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  • Getting random record from database with group by

    - by Saif Bechan
    Hello i have a question on picking random entries from a database. I have 4 tables, products, bids and autobids, and users. Products ------- id 20,21,22,23,24(prime_key) price........... etc........... users ------- id(prim_key) name user1,user2,user3 etc bids ------- product_id user_id created autobids -------- user_id product_id Now a multiple users can have an autobid on an product. So for the next bidder I want to select a random user from the autobid table example of the query in language: for each product in the autobid table I want a random user, which is not the last bidder. On product 20 has user1,user2,user3 an autobidding. On product 21 has user1,user2,user3 an autobidding Then I want a resultset that looks for example like this 20 – user2 21 – user3 Just a random user. I tried miximg the GOUP BY (product_id) and making it RAND(), but I just can't get the right values from it. Now I am getting a random user, but all the values that go with it don't match. Can someone please help me construct this query, I am using php and mysql

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  • Random forests for short texts

    - by Jasie
    Hi all, I've been reading about Random Forests (1,2) because I think it'd be really cool to be able to classify a set of 1,000 sentences into pre-defined categories. I'm wondering if someone can explain to me the algorithm better, I think the papers are a bit dense. Here's the gist from 1: Overview We assume that the user knows about the construction of single classification trees. Random Forests grows many classification trees. To classify a new object from an input vector, put the input vector down each of the trees in the forest. Each tree gives a classification, and we say the tree "votes" for that class. The forest chooses the classification having the most votes (over all the trees in the forest). Each tree is grown as follows: If the number of cases in the training set is N, sample N cases at random - but with replacement, from the original data. This sample will be the training set for growing the tree. If there are M input variables, a number m « M is specified such that at each node, m variables are selected at random out of the M and the best split on these m is used to split the node. The value of m is held constant during the forest growing. Each tree is grown to the largest extent possible. There is no pruning. So, does this look right? I'd have N = 1,000 training cases (sentences), M = 100 variables (let's say, there are only 100 unique words across all sentences), so the input vector is a bit vector of length 100 corresponding to each word. I randomly sample N = 1000 cases at random (with replacement) to build trees from. I pick some small number of input variables m « M, let's say 10, to build a tree off of. Do I build tree nodes randomly, using all m input variables? How many classification trees do I build? Thanks for the help!

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  • Set seed on Math.random()

    - by Kevin
    Hi - I need to write some junit tests on java code that calls Math.random(). I know that I can set the seed if I was instantiating my own Random object to produce repeatable results. Is there a way to do this also for Math.random() ?

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  • Random number in a loop

    - by Sam
    Hi all, having an issue generating random numbers in a loop. Can get around it by using Thread.Sleep but after a more elegant solution. for ... Random r = new Random(); string += r.Next(4); Will end up with 11111... 222... etc. Suggestions?

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  • SQL SERVER – Retrieving Random Rows from Table Using NEWID()

    - by pinaldave
    I have previously written about how to get random rows from SQL Server. SQL SERVER – Generate A Single Random Number for Range of Rows of Any Table – Very interesting Question from Reader SQL SERVER – Random Number Generator Script – SQL Query However, I have not blogged about following trick before. Let me share the trick here as well. You can generate random scripts using following methods as well. USE AdventureWorks2012 GO -- Method 1 SELECT TOP 100 * FROM Sales.SalesOrderDetail ORDER BY NEWID() GO -- Method 2 SELECT TOP 100 * FROM Sales.SalesOrderDetail ORDER BY CHECKSUM(NEWID()) GO You will notice that using NEWID() in the ORDER BY will return random rows in the result set. How many of you knew this trick? You can run above script multiple times and it will give random rows every single time. Reference: Pinal Dave (http://blog.sqlauthority.com)   Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Java random values and duplicates

    - by f-Prime
    I have an array (cards) of 52 cards (13x4), and another array (cardsOut) of 25 cards (5x5). I want to copy elements from the 52 cards into the 25 card array by random. Also, I dont want any duplicates in the 5x5 array. So here's what I have: double row=Math.random() *13; double column=Math.random() *4; boolean[][] duplicates=new boolean[13][4]; pokerGame[][] cardsOut = new pokerGame[5][5]; for (int i=0;i<5;i++) for (int j=0;j<5;j++){ if(duplicates[(int)row][(int)column]==false){ cardsOut[i][j]=cards[(int)row][(int)column]; duplicates[(int)row][(int)column]=true; } } 2 problems in this code. First, the random values for row and column are only generated once, so the same value is copied into the 5x5 array every time. Since the same values are being copied every time, I'm not sure if my duplicate checker is very effective, or if it works at all. How do I fix this?

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  • random image and its url

    - by venom
    i want to create a random image and its url, i mean not the link of the image, but in addition to image's link, i want the specified URL, so that random image was displayed and when u click on it, u go to the specified URL here is my javascript: function random_imglink(){ var myimages=new Array() //specify random images below. You can have as many as you wish myimages[1]="/documents/templates/projedepo/banner/canon.jpg" myimages[2]="/documents/templates/projedepo/banner/indigovision.jpg" var ry=Math.floor(Math.random()*myimages.length) if (ry==0) ry=1 var randomImage = '<img src="'+myimages[ry]+'" height="420" width="964" />'; document.getElementById("image2").innerHTML = randomImage; } random_imglink() Here is my HTML: <div id="slider_container"> <div id="image2"> </div> <div id="thumb2"> <a href="#" rel="/documents/templates/projedepo/banner/canon.jpg" class="image2" ><img title="Canon" class="slider_thumb" src="/documents/templates/bilgiteknolojileri/images/t_flash/t1.png" border="0"/></a> <a href="#" rel="/documents/templates/projedepo/banner/indigovision.jpg" class="image2"><img title="IndogoVision" class="slider_thumb" src="/documents/templates/bilgiteknolojileri/images/t_flash/t2.png" border="0"/></a> </div></div>

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  • Random Computer Crashes

    - by Josh W.
    Ok, here's a wierd one for you all. Occasionally my PC here at work will crash in a very peculiar way. My dual monitors will suddenly go blank as if there is no longer a video signal, the USB mouse light will go dark and mouse stays unresponsive, the keyboard lights will not change status when the appropriate keys are pressed (Num/Caps/Scoll Lock). The CD Tray WILL open and close. But the computer will not respond to a ping request. For all intents & purposes it's as if the computer is off, except it wasn't intentional by me. The power light and internal fans are still on and I've now lost any unsaved work. Now here's where it gets wierd. This PC is part of a batch of PC's we got from a local vendor who does our initial system builds. Mine, and 6 other co-workers PCs all have the same issue. Originally we thought it was a bad combination of hardware, but through trial and error the only thing we haven't eliminated are the OS, Mobo & CPU. The problem was so bad for some of them that they ended up going back to their 5 year old dinosaurs in order to get some work done, for me the problem isn't as bad, maybe once every other day or so, but still enough to bite me in the ass if I've forgotten my ritualistic pressing of CTRL-S every 1-5 minutes. In this case we've tried two different video cards, two different power supplies, two different memory configurations, running on a UPS/not on UPS, updating/rolling back video drivers, three different bios revisions. The only things we haven't swapped are the mobo & cpu, mainly because a new mobo means a new Hardware Abstraction Layer, ie re-install of windows and there's alot of other software on this PC that takes forever to reload by hand. There was a base image that our systems team created with all the drivers installed and the basic setup of software our company uses, but they then must customize the setup for us programmers so it takes a while to get a new configuration up and going. I'm a programmer by day and am usually pretty good at diagnosing computer problems whether through trial and error or not. We've pretty much exhausted all the ideas we can think of here, short of a new mobo/cpu. Was hoping someone out there might have anything else we can try.. Relevant Parts: OS: XP Pro 32-bit Motherboard: Intel DG41RQ CPU: Intel Core-2 Quad Q9400 @ 2.66GHz Current BIOS Version/Date Intel Corp. RQG4110H.86A.0014.2010.0306.1151, 3/6/2010 Dual LCD's, Viewsonic VG930m & Samsung SyncMaster 910v (other people have different models, but listed in case there's some very wierd problem with the signals being sent/received) PS/2 Keyboard USB Microsoft Intellimouse BIOS Versions Tried: R 0013 12/23/2009 R 0014 3/6/2010 Video cards Tried GeForce 8400 GS Radeon HD 4350 - ASUS EAH4350 Two Different Power Supplies a 380W & 550W Ram Configurations 2GB - 1 x 2GB 4GB - 2 x 2GB

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  • Random Number on SQL without using NewID()

    - by Angel Escobedo
    Hello I want to generate a Unique Random number with out using the follow statement : Convert(int, (CHECKSUM(NEWID()))*100000) AS [ITEM] Cause when I use joins clauses on "from" it generates double registers by using NEWID() Im using SQL Server 2000 *PD : When I use Rand() it probably repeat on probability 1 of 100000000 but this is so criticall so it have to be 0% of probability to repeat a random value generated My Query with NewID() and result on SELECT statement is duplicated (x2) My QUery without NewID() and using Rand() on SELECT statement is single (x1) but the probability of repeat the random value generated is uncertainly but exists! Thanks!

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  • Generating random numbers in C

    - by moonstruckhorrors
    While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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  • Read random lines from huge CSV file in Python

    - by jbssm
    I have this quite big CSV file (15 Gb) and I need to read about 1 million random lines from it. As far as I can see - and implement - the CSV utility in Python only allows to iterate sequentially in the file. It's very memory consuming to read the all file into memory to use some random choosing and it's very time consuming to go trough all the file and discard some values and choose others, so, is there anyway to choose some random line from the CSV file and read only that line? I tried without success: import csv with open('linear_e_LAN2A_F_0_435keV.csv') as file: reader = csv.reader(file) print reader[someRandomInteger] A sample of the CSV file: 331.093,329.735 251.188,249.994 374.468,373.782 295.643,295.159 83.9058,0 380.709,116.221 352.238,351.891 183.809,182.615 257.277,201.302 61.4598,40.7106

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  • Good Form for Random Number Generator?

    - by JackCJR
    I wanted to get a few opinions on doing a random number generator. I read through a couple different ways to do it and this is the way that I created after doing a little reading. Is it acceptable form? Any foreseeable issues? function master(){ function generate(){ var pickFrom= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; var j = pickFrom.length; var i = Math.floor(Math.random()*j+1); //Generates a random number var code = pickFrom.charAt(i) //Picks a number based on what number was picked. document.write(code) } x = 1; while(x){ generate(); x--; } } master();

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  • Help A Hacker: Give ‘Em The Windows Source Code

    - by Ken Cox [MVP]
    The announcement of another Windows megapatch reminded me of a WikiLeaks story about Microsoft Windows that hasn’t attracted much attention. Alarmingly, we learn that the hackers have the Windows source code to study and test for vulnerabilities. Chinese hackers used the knowledge to breach Google’s accounts and servers: “In 2003, the CNITSEC signed a Government Security Program (GSP) international agreement with Microsoft that allowed select companies such as TOPSEC access to Microsoft source code in order to secure the Windows platform” “CNITSEC enterprises has recruited Chinese hackers in support of nationally-funded "network attack scientific research projects." From June 2002 to March 2003, TOPSEC employed a known Chinese hacker, Lin Yong (a.k.a. Lion and owner of the Honker Union of China), as senior security service engineer…” Windows is widely seen as unsecurable. It doesn’t help that Chinese government-funded hackers are probing the source code for vulnerabilities. It seems odd that people who didn’t write the code can find vulnerabilities faster than the owners of the code. Perhaps the U.S. government should hire its own hackers to go over the same Windows source code and then tell Microsoft how to secure its product?

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  • Get the MakeUseOf eBook Guide to Hacker Proofing Your PC

    - by ETC
    If you’re interested in checking out a solid overview of PC security best practices and tips, our friends over at MakeUseOf.com have released another free book in their computer-oriented eBook series. The fifty-page ebook HackerProof: Your Guide to PC Security covers a variety of topics including types of malware, operating systems and their inherent vulnerabilities, security best practices, tools for protecting your PC, the importance of security prep and backups, and recovering from malware attacks. It’s a nice and compact text, perfect for brushing up on security best practices for your own machine or sending to friends and relatives that could use a little after-school tutoring on keeping their computer secure and out of trouble. The best tip from the book? The overall message to be cautious and be preemptive in your security efforts is a great meta-tip to take away. Up-to-date definition files and a healthy sense of random links and emails attachments goes a long, long way towards staying safe. HackerProof: Your Guide to PC Security [Direct Link via MakeUseOf] Latest Features How-To Geek ETC How to Get Amazing Color from Photos in Photoshop, GIMP, and Paint.NET Learn To Adjust Contrast Like a Pro in Photoshop, GIMP, and Paint.NET Have You Ever Wondered How Your Operating System Got Its Name? Should You Delete Windows 7 Service Pack Backup Files to Save Space? What Can Super Mario Teach Us About Graphics Technology? Windows 7 Service Pack 1 is Released: But Should You Install It? Get the MakeUseOf eBook Guide to Hacker Proofing Your PC Sync Your Windows Computer with Your Ubuntu One Account [Desktop Client] Awesome 10 Meter Curved Touchscreen at the University of Groningen [Video] TV Antenna Helper Makes HDTV Antenna Calibration a Snap Turn a Green Laser into a Microscope Projector [Science] The Open Road Awaits [Wallpaper]

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  • JSF - Random Number using Beans (JAVA)

    - by Alex Encore Tr
    I am trying to create a jsf application which, upon page refresh increments the hit counter and generates two random numbers. What should be displayed on the window may look something like this: On your On your roll x you have thrown x and x For this program I decided to create two Beans, one to hold the page refresh counter and one to generate a random number. Those look like this for the moment: CounterBean.java package diceroll; public class CounterBean { int count=0; public CounterBean() { } public void setCount(int count) { this.count=count; } public int getCount() { count++; return count; } } RandomNumberBean.java package diceroll; import java.util.Random; public class RandomNumberBean { int rand=0; Random r = new Random(); public RandomNumberBean() { rand = r.nextInt(6); } public void setNextInt(int rand) { this.rand=rand; } public int getNextInt() { return rand; } } I have then created an index.jsp to display the above message. <html> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%> <f:view> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Roll the Dice</title> </head> <body> <h:form> <p> On your roll # <h:outputText value="#{CounterBean.count} " /> you have thrown <h:outputText value="#{RandomNumberBean.rand}" />and <h:outputText value="#{RandomNumberBean.rand} " /> </p> </h:form> </body> </f:view> </html> However, when I run the application, I get the following message: org.apache.jasper.el.JspPropertyNotFoundException: /index.jsp(14,20) '#{RandomNumberBean.rand}' Property 'rand' not found on type diceroll.RandomNumberBean Caused by: org.apache.jasper.el.JspPropertyNotFoundException - /index.jsp(14,20) '#{RandomNumberBean.rand}' Property 'rand' not found on type diceroll.RandomNumberBean I suppose there's a mistake with my faces-config.xml file, so I will post this here as well, see if somebody can provide some help: faces-config.xml <?xml version="1.0" encoding="UTF-8"?> <faces-config xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd" version="2.0"> <managed-bean> <managed-bean-name>CounterBean</managed-bean-name> <managed-bean-class>diceroll.CounterBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> <managed-bean> <managed-bean-name>RandomNumberBean</managed-bean-name> <managed-bean-class>diceroll.RandomNumberBean</managed-bean-class> <managed-bean-scope>session</managed-bean-scope> </managed-bean> </faces-config>

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  • C# Monte Carlo Incremental Risk Calculation optimisation, random numbers, parallel execution

    - by m3ntat
    My current task is to optimise a Monte Carlo Simulation that calculates Capital Adequacy figures by region for a set of Obligors. It is running about 10 x too slow for where it will need to be in production and number or daily runs required. Additionally the granularity of the result figures will need to be improved down to desk possibly book level at some stage, the code I've been given is basically a prototype which is used by business units in a semi production capacity. The application is currently single threaded so I'll need to make it multi-threaded, may look at System.Threading.ThreadPool or the Microsoft Parallel Extensions library but I'm constrained to .NET 2 on the server at this bank so I may have to consider this guy's port, http://www.codeproject.com/KB/cs/aforge_parallel.aspx. I am trying my best to get them to upgrade to .NET 3.5 SP1 but it's a major exercise in an organisation of this size and might not be possible in my contract time frames. I've profiled the application using the trial of dotTrace (http://www.jetbrains.com/profiler). What other good profilers exist? Free ones? A lot of the execution time is spent generating uniform random numbers and then translating this to a normally distributed random number. They are using a C# Mersenne twister implementation. I am not sure where they got it or if it's the best way to go about this (or best implementation) to generate the uniform random numbers. Then this is translated to a normally distributed version for use in the calculation (I haven't delved into the translation code yet). Also what is the experience using the following? http://quantlib.org http://www.qlnet.org (C# port of quantlib) or http://www.boost.org Any alternatives you know of? I'm a C# developer so would prefer C#, but a wrapper to C++ shouldn't be a problem, should it? Maybe even faster leveraging the C++ implementations. I am thinking some of these libraries will have the fastest method to directly generate normally distributed random numbers, without the translation step. Also they may have some other functions that will be helpful in the subsequent calculations. Also the computer this is on is a quad core Opteron 275, 8 GB memory but Windows Server 2003 Enterprise 32 bit. Should I advise them to upgrade to a 64 bit OS? Any links to articles supporting this decision would really be appreciated. Anyway, any advice and help you may have is really appreciated.

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  • Code Golf: MSM Random Number Generator

    - by Vivin Paliath
    The challenge The shortest code by character count that will generate (pseudo)random numbers using the Middle-Square Method. The Middle-Square Method of (pseudo)random number generation was first suggested by John Von Neumann in 1946 and is defined as follows: Rn+1 = mid((Rn)2, m) For example: 34562 = 11943936 mid(11943936) = 9439 94392 = 89094721 mid(89094721) = 0947 9472 = 896809 mid(896809) = 9680 96802 = 93702400 mid(93702400) = 7024 Test cases: A seed of 8653 should give the following numbers (first 10): 8744, 4575, 9306, 6016, 1922, 6940, 1636, 6764, 7516, 4902

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  • random() in python

    - by Arkapravo
    In python the function random() generates a random float uniformly in the semi-open range [0.0, 1.0). In principle can it ever generate 0.0 (i.e. zero) and 1.0 (i.e. unity)? What is the scenario in practicality?

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  • Random position without overlapping

    - by Hwang
    How to stop MCs from overlapping each other? private function loadWishes():void { for (i; i } } private function checkOverlap(wishB:MovieClip) { wishB.x=Math.random()*stage.stageWidth; wishB.y=Math.random()*stage.stageHeight; for (var i:uint=0; i This doesn't seems to be working cause the amount of it checking whether MC is overlapping is about the amount of MC on stage. how to make it keep checking till everything's fine?

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  • How would I create a random number?

    - by Elliot Bonneville
    How would I create a random number using C++? I've heard that one should use the time as a seed, but I'm not sure how to do that with the correct syntax. How would I do this? One more thing - how would I limit the random number to a particular range? I'm simulating a dice roll and getting numbers in the millions...

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  • how to generate a random String? in java

    - by chandra wibowo
    hi everyone, i have an object called Student, and it has studentName, studentId, studentAddress, etc. for the studentId, i have to generate random string consist of seven numeric charaters, eg. studentId = getRandomId(); studentId = "1234567" <-- from the random generator. and i have to make sure that there is no duplicate id. thanks in advance

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  • True random number generator

    - by goldenmean
    Sorry for this not being a "real" question, but Sometime back i remember seeing a post here about randomizing a randomizer randomly to generate truly random numbers, not just pseudo random. I dont see it if i search for it. Does anybody know about that article?

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