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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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  • 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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  • How do you keep a balance between working, training, health and family?

    - by Jim Burger
    One trend I see in the awesome developers I've met, is that they devote inordinate amounts of time to coding at the expense of (usually) their health. Personally, I also find it hard to motivate myself to keep healthy. Every now and again, I meet a fantastic coder who has it clocked; they are up to date with the latest dev news, have time to read about good programming practices, and to finish it off, have happy wives/husbands and families. How do you guys/gals manage it in the short 24 hours a day that we all have?

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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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  • 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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  • PHP Tag Cloud System

    - by deniz
    Hi, I am implementing a tag cloud system based on this recommendation. (However, I am not using foreign keys) I am allowing up to 25 tags. My question is, how can I handle editing on the items? I have this item adding/editing page: Title: Description: Tags: (example data) computer, book, web, design If someone edits an item details, do I need to delete all the tags from Item2Tag table first, then add the new elements? For instance, someone changed the data to this: Tags: (example data) computer, book, web, newspaper Do I need to delete all the tags from Item2Tag table, and then add these elements? It seems inefficient, but I could find a more efficient way. The other problem is with this way is, if someone edits description but does not change the tags box, I still need to delete all the elements from Item2Tag table and add the same element. I am not an experienced PHP coder, so could you suggest a better way to handle this? (pure PHP/MySQL solution is preferable) Thanks in advance,

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  • Coding in Other (Spoken) Languages

    - by contagious
    Something i've always wondered, and I can't find any mention of it anywhere online. When a shop from, say Japan, writes code, would I be able to read it in english? Or do languages, like C, php, anything, have Japanese translations that they write? I guess what i'm asking is does every single coder in the world know enough english to use the exact same reserved words I do? Would this code: If (i < size){ switch case 1: print "hi there" default: print "no, thank you" } else { print "yes, thank you" } display the exact same as I'm seeing it right now in english, or would some other non-english-speaking person see the words "if", "switch", "case", "default", "print", and "else" in their native language? EDIT - yes, this is serious. I didn't know if different localiztions of a language have different keywords. or if there are even different localizations at all.

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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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  • Why use MVVM???

    - by LnDCobra
    Okay, I have been looking into MVVM pattern, and each time I have previously tried looking into it, I gave up for a number of reasons: Unnecessary Extra Long Winded Coding No apparent advantages for coders (no designers in my office. Currently only myself soon to be another coder) Not a lot of resources/documentation of good practices! (Or at least hard to find) Cannot think of a single scenario where this is advantageous. I'm about to give up on it yet again, and thought I'd ask to see if someone answer the reasons above. I honestly can't see an advantage of using this for a single/partner coding. Even in complex projects with 10's of windows. To me the DataSet is a good enough view and binding like in the answer by Brent following question

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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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  • Fragment shaders on a texture

    - by Snowangelic
    Hello stack overflow. I am trying to add some post-processing capabilities to a program. The rendering is done using openGL. I just want to allow the program to load some home made fragment shader and use them on the video stream. I wrote a little piece of shader using "OpenGL Shader Builder" that just turns a texture in grayscale. The shaders works well in the shader builder but I can't make it work in the main program. The screens stays all black. Here is the setup : @implementation PluginGLView - (id) initWithCoder: (NSCoder *) coder { const GLubyte * strExt; if ((self = [super initWithCoder:coder]) == nil) return nil; glLock = [[NSLock alloc] init]; if (nil == glLock) { [self release]; return nil; } // Init pixel format attribs NSOpenGLPixelFormatAttribute attrs[] = { NSOpenGLPFAAccelerated, NSOpenGLPFANoRecovery, NSOpenGLPFADoubleBuffer, 0 }; // Get pixel format from OpenGL NSOpenGLPixelFormat* pixFmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs]; if (!pixFmt) { NSLog(@"No Accelerated OpenGL pixel format found\n"); NSOpenGLPixelFormatAttribute attrs2[] = { NSOpenGLPFANoRecovery, 0 }; // Get pixel format from OpenGL pixFmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attrs2]; if (!pixFmt) { NSLog(@"No OpenGL pixel format found!\n"); [self release]; return nil; } } [self setPixelFormat:[pixFmt autorelease]]; /* long swapInterval = 1 ; [[self openGLContext] setValues:&swapInterval forParameter:NSOpenGLCPSwapInterval]; */ [glLock lock]; [[self openGLContext] makeCurrentContext]; // Init object members strExt = glGetString (GL_EXTENSIONS); texture_range = gluCheckExtension ((const unsigned char *)"GL_APPLE_texture_range", strExt) ? GL_TRUE : GL_FALSE; texture_hint = GL_STORAGE_SHARED_APPLE ; client_storage = gluCheckExtension ((const unsigned char *)"GL_APPLE_client_storage", strExt) ? GL_TRUE : GL_FALSE; rect_texture = gluCheckExtension((const unsigned char *)"GL_EXT_texture_rectangle", strExt) ? GL_TRUE : GL_FALSE; // Setup some basic OpenGL stuff glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); glColor4f(1.0f, 1.0f, 1.0f, 1.0f); glClearColor(0.0f, 0.0f, 0.0f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); // Loads the shaders shader=LoadShader(GL_FRAGMENT_SHADER,"/Users/alexandremathieu/fragment.fs"); program=glCreateProgram(); glAttachShader(program, shader); glLinkProgram(program); glUseProgram(program); [NSOpenGLContext clearCurrentContext]; [glLock unlock]; image_width = 1024; image_height = 512; image_depth = 16; image_type = GL_UNSIGNED_SHORT_1_5_5_5_REV; image_base = (GLubyte *) calloc(((IMAGE_COUNT * image_width * image_height) / 3) * 4, image_depth >> 3); if (image_base == nil) { [self release]; return nil; } // Create and load textures for the first time [self loadTextures:GL_TRUE]; // Init fps timer //gettimeofday(&cycle_time, NULL); drawBG = YES; // Call for a redisplay noDisplay = YES; PSXDisplay.Disabled = 1; [self setNeedsDisplay:true]; return self; } And here is the "render screen" function wich basically...renders the screen. - (void)renderScreen { int bufferIndex = whichImage; glBindTexture(GL_TEXTURE_RECTANGLE_EXT, bufferIndex+1); glUseProgram(program); int loc=glGetUniformLocation(program, "texture"); glUniform1i(loc,bufferIndex+1); glTexSubImage2D(GL_TEXTURE_RECTANGLE_EXT, 0, 0, 0, image_width, image_height, GL_BGRA, image_type, image[bufferIndex]); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex2f(-1.0f, 1.0f); glTexCoord2f(0.0f, image_height); glVertex2f(-1.0f, -1.0f); glTexCoord2f(image_width, image_height); glVertex2f(1.0f, -1.0f); glTexCoord2f(image_width, 0.0f); glVertex2f(1.0f, 1.0f); glEnd(); [[self openGLContext] flushBuffer]; [NSOpenGLContext clearCurrentContext]; //[glLock unlock]; } and finally here's the shader. uniform sampler2DRect texture; void main() { vec4 color, texel; color = gl_Color; texel = texture2DRect(texture, gl_TexCoord[0].xy); color *= texel; // Begin Shader float gray=0.0; gray+=(color.r + color.g + color.b)/3.0; color=vec4(gray,gray,gray,color.a); // End Shader gl_FragColor = color; } The loading and using of shaders works since I am able to turn the screen all red with this shader void main(){ gl_FragColor=vec4(1.0,0.0,0.0,1.0); } If the shader contains a syntax error I get an error message from the LoadShader function etc. If I remove the use of the shader, everything works normally. I think the problem comes from the "passing the texture as a uniform parameter" thing. But these are my very firsts step with openGL and I cant be sure of anything. Don't hesitate to ask for more info. Thank you Stack O.

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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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  • Managing multiple .NET languages in a web application

    - by tomfanning
    I am part of a development team building a new ASP.NET 3.5 web application. Two of us are C# coders, and the other is a VB.NET coder. I know that we can mix languages on a per-project basis, and one can build classes in one language that inherit from classes written in the other language in a different project (which we are already doing), but I can see us getting into a situation where we might well end up with cyclic dependencies between our various project DLLs. Other than simply having a high number of projects (more seperation of concerns into more libraries), how have you managed this situation on your own projects? Note - I believe this question to be different enough from the only similar match I could find (this one) on the basis that we are not wanting to use different languages in order to take advantage of their specific features per se, but rather to make use of what developer resource is available to us (i.e. one dev just happens to be VB.NET only).

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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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  • Generating C code from a Matlab-Simulink model for DSP C6748

    - by Juanma
    I'm trying to generate C code from a Matlab-Simulink simple model (eg.: sine wave generator with a DAC at the output). This code must be executed with Code Composer Studio for TMS320C6748 DSP (Texas Instrument C6748). Specifically, for the development board OMAP-L138 ZOOM ™EVM DEVELOPMENT KIT. For this, I am using the following versions: Simulink (Version 7.7 - R2011a) Embedded Coder (Version 6.0 - R2011a) Code Composer Studio v3.3 I tried several options (with generic modules in Simulink and programming the C6748 timers, configuring a module "Target Preferences" with "OMAP_L138/C6748 EVM"...) but it isn't working. Is it possible to implement this idea? Is there an example working? Thanks

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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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  • 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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  • 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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  • Web Page Opinions and Suggestions

    - by MrEnder
    Been working my * off on this for a few days trying to keep updating it to make it most efficient with everything I learn... I'm quite proud of it so far considering I'm not actually the best coder lol most JS and PHP confuses the crap outa me unless I do it from scratch. So anyways here is the link. Tell me what you think. Suggestions would be amazing. I'd love to know what I screwed up as long as you explain in detail as to why and how to fix it. I really hate when people hand me a huge snippet and expect me to understand it -_- Thanks Shelby LINK http://opentech.durhamcollege.ca/~in...rittains/labs/

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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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  • 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 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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  • 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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  • 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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