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  • Gathering entropy in web apps to create (more) secure random numbers

    - by H M
    after several days of research and discussion i came up with this method to gather entropy from visitors (u can see the history of my research here) when a user visits i run this code: $entropy=sha1(microtime().$pepper.$_SERVER['REMOTE_ADDR'].$_SERVER['REMOTE_PORT']. $_SERVER['HTTP_USER_AGENT'].serialize($_POST).serialize($_GET).serialize($_COOKIE)); note: pepper is a per site/setup random string set by hand. then i execute the following (My)SQL query: $query="update `crypto` set `value`=sha1(concat(`value`, '$entropy')) where name='entropy'"; that means we combine the entropy of the visitor's request with the others' gathered already. that's all. then when we want to generate random numbers we combine the gathered entropy with the output: $query="select `value` from `crypto` where `name`='entropy'"; //... extract(unpack('Nrandom', pack('H*', sha1(mt_rand(0, 0x7FFFFFFF).$entropy.microtime())))); note: the last line is a part of a modified version of the crypt_rand function of the phpseclib. please tell me your opinion about the scheme and other ideas/info regarding entropy gathering/random number generation. ps: i know about randomness sources like /dev/urandom. this system is just an auxiliary system or (when we don't have (access to) these sources) a fallback scheme.

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  • R Random Data Sets within loops

    - by jugossery
    Here is what I want to do: I have a time series data frame with let us say 100 time-series of length 600 - each in one column of the data frame. I want to pick up 4 of the time-series randomly and then assign them random weights that sum up to one (ie 0.1, 0.5, 0.3, 0.1). Using those I want to compute the mean of the sum of the 4 weighted time series variables (e.g. convex combination). I want to do this let us say 100k times and store each result in the form ts1.name, ts2.name, ts3.name, ts4.name, weight1, weight2, weight3, weight4, mean so that I get a 9*100k df. I tried some things already but R is very bad with loops and I know vector oriented solutions are better because of R design. Thanks Here is what I did and I know it is horrible The df is in the form v1,v2,v2.....v100 1,5,6,.......9 2,4,6,.......10 3,5,8,.......6 2,2,8,.......2 etc e=NULL for (x in 1:100000) { s=sample(1:100,4)#pick 4 variables randomly a=sample(seq(0,1,0.01),1) b=sample(seq(0,1-a,0.01),1) c=sample(seq(0,(1-a-b),0.01),1) d=1-a-b-c e=c(a,b,c,d)#4 random weights average=mean(timeseries.df[,s]%*%t(e)) e=rbind(e,s,average)#in the end i get the 9*100k df } The procedure runs way to slow. EDIT: Thanks for the help i had,i am not used to think R and i am not very used to translate every problem into a matrix algebra equation which is what you need in R. Then the problem becomes a little bit complex if i want to calculate the standard deviation. i need the covariance matrix and i am not sure i can if/how i can pick random elements for each sample from the original timeseries.df covariance matrix then compute the sample variance (t(sampleweights)%*%sample_cov.mat%*%sampleweights) to get in the end the ts.weighted_standard_dev matrix Last question what is the best way to proceed if i want to bootstrap the original df x times and then apply the same computations to test the robustness of my datas thanks

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  • Objective C : UIButton image with NSArray in a random order

    - by Sarah
    Brief Idea about the flow : I have say minimum 1 and maximum 18 records in my database with a text and an image from which I have to fetch images and place any 3 of the same randomly to 3 UIButtons among which one image should match with my question. i.e. 1 is the answer and other 2 are the distractors. For Example : Question is : where is Apple? Now among the bunch of images, I want to place any 3 images on the 3 UIButtons(1 answer i.e. An Apple and 2 distractors) in a random order and on selecting the UIButton it should prompt me if it's a right answer or not. I am implementing below code for placing the UIImages in a random order : -(void) placeImages { NSMutableArray *images = [NSMutableArray arrayWithArray:arrImg]; NSArray *buttons = [NSArray arrayWithObjects:btn1,btn2,btn3, nil]; for (UIButton *btn in buttons) { int randomIndex= random() % images.count; UIImage *img = [images objectAtIndex:randomIndex]; [btn setImage:img forState:UIControlStateNormal]; [images removeObjectAtIndex:randomIndex]; } } But I am stuck at a point that how should I get 1 UIButton image with an answer and other as distractors also that how should i maintain the index of the image from the NSArray? Kindly guide me. Thank you.

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  • Are random packets normal?

    - by TheLQ
    About a month ago on one of my servers I started receiving random packets from IPs all over the world. So I did the smart thing and stopped putting off installing an IDS. This IDS is a ClearOS Gateway which comes with Snort and SnortSam. I enabled it, checked There is a total of 4 ports open, two of which forward to the server I'm talking about. These ports are 3724 and 8085, so they aren't going to be easily detected in a port scan. However checking some logs of this server I found that the attack is resuming. I found this ... Accepting connection from '75.166.155.122' [Auth] got unknown packet from '75.166.155.122' Accepting connection from '98.164.154.93' [Auth] got unknown packet from '98.164.154.93' Ping MySQL to keep connection alive Accepting connection from '70.241.195.129' [Auth] got unknown packet from '70.241.195.129' Accepting connection from '67.182.229.169' [Auth] got unknown packet from '67.182.229.169' Accepting connection from '69.137.140.38' [Auth] got unknown packet from '69.137.140.38' Accepting connection from '76.31.72.55' [Auth] got unknown packet from '76.31.72.55' Accepting connection from '97.88.139.39' [Auth] got unknown packet from '97.88.139.39' Accepting connection from '173.35.62.112' [Auth] got unknown packet from '173.35.62.112' Accepting connection from '187.15.10.73' [Auth] got unknown packet from '187.15.10.73' Accepting connection from '66.66.94.124' [Auth] got unknown packet from '66.66.94.124' Accepting connection from '75.159.219.124' [Auth] got unknown packet from '75.159.219.124' Accepting connection from '99.102.100.82' [Auth] got unknown packet from '99.102.100.82' Accepting connection from '24.128.240.45' [Auth] got unknown packet from '24.128.240.45' Accepting connection from '99.231.7.39' [Auth] got unknown packet from '99.231.7.39' Accepting connection from '206.255.79.56' [Auth] got unknown packet from '206.255.79.56' Accepting connection from '68.97.106.235' [Auth] got unknown packet from '68.97.106.235' Accepting connection from '69.134.67.251' [Auth] got unknown packet from '69.134.67.251' Accepting connection from '63.228.138.186' [Auth] got unknown packet from '63.228.138.186' Accepting connection from '184.39.146.193' [Auth] got unknown packet from '184.39.146.193' Accepting connection from '69.171.161.102' [Auth] got unknown packet from '69.171.161.102' Accepting connection from '76.0.47.228' [Auth] got unknown packet from '76.0.47.228' Ping MySQL to keep connection alive Accepting connection from '126.112.201.14' [Auth] got unknown packet from '126.112.201.14' Ping MySQL to keep connection alive Now that scares me. Why isn't Snort detecting this? How were they able to find this specific port? More importantly, what normally would these packets contain? Is this something I should be worried about? How can I stop this?

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  • How to store data on a machine whose power gets cut at random

    - by Sevas
    I have a virtual machine (Debian) running on a physical machine host. The virtual machine acts as a buffer for data that it frequently receives over the local network (the period for this data is 0.5s, so a fairly high throughput). Any data received is stored on the virtual machine and repeatedly forwarded to an external server over UDP. Once the external server acknowledges (over UDP) that it has received a data packet, the original data is deleted from the virtual machine and not sent to the external server again. The internet connection that connects the VM and the external server is unreliable, meaning it could be down for days at a time. The physical machine that hosts the VM gets its power cut several times per day at random. There is no way to tell when this is about to happen and it is not possible to add a UPS, a battery, or a similar solution to the system. Originally, the data was stored on a file-based HSQLDB database on the virtual machine. However, the frequent power cuts eventually cause the database script file to become corrupted (not at the file system level, i.e. it is readable, but HSQLDB can't make sense of it), which leads to my question: How should data be stored in an environment where power cuts can and do happen frequently? One option I can think of is using flat files, saving each packet of data as a file on the file system. This way if a file is corrupted due to loss of power, it can be ignored and the rest of the data remains intact. This poses a few issues however, mainly related to the amount of data likely being stored on the virtual machine. At 0.5s between each piece of data, 1,728,000 files will be generated in 10 days. This at least means using a file system with an increased number of inodes to store this data (the current file system setup ran out of inodes at ~250,000 messages and 30% disk space used). Also, it is hard (not impossible) to manage. Are there any other options? Are there database engines that run on Debian that would not get corrupted by power cuts? Also, what file system should be used for this? ext3 is what is used at the moment. The software that runs on the virtual machine is written using Java 6, so hopefully the solution would not be incompatible.

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  • Ubuntu server random hangups.

    - by Ebbe
    Hello all. this is my first post to this forum which I found through the superb podcast "It Conversations" from StackOverFlow. I am quite in my role as server administrator for an exhibition center in London. Basically we have a central file and sql server to which roughly 40 stations connects to to upload/download data used/captured by a set of applications. Over the last weeks we have experienced a few random hangups to our applications, and as it always happen to multiple applications simultaneously I do not believe that the applications are the source of the problem. We also monitor the network using Dartware Intermapper which indicates that all switches and stations on the network has been reachable during the downtime. Thus, its all pointing to the server. I have been looking through all log files I can think of and the only thing so far that I have found suspicious is the following lines in the syslog which are from the time of one of the hangups: Feb 6 17:14:27 es named[5582]: client 127.0.0.1#33721: RFC 1918 response from Internet for 150.0.168.192.in-addr.arpa Feb 6 17:14:40 es named[5582]: client 127.0.0.1#32899: RFC 1918 response from Internet for 152.0.168.192.in-addr.arpa Feb 6 17:15:01 es /USR/SBIN/CRON[1956]: (es) CMD (/home/es/apps/es/bin/es_checksum.sh) Feb 6 17:16:06 es /USR/SBIN/CRON[2031]: (es) CMD (/home/es/apps/es/bin/es_checksum.sh) Feb 6 17:21:00 es named[5582]: *** POKED TIMER *** Feb 6 17:21:00 es last message repeated 2 times Feb 6 17:21:07 es named[5582]: client 127.0.0.1#44194: RFC 1918 response from Internet for 143.0.168.192.in-addr.arpa Feb 6 17:21:12 es named[5582]: client 127.0.0.1#59004: RFC 1918 response from Internet for 164.0.168.192.in-addr.arpa I find a few lines of interesting lines here: 1) "RFC 1918 response from Internet for 150.1.168.192.in-addr.arpa". I see this a lot in the syslog. And basically everytime I do a nslookup for any of the computers in the cluster I get a new similar line in the syslog. I understand from google that this has to do with reverse lookup problems. But I do not know how that could effect the systems. Lets say that one of these lines appear every time one of the userstations connects to the server, which may happen several times a second. Could this possible cause a hangup of the entire server? 2) POKED TIMER, I have googled this quite a lot, but not found an explaination that I can relate to. What does this mean? 3) The timestamps, it seems like the entire server has stopped responding for several minutes. Normally there are many printouts to the syslog per minute on this server. Furthermore the CRON job is set to run once every minute. Which according to the log, hasent happened here. OS: Ubuntu 8.04 Kernel: Linux 2.6.24-24-server x86_64 GNU/Linux. Hardware: Dell R710, RAID1, CPU: 2x XEON E5530. 16GB Memory. Average load is very low, and memory should not be a problem. Please let me know if you need any additional information. Best wishes, Ebbe

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  • Distinct rand() sequences yielding the same results in an expression

    - by suszterpatt
    Ok, this is a really weird one. I have an MPI program, where each process has to generate random numbers in a fixed range (the range is read from file). What happens is that even though I seed each process with a different value, and the numbers generated by rand() are different in each process, the expression to generate the random numbers still yields the same sequence between them. Here's all relevant code: // 'rank' will be unique for each process int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank); // seed the RNG with a different value for each process srand(time(NULL) + rank); // print some random numbers to see if we get a unique sequence in each process // 'log' is a uniquely named file, each process has its own log << rand() << " " << rand() << " " << rand() << std::endl; // do boring deterministic stuff while (true) { // waitTimeMin and waitTimeMax are integers, Max is always greater than Min waitSecs = waitTimeMin + rand() % (waitTimeMax - waitTimeMin); log << "waiting " << waitSecs << " seconds" << std::endl; sleep(waitSecs); // do more boring deterministic stuff } Here's the output of each process, with 3 processes generating numbers in the range [1,9]. process 1: 15190 28284 3149 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds process 2: 286 6264 3153 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds process 3: 18151 17013 3156 waiting 6 seconds waiting 8 seconds waiting 9 seconds waiting 4 seconds So while rand() clearly generates different numbers, the expression to calculate waitSecs still evaluates to the same sequence on all processes. What's even weirder: if I run the program with the same parameteres again, only the first 3 random numbers will change, the rest of the "random" sequence will be exactly the same in each run! Changing the range of numbers will obviously produce a different result from this one, but the same parameters always yield the same sequence, between processes and between executions: except for the first 3 numbers. Just what the hell is going on here?

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  • Randomised objects are assigning themselves to more than one array location

    - by Thaddeus Aid
    this.size = 9; this.populationSize = 10; Random rand = new Random(); Integer[][] easy1 = new Integer[size][size]; easy1 = this.initializeEasy1(easy1); this.sudokuArray = new Sudoku[this.populationSize]; for (int i = 0; i < this.sudokuArray.length; i++){ long seed = rand.nextLong(); System.out.println("" + seed); this.sudokuArray[i] = new Sudoku(easy1, this.size, seed); } I am building an evolutionary sudoku solver and I am having a problem where the last Sudoku object is overwriting all the other objects in the array. Where in the code did I mess up? /edit here is the constructor of the class public Sudoku(Integer[][] givensGrid, int s, long seed){ this.size = s; this.givens = givensGrid; this.grid = this.givens.clone(); Random rand = new Random(seed); System.out.println("Random " + rand.nextInt()); // step though each row of the grid for (int i = 0; i < size; i++){ ArrayList<Integer> numbers = new ArrayList<Integer>(); numbers = this.makeNumbers(numbers); // step through each column to find the givens and remove from numbers for (int j = 0; j < size; j++){ if (this.grid[i][j] != 0){ numbers.remove(this.grid[i][j]); } } // go back through the row and assign the numbers randomly for (int j = 0; j < size; j++){ if (this.grid[i][j] == 0){ int r = rand.nextInt(numbers.size()); this.grid[i][j] = numbers.get(r); numbers.remove(r); } } } System.out.println("============="); System.out.println(this.toString()); }

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  • rand() generating the same number – even with srand(time(NULL)) in my main!

    - by Nick Sweet
    So, I'm trying to create a random vector (think geometry, not an expandable array), and every time I call my random vector function I get the same x value, thought y and z are different. int main () { srand ( (unsigned)time(NULL)); Vector<double> a; a.randvec(); cout << a << endl; return 0; } using the function //random Vector template <class T> void Vector<T>::randvec() { const int min=-10, max=10; int randx, randy, randz; const int bucket_size = RAND_MAX/(max-min); do randx = (rand()/bucket_size)+min; while (randx <= min && randx >= max); x = randx; do randy = (rand()/bucket_size)+min; while (randy <= min && randy >= max); y = randy; do randz = (rand()/bucket_size)+min; while (randz <= min && randz >= max); z = randz; } For some reason, randx will consistently return 8, whereas the other numbers seem to be following the (pseudo) randomness perfectly. However, if I put the call to define, say, randy before randx, randy will always return 8. Why is my first random number always 8? Am I seeding incorrectly?

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  • [MySQL/PHP] Avoid using RAND()

    - by Andrew Ellis
    So... I have never had a need to do a random SELECT on a MySQL DB until this project I'm working on. After researching it seems the general populous says that using RAND() is a bad idea. I found an article that explains how to do another type of random select. Basically, if I want to select 5 random elements, I should do the following (I'm using the Kohana framework here)? If not, what is a better solution? Thanks, Andrew <?php final class Offers extends Model { /** * Loads a random set of offers. * * @param integer $limit * @return array */ public function random_offers($limit = 5) { // Find the highest offer_id $sql = ' SELECT MAX(offer_id) AS max_offer_id FROM offers '; $max_offer_id = DB::query(Database::SELECT, $sql) ->execute($this->_db) ->get('max_offer_id'); // Check to make sure we're not trying to load more offers // than there really is... if ($max_offer_id < $limit) { $limit = $max_offer_id; } $used = array(); $ids = ''; for ($i = 0; $i < $limit; ) { $rand = mt_rand(1, $max_offer_id); if (!isset($used[$rand])) { // Flag the ID as used $used[$rand] = TRUE; // Set the ID if ($i > 0) $ids .= ','; $ids .= $rand; ++$i; } } $sql = ' SELECT offer_id, offer_name FROM offers WHERE offer_id IN(:ids) '; $offers = DB::query(Database::SELECT, $sql) ->param(':ids', $ids) ->as_object(); ->execute($this->_db); return $offers; } }

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  • Getting a "for each" loop in Java to run in different order everytime

    - by R Stokes
    Hi, Basically my problem is that I'm trying to write a method that finds a random path in a graph of strings, which takes as it's parameters a start string, an integer length and a Vector of strings that will store the path. I'm attempting to do this by first adding the starting string to our blank vector, recursing through its neighbors until the vector's length (not including the start node) is the same as the integer length specified in the parameters. I've provided my code so far here: public Vector<String> findRandomPathFrom(String n, int len, Vector<String> randomPath){ randomPath.add(n); if (randomPath.size() == len + 1) return randomPath; for (String m : this.neighbours(n)){ if (!randomPath.contains(m) && findRandomPathFrom(m, len, randomPath) != null) return randomPath; } path.setSize(path.size() - 1); return null; } It seems to be working fine, returning a path with exactly the number of strings specified after the given start string. However, for any given starting string it generates the EXACT same path everytime, which kind of defeats the purpose of it being a random path generator. I'm guessing this problem is related to my "for each" loop, which loops through all the neighbouring strings of your current string. It seems to just be going with the first string in the neighbours vector every single time. Can anyone help me fix this problem so that it will choose a random neighbour instead of going in order? tl;dr - Any way of getting a "for each" loop in java to process a collection in a random order as oppoosed to start-to-finsih? Thanks in advance

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  • Simple POST random number issue in PHP

    - by MrEnder
    Ok I am trying to make something to ask you random multiplication questions. Now it asks the questions fine. Generates the random questions fine. But when it reloads the page the random numbers are different... how can I fix this? <?php $rndnum1 = rand(1, 12); $rndnum2 = rand(1, 12); echo "<h3>". $rndnum1 . " x "; echo $rndnum2 . "</h3>"; if($_SERVER["REQUEST_METHOD"] == "GET") { $answer=0; } else if($_SERVER["REQUEST_METHOD"] == "POST") { $answer=trim($_POST["answerInput"]); $check=$rndnum1*$rndnum2; if($answer==$check) { echo "Correct!"; } else { echo "Wrong!"; } } ?> <form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" > <table> <tr> <td> First Name:&nbsp; </td> <td> <input type="text" name="answerInput" value="<?php echo $answer; ?>" size="20"/> </td> <td> <?php echo $answerError; ?> </td> </tr> <tr> <td class="signupTd" colspan="2"> <input type="submit" name="submit" value="Submit"/> </td> </tr> </table> </form>

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  • Random value from Flags enum

    - by Chris Porter
    Say I have a function that accepts an enum decorated with the Flags attribute. If the value of the enum is a combination of more than one of the enum elements how can I extract one of those elements at random? I have the following but it seems there must be a better way. [Flags] enum Colours { Blue = 1, Red = 2, Green = 4 } public static void Main() { var options = Colours.Blue | Colours.Red | Colours.Green; var opts = options.ToString().Split(','); var rand = new Random(); var selected = opts[rand.Next(opts.Length)].Trim(); var myEnum = Enum.Parse(typeof(Colours), selected); Console.WriteLine(myEnum); Console.ReadLine(); }

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  • Stable random color algorithm

    - by Olmo
    Here we have an interesting real-world algorithm requirement involving colors. 1) Nice random colors: In ordeeing to draw a beautifull chart (i.e: pie chart) we need to pick a random set of Colors that: a) are different enought b) Play nicely Doesnt Look hard. For example u fix bright and saturation and divide hue in steps of 360/Num_sectors 2) Stable: given Pie1 with sectors with labes ('A','B','C') and Pie2 with sector with labels ('B','C','D'), will be nice if color('B',pie1)= color('B',pie2) and the same for 'C' and so on, so people don't get crazy when seeing similar updated charts, even if some sectors appear some dissapeared or the number of sectors changed. The label is the only stable thing. 3) hard-coded colors: the algorithm allows hardcoded label-color relationships as an input but stills doing a good work (1 & 2) for the rest of free labels. I think this algorithm, even if it looks quite ad-hoc, will be usefull in more then one situation. Any ideas?

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  • mysql random generated value

    - by bbutle01
    I need to generate a random alpha/numeric to give to users that they come to the site to enter. I dont' know much about random numbers and such, I know there are seeding issues and such, but I'm not sure what they are. So, I used this: select substrING(md5(concat_ws('-',md5(username_usr), MD5(zip_usr), MD5(id_usr), MD5(created_usr))),-12) from users_usr Is this safe? I used concat_ws because sometimes zip is null, but the others never are. And yes, I know this is kinda short, but 1. They have to enter the last 4 of their social, 2. It's 1 time use, 3. There's no private data displayed back in the application and 4. I may use captcha, but since there's no private data, thats probably overkill. THanks

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  • random products instead of related products in magento

    - by abnab
    BElow is the function that selects related product of a single product. I wanted it to work in such a way that if there are no related products other random products will be added to the array. Random could be other products of the same category and if there is no procut in the same category we could fetch from other categories. protected function _prepareData() { $product = Mage::registry('product'); /* @var $product Mage_Catalog_Model_Product */ $this->_itemCollection = $product->getRelatedProductCollection() ->addAttributeToSelect('required_options') ->addAttributeToSort('position', Varien_Db_Select::SQL_ASC) ->addStoreFilter() ; if (Mage::helper('catalog')->isModuleEnabled('Mage_Checkout')) { Mage::getResourceSingleton('checkout/cart')->addExcludeProductFilter($this->_itemCollection, Mage::getSingleton('checkout/session')->getQuoteId() ); $this->_addProductAttributesAndPrices($this->_itemCollection); } // Mage::getSingleton('catalog/product_status')->addSaleableFilterToCollection($this->_itemCollection); Mage::getSingleton('catalog/product_visibility')->addVisibleInCatalogFilterToCollection($this->_itemCollection); $this->_itemCollection->load(); foreach ($this->_itemCollection as $product) { $product->setDoNotUseCategoryId(true); } return $this; } Thanks Abnab

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  • select random value from each type

    - by Joseph Mastey
    I have two tables, rating: +-----------+-----------+-------------+----------+ | rating_id | entity_id | rating_code | position | +-----------+-----------+-------------+----------+ | 1 | 1 | Quality | 0 | | 2 | 1 | Value | 0 | | 3 | 1 | Price | 0 | +-----------+-----------+-------------+----------+ And rating_option +-----------+-----------+------+-------+----------+ | option_id | rating_id | code | value | position | +-----------+-----------+------+-------+----------+ | 1 | 1 | 1 | 1 | 1 | | 2 | 1 | 2 | 2 | 2 | | 3 | 1 | 3 | 3 | 3 | | 4 | 1 | 4 | 4 | 4 | | 5 | 1 | 5 | 5 | 5 | | 6 | 2 | 1 | 1 | 1 | | 7 | 2 | 2 | 2 | 2 | | 8 | 2 | 3 | 3 | 3 | | 9 | 2 | 4 | 4 | 4 | | 10 | 2 | 5 | 5 | 5 | | 11 | 3 | 1 | 1 | 1 | | 12 | 3 | 2 | 2 | 2 | | 13 | 3 | 3 | 3 | 3 | | 14 | 3 | 4 | 4 | 4 | | 15 | 3 | 5 | 5 | 5 | +-----------+-----------+------+-------+----------+ I need a SQL query (not application level, must stay in the database) which will select a set of ratings randomly. A sample result would look like this, but would pick a random value for each rating_id on subsequent calls: +-----------+-----------+------+-------+----------+ | option_id | rating_id | code | value | position | +-----------+-----------+------+-------+----------+ | 1 | 1 | 1 | 1 | 1 | | 8 | 2 | 3 | 3 | 3 | | 15 | 3 | 5 | 5 | 5 | +-----------+-----------+------+-------+----------+ I'm totally stuck on the random part, and grouping by rating_id has been a crap shoot so far. Any MySQL ninjas want to take a stab? Thanks, Joe

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  • Random access gzip stream

    - by jkff
    I'd like to be able to do random access into a gzipped file. I can afford to do some preprocessing on it (say, build some kind of index), provided that the result of the preprocessing is much smaller than the file itself. Any advice? My thoughts were: Hack on an existing gzip implementation and serialize its decompressor state every, say, 1 megabyte of compressed data. Then to do random access, deserialize the decompressor state and read from the megabyte boundary. This seems hard, especially since I'm working with Java and I couldn't find a pure-java gzip implementation :( Re-compress the file in chunks of 1Mb and do same as above. This has the disadvantage of doubling the required disk space. Write a simple parser of the gzip format that doesn't do any decompressing and only detects and indexes block boundaries (if there even are any blocks: I haven't yet read the gzip format description)

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  • Random directions, with no repeat.. (Bad Description)

    - by Neurofluxation
    Hey there, So I'm knocking together a random pattern generation thing. My code so far: int permutes = 100; int y = 31; int x = 63; while (permutes > 0) { int rndTurn = random(1, 4); if (rndTurn == 1) { y = y - 1; } //go up if (rndTurn == 2) { y = y + 1; } //go down if (rndTurn == 3) { x = x - 1; } //go right if (rndTurn == 4) { x = x + 1; } //go left setP(x, y, 1); delay(250); } My question is, how would I go about getting the code to not go back on itself? e.g. The code says "Go Left" but the next loop through it says "Go Right", how can I stop this? NOTE: setP turns a specific pixel on. Cheers peoples!

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  • Using Geo APIs to pick a random town from anywhere in the world

    - by Dan Forys
    Hi all, I'm trying to use Yahoo's excellent GeoPlanet API: http://developer.yahoo.com/geo/geoplanet/guide/api-reference.html I would like to pick a random town from anywhere in the world but can't see an easy way to do it. I have tried querying by country and asking for children of type 'town', but can't seem to do that directly. Can anyone think of a way to pluck out a random town WOEID without having to query the country, then the admin regions, then the admin 2, then the admin 3 etc. I have also experimented using YQL, but don't have enough of an understanding about the available APIs.

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  • My AES encryption/decryption functions don't work with random ivecs

    - by Brendan Long
    I was bored and wrote a wrapper around openSSL to do AES encryption with less work. If I do it like this: http://pastebin.com/V1eqz4jp (ivec = 0) Everything works fine, but the default ivec is all 0's, which has some security problems. Since I'm passing the data back as a string anyway, I figured, why not generate a random ivec and stick it to the front, the take it back off when I decrypt the string? For some reason it doesn't work though. With random ivec: http://pastebin.com/MkDBFcn6 Well actually, it almost works. It seems to decrypt the middle of the string, but not the beginning or end: String is: 0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF Encrypting.. ???l%%1u???B! ?????`pN)?????[l????{?Q???2?/?H??y"?=Z?Cu????l%%1u???B! Decrypting.. String is: ?%???G*?5J?0??0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF!-e????V?5 I honestly have no idea what's going wrong. Maybe some stupid mistake, or maybe I'm missing something about AES?

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  • random quote generator with php, ajax and mysql

    - by fusion
    i've tried using this code and this to make a random quote generator, but it doesn't display anything. my questions are: what is wrong with my code? in the above tut, the quote is generated on a button click, i'd like a random quote to be displayed every 30 mins automatically. how do i do this? //////////////////////// quote.html: <!DOCTYPE html> <script src="ajax.js" type="text/javascript"></script> <body> <!–create the div for the quotes land–> <div id="quote"><strong>this</strong></div> <div><a style="cursor:pointer" onclick="run_query();">Next quote …</a></div> </body> </html> ///////////////////// quote.php: <?php include 'config.php'; // 'text' is the name of your table that contains // the information you want to pull from $rowcount = mysql_query("select count(*) as rows from quotes"); // Gets the total number of items pulled from database. while ($row = mysql_fetch_assoc($rowcount)) { $max = $row["rows"]; } // Selects an item's index at random $rand = rand(1,$max)-1; $result = mysql_query("select * from quotes limit $rand, 1"); $row = mysql_fetch_array($result); $randomOutput = $row['storedText']; echo '<p>' . $randomOutput . '</p>'; //////////// ajax.js: var xmlHttp function run_query() { xmlHttp=GetXmlHttpObject(); if (xmlHttp==null) { alert ("This browser does not support HTTP Request"); return; } // end if var url="quote.php"; xmlHttp.onreadystatechange=stateChanged; xmlHttp.open("GET",url,true); xmlHttp.send(null); } //end function function stateChanged(){ if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){ document.getElementById("quote").innerHTML=xmlHttp.responseText; } //end if } //end function function GetXmlHttpObject() { var xmlHttp=null; try { // For these browsers: Firefox, Opera 8.0+, Safari xmlHttp=new XMLHttpRequest(); }catch (e){ //For Internet Explorer try{ xmlHttp=new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); } } return xmlHttp; } //end function

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