasing all probabilities slowly with each selection. I assume there's an established way of doing this, but I just don't know the terminology so I can't find it. Anyone know? Or has anyone solved this in a pleasing way?

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