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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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• Fastest Way to generate 1,000,000+ random numbers in python

  - by Sandro

  I am currently writing an app in python that needs to generate large amount of random numbers, FAST. Currently I have a scheme going that uses numpy to generate all of the numbers in a giant batch (about ~500,000 at a time). While this seems to be faster than python's implementation. I still need it to go faster. Any ideas? I'm open to writing it in C and embedding it in the program or doing w/e it takes. Constraints on the random numbers: A Set of numbers 7 numbers that can all have different bounds: eg: [0-X1, 0-X2, 0-X3, 0-X4, 0-X5, 0-X6, 0-X7] Currently I am generating a list of 7 numbers with random values from [0-1) then multiplying by [X1..X7] A Set of 13 numbers that all add up to 1 Currently just generating 13 numbers then dividing by their sum Any ideas? Would pre calculating these numbers and storing them in a file make this faster? Thanks!

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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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• rng random number

  - by wano3

  Hi, I have a question. How can I calculate/estimate upper bound of random number, that a random number can generate ? Thanks in advance!

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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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• Releasing the new Sample Browser Phone app

  - by Jialiang

  Originally posted on: http://geekswithblogs.net/Jialiang/archive/2014/06/05/releasing-the-new-sample-browser-phone-app.aspx Starting its journey in 2010, Sample Browser is achieving its tetralogy by releasing a Windows Phone version Sample Browser today. The new Windows Phone app is the fourth milestone of Sample Browser since we released the desktop version and the Visual Studio version in 2012 and the Windows Store version in 2013. This time, by providing a sample browser designed for a ‘walking’ platform in response to MVPs’ suggestions during last year’s MVP Global Summit, we are literally putting a world of code samples "at developers’ fingertips”. If you like to have a code gallery of over 7000 quality code samples in your pocket, then click here to download our Windows Phone Sample Browser and start a fantastic mobile experience. With Windows Phone version Sample Browser and the Internet, you can search for code samples on MSDN at anytime and anywhere you want, 24/7 and–even to bed. You can also check code sample details and share them with your friends. Compared to the other 3 pieces in the tetralogy (desktop version, Visual Studio version, and the Windows Store version), the Windows Phone version Sample Browser sells itself for convenience and instant connectivity. For those who need to reach code samples under mobile circumstances where no PCs is available, Windows Phone version Sample Browser will definitely be the right service you are seeking for. Aside from sharing samples via emails as the other 3 do, the Windows Phone version Sample Browser also allows you to share the sample via SMS and Near Field Communication (NFC).   What's Next Currently, the Windows Phone Sample Browser only supports online MSDN code searching, but we already plan to upgrade Sample Browser to allow users to do ‘Bing code search’, and add and manage their private code snippets.  We will also upgrade the app to universal app. Universal App is a new concept brought up in the Microsoft Build Developer Conference 2014. It is a new development model that allows for a single app to be deployed across multiple Windows devices such as Windows Phone, Windows 8.1, and XBox. Therefore, once we finish upgrading Sample Browser to a universal app, you can synchronize your own code snippets across different devices; You can also mark a code sample as favorite on your Windows Phone and continue to study the sample when you are on your desktop. By then, sharing data between platforms will be a piece of cake. Also, the user experience of Sample Browser on different platforms will be more consistent.  The best is yet to come!   We sincerely suggest you give Sample Browser a try (click here to download). If you love what you see in Sample Browser, please recommend it to your friends and colleagues. If you encounter any problems or have any suggestions for us, please contact us at [email protected]. Your precious opinions and comments are more than welcome.

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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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• 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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• 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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• Random generation of interesting puzzle levels?

  - by monsterfarm

  I'm making a Sokoban-like game i.e. there's a grid that has some crates on it you can push and you have to get the crates on crosses to win the level (although I'm going to add some extra elements to it). Are there any general algorithms or reading material I can look at for how I could go about generating interesting (as in, not trivial to solve) levels for this style of game? I'm aware that random level generators exist for Sokoban but I'm having trouble finding the algorithm descriptions. I'm interested in making a game where the machine can generate lots of levels for me, sorted by difficulty. I'm even willing to constrain the rules of the game to make the level generation easier (e.g. I'll probably limit the grid size to about 7x7). I suspect there are some general ways to do level generation here as I've seen e.g. Traffic Jam-like games (where you have to move blocks around the free some block) with 1000s of levels where each one has a unique solution. One idea I had was to generate a random map in its final state (i.e. where all crates are on top of their crosses) and then the computer would pull (instead of push) these crates around to create a level. The nice property here is that we know the level is solvable. However, I'd need some heuristics to ensure the level was interesting.

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• is Microsoft LC random generator patented?

  - by user396672

  I need a very simple pseudo random generator (no any specific quality requirements) and I found Microsoft's variant of LCG algorithm used for rand() C runtime library function fit my needs (gcc's one seems too complex). I found the algorithm here: http://rosettacode.org/wiki/Linear_congruential_generator#C However, I worry the algorithm (including its "magic numbers" i.e coefficients) may by patented or restricted for use in some another way. Is it allowed to use this algorithm without any licence or patent restrictions or not? I can't use library rand() because I need my results to be exactly reproducible on different platforms

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• Random Position between ranges.

  - by blakey87

  Does anyone have a good algorithm for generating a random y position for spawning a block, which takes into account a minimum and maximum height, allowing player to to jump on the block. Blocks will continually be spawned, so the player must always be able to jump onto the next block, bearing in mind the minimum position which would be the ground, and the maximum which would the players jump height bearing in mind the ceiling

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• Best way to choose random element from weighted list

  - by Qqwy

  I want to create a simple game. Every so often, a power up should appear. Right now the different kinds of power ups are stored in an array. However, not every power up should appear equally often: For instance, a score multiplier should appear much more often than an extra life. What is the best/fastest way to pick an element at random from a list where some of the elements should be picked more often than others?

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