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  • Computationally simple Pseudo-Gaussian Distribution with varying mean and standard deviation?

    - by mstksg
    This picture from wikipedia has a nice example of the sort of functions I'd ideally like to generate http://en.wikipedia.org/wiki/File:Normal_Distribution_PDF.svg Right now I'm using the Irwin-Hall Distribution, which is more or less a Polynomial approximation of the Gaussian distribution...basically, you use uniform random number generator and iterate it x times, and take the average. The more iterations, the more like a Gaussian Distribution it is. It's pretty nice; however I'd like to be able to have one where I can vary the mean. For example, let's say I wanted a number between the range 0 and 10, but around 7. Like, the mean (if I repeated this function multiple times) would turn out to be 7, but the actual range is 0-10. Is there one I should look up, or should I work on doing some fancy maths with standard Gaussian Distributions?

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  • Efficiently generate a 16-character, alphanumeric string

    - by ensnare
    I'm looking for a very quick way to generate an alphanumeric unique id for a primary key in a table. Would something like this work? def genKey(): hash = hashlib.md5(RANDOM_NUMBER).digest().encode("base64") alnum_hash = re.sub(r'[^a-zA-Z0-9]', "", hash) return alnum_hash[:16] What would be a good way to generate random numbers? If I base it on microtime, I have to account for the possibility of several calls of genKey() at the same time from different instances. Or is there a better way to do all this? Thanks.

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  • What's going on here? Repeating rows in random list of lists.

    - by Jesse Aldridge
    I expected to get a grid of unique random numbers. Instead each row is the same sequence of numbers. What's going on here? from pprint import pprint from random import random nrows, ncols = 5, 5 grid = [[0] * ncols] * nrows for r in range(nrows): for c in range(ncols): grid[r][c] = int(random() * 100) pprint(grid) Example output: [[64, 82, 90, 69, 36], [64, 82, 90, 69, 36], [64, 82, 90, 69, 36], [64, 82, 90, 69, 36], [64, 82, 90, 69, 36]]

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  • How to generate a number in arbitrary range using random()={0..1} preserving uniformness and density?

    - by psihodelia
    Generate a random number in range [x..y] where x and y are any arbitrary floating point numbers. Use function random(), which returns a random floating point number in range [0..1] from P uniformly distributed numbers (call it "density"). Uniform distribution must be preserved and P must be scaled as well. I think, there is no easy solution for such problem. To simplify it a bit, I ask you how to generate a number in interval [-0.5 .. 0.5], then in [0 .. 2], then in [-2 .. 0], preserving uniformness and density? Thus, for [0 .. 2] it must generate a random number from P*2 uniformly distributed numbers. The obvious simple solution random() * (x - y) + y will generate not all possible numbers because of the lower density for all abs(x-y)>1.0 cases. Many possible values will be missed. Remember, that random() returns only a number from P possible numbers. Then, if you multiply such number by Q, it will give you only one of P possible values, scaled by Q, but you have to scale density P by Q as well.

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  • Software/Application needed to store and organize random content [on hold]

    - by Rami.Shareef
    I have the need to store random contents (on my local hard drive/ laptop hard drive) for personal use so I can look these contents up later on when I need them. What I mean by random content is one of the following: Some sort of code Random fact Css / html / Javascript tips Or anything I might find interesting and want to keep for future reference I want to look up these entries by tags, the software should give me the ability to associate every entry with one tag or more. I have been having difficult time find applications offer this functionality, it is like a local database with search ability and easy data-entry methods. I can build one, but I don't have the time to invest in doing so. Can you refer me to any application/software that can do that, it would be great. It does not matter if it is paid or free.

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  • reservoir sampling problem: correctness of proof

    - by eSKay
    This MSDN article proves the correctness of Reservoir Sampling algorithm as follows: Base case is trivial. For the k+1st case, the probability a given element i with position <= k is in R is s/k. The probability i is replaced is the probability k+1st element is chosen multiplied by i being chosen to be replaced, which is: s/(k+1) * 1/s = 1/(k+1), and prob that i is not replaced is k/k+1. So any given element's probability of lasting after k+1 rounds is: (chosen in k steps, and not removed in k steps) = s/k * k/(k+1), which is s/(k+1). So, when k+1 = n, any element is present with probability s/n. about step 3: What are the k+1 rounds mentioned? What is chosen in k steps, and not removed in k steps? Why are we only calculating this probability for elements that were already in R after the first s steps?

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  • reservoir sampling problem

    - by eSKay
    This MSDN article proves the correctness of Reservoir Sampling algorithm as follows: Base case is trivial. For the k+1st case, the probability a given element i with position <= k is in R is s/k. The probability i is replaced is the probability k+1st element is chosen multiplied by i being chosen to be replaced, which is: s/(k+1) * 1/s = 1/(k+1), and prob that i is not replaced is k/k+1. So any given element's probability of lasting after k+1 rounds is: (chosen in k steps, and not removed in k steps) = s/k * k/(k+1), which is s/(k+1). So, when k+1 = n, any element is present with probability s/n. about step 3: What are the k+1 rounds mentioned? What is chosen in k steps, and not removed in k steps? Why are we only calculating this probability for elements that were already in R after the first s steps?

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  • Basic procedural generated content works, but how could I do the same in reverse?

    - by andrew
    My 2D world is made up of blocks. At the moment, I create a block and assign it a number between 1 and 4. The number assigned to the nth block is always the same (i.e if the player walks backwards or restarts the game.) and is generated in the function below. As shown here by this animation, the colours represent the number. function generate_data(n) math.randomseed(n) -- resets the random so that the 'random' number for n is always the same math.random() -- fixes lua random bug local no = math.random(4) --print(no, n) return no end Now I want to limit the next block's number - a block of 1 will always have a block 2 after it, while block 2 will either have a block 1,2 or 3 after it, etc. Before, all the blocks data was randomly generated, initially, and then saved. This data was then loaded and used instead of being randomly called. While working this way, I could specify what the next block would be easily and it would be saved for consistency. I have now removed this saving/loading in favour of procedural generation as I realised that save whiles would get very big after travelling. Back to the present. While travelling forward (to the right), it is easy to limit what the next blocks number will be. I can generate it at the same time as the other data. The problem is when travelling backwards (to the left) I can not think of a way to load the previous block so that it is always the same. Does anyone have any ideas on how I could sort this out?

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  • stripping random number with substr problem

    - by Jim
    Using a random number to be included with another character. Then I want to strip out the random number and just leave the other character. I have this code that generates the random number (8 characters long) consistently. If you hit your refresh button multiple times, the “ID” field disappears even though the “Random Number” plus “ID” are still there. Not sure what is happening to the random number on refresh in the substr function. This is the code: // Begin Create Random ID Code ///////////////////////////////////////// function gRanStr1() { $length1 = 8; $characters = “0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ”; for ($p = 0; $p < $length1; $p++) { $lcrs1 .= $characters[mt_rand(0, strlen($characters)-1)]; } $lcrs9 = str_replace(' ', '', $lcrs9); return $lcrs1; } // End Create Random ID Code ///////////////////////////////////////// // Begin Decode Random ID Code ///////////////////////////////////////// $TrkR99 = "c"; $ResHeadID = gRanStr1() . $TrkR99; $ResHeadID = preg_replace('/[\s]+/',' ',$ResHeadID); echo "”; echo $ResHeadID . ” = echo of Random Number plus ID“; for($i=0; $i if ($ResHeadID == "") { ""; } else { $ResHeadID = preg_replace('/[\s]+/',' ',$ResHeadID); $TrkRa1 = substr($ResHeadID, $Index1 + 8, 1); } $dTrkRes = $TrkRa1; echo $TrkRa1 . " = echo of ID after random number stripped.“; echo “”; // End Decode Random ID Code /////////////////////////////////////////

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  • Random memory corruption going undetected by memtest86

    - by sds
    Thinkpad t520; Ubuntu 12.04.1 LTS; 3.2.0-33-generic 16GB of ram Memtest86+ ran for 26 hours, 9 passes, no errors Booted into "recovery mode"; Ran fsck all filesystems - no errors; "check all packages" - no errors apparent random memory corruption: perl/R/chrome segfault every now and then, seemingly at random; sort(1) produces corrupt unsorted files. What could be possibly wrong and how do I debug it?

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  • SQL Server stored procedure to generate random passwords

    SQL Server is used to support many applications and one such feature of most applications is the storage of passwords. Sometimes there is a need to reset a password using a temporary password or generate a random password for a new user. In this tip I cover a simple stored procedure to generate random passwords that can be incorporated into your applications. Get Smart with SQL Backup Pro Powerful centralised management, encryption and more.SQL Backup Pro was the smartest kid at school Discover why.

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  • SQL: select random row from table where the ID of the row isn't in another table?

    - by johnrl
    I've been looking at fast ways to select a random row from a table and have found the following site: http://74.125.77.132/search?q=cache:http://jan.kneschke.de/projects/mysql/order-by-rand/&hl=en&strip=1 What I want to do is to select a random url from my table 'urls' that I DON'T have in my other table 'urlinfo'.The query I am using now selects a random url from 'urls' but I need it modified to only return a random url that is NOT in the 'urlinfo' table. Heres the query: SELECT url FROM urls JOIN (SELECT CEIL(RAND() * (SELECT MAX(urlid) FROM urls ) ) AS urlid ) AS r2 USING(urlid); And the two tables: CREATE TABLE urls ( urlid INT NOT NULL AUTO_INCREMENT PRIMARY KEY, url VARCHAR(255) NOT NULL, ) ENGINE=INNODB; CREATE TABLE urlinfo ( urlid INT NOT NULL PRIMARY KEY, urlinfo VARCHAR(10000), FOREIGN KEY (urlid) REFERENCES urls (urlid) ) ENGINE=INNODB;

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  • How do I generate (and label) a random integer with python 3.2?

    - by An hero
    Okay, so I'm admittedly a newbie to programming, but I can't determine how to get python v3.2 to generate a random positive integer between parameters I've given it. Just so you can understand the context, I'm trying to create a guessing-game where the user inputs parameters (say 1 to 50), and the computer generates a random number between the given numbers. The user would then have to guess the value that the computer has chosen. I've searched long and hard, but all of the solutions I can find only tell one how to get earlier versions of python to generate a random integer. As near as I can tell, v.3.2 changed how to generate and label a random integer. Anyone know how to do this? Thanks!

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  • How to generate a random BigInteger value in Java?

    - by Bill the Lizard
    I need to generate arbitrarily large random integers in the range 0 (inclusive) to n (exclusive). My initial thought was to call nextDouble and multiply by n, but once n gets to be larger than 253, the results would no longer be uniformly distributed. BigInteger has the following constructor available: public BigInteger(int numBits, Random rnd) Constructs a randomly generated BigInteger, uniformly distributed over the range 0 to (2numBits - 1), inclusive. How can this be used to get a random value in the range 0 - n, where n is not a power of 2?

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  • How to generate distinct random numbers per distinct threads in .NET?

    - by mark
    Dear ladies and sirs. I have to generate 19 bit random numbers. However, there is a constraint - two threads may not generate the same random number when running certain code. The simplest solution is lock the entire code. However, I would like to know if there is a non locking solution. I thought, I can incorporate ManagedThreadId within the produced random numbers, but the ManagedThreadId documentation on the Internet mentions that it may span the whole Int32 range. Unmanaged thread id seems to be limited to 11 bits, still this leaves me with just 8 truly random bits. Are there any other ways? Somehow to utilize the Thread Local Storage, may be? Thanks.

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  • Random number Generator in C#

    - by Sunil
    Why do i need to create an instance of Random class, if i want to create a random number between 1 and 100 ....like Random rand = new Random(); rand.Next(1,100); Is there any static function of Random class to do the same? like... Random.Next(1,100); I don't want to create an instance unnecessarily

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  • ZFS with L2ARC (SSD) slower for random seeks than without L2ARC

    - by Florian Kruse
    I am currently testing ZFS (Opensolaris 2009.06) in an older fileserver to evaluate its use for our needs. Our current setup is as follows: Dual core (2,4 GHz) with 4 GB RAM 3x SATA controller with 11 HDDs (250 GB) and one SSD (OCZ Vertex 2 100 GB) We want to evaluate the use of a L2ARC, so the current ZPOOL is: $ zpool status pool: tank state: ONLINE scrub: none requested config: NAME STATE READ WRITE CKSUM afstank ONLINE 0 0 0 raidz1 ONLINE 0 0 0 c11t0d0 ONLINE 0 0 0 c11t1d0 ONLINE 0 0 0 c11t2d0 ONLINE 0 0 0 c11t3d0 ONLINE 0 0 0 raidz1 ONLINE 0 0 0 c13t0d0 ONLINE 0 0 0 c13t1d0 ONLINE 0 0 0 c13t2d0 ONLINE 0 0 0 c13t3d0 ONLINE 0 0 0 cache c14t3d0 ONLINE 0 0 0 where c14t3d0 is the SSD (of course). We run IO tests with bonnie++ 1.03d, size is set to 200 GB (-s 200g) so that the test sample will never be completely in ARC/L2ARC. The results without SSD are (average values over several runs which show no differences) write_chr write_blk rewrite read_chr read_blk random seeks 101.998 kB/s 214.258 kB/s 96.673 kB/s 77.702 kB/s 254.695 kB/s 900 /s With SSD it becomes interesting. My assumption was that the results should be in worst case at least the same. While write/read/rewrite rates are not different, the random seek rate differs significantly between individual bonnie++ runs (between 188 /s and 1333 /s so far), average is 548 +- 200 /s, so below the value w/o SSD. So, my questions are mainly: Why do the random seek rates differ so much? If the seeks are really random, they should not differ much (my assumption). So, even if the SSD is impairing the performance it should be the same in each bonnie++ run. Why is the random seek performance worse in most of the bonnie++ runs? I would assume that some part of the bonnie++ data is in the L2ARC and random seeks on this data performs better while random seeks on other data just performs similarly like before.

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  • Java: How to check the random letters from a-z, out of 10 letters minimum 2 letter should be a vowel

    - by kalandar
    I am writing a program to validate the following scenarios: Scenario 1: I am using the Random class from java.util. The random class will generate 10 letters from a-z and within 10 letter, minimum 2 letters must be a vowels. Scenario 2: When the player 1 and player 2 form a word from A-Z, he will score some points. There will be a score for each letter. I have already assigned the values for A-Z. At the end of the game, the system should display a scores for player 1 and player 2. How do i do it? Please help. I will post my code here. Thanks a lot. =========================================== import java.util.Random; import java.util.Scanner; public class FindYourWords { public static void main(String[] args) { Random rand = new Random(); Scanner userInput = new Scanner(System.in); //==================Player object=============================================== Player playerOne = new Player(); playerOne.wordScore = 0; playerOne.choice = "blah"; playerOne.turn = true; Player playerTwo = new Player(); playerTwo.wordScore = 0; playerTwo.choice = "blah"; playerTwo.turn = false; //================== Alphabet ================================================== String[] newChars = { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z" }; //values of the 26 alphabets to be used int [] letterScore = {1,3,3,2,1,4,2,4,1,8,5,1,3,1,1,3,10,1,1,1,1,4,4,8,4,10}; // to assign score to the player1 and player 2 String[] vowel = { "a", "e", "i", "o", "u" }; // values for vowels int vow=0; System.out.println("FINDYOURWORDS\n"); int[] arrayRandom = new int[10]; //int array for word limiter String[] randomLetter = new String[10]; //storing the letters in newChars into this array //=============================================================================== boolean cont = true; while (cont) { if (playerOne.turn) { System.out.print("Letters of Player 1: "); } else if (!playerOne.turn) { System.out.print("Letters of Player 2: "); } for (int i = 0; i < arrayRandom.length; i++) { //running through the array limiter int r = rand.nextInt(newChars.length); //assigning random nums to the array of letters randomLetter[i] = newChars[r]; System.out.print(randomLetter[i]+ " "); } //input section for player System.out.println(""); System.out.println("Enter your word (or '@' to pass or '!' to quit): "); if (playerOne.turn) { playerOne.choice = userInput.next(); System.out.println(playerOne.turn); playerOne.turn = false; } else if (!playerOne.turn){ playerTwo.choice = userInput.next(); System.out.println(playerOne.turn); playerOne.turn = true; } //System.out.println(choice); String[] wordList = FileUtil.readDictFromFile("words.txt"); //Still dunno what this is for if (playerOne.choice.equals("@")) { playerOne.turn = false; } else if (playerTwo.choice.equals("@")) { playerOne.turn = true; } else if (playerOne.choice.equals("!")) { cont = false; } for (int i = 0; i < wordList.length; i++) { //System.out.println(wordList[i]); if (playerOne.choice.equalsIgnoreCase(wordList[i]) || playerTwo.choice.equalsIgnoreCase(wordList[i])){ } } } }}

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  • one 16K random read I/O issues 2 scsi I/O (16K and 4K) requests in linux

    - by hiroyuki
    I noticed weird issue when benchmarking random read I/O for files in linux (2.6.18). The Benchmarking program is my own program and it simply keeps reading 16KB of a file from a random offset. I traced I/O behavior at system call level and scsi level by systemtap and I noticed that one 16KB sysread issues 2 scsi I/Os as following. SYSPREAD random(8472) 3, 0x16fc5200, 16384, 128137183232 SCSI random(8472) 0 1 0 0 start-sector: 226321183 size: 4096 bufflen 4096 FROM_DEVICE 1354354008068009 SCSI random(8472) 0 1 0 0 start-sector: 226323431 size: 16384 bufflen 16384 FROM_DEVICE 1354354008075927 SYSPREAD random(8472) 3, 0x16fc5200, 16384, 21807710208 SCSI random(8472) 0 1 0 0 start-sector: 1889888935 size: 4096 bufflen 4096 FROM_DEVICE 1354354008085128 SCSI random(8472) 0 1 0 0 start-sector: 1889891823 size: 16384 bufflen 16384 FROM_DEVICE 1354354008097161 SYSPREAD random(8472) 3, 0x16fc5200, 16384, 139365318656 SCSI random(8472) 0 1 0 0 start-sector: 254092663 size: 4096 bufflen 4096 FROM_DEVICE 1354354008100633 SCSI random(8472) 0 1 0 0 start-sector: 254094879 size: 16384 bufflen 16384 FROM_DEVICE 1354354008111723 SYSPREAD random(8472) 3, 0x16fc5200, 16384, 60304424960 SCSI random(8472) 0 1 0 0 start-sector: 58119807 size: 4096 bufflen 4096 FROM_DEVICE 1354354008120469 SCSI random(8472) 0 1 0 0 start-sector: 58125415 size: 16384 bufflen 16384 FROM_DEVICE 1354354008126343 As shown above, one 16KB pread issues 2 scsi I/Os. (I traced scsi io dispatching with probe scsi.iodispatching. Please ignore values except for start-sector and size.) One scsi I/O is 16KB I/O as requested from the application and it's OK. The thing is the other 4KB I/O which I don't know why linux issues that I/O. of course, I/O performance is degraded by the weired 4KB I/O and I am having trouble. I also use fio (famous I/O benchmark tool) and noticed the same issue, so it's not from the application. Does anybody know what is going on ? Any comments or advices are appreciated. Thanks

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  • Random Map Generation in Java

    - by Thomas Owers
    I'm starting/started a 2D tilemap RPG game in Java and I want to implement random map generation. I have a list of different tiles, (dirt/sand/stone/grass/gravel etc) along with water tiles and path tiles, the problem I have is that I have no idea where to start on generating a map randomly. It would need to have terrain sections (Like a part of it will be sand, part dirt etc) Similar to how Minecraft is where you have different biomes and they seamlessly transform into each other. Lastly I would also need to add random paths into this as well going in different directions all over the map. I'm not asking anyone to write me all the code or anything, just piont me into the right direction please. tl;dr - Generate a tile map with biomes, paths and make sure the biomes seamlessly go into each other. Any help would be much appreciated! :) Thank you.

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  • Random map generation

    - by Thomas Owers
    I'm starting/started a 2D tilemap RPG game in Java and I want to implement random map generation. I have a list of different tiles, (dirt/sand/stone/grass/gravel etc) along with water tiles and path tiles, the problem I have is that I have no idea where to start on generating a map randomly. It would need to have terrain sections (Like a part of it will be sand, part dirt, etc.) Similar to how Minecraft is where you have different biomes and they seamlessly transform into each other. Lastly I would also need to add random paths into this as well going in different directions all over the map. I'm not asking anyone to write me all the code or anything, just piont me into the right direction please. tl;dr - Generate a tile map with biomes, paths and make sure the biomes seamlessly go into each other.

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