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  • Machine Learning Algorithm for Predicting Order of Events?

    - by user213060
    Simple machine learning question. Probably numerous ways to solve this: There is an infinite stream of 4 possible events: 'event_1', 'event_2', 'event_4', 'event_4' The events do not come in in completely random order. We will assume that there are some complex patterns to the order that most events come in, and the rest of the events are just random. We do not know the patterns ahead of time though. After each event is received, I want to predict what the next event will be based on the order that events have come in in the past. The predictor will then be told what the next event actually was: Predictor=new_predictor() prev_event=False while True: event=get_event() if prev_event is not False: Predictor.last_event_was(prev_event) predicted_event=Predictor.predict_next_event(event) The question arises of how long of a history that the predictor should maintain, since maintaining infinite history will not be possible. I'll leave this up to you to answer. The answer can't be infinte though for practicality. So I believe that the predictions will have to be done with some kind of rolling history. Adding a new event and expiring an old event should therefore be rather efficient, and not require rebuilding the entire predictor model, for example. Specific code, instead of research papers, would add for me immense value to your responses. Python or C libraries are nice, but anything will do. Thanks! Update: And what if more than one event can happen simultaneously on each round. Does that change the solution?

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  • Delphi 2010 - Source files randomly become read-only in editor?

    - by Justin
    Does anyone else have this problem or is my Delphi cursed somehow? I'll have a bunch of forms and files open in tabs in the editor and I'll be typing away and then suddenly everything stops - my .pas file has, seemingly at random, become read-only. Sometimes I can just right-click the tab at the top and uncheck "Read-Only" and continue, but sometimes this option is checked and greyed-out (disabled), meaning I can't uncheck it and I can't make any further edits to the file. This too seems to be random. In the latter case, the only solution is to save the file in question, which works, despite Delphi's assertion that the file is read-only, close its tab in the editor, and re-open it. Not catastrophic, really, but it's starting to become annoying. Could it be that I am hitting a keyboard command combination accidentally to do this or is this a bug in Delphi? I'm in Delphi 2010, Windows 7. Doubt it's anything to do with installed packages, but if anyone wants the list I'll generate it and attach it here.

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  • Cannot create instance of abstract class

    - by SmartestVEGA
    I am trying to compile the following code and i am getting the error: Cannot create instance of abstract class . Please help m_objExcel = new Excel.Application(); m_objBooks = (Excel.Workbooks)m_objExcel.Workbooks; m_objBook = (Excel._Workbook)(m_objBooks.Add(m_objOpt)); m_objSheets = (Excel.Sheets)m_objBook.Worksheets; m_objSheet = (Excel._Worksheet)(m_objSheets.get_Item(1)); // Create an array for the headers and add it to cells A1:C1. object[] objHeaders = {"Order ID", "Amount", "Tax"}; m_objRange = m_objSheet.get_Range("A1", "C1"); m_objRange.Value = objHeaders; m_objFont = m_objRange.Font; m_objFont.Bold=true; // Create an array with 3 columns and 100 rows and add it to // the worksheet starting at cell A2. object[,] objData = new Object[100,3]; Random rdm = new Random((int)DateTime.Now.Ticks); double nOrderAmt, nTax; for(int r=0;r<100;r++) { objData[r,0] = "ORD" + r.ToString("0000"); nOrderAmt = rdm.Next(1000); objData[r,1] = nOrderAmt.ToString("c"); nTax = nOrderAmt*0.07; objData[r,2] = nTax.ToString("c"); } m_objRange = m_objSheet.get_Range("A2", m_objOpt); m_objRange = m_objRange.get_Resize(100,3); m_objRange.Value = objData; // Save the Workbook and quit Excel. m_objBook.SaveAs(m_strSampleFolder + "Book2.xls", m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, Excel.XlSaveAsAccessMode.xlNoChange, m_objOpt, m_objOpt, m_objOpt, m_objOpt); m_objBook.Close(false, m_objOpt, m_objOpt); m_objExcel.Quit();

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  • Is it viable and necessary to encrypt bytes?

    - by Shervin
    We have a requirement from customer that if someone gets access to the database, all data that includes personal information should be encrypted, so that when they do select calls, they shouldn't be able to see anything in clear text. Now this isn't any problem for Strings, but what about bytearrays? (that can potentially be quite huge (several 100mb)) When you do a select call, you get gibberish anyways. Is it possible for a hacker to somehow read the bytes and get the sensitive information without knowing how the structure of the object it is mapped against is? Because if that is the case, then I guess we should encrypt those bytes, even if they can potentially be quite huge. (I am guessing adding encryption will make them even bigger)

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  • Use jquery to create a multidimensional array

    - by Simon M White
    I'd like to use jquery and a multidemensional array to show a random quote plus the name of the individual who wrote it as a separate item. I'll then be able to use css to style them differently. The quote will change upon page refresh. So far i have this code which combines the quote and the name and person who wrote it: $(document).ready(function(){ var myQuotes = new Array(); myQuotes[0] = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec in tortor mauris. Peter Jones, Dragons Den"; myQuotes[1] = "Curabitur interdum, nibh et fringilla facilisis, lacus ipsum pulvinar mauris, eu facilisis justo arcu eget diam. Duis id sagittis elit. Theo Pathetis, Dragons Den"; myQuotes[2] = "Vivamus purus purus, tincidunt et porttitor et, euismod sit amet urna. Etiam sollicitudin eros nec metus pretium scelerisque. James Caan, Dragons Den"; var myRandom = Math.floor(Math.random()*myQuotes.length); $('.quote-holder blockquote span').html(myQuotes[myRandom]); }); any help would be greatly appreciated.

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  • Trouble with C# array

    - by Biosci3c
    Hi, I am writing a card playing program as a way of learning C#. I ran into an issue with an array going out of bounds. Here is my code: namespace Pcardconsole { class Deck { public Deck() { // Assign standard deck to new deck object int j; for (int i = 0; i != CurrentDeck.Length; i++) { CurrentDeck[i] = originalCards[i]; } // Fisher-Yates Shuffling Algorithim Random rnd = new Random(); for (int k = CurrentDeck.Length - 1; k >= 0; k++) { int r = rnd.Next(0, k + 1); int tmp = CurrentDeck[k]; CurrentDeck[k] = CurrentDeck[r]; CurrentDeck[r] = tmp; // Console.WriteLine(i); } } public void Shuffle() { // TODO } // public int[] ReturnCards() // { // TODO // } public int[] originalCards = new int[54] { 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x50, 0x51 }; public int[] CurrentDeck = new int[54]; } class Program { static void Main(string[] args) { // Create a Deck object Deck mainDeck = new Deck(); Console.WriteLine("Here is the card array:"); for (int index = 0; index != mainDeck.CurrentDeck.Length; index++) { string card = mainDeck.CurrentDeck[index].ToString("x"); Console.WriteLine("0x" + card); } } } The hexidecimal numbers stand for different cards. When I compile it I get an array index out of bounds error, and a crash. I don't understand what is wrong. Any help would be much appreciated.

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  • Shouldn't prepared statements be much faster?

    - by silversky
    $s = explode (" ", microtime()); $s = $s[0]+$s[1]; $con = mysqli_connect ('localhost', 'test', 'pass', 'db') or die('Err'); for ($i=0; $i<1000; $i++) { $stmt = $con -> prepare( " SELECT MAX(id) AS max_id , MIN(id) AS min_id FROM tb "); $stmt -> execute(); $stmt->bind_result($M,$m); $stmt->free_result(); $rand = mt_rand( $m , $M ).'<br/>'; $res = $con -> prepare( " SELECT * FROM tb WHERE id >= ? LIMIT 0,1 "); $res -> bind_param("s", $rand); $res -> execute(); $res->free_result(); } $e = explode (" ", microtime()); $e = $e[0]+$e[1]; echo number_format($e-$s, 4, '.', ''); // and: $link = mysql_connect ("localhost", "test", "pass") or die (); mysql_select_db ("db") or die ("Unable to select database".mysql_error()); for ($i=0; $i<1000; $i++) { $range_result = mysql_query( " SELECT MAX(`id`) AS max_id , MIN(`id`) AS min_id FROM tb "); $range_row = mysql_fetch_object( $range_result ); $random = mt_rand( $range_row->min_id , $range_row->max_id ); $result = mysql_query( " SELECT * FROM tb WHERE id >= $random LIMIT 0,1 "); } defenitly prepared statements are much more safer but also every where it says that they are much faster BUT in my test on the above code I have: - 2.45 sec for prepared statements - 5.05 sec for the secon example What do you think I'm doing wrong? Should I use the second solution or I should try to optimize the prep stmt?

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  • Rot13 for numbers.

    - by dreeves
    EDIT: Now a Major Motion Blog Post at http://messymatters.com/sealedbids The idea of rot13 is to obscure text, for example to prevent spoilers. It's not meant to be cryptographically secure but to simply make sure that only people who are sure they want to read it will read it. I'd like to do something similar for numbers, for an application involving sealed bids. Roughly I want to send someone my number and trust them to pick their own number, uninfluenced by mine, but then they should be able to reveal mine (purely client-side) when they're ready. They should not require further input from me or any third party. (Added: Note the assumption that the recipient is being trusted not to cheat.) It's not as simple as rot13 because certain numbers, like 1 and 2, will recur often enough that you might remember that, say, 34.2 is really 1. Here's what I'm looking for specifically: A function seal() that maps a real number to a real number (or a string). It should not be deterministic -- seal(7) should not map to the same thing every time. But the corresponding function unseal() should be deterministic -- unseal(seal(x)) should equal x for all x. I don't want seal or unseal to call any webservices or even get the system time (because I don't want to assume synchronized clocks). (Added: It's fine to assume that all bids will be less than some maximum, known to everyone, say a million.) Sanity check: > seal(7) 482.2382 # some random-seeming number or string. > seal(7) 71.9217 # a completely different random-seeming number or string. > unseal(seal(7)) 7 # we always recover the original number by unsealing.

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  • Understanding CSRF - Simple Question

    - by byronh
    I know this might make me seem like an idiot, I've read everything there is to read about CSRF and I still don't understand how using a 'challenge token' would add any sort of prevention. Please help me clarify the basic concept, none of the articles and posts here on SO I read seemed to really explicitly state what value you're comparing with what. From OWASP: In general, developers need only generate this token once for the current session. After initial generation of this token, the value is stored in the session and is utilized for each subsequent request until the session expires. If I understand the process correctly, this is what happens. I log in at http://example.com and a session/cookie is created containing this random token. Then, every form includes a hidden input also containing this random value from the session which is compared with the session/cookie upon form submission. But what does that accomplish? Aren't you just taking session data, putting it in the page, and then comparing it with the exact same session data? Seems like circular reasoning. These articles keep talking about following the "same-origin policy" but that makes no sense, because all CSRF attacks ARE of the same origin as the user, just tricking the user into doing actions he/she didn't intend. Is there any alternative other than appending the token to every single URL as a query string? Seems very ugly and impractical, and makes bookmarking harder for the user.

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  • Control Windows VM from Linux Host

    - by vy32
    I am looking for a tool that will allow me to monitor and control programs running inside a Windows VM from the Linux host machine. I realize that this is similar to what a rootkit would do, and I am completely happy to use some hacker software if it provides the necessary functionality (and if I can get it in source-code form). If I can't find something, I'll have to write it using C. Probably an embedded HTTP server running on an odd port and doing some kind of XMLRPC thing. Here is the basic functionality I need: Get list of running processes Kill a process. Start a process Read/write/create/delete files I would like to: - Read contents of screen - Read all controls on screen. - Send arbitrary click to a Windows control. Does anything like this exist?

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  • How do you embed a resource so that it can be accessed for icons?

    - by fneep
    I have a C# project using VS2005. Basically I have two icons, one for the application, and one for files that are associated with the application. I have associated these files with the application, and I know how to set their icons in the Registry, but I can only set them to the application icon because it seems to be the only external resource. To show what I mean, I've built the app and opened it with Resource Hacker, and you'll notice only one of the two icons is there, using one icon and one icon group.

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  • Is a red-black tree my ideal data structure?

    - by Hugo van der Sanden
    I have a collection of items (big rationals) that I'll be processing. In each case, processing will consist of removing the smallest item in the collection, doing some work, and then adding 0-2 new items (which will always be larger than the removed item). The collection will be initialised with one item, and work will continue until it is empty. I'm not sure what size the collection is likely to reach, but I'd expect in the range 1M-100M items. I will not need to locate any item other than the smallest. I'm currently planning to use a red-black tree, possibly tweaked to keep a pointer to the smallest item. However I've never used one before, and I'm unsure whether my pattern of use fits its characteristics well. 1) Is there a danger the pattern of deletion from the left + random insertion will affect performance, eg by requiring a significantly higher number of rotations than random deletion would? Or will delete and insert operations still be O(log n) with this pattern of use? 2) Would some other data structure give me better performance, either because of the deletion pattern or taking advantage of the fact I only ever need to find the smallest item? Update: glad I asked, the binary heap is clearly a better solution for this case, and as promised turned out to be very easy to implement. Hugo

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  • CONFUSING : CGAffineTransform - rotation on uibutton resizes buttonimage ?! (iPad)

    - by Michael
    hi there, i've got a strange problem using uibuttons, type custom. i'm placing 4 of those buttons on a scrollview, rotating each button by a random angle using CGAffineTransform. now it seems, that the buttons itself change size depending on the angle of rotation. can't get this problem solved :( UIGraphicsBeginImageContext(tempCtxSize); [cookbookImage drawInRect:CGRectMake(imgOffsetX, imgOffsetY+frmOffsetY, cookbookImage.size.width, cookbookImage.size.height)]; [cookbookFrame drawInRect:CGRectMake(0.0f, frmOffsetY, cookbookFrame.size.width, cookbookFrame.size.height)]; UIImage *combinedImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); ... ... UIButton *cookbookViewButton = [UIButton buttonWithType:UIButtonTypeCustom]; [cookbookViewButton setFrame:CGRectMake(0.0f, 0.0f, combinedImage.size.width, combinedImage.size.height)]; [cookbookViewButton setBackgroundColor:[UIColor clearColor]]; [cookbookViewButton setBackgroundImage:combinedImage forState:UIControlStateNormal]; CGAffineTransform rotation = [cookbookViewButton transform]; rotation = CGAffineTransformRotate(rotation, angle); // some random angle [cookbookViewButton setTransform:rotation]; thx for your help in advance!

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  • Browser for cross-site-script testing (for testing Mozilla Add-On)

    - by Anthony
    I am working on a Firefox extension that will involve ajax calls to domains that would normally fail due to the same-origin policy set by Firefox (and most modern browsers). I was wondering if there is a way to either turn off the same-origin restriction (in about:config, perhaps) or if there was a standard lite-browser that developers turn to for this. I really would like to avoid using any blackhat tools, if possible. Not because I'm against them, I just don't want to add another learning curve to the process. I can use curl in PHP to confirm that the requests work, but I want to get started on writing the js that the addon will actually use, so I need a client that will execute js. I also tried spidermonkey, but since I'm doing the ajax with jquery, it threw a fit at all of the browser-based default variables. So, short version: is there a reliable browser/client for cross site scripting that isn't primarily a hacker app? Or can I just turn off same-domain policy in Firefox?

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  • Passing youtube video id from video feed to flash

    - by Grant Anderson
    I'm working on a flash web application (Actionscript 2.0) for my honours project but am having trouble embedding youtube videos. Basically the user selects symbols which queries the youtube api with certain tags depending on the symbols chosenand a random video is then picked from the first 30 videos. I have this working using the following code: on (release) { url="http://gdata.youtube.com/feeds/api/videos?q=danger+passion&orderby=published&start-index="+random(30)+"&max-results=1&v=2" getURL(url); } but this just displays a webpage with a link to the youtube video. This is the code I'll be using as the foundations for the player: // create a MovieClip to load the player into var ytplayer:MovieClip = _root.createEmptyMovieClip("ytplayer", 1); // create a listener object for the MovieClipLoader to use var ytPlayerLoaderListener:Object = { onLoadInit: function() { // When the player clip first loads, we start an interval to // check for when the player is ready loadInterval = setInterval(checkPlayerLoaded, 250); } }; var loadInterval:Number; function checkPlayerLoaded():Void { // once the player is ready, we can subscribe to events, or in the case of // the chromeless player, we could load videos if (ytplayer.isPlayerLoaded()) { ytplayer.addEventListener("onStateChange", onPlayerStateChange); ytplayer.addEventListener("onError", onPlayerError); clearInterval(loadInterval); } } function onPlayerStateChange(newState:Number) { trace("New player state: "+ newState); } function onPlayerError(errorCode:Number) { trace("An error occurred: "+ errorCode); } // create a MovieClipLoader to handle the loading of the player var ytPlayerLoader:MovieClipLoader = new MovieClipLoader(); ytPlayerLoader.addListener(ytPlayerLoaderListener); // load the player ytPlayerLoader.loadClip("http://www.youtube.com/v/pv5zWaTEVkI", ytplayer); can anyone help me on how to get the id of the video (for example: pv5zWaTEVkI) from the feed? Or how to send a query from flash which will return the video url/id as opposed to the url of a feed. Any help would be much appreciated as my hand in rather soon. Thanks

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  • What's a reliable and practical way to protect software with a user license ?

    - by Frank
    I know software companies use licenses to protect their softwares, but I also know there are keygen programs to bypass them. I'm a Java developer, if I put my program online for sale, what's a reliable and practical way to protect it ? How about something like this, would it work ? <1> I use ProGuard to protect the source code. <2> Sign the executable Jar file. <3> Since my Java program only need to work on PC [I need to use JDIC in it], I wrap the final executable Jar into an .exe file which makes it harder to decompile. <4> When a user first downloads and runs my app, it checks for a Pass file on his PC. <5> If the Pass file doesn't exist, run the app in demo mode, exits in 5 minutes. <6> When demo exits a panel opens with a "Buy Now" button. This demo mode repeats forever unless step <7> happens. <7> If user clicks the "Buy Now" button, he fills out a detailed form [name, phone, email ...], presses a "Verify Info" button to save the form to a Pass file, leaving license Key # field empty in this newly generated Pass file. <8> Pressing "Verify Info" button will take him to a html form pre-filled with his info to verify what he is buying, also hidden in the form's input filed is a license Key number. He can now press a "Pay Now" button to goto Paypal to finish the process. <9> The hidden license Key # will be passed to Paypal as product Id info and emailed to me. <10> After I got the payment and Paypal email, I'll add the license Key # to a valid license Key list, and put it on my site, only I know the url. The list is updated hourly. <11> Few hours later when the user runs the app again, it can find the Pass file on his PC, but the license Key # value is empty, so it goes to the valid list url to see if its license Key # is on the list, if so, write the license Key # into the Pass file, and the next time it starts again, it will find the valid license Key # and start in purchased mode without exiting in 5 minutes. <12> If it can't find its license Key # on the list from my url, run in demo mode. <13> In order to prevent a user from copying and using another paid user's valid Pass file, the license Key # is unique to each PC [I'm trying to find how], so a valid Pass file only works on one PC. Only after a user has paid will Paypal email me the valid license Key # with his payment. <14> The Id checking goes like this : Use the CPU ID : "CPU_01-02-ABC" for example, encrypt it to the result ID : "XeR5TY67rgf", and compare it to the list on my url, if "XeR5TY67rgf" is not on my valid user list, run in demo mode. If it exists write "XeR5TY67rgf" into the Pass File license field. In order to get a unique license Key, can I use his PC's CPU Id ? Or something unique and useful [ relatively less likely to change ]. If so let's say this CPU ID is "CPU_01-02-ABC", I can encrypt it to something like "XeR5TY67rgf", and pass it to Paypal as product Id in the hidden html form field, then I'll get it from Paypal's email notification, and add it to the valid license Key # list on the url. So, even if a hacker knows it uses CPU Id, he can't write it into the Pass file field, because only encrypted Ids are valid Ids. And only my program knows how to generate the encrypted Ids. And even if another hacker knows the encrypted Id is hidden in the html form input field, as long as it's not on my url list, it's still invalid. Can anyone find any flaw in the above system ? Is it practical ? And most importantly how do I get hold of this unique ID that can represent a user's PC ? Frank

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  • Unexpected performance curve from CPython merge sort

    - by vkazanov
    I have implemented a naive merge sorting algorithm in Python. Algorithm and test code is below: import time import random import matplotlib.pyplot as plt import math from collections import deque def sort(unsorted): if len(unsorted) <= 1: return unsorted to_merge = deque(deque([elem]) for elem in unsorted) while len(to_merge) > 1: left = to_merge.popleft() right = to_merge.popleft() to_merge.append(merge(left, right)) return to_merge.pop() def merge(left, right): result = deque() while left or right: if left and right: elem = left.popleft() if left[0] > right[0] else right.popleft() elif not left and right: elem = right.popleft() elif not right and left: elem = left.popleft() result.append(elem) return result LOOP_COUNT = 100 START_N = 1 END_N = 1000 def test(fun, test_data): start = time.clock() for _ in xrange(LOOP_COUNT): fun(test_data) return time.clock() - start def run_test(): timings, elem_nums = [], [] test_data = random.sample(xrange(100000), END_N) for i in xrange(START_N, END_N): loop_test_data = test_data[:i] elapsed = test(sort, loop_test_data) timings.append(elapsed) elem_nums.append(len(loop_test_data)) print "%f s --- %d elems" % (elapsed, len(loop_test_data)) plt.plot(elem_nums, timings) plt.show() run_test() As much as I can see everything is OK and I should get a nice N*logN curve as a result. But the picture differs a bit: Things I've tried to investigate the issue: PyPy. The curve is ok. Disabled the GC using the gc module. Wrong guess. Debug output showed that it doesn't even run until the end of the test. Memory profiling using meliae - nothing special or suspicious. ` I had another implementation (a recursive one using the same merge function), it acts the similar way. The more full test cycles I create - the more "jumps" there are in the curve. So how can this behaviour be explained and - hopefully - fixed? UPD: changed lists to collections.deque UPD2: added the full test code UPD3: I use Python 2.7.1 on a Ubuntu 11.04 OS, using a quad-core 2Hz notebook. I tried to turn of most of all other processes: the number of spikes went down but at least one of them was still there.

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  • about Quick Sort

    - by matin1234
    Hi I have written this code but it will print these stack traces in the console please help me thanks! (Aslo "p" and "q" are the first and last index of our array ,respectively) public class JavaQuickSort { public static void QuickSort(int A[], int p, int q) { int i, last = 0; Random rand = new Random(); if (q < 1) { return; } **swap(A, p, rand.nextInt() % (q+1));** for (i = p + 1; i <= q; i++) { if (A[i] < A[p]) { swap(A, ++last, i); } } swap(A, p, last); QuickSort(A, p, last - 1); QuickSort(A, last + 1, q); } private static void swap(int[] A, int i, int j) { int temp; temp = A[i]; **A[i] = A[j];** A[j] = temp; } public static void main(String[] args){ int[] A = {2,5,7,3,9,0,1,6,8}; **QuickSort(A, 0,8 );** System.out.println(Arrays.toString(A)); } } the Stack traces : run: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -3 at JavaQuickSort.swap(JavaQuickSort.java:38) at JavaQuickSort.QuickSort(JavaQuickSort.java:22) at JavaQuickSort.main(JavaQuickSort.java:45) Java Result: 1 BUILD SUCCESSFUL (total time: 2 seconds) I also bold those statements that cause these stack traces. like == ** ...**

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  • How close can I get C# to the performance of C++ for small intensive tasks?

    - by SLC
    I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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  • Fastest way to generate delimited string from 1d numpy array

    - by Abiel
    I have a program which needs to turn many large one-dimensional numpy arrays of floats into delimited strings. I am finding this operation quite slow relative to the mathematical operations in my program and am wondering if there is a way to speed it up. For example, consider the following loop, which takes 100,000 random numbers in a numpy array and joins each array into a comma-delimited string. import numpy as np x = np.random.randn(100000) for i in range(100): ",".join(map(str, x)) This loop takes about 20 seconds to complete (total, not each cycle). In contrast, consider that 100 cycles of something like elementwise multiplication (x*x) would take than one 1/10 of a second to complete. Clearly the string join operation creates a large performance bottleneck; in my actual application it will dominate total runtime. This makes me wonder, is there a faster way than ",".join(map(str, x))? Since map() is where almost all the processing time occurs, this comes down to the question of whether there a faster to way convert a very large number of numbers to strings.

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  • How to return proper 404 for google while providing user friendly content to the user?

    - by Marek
    I am bouncing between posting this here and on Superuser. Please excuse me if you feel this does not belong here. I am observing the behavior described here - Googlebot is requesting random urls on my site, like aecgeqfx.html or sutwjemebk.html. I am sure that I am not linking these urls from anywhere on my site. I suspect this may be google probing how we handle non existent content - to cite from an answer to the linked question: [google is requesting random urls to] see if your site correctly handles non-existent files (by returning a 404 response header) We have a custom page for nonexistent content - a styled page saying "Content not found, if you believe you got here by error, please contact us", with a few internal links, served (naturally) with a 200 OK. The URL is served directly (no redirection to a single url). I am afraid this may discriminate the site at google - they may not interpret the user friendly page as a 404 - not found and may think we are trying to fake something and provide duplicate content. How should I proceed to ensure that google will not think the site is bogus while providing user friendly message to users in case they click on dead links by accident?

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  • Visual Studio 2008 project file does not load because of an unexpected encoding change.

    - by Xenan
    In our team we have a database project in visual Studio 2008 which is under source control by Team Foundation Server. Every two weeks or so, after one co-worker checks in, the project file won't load on the other developers machines. The error message is: The project file could not be loaded. Data at the root level is invalid. Line 1, position 1. When I look at the project file in Notepad++, the file looks like this: ??<NUL?NULxNULmNULlNUL NULvNULeNULrNULsNULiNULoNULnNUL ... and so on (you can see <?xml version in this) whereas an normal project file looks like: <?xml version="1.0" encoding="utf-16"?> ... So probably something is wrong with the encoding of the file. This is a problem for us because it turns out to be impossible to get the file encoding correct again. The 'solution' is to throw away the project file an get the last know working version from source control. According to the file, the encoding should be UTF-16. According to Notepad++, the corrupted file is actually UTF-8. My questions are: Why is Visual Studio messing up the encoding of the project file, apparently at random times and at random machines? What should we do to prevent this? When it has happened, is there a possibility to restore the current file in the correct encoding instead of pulling an older version from source control? As a last note: the problem is with one single project file, all other project files don't expose this problem.

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  • With regards to urllib AttributeError: 'module' object has no attribute 'urlopen'

    - by Matt
    import re import string import shutil import os import os.path import time import datetime import math import urllib from array import array import random filehandle = urllib.urlopen('http://www.google.com/') #open webpage s = filehandle.read() #read print s #display #what i plan to do with it once i get the first part working #results = re.findall('[<td style="font-weight:bold;" nowrap>$][0-9][0-9][0-9][.][0-9][0-9][</td></tr></tfoot></table>]',s) #earnings = '$ ' #for money in results: #earnings = earnings + money[1]+money[2]+money[3]+'.'+money[5]+money[6] #print earnings #raw_input() this is the code that i have so far. now i have looked at all the other forums that give solutions such as the name of the script, which is parse_Money.py, and i have tried doing it with urllib.request.urlopen AND i have tried running it on python 2.5, 2.6, and 2.7. If anybody has any suggestions it would be really welcome, thanks everyone!! --Matt ---EDIT--- I also tried this code and it worked, so im thinking its some kind of syntax error, so if anybody with a sharp eye can point it out, i would be very appreciative. import shutil import os import os.path import time import datetime import math import urllib from array import array import random b = 3 #find URL URL = raw_input('Type the URL you would like to read from[Example: http://www.google.com/] :') while b == 3: #get file name file1 = raw_input('Enter a file name for the downloaded code:') filepath = file1 + '.txt' if os.path.isfile(filepath): print 'File already exists' b = 3 else: print 'Filename accepted' b = 4 file_path = filepath #open file FileWrite = open(file_path, 'a') #acces URL filehandle = urllib.urlopen(URL) #display souce code for lines in filehandle.readlines(): FileWrite.write(lines) print lines print 'The above has been saved in both a text and html file' #close files filehandle.close() FileWrite.close()

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  • Radix Sort in Python [on hold]

    - by Steven Ramsey
    I could use some help. How would you write a program in python that implements a radix sort? Here is some info: A radix sort for base 10 integers is a based on sorting punch cards, but it turns out the sort is very ecient. The sort utilizes a main bin and 10 digit bins. Each bin acts like a queue and maintains its values in the order they arrive. The algorithm begins by placing each number in the main bin. Then it considers the ones digit for each value. The rst value is removed and placed in the digit bin corresponding to the ones digit. For example, 534 is placed in digit bin 4 and 662 is placed in the digit bin 2. Once all the values in the main bin are placed in the corresponding digit bin for ones, the values are collected from bin 0 to bin 9 (in that order) and placed back in the main bin. The process continues with the tens digit, the hundreds, and so on. After the last digit is processed, the main bin contains the values in order. Use randint, found in random, to create random integers from 1 to 100000. Use a list comphrension to create a list of varying sizes (10, 100, 1000, 10000, etc.). To use indexing to access the digits rst convert the integer to a string. For this sort to work, all numbers must have the same number of digits. To zero pad integers with leading zeros, use the string method str.zfill(). Once main bin is sorted, convert the strings back to integers. I'm not sure how to start this, Any help is appreciated. Thank you.

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  • Rebol Multitasking with Async: why do I get Invalid port spec

    - by Rebol Tutorial
    I tried http://www.mail-archive.com/[email protected]/msg19437.html (I just changed to www.reboltutorial.com) : do http://www.rebol.it/giesse/async-protocol.r handler: func [port [port!] state [word! error!] /local tmp cmd] [ if error? :state [print mold disarm state return true] switch state [ connect [ ; do HTTP request insert port {GET /files/2009/10/word.png HTTP/1.0^M^JHost: www.reboltutorial.com^M^J^M^J} false ] read [false] write [false] close [ ; get data data: copy port close port ;print copy/part data find data "^M^J^M^J" data: to binary! find/tail data "^M^J^M^J" other/image: attempt [load data] other/text: "" show other false ] ] ] port: open async://www.reboltutorial.com:80 port/awake: :handler view layout [ across me: box 100x100 random 255.255.255 0:00:00.5 feel [ engage: func [f a e] [ if a = 'time [ me/color: random 255.255.255 show me ] ] ] other: box 100x100 255.255.255 "Downloading image..." Return Area 208x100 "You can type here while downloading." ] ] But I'm getting this error: >> port: open async://reboltutorial.com:80 ** Access Error: Invalid port spec: async://reboltutorial.com:80 ** Near: port: open async://reboltutorial.com:80 >> port/awake: :handler ** Script Error: port has no value ** Near: port/awake: :handler

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