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  • Unknown error in the memory in C

    - by Sergey Gavruk
    I have a 2D dynamic array. I enter a line of 0's after line which has a biggest number: void InsertZero(int **a, int pos){ int i, j; a = (int**)realloc(a, n * sizeof(*a)); a[n-1] = (int*)calloc(n, sizeof(**a)); d = 0; for(i = n-1; i > pos; i--){ for(j = 0; j < n; j++){ a[i][j] = a[i-1][j]; printf("%d ", a[i][j]); } } for(i = 0; i < n; i++){ a[pos][i] = 0; } } If i make a size of array 3, 5, 7, 9, ... it works correctly. But if a number of lines is 2, 4, 6, ... , it is an access violation error, when i try to print my array: void Print(void){ int i, j; for(i = 0; i < (n-d); i++){ for(j = 0; j < n; j++){ printf("%d\t", arr[i][j]); } printf("\n"); } } code: http://codepad.org/JcUis6W4

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  • How CPU finds ISR and distinguishes between devices

    - by ripunjay-tripathi-gmail-com
    I should first share all what I know - and that is complete chaos. There are several different questions on the topic, so please don't get irritated :). 1) To find an ISR, CPU is provided with a interrupt number. In x86 machines (286/386 and above) there is a IVT with ISRs in it; each entry of 4 bytes in size. So we need to multiply interrupt number by 4 to find the ISR. So first bunch of questions is - I am completely confused in mechanism of CPU receiving the interrupt. To raise an interrupt, firstly device shall probe for IRQ - then what ? The interrupt number travels "on IRQ" towards CPU? I also read something like device putting ISR address on data bus ; whats that then ? What is the concept of devices overriding the ISR. Can somebody tell me few example devices where CPU polls for interrupts? And where does it finds ISR for them ? 2) If two devices share an IRQ (which is very much possible), how does CPU differs amongst them ? What if both devices raise an interrupt of same priority simultaneously. I got to know there will be masking of same type and low priority interrupts - but how this communication happens between CPU and device controller? I studied the role of PIC and APIC for this problem, but could not understand. Thanks for reading. Thank you very much for answering.

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  • Bubble sort algorithm implementations (Haskell vs. C)

    - by kingping
    Hello. I have written 2 implementation of bubble sort algorithm in C and Haskell. Haskell implementation: module Main where main = do contents <- readFile "./data" print "Data loaded. Sorting.." let newcontents = bubblesort contents writeFile "./data_new_ghc" newcontents print "Sorting done" bubblesort list = sort list [] False rev = reverse -- separated. To see rev2 = reverse -- who calls the routine sort (x1:x2:xs) acc _ | x1 > x2 = sort (x1:xs) (x2:acc) True sort (x1:xs) acc flag = sort xs (x1:acc) flag sort [] acc True = sort (rev acc) [] False sort _ acc _ = rev2 acc I've compared these two implementations having run both on file with size of 20 KiB. C implementation took about a second, Haskell — about 1 min 10 sec. I have also profiled the Haskell application: Compile for profiling: C:\Temp ghc -prof -auto-all -O --make Main Profile: C:\Temp Main.exe +RTS -p and got these results. This is a pseudocode of the algorithm: procedure bubbleSort( A : list of sortable items ) defined as: do swapped := false for each i in 0 to length(A) - 2 inclusive do: if A[i] > A[i+1] then swap( A[i], A[i+1] ) swapped := true end if end for while swapped end procedure I wonder if it's possible to make Haskell implementation work faster without changing the algorithm (there's are actually a few tricks to make it work faster, but neither implementations have these optimizations)

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  • Corrupted mysql table, cause crash in mysql.h (c++)

    - by Francesco
    i've created a very simple mysql class in c+, but when happen that mysql crash , indexes of tables become corrupted, and all my c++ programs crash too because seems that are unable to recognize corrupted table and allowing me to handle the issue .. Q_RES = mysql_real_query(MY_mysql, tmp_query.c_str(), (unsigned int) tmp_query.size()); if (Q_RES != 0) { if (Q_RES == CR_COMMANDS_OUT_OF_SYNC) cout << "errorquery : CR_COMMANDS_OUT_OF_SYNC " << endl; if (Q_RES == CR_SERVER_GONE_ERROR) cout << "errorquery : CR_SERVER_GONE_ERROR " << endl; if (Q_RES == CR_SERVER_LOST) cout << "errorquery : CR_SERVER_LOST " << endl; LAST_ERROR = mysql_error(MY_mysql); if (n_retrycount < n_retry_limit) { // RETRY! n_retrycount++; sleep(1); cout << "SLEEP - query retry! " << endl; ping(); return select_sql(tmp_query); } return false; } MY_result = mysql_store_result(MY_mysql); B_stored_results = true; cout << "b8" << endl; LAST_affected_rows = (mysql_num_rows(MY_result) + 1); // coult return -1 cout << "b8-1" << endl; the program terminate with a "segmentation fault" after doing the "b8" and before the "b8-1" , Q_RES have no issue even if the table is corrupted.. i would like to know if there is a way to recognize that the table have problems and so then i can run a mysql repair or mysql check .. thanks, Francesco

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  • Help me re-center a ModalPopup within an iframe when the iframe's parent window scrolls

    - by Cory Larson
    I have a web page with an iframe in it (I don't like it, but that's the way it has to be). It's not a cross-domain iframe so there's nothing to worry about there. I have written a jQuery extension that does the centering of a ModalPopup (which is called from an overridden AjaxControlToolkit.ModalPopupBehavior._layout method) based on the width and height of the iframe's parent, so that it looks centered even though the iframe is not in the center of the page. It's a lot of tricky stuff, especially since the web page I added the iframe to runs in quirks mode. Now, I've also overridden AjaxControlToolkit.ModalPopupBehavior._attachPopup, so that when the parent window resizes or scrolls, the ModalPopup inside of the iframe recenter's itself relative to the new size of the parent window. However, the same code that attaches the popup to the parent window's resize event does NOT work for the parent window's scroll event. See the code below, and the comments: AjaxControlToolkit.ModalPopupBehavior.prototype._attachPopup = function() { /// <summary> /// Attach the event handlers for the popup to the PARENT window /// </summary> if (this._DropShadow && !this._dropShadowBehavior) { this._dropShadowBehavior = $create(AjaxControlToolkit.DropShadowBehavior, {}, null, null, this._popupElement); } if (this._dragHandleElement && !this._dragBehavior) { this._dragBehavior = $create(AjaxControlToolkit.FloatingBehavior, {"handle" : this._dragHandleElement}, null, null, this._foregroundElement); } $addHandler(parent.window, 'resize', this._resizeHandler); // <== This WORKS $addHandler(parent.window, 'scroll', this._scrollHandler); // <== This DOES NOT work this._windowHandlersAttached = true; } Can anybody explain to me why the resize event works while the scroll event doesn't? Any suggestions or alternatives out there to help me out? I am working with jQuery, so if I can use something besides the $addHandler method from MS that'd be fine. Be aware that I also have to override the _detachPopup function to remove the handler, so I need to take that into account. Thanks!

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  • Custom UIButton for Iphone.

    - by Amal
    I have an view in my App which has a number of buttons based on the number of items returned by the server. So if the server returns say 10 items, there should be 10 buttons and clicking on each button should call a different person. For the above purpose I created a custom button class deriving from UIButton. @implementation HopitalButton @synthesize index; @synthesize button_type; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { UIImage* img = [UIImage imageNamed:@"dr_btn.png"]; [img stretchableImageWithLeftCapWidth:10 topCapHeight:10]; [self setBackgroundImage:img forState:UIControlStateNormal]; [self setTitleColor:[UIColor colorWithRed:0.698 green:0.118 blue:0.376 alpha:1] forState:UIControlStateNormal] ; [self setFont:[UIFont fontWithName:@"Helvetica Bold" size:13]]; self.titleLabel.textColor = [UIColor colorWithRed:178 green:48 blue:95 alpha:1]; self.adjustsImageWhenHighlighted = YES; } return self; } - (void)dealloc { [super dealloc]; } @end Now the problem with the above code is that it does not create buttons that look similar to the buttons created by default in Interface builder. The borders are missing. And I create buttons of the above type by the following code: HopitalButton* hb = [[HopitalButton alloc] init]; hb.button_type = @"call"; hb.frame = CGRectMake(50, 50 + i * 67, 220, 40); [self.scroll_view addSubview:hb]; [hb setTitle:[[[self.office_full_list objectAtIndex:i] objectForKey:@"Staff" ]objectForKey:@"FullName"] forState:UIControlStateNormal]; hb.index = [NSNumber numberWithInt:[self.button_items count]]; [self.button_items insertObject:hb atIndex:[self.button_items count]]; [hb addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside]; I am not finding a way to set the button type for this custom button. Is there a way i can do it ? Or is there a better way to design the code.

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  • iphone certain PDFs rendering as black image

    - by skantner
    I'm trying to draw the pages of a PDF using the code below. Some PDF's render correctly, but others simply show as a completely black image, or have partial portions rendered and the rest black. In comparing what's going on, the ones that show OK seem to have always have "regular" text in them along with some graphics (diagrams, etc.), while the ones that come out black are typically all graphics (like a page of sheet music, for example). Can anyone point me in the right direction on this? I building this on the new 3.2 SDK. Thanks! // PDF page drawing expects a Lower-Left coordinate system, so we flip the coordinate system // before we start drawing. CGContextTranslateCTM(context, 0.0, self.bounds.size.height); CGContextScaleCTM(context, 1.0, -1.0); // Grab the first PDF page CGPDFPageRef page = CGPDFDocumentGetPage(myPDF, pageNo); // We're about to modify the context CTM to draw the PDF page where we want it, so save the graphics state in case we want to do more drawing CGContextSaveGState(context); // CGPDFPageGetDrawingTransform provides an easy way to get the transform for a PDF page. It will scale down to fit, including any // base rotations necessary to display the PDF page correctly. CGAffineTransform pdfTransform = CGPDFPageGetDrawingTransform(page, kCGPDFCropBox, self.bounds, 0, true); // And apply the transform. CGContextConcatCTM(context, pdfTransform); // Finally, we draw the page and restore the graphics state for further manipulations! CGContextDrawPDFPage(context, page); CGContextRestoreGState(context);

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  • problem drawing gRaphaeljs pie chart

    - by Aswad
    Hi, I was trying to draw the raphaeljs piechart. I used the same example as shown on "http://g.raphaeljs.com/piechart2.html". It renders me the text but the pie charts goes missing.Can someone please help? please find the code below. g·Raphaël Dynamic Pie Chart Demo window.onload = function () { var r = Raphael("holder"); r.g.txtattr.font = "12px 'Fontin Sans', Fontin-Sans, sans-serif"; r.g.text(320, 100, "Interactive Pie Chart Demo").attr({"font-size": 20}); var pie = r.g.piechart(320, 240, 100, [55, 20, 13, 32, 5, 1, 2, 10], {legend: ["%%.%% – Enterprise Users", "IE Users"], legendpos: "west", href: ["http://raphaeljs.com", "http://g.raphaeljs.com"]}); pie.hover(function () { this.sector.stop(); this.sector.scale(1.1, 1.1, this.cx, this.cy); if (this.label) { this.label[0].stop(); this.label[0].scale(1.5); this.label[1].attr({"font-weight": 800}); } }, function () { this.sector.animate({scale: [1, 1, this.cx, this.cy]}, 500, "bounce"); if (this.label) { this.label[0].animate({scale: 1}, 500, "bounce"); this.label[1].attr({"font-weight": 400}); } }); }; </script> </head> <body class="raphael" id="g.raphael.dmitry.baranovskiy.com"> <div id="holder"></div> <p> Pie chart with legend, hyperlinks on two first sectors and hover effect. </p> <p> Demo of <a href="http://g.raphaeljs.com/">g·Raphaël</a> JavaScript library. </p> </body>

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  • dynamic date formats in eyecon's Bootstrap Datepicker

    - by Jennifer Michelle
    I need to update my datepickers' date format (mm.dd.yyyy etc) using a select box. I am currently using Eyecon's Bootstrap Datepicker because it had the smallest files size that I could find (8k minified), and includes the date formats I need. I also tried to trigger date format changes in several other datepickers without any success. Fiddle: http://jsfiddle.net/Yshy7/8/ Is there an obvious way to trigger a change from the select box to the datepickers? //date format var dateFormat = $('#custom_date_format').val() || "mm/dd/yyyy"; $('#custom_date_format').change(function() { var dateFormat = $(this).val(); }); //start and end dates var nowTemp = new Date(); var now = new Date(nowTemp.getFullYear(), nowTemp.getMonth(), nowTemp.getDate(), 0, 0, 0, 0); var checkin = $('.j-start-date').datepicker({ format: dateFormat, onRender: function(date) { //return date.valueOf() < now.valueOf() ? 'disabled' : ''; } }).on('changeDate', function(ev) { if (ev.date.valueOf() > checkout.date.valueOf()) { var newDate = new Date(ev.date) newDate.setDate(newDate.getDate()); checkout.setValue(newDate); } checkin.hide(); $('.j-end-date')[0].focus(); }).data('datepicker'); var checkout = $('.j-end-date').datepicker({ format: dateFormat, onRender: function(date) { return date.valueOf() <= checkin.date.valueOf() ? 'disabled' : ''; } }).on('changeDate', function(ev) { checkout.hide(); }).data('datepicker');

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  • Overlaying 2D paths on UIImage without scaling artifacts

    - by tat0
    I need to draw a path along the shape of an image in a way that it is always matching its position on the image independent of the image scale. Think of this like the hybrid view of Google Maps where streets names and roads are superimposed on top of the aerial pictures. Furthermore, this path will be drawn by the user's finger movements and I need to be able to retrieve the path keypoints on the image pixel coordinates. The user zooms-in in order to more precisely set the paths location. I manage to somehow make it work using this approach: -Create a custom UIView called CanvasView that handles touches interaction and delivers scaling, rotation, translation values to either the UIImageView or PathsView (see bellow) depending on a flag: deliverToImageOrPaths. -Create a UIImageView holding the base image. This is set as a children of CanvasView -Create a custom UIView called PathsView that keeps track of the 2D paths geometry and draws itself with a custom drawRect. This is set as children of the UIImageView. So hierarchy: CanvasView - UIImageView -PathsView In this way when deliverToImageOrPaths is YES, finger gestures transforms both the UIImageView and its child PathsView. When deliverToImageOrPaths is NO the gestures affect only the PathsView altering its geometry. So far so good. QUESTION: The problem I have is that when scaling the base UIImageView (via its .transform property) the PathsView is scaled with aliasing artifacts. drawRect is still being called on the PathsView but I guess it's performing the drawing using the original buffer size and then interpolating. How can I solve this issue? Are there better ways to implement these features? PS: I tried changing the PathsView layer class to CATiledLayer with levelsOfDetailBias 4 and levelsOfDetail 4. It solves the aliasing problem to some extent but it's unacceptable slow to render.

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  • Should I move big data blobs in JSON or in separate binary connection?

    - by Amagrammer
    QUESTION: Is it better to send large data blobs in JSON for simplicity, or send them as binary data over a separate connection? If the former, can you offer tips on how to optimize the JSON to minimize size? If the latter, is it worth it to logically connect the JSON data to the binary data using an identifier that appears in both, e.g., as "data" : "< unique identifier " in the JSON and with the first bytes of the data blob being < unique identifier ? CONTEXT: My iPhone application needs to receive JSON data over the 3G network. This means that I need to think seriously about efficiency of data transfer, as well as the load on the CPU. Most of the data transfers will be relatively small packets of text data for which JSON is a natural format and for which there is no point in worrying much about efficiency. However, some of the most critical transfers will be big blobs of binary data -- definitely at least 100 kilobytes of data, and possibly closer to 1 megabyte as customers accumulate a longer history with the product. (Note: I will be caching what I can on the iPhone itself, but the data still has to be transferred at least once.) It is NOT streaming data. I will probably use a third-party JSON SDK -- the one I am using during development is here. Thanks

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  • IE7 navbar margin and padding way off

    - by user269959
    <div id="nav"> <ul> <li><a href="#"></li> <li><a href="#"></li> <li><a href="#"></li> <li><a href="#"></li> </ul> </div> #nav { color: #ffffff; font-size: 12px; font-weight: bold; margin-left: 4px; position: absolute; top: 230px; width: 800px; } #nav a{ color: #ffffff; text-decoration: none; } #nav li { display: inline; margin: -4px; padding-left: 15px; padding-right: 15px; padding-top: 19px; padding-bottom: 12px; } #nav li a { background-color: transparent; } the code above works fine in firefox with the highlighting filling out the entire "tab" of the navbar. however in ie7 it is off center and not filling up the same way. any ideas ?

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  • create TableModel and populate jTable dynamically

    - by Julia
    Hi all! I want to store the results of reading lucene index into jTable, so that I can make it sortable by different columns. From index I am reading terms with different measures of their frequencies. Table columns are these : [string term][int absFrequency][int docFrequency][double invFrequency] So i in AbstractTableModel I can define column names, but i dont know how to get the Object[][]data with results from the following method: public static void FrequencyMap(Directory indexDir) throws Exception { List<Object>redoviLista = new ArrayList<Object>(); //final Map<String,TermRow> map = new TreeMap<String,TermRow>(); List<String>termList = new ArrayList<String>(); IndexReader iReader = IndexReader.open(indexDir); FilterIndexReader fReader = new FilterIndexReader(iReader); int numOfDocs = fReader.numDocs(); TermEnum terms = fReader.terms(); while (terms.next()){ Term term = terms.term(); String termText = term.text(); termList.add(termText); //Calculating the frequencies int df = iReader.docFreq(term); double idf = 0.0F; idf = Math.log10((double) numOfDocs / df); double tfidf = (df*idf); //Here comes important part Object oneTableRow[] = {termText, df, idf, tfidf}; redoviLista.add(jedanRed); // So i thaught to store them into list, and then later to copy into table, but didnt manage } iReader.close(); // So I need something like this, and i Neeed this array to be stored out of this method Object[][]data = new Object[redoviLista.size()][]; for (int i = 0; i < data.length; i++) { data[i][0] = redoviLista.get(i); } So I am kindda stuck here to proceed to implement AbstractTableModel and populate and display this table .... :/ Please help!

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  • Algorithm to determine which points should be visible on a map based on zoom

    - by lgratian
    Hi! I'm making a Google Maps-like application for a course at my Uni (not something complex, it should load the map of a city for example, not the whole world). The map can have many layers, including markers (restaurants, hospitals, etc.) The problem is that when you have many points and you zoom out the map it doesn't look right. At this zoom level only some points need to be visible (and at the maximum map size, all points). The question is: how can you determine which points should be visible for a specified zoom level? Because I have implemented a PR Quadtree to speed up rendering I thought that I could define some "high-priority" markers (that are always visible, defined in the map editor) and put them in a queue. At each step a marker is removed from the queue and all it's neighbors that are at least D units away (D depends on the zoom levels) are chosen and inserted in the queue, and so on. Is there any better way than the algorithm I thought of? Thanks in advance!

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  • nested form collection_select new value overwriting previous selected values

    - by bharath
    Nested form <%= nested_form_for(@bill) do |f| %> <p><%= f.link_to_add "Add Product", :bill_line_items %> </p> Partial of bill line items <%= javascript_include_tag 'bill'%> <%= f.hidden_field :bill_id %> <%- prices = Hash[Product.all.map{|p| [p.id, p.price]}].to_json %> <%= f.label :product_id %> <%= f.collection_select :product_id ,Product.all,:id,:name, :class => 'product', :prompt => "Select a Product", input_html: {data: {prices: prices}}%> <br/ > <%= f.label :price, "price"%> <%= f.text_field :price, :size=>20, :class =>"price" %><br/> bill.js jQuery(document).ready(function(){ jQuery('.product').change(function() { var product_id = jQuery(this).val(); var price = eval(jQuery(this).data("prices"))[product_id]; jQuery('.price').val(price); }); }); Rails 3.2 Issue: Second click on Add Product & on selecting the product When we select the second product the price of second product is overwriting on the price of the first selected product. Request help.

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  • What is the correct way to implement a massive hierarchical, geographical search for news?

    - by Philip Brocoum
    The company I work for is in the business of sending press releases. We want to make it possible for interested parties to search for press releases based on a number of criteria, the most important being location. For example, someone might search for all news sent to New York City, Massachusetts, or ZIP code 89134, sent from a governmental institution, under the topic of "traffic". Or whatever. The problem is, we've sent, literally, hundreds of thousands of press releases. Searching is slow and complex. For example, a press release sent to Queens, NY should show up in the search I mentioned above even though it wasn't specifically sent to New York City, because Queens is a subset of New York City. We may also want to implement "and" and "or" and negation and text search to the query to create complex searches. These searches also have to be fast enough to function as dynamic RSS feeds. I really don't know anything about search theory, or how it's properly done. The way we are getting by right now is using a data mart to store the locations the releases were sent to in a single table. However, because of the subset thing mentioned above, the data mart is gigantic with millions of rows. And we haven't even implemented cities yet, and there are about 50,000 cities in the United States, which will exponentially increase the size of the data mart by so much I'm afraid it just won't work anymore. Anyway, I realize this is not a simple question and there won't be a "do this" answer. However, I'm hoping one of you can point me in the right direction where I can learn about how massive searches are done? Because I really know nothing about it. And such a search engine is turning out to be incredibly difficult to make. Thanks! I know there must be a way because if Google can search the entire internet we must be able to search our own database :-)

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  • Increase performance on iphone at pdf rendering

    - by burki
    Hi! I have a UITableView, and in every cell there's displayed a UIImage created from a pdf. But now the performance is very bad. Here's my code I use to generate the UIImage from the PDF. Creating CGPDFDocumentRef and UIImageView (in cellForRowAtIndexPath method): ... CFURLRef pdfURL = CFBundleCopyResourceURL(CFBundleGetMainBundle(), (CFStringRef)formula.icon, NULL, NULL); CGPDFDocumentRef documentRef = CGPDFDocumentCreateWithURL((CFURLRef)pdfURL); CFRelease(pdfURL); UIImageView *imageView = [[UIImageView alloc] initWithImage:[self imageFromPDFWithDocumentRef:documentRef]]; ... Generate UIImage: - (UIImage *)imageFromPDFWithDocumentRef:(CGPDFDocumentRef)documentRef { CGPDFPageRef pageRef = CGPDFDocumentGetPage(documentRef, 1); CGRect pageRect = CGPDFPageGetBoxRect(pageRef, kCGPDFCropBox); UIGraphicsBeginImageContext(pageRect.size); CGContextRef context = UIGraphicsGetCurrentContext(); CGContextTranslateCTM(context, CGRectGetMinX(pageRect),CGRectGetMaxY(pageRect)); CGContextScaleCTM(context, 1, -1); CGContextTranslateCTM(context, -(pageRect.origin.x), -(pageRect.origin.y)); CGContextDrawPDFPage(context, pageRef); UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return finalImage; } What can I do to increas the speed and keep the memory low?

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  • Java error on bilinear interpolation of 16 bit data

    - by Jon
    I'm having an issue using bilinear interpolation for 16 bit data. I have two images, origImage and displayImage. I want to use AffineTransformOp to filter origImage through an AffineTransform into displayImage which is the size of the display area. origImage is of type BufferedImage.TYPE_USHORT_GRAY and has a raster of type sun.awt.image.ShortInterleavedRaster. Here is the code I have right now displayImage = new BufferedImage(getWidth(), getHeight(), origImage.getType()); try { op = new AffineTransformOp(atx, AffineTransformOp.TYPE_BILINEAR); op.filter(origImage, displayImage); } catch (Exception e) { e.printStackTrace(); } In order to show the error I have created 2 gradient images. One has values in the 15 bit range (max of 32767) and one in the 16 bit range (max of 65535). Below are the two images 15 bit image 16 bit image These two images were created in identical fashions and should look identical, but notice the line across the middle of the 16 bit image. At first I thought that this was an overflow problem however, it is weird that it's manifesting itself in the center of the gradient instead of at the end where the pixel values are higher. Also, if it was an overflow issue than I would suspect that the 15 bit image would have been affected as well. Any help on this would be greatly appreciated.

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  • Lazy non-modifiable list in Google Collections

    - by mindas
    I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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  • How do I insert an input's value into a separate form?

    - by ryan
    I'm making a tool for my university that allows students to create a list of classes by doing the following: Searching by course title for their course via an autocomplete input field. Adding that course to a separate form that upon being submitted creates a course list. I am trying to link the autocomplete and the course list form with an 'add to course list' button that inserts a hidden input field into the course list form which can subsequently be submitted by a 'create course list' button. My question is this: How do I take the value of the autocomplete input and insert it into the course list form without using AJAX? So far I have something like the following: <%= text_field_with_auto_complete :course, :title, :size => 40 %> <%= link_to_function "Add to Course List" do |page| page.insert_html :top, :course_list, hidden_field(:courses, :course, {:value => "$('course_title').value"}) %> <% form_for(@course_list) do |f|%> <div id="course_list">Insert selected courses here.</div> <% end %>

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  • priority queue with limited space: looking for a good algorithm

    - by SigTerm
    This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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  • If I'm using a 1d array to represent a square board, how can I take my index and check the sqaures a

    - by FrankTheTank
    If I have a 4x4 gameboard which I'm representing in my program as a 1d integer array of size 16. How can I get the indexs of the squares above, below, to the left and to the right any given index? So, for example: A = { 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 } Which represents this board 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Lets say I am currently on index #8 in the board (value = 7). How can I get the index for 4 (value = 3) , 5 (value = 6), 10 (value = 11) and realize that there is no right square because it is on the right hand edge of the board. I know I need to use some modulus math but I'm failing to come up with the right way to get the indexes for adjacent squares. I'm thinking something like... if ((i % 4) + 1 < 3) right = i + 1; if ((i % 4) - 1 > 0) left = i - 1; if ((i % 4) + 4 < 15) bottom = i + 4; if ((i % 4) - 4 > 0 ) top = i - 4; Does this seem like it is the right approach?

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  • Possible to Inspect Innards of Core C# Functionality

    - by Nick Babcock
    I was struck today, with the inclination to compare the innards of Buffer.BlockCopy and Array.CopyTo. I am curious to see if Array.CopyTo called Buffer.BlockCopy behind the scenes. There is no practical purpose behind this, I just want to further my understanding of the C# language and how it is implemented. Don't jump the gun and accuse me of micro-optimization, but you can accuse me of being curious! When I ran ILasm on mscorlib.dll I received this for Array.CopyTo .method public hidebysig newslot virtual final instance void CopyTo(class System.Array 'array', int32 index) cil managed { // Code size 0 (0x0) } // end of method Array::CopyTo and this for Buffer.BlockCopy .method public hidebysig static void BlockCopy(class System.Array src, int32 srcOffset, class System.Array dst, int32 dstOffset, int32 count) cil managed internalcall { .custom instance void System.Security.SecuritySafeCriticalAttribute::.ctor() = ( 01 00 00 00 ) } // end of method Buffer::BlockCopy Which, frankly, baffles me. I've never run ILasm on a dll/exe I didn't create. Does this mean that I won't be able to see how these functions are implemented? Searching around only revealed a stackoverflow question, which Marc Gravell said [Buffer.BlockCopy] is basically a wrapper over a raw mem-copy While insightful, it doesn't answer my question if Array.CopyTo calls Buffer.BlockCopy. I'm specifically interested in if I'm able to see how these two functions are implemented, and if I had future questions about the internals of C#, if it is possible for me to investigate it. Or am I out of luck?

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  • Can you force a crash if a write occurs to a given memory location with finer than page granularity?

    - by Joseph Garvin
    I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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  • Quick question on using the constructer with multiple files.

    - by sil3nt
    Hi there, I have this class header //header for class. #ifndef Container_H #define Container_H #include <iostream> using namespace std; const int DEFAULT=32; class Container{ public: Container(int maxCapacity = DEFAULT); ~Container(); void insert(int item, int index); void erase(int index); int size()const; private: int sizeC; int capacityC; int * elements; }; void info(); #endif and this source file #include "container.h" Container::Container(int maxCapacity = DEFAULT){ int y; } void Container::insert(int item, int index){ int x; } and when i compile this i get the following error message test.cpp:4: error: default argument given for parameter 1 of `Container::Container(int)' container.h:12: error: after previous specification in `Container::Container(int) what have i done wrong here?

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