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  • RANDOM Number Generation in C

    - by CVS-2600Hertz-wordpress-com
    Recently i have begun development of a simple game. It is improved version of an earlier version that i had developed. Large part of the game's success depends on Random number generation in different modes: MODE1 - Truly Random mode myRand(min,max,mode=1); Should return me a random integer b/w min & max. MODE2 - Pseudo Random : Token out of a bag mode myRand(min,max,mode=2); Should return me a random integer b/w min & max. Also should internally keep track of the values returned and must not return the same value again until all the other values are returned atleast once. MODE3 - Pseudo Random : Human mode myRand(min,max,mode=3); Should return me a random integer b/w min & max. The randomisation ought to be not purely mathematically random, rather random as user perceive it. How Humans see RANDOM. * Assume the code is time-critical (i.e. any performance optimisations are welcome) * Pseudo-code will do but an implementation in C is what i'm looking for. * Please keep it simple. A single function should be sufficient (thats what i'm looking for) Thank You

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  • A function where small changes in input always result in large changes in output

    - by snowlord
    I would like an algorithm for a function that takes n integers and returns one integer. For small changes in the input, the resulting integer should vary greatly. Even though I've taken a number of courses in math, I have not used that knowledge very much and now I need some help... An important property of this function should be that if it is used with coordinate pairs as input and the result is plotted (as a grayscale value for example) on an image, any repeating patterns should only be visible if the image is very big. I have experimented with various algorithms for pseudo-random numbers with little success and finally it struck me that md5 almost meets my criteria, except that it is not for numbers (at least not from what I know). That resulted in something like this Python prototype (for n = 2, it could easily be changed to take a list of integers of course): import hashlib def uniqnum(x, y): return int(hashlib.md5(str(x) + ',' + str(y)).hexdigest()[-6:], 16) But obviously it feels wrong to go over strings when both input and output are integers. What would be a good replacement for this implementation (in pseudo-code, python, or whatever language)?

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  • How can I get IE8 to accept a css :before tag?

    - by William Calleja
    I have the following CSS code .editable:before { content: url(../images/icons/icon1.png); padding-right:5px; } this is used in conjuntion with the following markup: <span class="editable"></span> In every other blessed browser in the world my icon is appearing, but IE8 seems to have a problem with this. Isn't the :before pseudo-element CSS2? isn't content: also a CSS2 command? what gives?

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  • CSS: a:link vs just a (without the :link part)

    - by Rob
    So we're required to use the following order for CSS anchor pseudo-classes a:link { color: red } a:visited { color: blue } a:hover { color: yellow } a:active { color: lime } But my question is why bother with the a:link part? Rather, is there any advantage to the above (other than perhaps clarity) over: a { color:red; } /* notice no :link part */ a:visited { color: blue; } etc.,etc.

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  • Is there such a concept as "pseudo implementation" in software development?

    - by MachuPichu
    I'm looking for a label to describe the practice of using human-based computation methods or other means of "faking" an algorithm for the sake of getting a product or demo off the ground quickly without spending the time to develop an technical/scalable/analytical solution? Eg: using Amazon Turk to count the number of empty tables in a restaurant. I'm also looking to learn more about this subject, but not sure what to search for. Human-based computation is only one method, I'm interested in the general idea of pseudo-implementation. Any ideas, recommended reading? Thanks

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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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  • MSDN "pseudoframe"

    - by bobobobo
    So, I'm trying to replicate MSDN "pseudoframes" here. Their pages are laid out like they're using an old-school frameset, but inspecting their elements with firebug reveals they've done this with purely div's. Here's my attempt at it. Its not perfect though, it only works in Chrome and Firefox, it has this weird highlight select behavior that I don't like, any takers? <!doctype html> <html> <head> <title>msdn "pseudoframe"</title> <style> body { background-color: #aaa; margin: 0; padding: 0; } div#pseudoframe, div#main { border: solid 1px black; background-color: #fff; } div#pseudoframe { position: absolute; left: 0; width: 180px; height: 100%; overflow-x: auto; overflow-y: none; } div#sizeMod { background-color: #a0a; position: absolute; left: 220px; height: 100%; cursor: e-resize; } div#main { font-weight: bold; font-size: 2em; padding: 24px; margin-left: 224px; } </style> <script type="text/javascript"> function initialize() { // get the pseudoframe and attach an event to the mouse flyover. var pf = document.getElementById('pseudoframe'); var main = document.getElementById('main'); var resize = document.getElementById( 'sizeMod' ); pf['onmouseover'] = function( event ) { event = event || window.event; var el = event.srcElement || event.target ; // are we within 5 px of the border? if we are, // change the mouse cursor to resize. }; pf['onscroll'] = function( event ) { event = event || window.event; var el = event.srcElement || event.target ; var sizeMod = document.getElementById( 'sizeMod' ); //alert( el.scrollLeft ); sizeMod.style.right = '-' + (el.scrollLeft) + 'px'; //alert( sizeMod.style.right ); // are we within 5 px of the border? if we are, // change the mouse cursor to resize. }; resize['onmousedown'] = function( event ) { event = event || window.event; var el = event.srcElement || event.target ; window.lockResize = true; }; window['onmouseup'] = function( event ) { event = event || window.event; var el = event.srcElement || event.target ; window.lockResize = false; //release on any mouse up event //alert('unlocked'); }; window['onmousemove'] = function( event ) { event = event || window.event; var el = event.srcElement || event.target ; if( window.lockResize == true ) { // resize. get client x and y. var x = event.clientX; var y = event.clientY; pf.style.width = x + 'px'; resize.style.left = x + 'px'; main.style.marginLeft = x + 'px'; //alert( pf.style.width ); event.stopPropagation(); event.preventDefault(); return false; } }; } </script> </head> <body onload=" initialize(); "> <div id="pseudoframe"> <ul> <li>Code</li> <li>MICROSOFT CODE <ul> <li>WINDOWS XP SOURCE</li> <li>WINDOWS VISTA SOURCE</li> <li>WINDOWS 7 SOURCE</li> <li>WINDOWS 8 SOURCE</li> </ul> </li> <li>DOWNLOAD ALL MICROSOFT CODE EVER WRITTEN</li> <li>DOWNLOAD ALL MAC OS CODE EVER WRITTEN</li> <li>DOWNLOAD ALL AMIGA GAME CONSOLE CODE</li> <li>DOWNLOAD ALL CODE EVER WRITTEN PERIOD</li> </ul> </div> <div id="sizeMod">&nbsp;&nbsp;</div> <div id="main"> lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe lorem ipsum microsoft pseudoframe </div> </body> </html>

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  • Are jQuery's :first and :eq(0) selectors functionally equivalent?

    - by travis
    I'm not sure whether to use :first or :eq(0) in a selector. I'm pretty sure that they'll always return the same object, but is one speedier than the other? I'm sure someone here must have benchmarked these selectors before and I'm not really sure the best way to test if one is faster. Update: here's the bench I ran: /* start bench */ for (var count = 0; count < 5; count++) { var i = 0, limit = 10000; var start, end; start = new Date(); for (i = 0; i < limit; i++) { var $radeditor = $thisFrame.parents("div.RadEditor.Telerik:eq(0)"); } end = new Date(); alert("div.RadEditor.Telerik:eq(0) : " + (end-start)); var start = new Date(); for (i = 0; i < limit; i++) { var $radeditor = $thisFrame.parents("div.RadEditor.Telerik:first"); } end = new Date(); alert("div.RadEditor.Telerik:first : " + (end-start)); start = new Date(); for (i = 0; i < limit; i++) { var radeditor = $thisFrame.parents("div.RadEditor.Telerik")[0]; } end = new Date(); alert("(div.RadEditor.Telerik)[0] : " + (end-start)); start = new Date(); for (i = 0; i < limit; i++) { var $radeditor = $($thisFrame.parents("div.RadEditor.Telerik")[0]); } end = new Date(); alert("$((div.RadEditor.Telerik)[0]) : " + (end-start)); } /* end bench */ I assumed that the 3rd would be the fastest and the 4th would be the slowest, but here's the results that I came up with: FF3: :eq(0) :first [0] $([0]) trial1 5275 4360 4107 3910 trial2 5175 5231 3916 4134 trial3 5317 5589 4670 4350 trial4 5754 4829 3988 4610 trial5 4771 6019 4669 4803 Average 5258.4 5205.6 4270 4361.4 IE6: :eq(0) :first [0] $([0]) trial1 13796 15733 12202 14014 trial2 14186 13905 12749 11546 trial3 12249 14281 13421 12109 trial4 14984 15015 11718 13421 trial5 16015 13187 11578 10984 Average 14246 14424.2 12333.6 12414.8 I was correct about just returning the first native DOM object being the fastest ([0]), but I can't believe the wrapping that object in the jQuery function was faster that both :first and :eq(0)! Unless I'm doing it wrong.

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  • Generate n-dimensional random numbers in Python

    - by Magsol
    I'm trying to generate random numbers from a gaussian distribution. Python has the very useful random.gauss() method, but this is only a one-dimensional random variable. How could I programmatically generate random numbers from this distribution in n-dimensions? For example, in two dimensions, the return value of this method is essentially distance from the mean, so I would still need (x,y) coordinates to determine an actual data point. I suppose I could generate two more random numbers, but I'm not sure how to set up the constraints. I appreciate any insights. Thanks!

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  • Is this a correct porting of java.util.Random in objectiveC

    - by dipu
    I have ported the code inside java.util.Random class in objectivec. I want to have an identical random number generator so that it synchs with the server app running on java. Now is this a safe porting and if not is there a way to mimic AtomicLong as it is found in java? Please see my code below. static long long multiplier = 0x5DEECE66DL; static long addend = 0xBL; static long long mask = (0x1000000000000001L << 48) - 1; -(void) initWithSeed:(long long) seed1 { [self setRandomSeed: 0L];// = new AtomicLong(0L); [self setSeed: seed1]; } -(int) next:(int)bits { long long oldseed, nextseed; long long seed1 = [self.randomSeed longLongValue]; //AtomicLong //do { oldseed = seed1; nextseed = (oldseed * multiplier + addend) & mask; //} while (!seed.compareAndSet(oldseed, nextseed)); [self setRandomSeed: [NSNumber numberWithLongLong:nextseed]]; ///int ret = (int)(nextseed >>> (48 - bits)); int ret = (unsigned int)(nextseed >> (48 - bits)); return ret; } -(void) setSeed:(long long) seed1 { seed1 = (seed1 ^ multiplier) & mask; [self setRandomSeed: [NSNumber numberWithLongLong:seed1]]; }

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  • How can I make an even more random number in ActionScript 2.0

    - by Theo
    I write a piece of software that runs inside banner ads which generates millions of session IDs every day. For a long time I've known that the random number generator in Flash is't random enough to generate sufficiently unique IDs, so I've employed a number of tricks to get even more random numbers. However, in ActionScript 2.0 it's not easy, and I'm seeing more and more collisions, so I wonder if there is something I've overlooked. As far as I can tell the problem with Math.random() is that it's seeded by the system time, and when you have sufficient numbers of simultaneous attempts you're bound to see collisions. In ActionScript 3.0 I use the System.totalMemory, but there's no equivalent in ActionScript 2.0. AS3 also has Font.enumerateFonts, and a few other things that are different from system to system. On the server side I also add the IP address to the session ID, but even that isn't enough (for example, many large companies use a single proxy server and that means that thousands of people all have the same IP -- and since they tend to look at the same sites, with the same ads, roughly at the same time, there are many session ID collisions). What I need isn't something perfectly random, just something that is random enough to dilute the randomness I get from Math.random(). Think of it this way: there is a certain chance that two people will generate the same random number sequence using only Math.random(), but the chance of two people generating the same sequence and having, say, the exact same list of fonts is significantly lower. I cannot rely on having sufficient script access to use ExternalInterface to get hold of things like the user agent, or the URL of the page. I don't need suggestions of how to do it in AS3, or any other system, only AS2 -- using only what's available in the standard APIs. The best I've come up with so far is to use the list of microphones (Microphone.names), but I've also tried to make some fingerprinting using some of the properties in System.capabilities, I'm not sure how much randomness I can get out of that though so I'm not using that at the moment. I hope I've overlooked something.

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  • Can Java's random function be zero?

    - by ThirdD3gree
    Just out of curiosity, can Math.random() ever be zero? For example, if I were to have: while (true){ if (Math.random() == 0) return 1; } Would I ever actually get a return of one? There's also rounding error to consider because Math.random() returns a double. I ask because my CS professor stated that random() goes from 0 to 1 inclusive, and I always thought it was exclusive.

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  • :first-child fails when an element of a different class is dynamically inserted above

    - by koko
    So, I've encountered a situation where inserting an element of a different class/id breaks all css-rules on that :first-child. <div id="nav"> <div class="nSub">abcdef</div> <div class="nSub">abcdef</div> <div class="nSub">abcdef</div> <div class="nSub">abcdef</div> <div class="nSub">abcdef</div> </div> .nSub:first-child { margin-top:15px; -moz-border-radius-topleft:5px; /* ... */ } .nSub { background:#666; /* ... */ } .nSub:last-child { -moz-border-radius-bottomleft:5px; /* ... */ } As soon as I insert an element of another class/id above, like this: $('nav').insert({top:'<div id="newWF"></div>'}); all declarations for .nSub:first-child are being ignored in both FF 3.6 and Safari 4.

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  • C: Random Number Generation - What (If Anything) Is Wrong With This

    - by raoulcousins
    For a simple simulation in C, I need to generate exponential random variables. I remember reading somewhere (but I can't find it now, and I don't remember why) that using the rand() function to generate random integers in a fixed range would generate non-uniformly distributed integers. Because of this, I'm wondering if this code might have a similar problem: //generate u ~ U[0,1] u = ( (double)rand() / ((double)(RAND_MAX)); //inverse of exponential CDF to get exponential random variable expon = -log(1-u) * mean; Thank you!

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  • Get :first-letter of :hover element with CSS

    - by Rudie
    Is it possible to get the first letter of an element while in 'hover mode'? This is how it would look - I think - but it's not working in Chrome 10: a:hover:first-letter or a:first-letter:hover Technically (imho) they're not the same. The first takes the first letter of the hovering element. The second takes the entire element if the first letter is hovering. I require the first. As you can see on http://css4.hotblocks.nl (if you have a 1900px screen and a dom inspector) if you uncomment the CSS, both don't work. I want only the first letter of the element to color red, when the entire element is in :hover mode. Is it possible without additional HTML tags? Thanks. -- edit I've changed my online example for the better. CSS is now divided in separate <style> blocks. Makes for easier turning on and off try-outs. Conclusion - so far!? - is this: In Firefox 3.6/4 a:first-letter:hover does nothing (good) and a:hover:first-letter works perfectly (good!). In Chrome 10 a:first-letter:hover does nothing (good) and a:first-letter:hover breaks the previous CSS 'statement'. (In my example it breaks nothing because it's in a separate <style> block.) Which brings us to: once again Google Chrome lags behind Firefox =( --edit

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  • K-Means Algorithm and java code

    - by Thandar
    Hi all, I need to calculate for grouping objects according to their size. I got k-means algorithms in java which calculate mostly for classifying according to their two or more features and the results are not satisfy for me.I only want to calculate for grouping objects based on one feature.Pseudocode or code would be helpful, too. Thanks u all for helping.

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  • Continuing JavaScript "classes" - enums within

    - by espais
    From a previous question, I have the following: So I have implemented a resource class, now I'd like to continue extending it and add all my constants and enums (or as far as JS will allow...). This is what I currently have: var resources = { // images player : new c_resource("res/player.png"), enemies : new c_resource("res/enemies.png"), tilemap : new c_resource("res/tilemap.png") }; And this is what I would like to continue to extend it to: var resources = { // images player : new c_resource("res/player.png"), enemies : new c_resource("res/enemies.png"), tilemap : new c_resource("res/tilemap.png"), // enums directions : {up:0, right:1, down:2, left:3}, speeds : {slow: 1, medium: 3, fast: 5} }; ... function enemies() { this.dir = resources.directions.down; // initialize to down } When I attempt to access resources.directions.up, my JS script goes down in a flaming pile of burning code. Are enums allowed in this context, and if not, how can I properly insert them to be used outside of a normal function? I have also tried defining them as global to a similar effect. edits: fixed the comma...that was just an error in transcribing it. When I run it in Firefox and watch the console, I get an error that says resources is undefined. The resources 'class' is defined at the top of my script, and function enemies() directly follows...so from what I understand it should still be in scope...

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  • Initializing a C++ vector to random values... fast

    - by Flamewires
    Hey, id like to make this as fast as possible because it gets called A LOT in a program i'm writing, so is there any faster way to initialize a C++ vector to random values than: double range;//set to the range of a particular function i want to evaluate. std::vector<double> x(30, 0.0); for (int i=0;i<x.size();i++) { x.at(i) = (rand()/(double)RAND_MAX)*range; } EDIT:Fixed x's initializer.

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  • PHP Game weapon accuracy

    - by noko
    I'm trying to come up with a way for players to fire their weapons and only hit for a certain percentage. For example, one gun can only hit 70% of the time while another only hits 34% of the time. So far all I could come up with is weighted arrays. Attempt 1: private function weighted_random(&$weight) { $weights = array(($weight/100), (100-$weight)/100); $r = mt_rand(1,1000); $offset = 0; foreach($weights as $k => $w) { $offset += $w*1000; if($r <= $offset) return $k; } } Attempt 2: private function weapon_fired(&$weight) { $hit = array(); for($i = 0; $i < $weight; $i++) $hit[] = true; for($i = $weight; $i < 100; $i++) $hit[] = false; shuffle($hit); return $hit[mt_rand(0,100)]; } It doesn't seem that the players are hitting the correct percentages but I'm not really sure why. Any ideas or suggestions? Is anything glaringly wrong with these? Thanks

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  • Stable/repeatable random sort (MySQL, Rails)

    - by Matt Rogish
    I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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  • Dedicated Servers: Is one better then two for LAMP pseudo HA setup? [closed]

    - by bikedorkseattle
    Possible Duplicate: How to find web hosting that meets my requirements? I know there are zillions of commentary about hosting out there, but I haven't read much about this. Our current well known host is having too many problems, the hardware we are on it subpar, and I'm ready to leave. A day of downtime can cost as much as our monthly hosting bill. A month of bad performance is just killing us right now, user and google wise. I'm wondering about running two dedicated boxes for LAMP, one running as the primary Nginx/Apache (proxy pass), and the other as the MySQL box. Running a single box scares the bejesus out of me because who knows how long it will take anyone to fix a raid card or whatever. The idea is to set this up using some sort of failover system using pacemaker and heartbeat. If one server goes down the other can take over for the other running both web and db. There are some good articles over at Linode about this. I have a few DBs that are 1GB+ and would like to load them into memory. Because of this, I'm shying away from a Linode HA setup because for the price I could do it with two dedicated like I described. Am I mad or an idiot? What are people out there doing for pseodu high availability good performance setups under $400/month? I'm a webmaster; I do a lot of things none of it that well :)

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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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  • Does Google penalize pseudo-duplicate pages for different locations?

    - by mikewowb
    My compony's site's home page was not specificly optimized to any location. Now, I am planning to optimize it to Boston, and create ten or so other landing pages for other locations we serve. If we made these new pages by copying the original Boston one and changing the location's name (s/Boston/Montreal/), would Google consider them as duplicate pages and penalize us? What is the best practice for this?

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