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  • Maximal Length of List to Shuffle with Python random.shuffle?

    - by Henrik
    I have a list which I shuffle with the Python built in shuffle function (random.shuffle) However, the Python reference states: Note that for even rather small len(x), the total number of permutations of x is larger than the period of most random number generators; this implies that most permutations of a long sequence can never be generated. Now, I wonder what this "rather small len(x)" means. 100, 1000, 10000,... Can anybody clarify? Thanks!

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  • How to adjust the distribution of values in a random data stream?

    - by BCS
    Given a infinite stream of random 0's and 1's that is from a biased (e.g. 1's are more common than 0's by a know factor) but otherwise ideal random number generator, I want to convert it into a (shorter) infinite stream that is just as ideal but also unbiased. Looking up the definition of entropy finds this graph showing how many bits of output I should, in theory, be able to get from each bit of input. The question: Is there any practical way to actually implement a converter that is nearly ideally efficient?

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  • iterate through fb:random

    - by fusion
    does anyone know how i would fill data from mysql database in fb:random and iterate through it, to pick a random quote? fb:random $facebook->api_client->fbml_setRefHandle('quotes', '<fb:random> <fb:random-option>Quote 1</fb:random-option> <fb:random-option>Quote 2</fb:random-option> </fb:random>'); mysql data: $rowcount = mysql_result($result, 0, 0); $rand = rand(0,$rowcount-1); $result = mysql_query("SELECT cQuotes, vAuthor, cArabic, vReference FROM thquotes LIMIT $rand, 1", $conn) or die ('Error: '.mysql_error()); $row = mysql_fetch_array($result, MYSQL_ASSOC); if ( !$row ) { echo "Empty"; } else{ $fb_box = "<p>" . h($row['cArabic']) . "</p>"; $fb_box .= "<p>" . h($row['cQuotes']) . "</p>"; $fb_box .= "<p>" . h($row['vAuthor']) . "</p>"; $fb_box .= "<p>" . h($row['vReference']) . "</p>"; }

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  • Strange Ubuntu Random Display [Video]

    - by d4v1dv00
    I had this random display issue ever since Ubuntu 11.04 and now running Ubuntu 11.10 and this problem still persist. It is very hard for me to explain, so I uploaded a video to elaborate itself. Before I convert from Windows 7, this issue never happened. The symptom is so random that I cannot reproduce or tell precisely when will this happen again. My wild guess is, should this be related to driver? Below are my detail system information: $ lspci 00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09) 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04) 00:1a.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 05) 00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05) 00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b5) 00:1c.3 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 (rev b5) 00:1d.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 05) 00:1f.0 ISA bridge: Intel Corporation H67 Express Chipset Family LPC Controller (rev 05) 00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller (rev 05) 00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 05) 02:00.0 Ethernet controller: Broadcom Corporation NetLink BCM57788 Gigabit Ethernet PCIe (rev 01) is there any other information i need to post and how do i do that?

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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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  • Random compositing lag

    - by user1020567
    My laptop specs: 512 mb of RAM, out of which 64 mb are shared with an integrated GPU - ATI Radeon Xpress 200 M. Intel 1,6 Ghz Celeron M single-core processor. I've spent months trying to figure out why compositing and effects sometimes lag on any distro I try. Now I've come to realise that no matter what drivers I try (the default ones work for me on pretty much any linux) compositing lag is random. When I used Ubuntu 10.10, for example, sometimes window compositing would lag and sometimes it wouldn't. The PC is able to render those effects so hardware is not the problem. It's completely random and unpredictable - sometimes when I turn on the computer the effects lag horribly and sometimes it's completely smooth. I've also checked startup items and there doesn't seem to be any unnecessary entries. I also tried building my own OS with Arch Linux and the problem persists there, therefore I can only assume that it's a driver issue of some sort. By default there are lots of drivers supplied with linux distributions. Could it be that they're in the way? The ones that I need are ati/radeon (or both? What's the difference between them?) and there seem to be a lot of others... What should I do?

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  • Creating a Function in SQL Server with a Phone Number as a parameter and returns a Random Number

    - by Emer
    Hi Guys, I am hoping someone can help me here as google is not being as forthcoming as I would have liked. I am relatively new to SQL Server and so this is the first function I have set myself to do. The outline of the function is that it has a Phone number varchar(15) as a parameter, it checks that this number is a proper number, i.e. it is 8 digits long and contains only numbers. The main character I am trying to avoid is '+'. Good Number = 12345678 Bad Number = +12345678. Once the number is checked I would like to produce a random number for each phone number that is passed in. I have looked at substrings, the like operator, Rand(), left(), Right() in order to search through the number and then produce a random number. I understand that Rand() will produce the same random number unless alterations are done to it but right now it is about actually getting some working code. Any hints on this would be great or even point me towards some more documentation. I have read books online and they haven't helped me, maybe I am not looking in the right places. Here is a snippet of code I was working on the Rand declare @Phone Varchar (15) declare @Counter Varchar (1) declare @NewNumber Varchar(15) set @Phone = '12345678' set @Counter = len(@Phone) while @Counter > 0 begin select case when @Phone like '%[0-9]%' then cast(rand()*100000000 as int) else 'Bad Number' end set @counter = @counter - 1 end return Thanks for the help in advance Emer

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  • How to generate a cryptographically secure Double between 0 and 1?

    - by Portman
    I know how to generate a random number between 0 and 1 using the NextDouble method of the pseudo-random number generator. var rng1 = new System.Random(); var random1 = rng1.NextDouble(); // generates a random double between 0 and 1.0 And I know how to fill a random byte array using the cryptographically secure random number generator. Byte[] bytes = new Byte[8]; var rng2 = new System.Security.Cryptography.RNGCryptoServiceProvider(); rng2.GetBytes(bytes); // generates 8 random bytes But how can I convert the byte-array output of RNGCryptoServiceProvider into a random number between 0 (inclusive) and 1 (exclusive)?

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  • Apprende à analyser un rapport de type RIST (Random System Information Tool), par Simon-Sayce

    Bonjour, Sayce, l'un des membres de l'équipe de rédaction souhaite vous inviter à la lecture de l'article suivant: Random System Information Tool . Cet article est à destination de toutes les personnes souhaitant vérifier l'intégrité de leur PC en utilisant le logiciel RSIT Ce cours explique ligne par ligne le rapport généré part l'outil. N'hésitez pas à partager vos remarques Nous vous souhaitons une bonne lecture

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  • how to programtically build a grid of interlocking but random sized squares

    - by Mrwolfy
    I want to create a two dimensional layout of rectangular shapes, a grid made up of random sized cubes. The cubed should fit together and have equal padding or margin (space between). Kind of like a comic book layout, or more like the image attached. How could I do this procedurally? Practically, I would probably be using Python and some graphic software to render an image, but I don't know the type of algorithm (or whatnot) I would need to use to generate the randomized grid.

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  • How do I do random isometric paths?

    - by user406470
    I'm working on an Isometric city generator, and I am looking for a little push in the right direction. I'm looking to randomly generate roads on a isometric plane. I have never done pathfinding before, and I've googled it and didn't find any articles relating to what I am trying to do. Basically, my program generates a random isometric city and, I am hoping to add roads to that. Any help is appreciated!

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  • Random Vector within a cone

    - by Paul
    I'm looking to create a random vector within a cone given the radius (base). It feels like I've been traversing through many pages on the internet and still I'm no further forward to getting an answer. I was thinking I could get a point within the base of the cone and have it point towards the apex (then just use the inverse of that for my animation) but this seems like an incredibly long winded approach.

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  • Possible applications of algorithm devised for differentiating between structured vs random text

    - by rooznom
    I have written a program that can rapidly (within 5 sec on a 2GB RAM desktop, 2.33 Ghz CPU) differentiate between structured text (e.g english text) and random alphanumeric strings. It can also provide a probability score for the prediction. Are there any practical applications/uses of such a program. Note that the program is based on entropy models and does not have any dictionary comparisons in its workflow. Thanks in advance for your responses

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  • How does this C# asp.net random password code work?

    - by quakkels
    Hello all, I'm new to .NET and C# and I'm trying to figure out how this code works: public static string CreateRandomPassword(int PasswordLength) { String _allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ23456789"; Byte[] randomBytes = new Byte[PasswordLength]; RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); rng.GetBytes(randomBytes); char[] chars = new char[PasswordLength]; int allowedCharCount = _allowedChars.Length; for(int i = 0;i<PasswordLength;i++) { /// /// I don't understand how this line works: /// chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount]; } return new string(chars); } I think I've got a pretty good handle on most of this. I haven't been able to understand the following line: chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount]; I understand that the code generates random binary numbers and uses those random numbers in the for loop to select a character from the _allowedChars string. What I don't get is why this code uses the modulous operator (%) to get the _allowedChars index value. Thanks for any help

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  • How to generate a good random seed to pass to srand()?

    - by zr
    Hi, I am writing a C++ program which needs to create a temporary file for its internal usage. I would like to allow concurrent executions of the program by running multiple proccesses, so the temporary file name needs to be randomized, that way each spawned process will generate a unique temporary file name for its own use. I am using rand() to generate random characters for part of the file name, so i need to initialize the random number generator's seed using srand(). What options are there for passing a good argument to srand() such that two processes will not be initialized with the same seed value? My code needs to work both on Windows and pn Linux TIA.

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  • Oracle aggregate function to return a random value for a group?

    - by tpdi
    The standard SQL aggregate function max() will return the highest value in a group; min() will return the lowest. Is there an aggregate function in Oracle to return a random value from a group? Or some technique to achieve this? E.g., given the table foo: group_id value 1 1 1 5 1 9 2 2 2 4 2 8 The SQL query select group_id, max(value), min(value), some_aggregate_random_func(value) from foo group by group_id; might produce: group_id max(value), min(value), some_aggregate_random_func(value) 1 9 1 1 2 8 2 4 with, obviously, the last column being any random value in that group.

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  • How hard is it to create a not-so-random number generator?

    - by Duracell
    Backstory: So I was driving to band practice this evening. My car has a USB port where you can plug in a USB stick with MP3 files on it and the stereo will play them. I have about 100 MP3s on my stick so I pushed the 'Random' button. So from here to band practice, it played: Track 22 Track 45 Track 4 Track 11 Track 87 Track 66 Track 98 Then on the way home, it played Track 16 Track 27 Track 33 And then I stopped at the petrol station. I filled up, got back in the car and the stereo fired up again. It played Track 22 Track 45 Track 4 Track 11 Track 87 I thought, WTF? What's with this 'random' generator? What are they using as a seed, if not time? Is a car stereo so memory-tight that it can't even use the C stdlib? Does anyone know how this kind of thing happens?

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  • What's the best way to return a random line in a text file using C?

    - by jeremy Ruten
    What's the best way to return a random line in a text file using C? It has to use the standard I/O library (<stdio.h>) because it's for Nintendo DS homebrew. Clarifications: Using a header in the file to store the number of lines won't work for what I want to do. I want it to be as random as possible (the best being if each line has an equal probability of being chosen as every other line.) The file will never change while the program is being run. (It's the DS, so no multi-tasking.)

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  • How to make a random number generator in matlab that is based on percentages?

    - by Ben Fossen
    I am currently using the built in random number generator. for example nAsp = randi([512, 768],[1,1]); 512 is the lower bound and 768 is the upper bound, the random number generator chooses a number from between these two values. What I want is to have two ranges for nAsp but I want one of them to get called 25% of the time and the other 75% of the time. Then gets plugged into he equation. Does anyone have any ideas how to do this or if there is a built in function in matlab already? for example nAsp = randi([512, 768],[1,1]); gets called 25% of the time nAsp = randi([690, 720],[1,1]); gets called 75% of the time

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  • Random select is not always returning a single row.

    - by Lieven
    The intention of following (simplified) code fragment is to return one random row. Unfortunatly, when we run this fragment in the query analyzer, it returns between zero and three results. As our input table consists of exactly 5 rows with unique ID's and as we perform a select on this table where ID equals a random number, we are stumped that there would ever be more than one row returned. Note: among other things, we already tried casting the checksum result to an integer with no avail. DECLARE @Table TABLE ( ID INTEGER IDENTITY (1, 1) , FK1 INTEGER ) INSERT INTO @Table SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 SELECT * FROM @Table WHERE ID = ABS(CHECKSUM(NEWID())) % 5 + 1

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  • How to generate random strings that match a given regexp?

    - by Pies
    Duplicate: Random string that matches a regexp No, it isn't. I'm looking for an easy and universal method, one that I could actually implement. That's far more difficult than randomly generating passwords. I want to create an application that takes a regular expression, and shows 10 randomly generated strings that match that expression. It's supposed to help people better understand their regexps, and to decide i.e. if they're secure enough for validation purposes. Does anyone know of an easy way to do that? One obvious solution would be to write (or steal) a regexp parser, but that seems really over my head. I repeat, I'm looking for an easy and universal way to do that. Edit: Brute force approach is out of the question. Assuming the random strings would just be [a-z0-9]{10} and 1 million iterations per second, it would take 65 years to iterate trough the space of all 10-char strings.

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  • Repeated calls with random Javascript append to the URL

    - by cjk
    I keep getting calls to my server where there is random Javascript appended on the end of lots of the calls, e.g.: /UI/Includes/JavaScript/).length)&&e.error( /UI/Includes/JavaScript/,C,!1),a.addEventListener( /UI/Includes/JavaScript/),l=b.createDocumentFragment(),m=b.documentElement,n=m.firstChild,o=b.createElement( /UI/Includes/JavaScript/&&a.getAttributeNode( /UI/Includes/JavaScript/&&a.firstChild.getAttribute( /UI/Includes/JavaScript/).replace(bd, /UI/Includes/JavaScript/)),a.getElementsByTagName( The user agent is always this: Mozilla/4.0+(compatible;+MSIE+6.0;+Windows+NT+5.1;+SV1;+.NET+CLR+2.0.50727) I have jQuery, Modernizr and other JS and originally thought that some browser was messing up it's JS calls, however this particular IP address hasn't requested any images so I'm wondering if it is some kind of attack. Is this a common occurence?

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