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  • byte + byte = int... why?

    - by Robert C. Cartaino
    Looking at this C# code... byte x = 1; byte y = 2; byte z = x + y; // ERROR: Cannot implicitly convert type 'int' to 'byte' The result of any math performed on byte (or short) types is implicitly cast back to an integer. The solution is to explicitly cast the result back to a byte, so... byte z = (byte)(x + y); // works What I am wondering is why? Is it architectural? Philosophical? We have: int + int = int long + long = long float + float = float double + double = double So why not: byte + byte = byte short + short = short ? A bit of background: I am performing a long list of calculations on "small numbers" (i.e. < 8) and storing the intermediate results in a large array. Using a byte array (instead of an int array) is faster (because of cache hits). But the extensive byte-casts spread through the code make it that much more unreadable.

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  • PageableListView Not rendering my data as required

    - by Robin
    i am working on wicket, where i am supposed to show my data's under <tr> <td>Name</td> <td>Single Player Score</td> <td>Double Player Score</td> <td>Total Score</td> </tr> <tr wicket:id="data"> <td wicket:id="name"></td> <td wicket:id="singlePlayerScore"></td> <td wicket:id="doublePlayerScore"></td> <td wicket:id="totalScore"></td> </tr> My Player model class is as: Player class with attributes singlePlayerScore, doublePlayerScore(), name with getter and setter and also a list data obtained from database. Data from SQLQuery is as; name score gamemode A 200 singlePlayerMode A 100 doublePLayerMode B 400 singlePlayerMode B 300 doublePLayerMode dataList == player.getScoreList(); My PageableListView is as: final PageableListView listView = new PageableListView("data",dataList,10){ @Override protected void populateItem(Item item){ player = (Player)item.getModelObject(); item.add(Label("name",player.getName())); item.add(Label("singlePlayerScore",player.getName())); item.add(Label("doublePlayerScore",player.getName())); item.add(Label("totalScore",String.valueOf(player.getSinglePlayerScore()+player.getDoublePlayerScore()))); } } My Problem is as: What view i get is as: Name single Player Score Double Player Score Total Score A 0 100 100 A 200 0 200 B 0 300 300 B 400 0 400 How do i achieve below view on my webpage? Name single Player Score Double Player Score Total Score A 200 100 300 B 400 300 700 Please help me as to why is this happening? I guess my list has size four that's one reason why as to it is rendering the view? So what can i do to get as require rendering view?

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  • import text file containing line breaks into excel

    - by Maximilian Tyrtania
    I have a plain text file looking like this: "some text containing line breaks" I'm trying to talk excel 2004 (Mac, v.11.5) into opening this file correctly. I'd expect to see only one cell (A1) containing all of the above (without the quotes)... But alas, I can't make it happen, because Excel seems to insist on using the CR's as row delimiters, even if I set the text qualifier to double quote. I was sort of hoping that Excel would understand that those line breaks are part of the value - they are embedded in double quotes which should qualify them as part of the value. So my Excel sheet has 5 rows, which is not what I want. I also tried this Applescript to no avail: tell application "Microsoft Excel" activate open text file filename ¬ "Users:maximiliantyrtania:Desktop:linebreaks" data type delimited ¬ text qualifier text qualifier double quote ¬ field info {{1, text format}} ¬ origin Macintosh with tab end tell If I could tell Excel to use a row delimiter other than CR (or LF), well, I'd be a happy camper, but excel seems to allow the change of the field delimiter only, not the row delimiter. Any pointers? Thanks, Max Excel's open

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  • C++ arrays as parameters, subscript vs. pointer

    - by awshepard
    Alright, I'm guessing this is an easy question, so I'll take the knocks, but I'm not finding what I need on google or SO. I'd like to create an array in one place, and populate it inside a different function. I define a function: void someFunction(double results[]) { for (int i = 0; i<100; ++i) { for (int n = 0; n<16; ++n) //note this iteration limit { results[n] += i * n; } } } That's an approximation to what my code is doing, but regardless, shouldn't be running into any overflow or out of bounds issues or anything. I generate an array: double result[16]; for(int i = 0; i<16; i++) { result[i] = -1; } then I want to pass it to someFunction someFunction(result); When I set breakpoints and step through the code, upon entering someFunction, results is set to the same address as result, and the value there is -1.000000 as expected. However, when I start iterating through the loop, results[n] doesn't seem to resolve to *(results+n) or *(results+n*sizeof(double)), it just seems to resolve to *(results). What I end up with is that instead of populating my result array, I just get one value. What am I doing wrong?

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  • How to easily Generate Synth Chords Sounds in Android?

    - by barata7
    How to easily Generate Synth Chords Sounds in Android? I wanna be able to generate dynamically an in game Music using 8bit. Tried with AudioTrack, but did not get good results of nice sounds yet. Any examples out there? I have tried the following code without success: public class BitLoose { private final int duration = 1; // seconds private final int sampleRate = 4200; private final int numSamples = duration * sampleRate; private final double sample[] = new double[numSamples]; final AudioTrack audioTrack; public BitLoose() { audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, sampleRate, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_8BIT, numSamples, AudioTrack.MODE_STREAM); audioTrack.play(); } public void addTone(final int freqOfTone) { // fill out the array for (int i = 0; i < numSamples; ++i) { sample[i] = Math.sin(2 * Math.PI * i / (sampleRate / freqOfTone)); } // convert to 16 bit pcm sound array // assumes the sample buffer is normalised. final byte generatedSnd[] = new byte[numSamples]; int idx = 0; for (final double dVal : sample) { // scale to maximum amplitude final short val = (short) ((((dVal * 255))) % 255); // in 16 bit wav PCM, first byte is the low order byte generatedSnd[idx++] = (byte) (val); } audioTrack.write(generatedSnd, 0, sampleRate); } public void stop() { audioTrack.stop(); }

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  • Vertical line on HxW canvas of pixels

    - by bobby williams
    I searched and found nothing. I'm trying to draw lines (simple y=mx+b ones) on a canvas of black pixels. It works fine, but no line occurs when it is vertical. I'm not sure why. My first if statement checks if the denominator is zero, therefore m is undefined and no need for a line equation. My second and third if statement check how steep it is and based on that, calculate the points in between. I don't think there is a need for other classes, since I think there is a bug in my code or I'm just not translating the mathematics into code properly. If more is needed, I'll be happy to post more. /** * Returns an collection of points that connects p1 and p2 */ public ArrayList getPoints() { ArrayList points = new ArrayList(); // checks to see if denominator in m is zero. if zero, undefined. if ((p2.getX() - p1.getX()) == 0) { for (int y = p1.getY(); y<p2.getY(); y++) { points.add(new Point(p1.getX(), y, getColor())); } } double m = (double)(p2.getY()-p1.getY())/(double)(p2.getX()-p1.getX()); int b = (int)(p1.getY() - (m * p1.getX())); // checks to see if slope is steep. if (m > -1 || m < 1) { for (int x = p1.getX(); x<p2.getX(); x++) { int y = (int) ((m*x)+b); points.add(new Point(x, y, getColor())); } } // checks to see if slope is not steep. if (m <= -1 || m >= 1) { for (int y = p1.getY(); y<p2.getY(); y++) { int x = (int) ((y-b)/m); points.add(new Point(x, y, getColor())); } } return points; }

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  • Trying to get focus onto JTextPane after doubleclicking on JList element (Java)

    - by Alex Cheng
    Hi all. Problem: I have the following JList which I add to the textPane, and show it upon the caret moving. However, after double clicking on the Jlist element, the text gets inserted, but the caret is not appearing on the JTextPane. This is the following code: listForSuggestion = new JList(str.toArray()); listForSuggestion.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); listForSuggestion.setSelectedIndex(0); listForSuggestion.setVisibleRowCount(visibleRowCount); listScrollPane = new JScrollPane(listForSuggestion); MouseListener mouseListener = new MouseAdapter() { @Override public void mouseClicked(MouseEvent mouseEvent) { JList theList = (JList) mouseEvent.getSource(); if (mouseEvent.getClickCount() == 2) { int index = theList.locationToIndex(mouseEvent.getPoint()); if (index >= 0) { Object o = theList.getModel().getElementAt(index); //System.out.println("Double-clicked on: " + o.toString()); //Set the double clicked text to appear on textPane String completion = o.toString(); int num= textPane.getCaretPosition(); textPane.select(num, num); textPane.replaceSelection(completion); textPane.setCaretPosition(num + completion.length()); int pos = textPane.getSelectionEnd(); textPane.select(pos, pos); textPane.replaceSelection(""); textPane.setCaretPosition(pos); textPane.moveCaretPosition(pos); } } theList.clearSelection(); Any idea on how to "de-focus" the selection on the Jlist, or make the caret appear on the JTextPane after the text insertion? I'll elaborate more if this is not clear enough. Please help, thanks!

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  • In MySql Stored Procedure updating more than one time

    - by Both FM
    In MySql UPDATE `inventoryentry` SET `Status` = 1 WHERE `InventoryID`=92 AND `ItemID`=28; It successfully update only one row , where inventoryID = 92 and itemID=28 , the following message displayed. 1 row(s) affected when I put this on stored procedure, as follow CREATE DEFINER=`root`@`localhost` PROCEDURE `Sample`(IN itemId INT, IN itemQnty DOUBLE, IN invID INT) BEGIN DECLARE crntQnty DOUBLE; DECLARE nwQnty DOUBLE; SET crntQnty=(SELECT `QuantityOnHand` FROM `item` WHERE id=itemId); SET nwQnty=itemQnty+crntQnty; UPDATE `item` SET `QuantityOnHand`=nwQnty WHERE `Id`=itemId; UPDATE `inventoryentry` SET `Status` = 1 WHERE `InventoryID`=invID AND `ItemID`=itemId; END$$ calling stored procedures CALL Sample(28,10,92) It update all the status = 1 in inventoryentry against InventoryID (i.e. 92) ignoring ItemID, instead of updating only one row. The following message displayed! 5 row(s) affected Why Stored procedure ignoring itemID in update statement ? or Why Stored procedure updating more than one time? But without Stored procedure it working fine.

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  • Specializing function templates outside class temp. definition - what is the correct way of doing t

    - by LoudNPossiblyRight
    I am attempting to specialize a function template that is a member of a template class. The two of them have different template parameters. The template function specialization inside the temp. class definition is never called and the one func. spec. outside the class definition does not even compile. Should i expect this to work in the first place, and if so, what do i have to change in this code to both compile and make it work correctly: using VS2010 #include<iostream> using namespace std; template <typename T> class klass{ public: template <typename U> void func(const U &u){ cout << "I AM A TEMPLATE FUNC" << endl; } //THIS NEVER GETS CALLED !!! template <> void klass<T>::func(const string &s){ cout << "I AM A STRING SPECIALIST" << endl; } }; //THIS SPECIALIZATION WILL NOT COMPILE !!! template <typename T> template <> void klass<T>::func(const double &s){ cout << "I AM A DOUBLE SPECIALIST" << endl; } int main(){ double d = 3.14159265; klass<int> k; k.func(1234567890); k.func("string"); k.func(3.14159265); return 0; }

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  • Asynchronous URL connection objective C

    - by tweety
    I created an asynchronous URL connection to call a web service using HTTP POST method. after I am pinging the web i set an NSTimerInterval in the completion handler. my problem is when I'm trying to display the time on the view controller it is not doing promptly. I know block is stored in the heap and gets executed later on anytime and probably that's why i'm not getting prompt answer. I was wondering is there any other way to do this? Thanks in advance. my code: __block NSDate *start= [NSDate date]; __block NSDate *end; __block double miliseconds; __block NSTimeInterval time; [NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) { if([data length]==0 && error==nil){ end=[NSDate date]; time=[end timeIntervalSinceDate:start]; NSLog(@"Successfully Pinged"); miliseconds = time; // calling a method to display ping time [self label:miliseconds]; } -(void) label:(double) mili{ double miliseconds=mili*1000; self.timeDisplay.text=[NSString stringWithFormat:@"Time: %.3f ms", miliseconds];

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  • Compare two variant with boost static_visitor

    - by Zozzzzz
    I started to use the boost library a few days ago so my question is maybe trivial. I want to compare two same type variants with a static_visitor. I tried the following, but it don't want to compile. struct compare:public boost::static_visitor<bool> { bool operator()(int& a, int& b) const { return a<b; } bool operator()(double& a, double& b) const { return a<b; } }; int main() { boost::variant<double, int > v1, v2; v1 = 3.14; v2 = 5.25; compare vis; bool b = boost::apply_visitor(vis, v1,v2); cout<<b; return 0; } Thank you for any help or suggestion!

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  • Calling base class constructor

    - by The Void
    In the program below, is the line Derived(double y): Base(), y_(y) correct/allowed? That is, does it follow ANSI rules? #include <iostream> class Base { public: Base(): x_(0) { std::cout << "Base default constructor called" << std::endl; } Base(int x): x_(x) { std::cout << "Base constructor called with x = " << x << std::endl; } void display() const { std::cout << x_ << std::endl; } protected: int x_; }; class Derived: public Base { public: Derived(): Base(1), y_(1.2) { std::cout << "Derived default constructor called" << std::endl; } Derived(double y): Base(), y_(y) { std::cout << "Derived constructor called with y = " << y << std::endl; } void display() const { std::cout << Base::x_ << ", " << y_ << std::endl; } private: double y_; }; int main() { Base b1; b1.display(); Derived d1; d1.display(); std::cout << std::endl; Base b2(-9); b2.display(); Derived d2(-8.7); d2.display(); return 0; }

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  • Please Help to locate the error

    - by jagdeep
    using System; using System.Collections; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq; public partial class expt2 : System.Web.UI.Page { double result ; protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack) result = 0.0; protected void Chkbxbd_CheckedChanged(object sender, EventArgs e) { if (Chkbxbd.Checked) { txtbxttl.Text = "" + 10000; result += double.Parse(txtbxttl.Text); } else result = result - 10000; } protected void Chkbxsfa_CheckedChanged(object sender, EventArgs e) { if (Chkbxsfa.Checked) { txtbxttl.Text = "" + 15000; result += double.Parse(txtbxttl.Text); } else result = result - 15000; } protected void btnttl_Click(object sender, EventArgs e) { txtbxttl.Text = "" + result; } } In this code the individual value for checkbox is ok but when the total is made it becomes 0. Please help me to fix it.

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  • Is it an example of decorator pattern?

    - by Supereme
    Hi, I've an example please tell me whether it is Decorator pattern or not? public abstract class ComputerComponent { String description ="Unknown Type"; public String getDescription() { return description; } public abstract double getCost(); } public abstract class AccessoryDecorator { ComputerComponent comp; public abstract String getDescription(); } public class PIIIConcreteComp extends ComputerComponent { public PIIIConcreteComp() { description=“Pentium III”; } public double getCost() { return 19950.00; } public class floppyConcreteDeco extends AccessoryDecorator { public floppyConcreteDeco(ComputerComponent comp) this.comp=comp; } public String getDescription() { return comp.getDescription() +”, floppy 1.44 mb”; } public double getCost() { return 250+comp.getCost(); } } public class ComponentAssembly { public static void createComponent() { ComputerComponent comp = new PIIConcreteComp(); // create a PIII computer object ComputerComponent deco1= new floppyConcreteDeco(comp); // decorate it with a floppy //ComputerComponent deco2= newCDRomConcreteDeco(deco1); ComputerComponent deco2= new floppyConcreteDeco(deco1); // decorate with a CDRom or with one more floppy System.out.println( deco2.getdescription() +” “+ deco2.getCost(); } } Thank you.

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  • Database/Object Mapping

    - by Eric
    Hello everyone, This is a beginner question, but it's been frustrating me... I am using C#, by the way. I'd like to make a few classes, each with their own properties and methods. I would also like to have a database to store certain instances of these classes in case I would ever need to look at them again. So, for example... class Polygon { String name; Double perimiter; int numSides; public Double GetArea() { // ... } } class Circle { String name; Double radius; public void PrintName() { // ... } } Say I've got these classes. I also want a database that has the TABLES "Polygon" and "Circle" with the COLUMNS "name" "perimeter" "radius" etc. And I want an easy way to save a class instance into the database, or pull a class instance out of the database. I have previously been using MS Access for my database stuff, which I don't mind using, but I would prefer if nothing other than .NET need to be installed. I've been researching online a bit, but I wanted to get some opinions on here. I have looked at Linq-to-Sql, but it seems you need Sql-Server. Is this true? If so, I'd really rather not use it because I don't want to have to have it installed everywhere. Anway, I'm just fishing for some ideas/insights/suggestions/etc. so please help me out if you can. Thanks.

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  • Validation for textfield is not working

    - by MaheshBabu
    Hi folks, I am using 4 Textfields in my application. I need to validate those textfields like,These 4 textfields Allow only o,1,....9 and . For that i use the code like this. - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { static NSCharacterSet *charSet = nil; if(!charSet) { charSet = [[[NSCharacterSet characterSetWithCharactersInString:@"0123456789."] invertedSet] retain]; } NSRange location = [string rangeOfCharacterFromSet:charSet]; return (location.location == NSNotFound); And first textfield allows digits 10,second third and fourth textfields allows less than 100. For that my code is if (textField.tag == 1) { NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string]; double homevaluedouble = [newString doubleValue]; return !(homevaluedouble > 10000000000); } if (textField.tag == 2) { NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string]; double validate = [newString doubleValue]; return !(validate > 100); } if (textField.tag == 3) { NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string]; double validate = [newString doubleValue]; return !(validate > 100); } I write this code in - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { But textfields allows 0,1,..9 and . but digit limit is not working, if i remove 0,1,...9 then limit to textfield working. i am getting confuse with it. can any one pls help me,How can i resolve it. Thank u in advance.

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  • Same Origin issue with web service call

    - by Wjdavis5
    My web server runs at http://mypc.com:80 ` Given the following snip: $(window).load(function () { var myURL = "http://mypc.com:8000/PSOCharts/service/HighChart_ColumnChart/i"; $.getJSON(myURL) .done(function(data) {alert(data);}); }); I am running to this error: XMLHttpRequest cannot load http://mypc.com:8000/PSOCharts/service/HighChart_ColumnChart/i. Origin http://mypc.com is not allowed by Access-Control-Allow-Origin. I understand why (I think) b/c my webservice runs at port 8000 which is different from what IIS is running on (port 80). I thought I could get around by using jsonp (according to the jQuery documentation here So I copied the example of making a call to the flickr api, but it isnt working. Any thoughts/sugggestions? UPDATE Ok so my request is being made now: var myURL = "http://192.168.1.104:8000/PSOCharts/service/HighChart_ColumnChart/i?jsoncallback=?"; $.ajax({ url :myURL, dataType: "jsonp", success: function(data) {a(data)} , error: function(){alert("err");}, }); But I am continually hitting the error function, here is what's being returned: [1.4,54.43,49.39,93.23] Now I'm assuming this is b/c the response text doesnt contain any type of callback here is the part of the interface I'm calling: [WebInvoke(Method = "GET", RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json, UriTemplate = "HighChart_ColumnChart/{id}?callback={cb}")] List<double> HighChart_ColumnChart(string id,string cb); Here is the actual function being called: public List<double> HighChart_ColumnChart(string id,string cb) { var z = new List<double>(); z.Add(1.4); z.Add(54.43); z.Add(49.39); z.Add(93.23); return z; } when I debug, the CB param is something like : "jQuery19108121746340766549_1372630643878". How do I modify the code to wrap it correctly? Thanks for the help thus far!

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  • My method is too specific. How can I make it more generic?

    - by EricBoersma
    I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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  • Multithreading for loop while maintaining order

    - by David
    I started messing around with multithreading for a CPU intensive batch process I'm running. Essentially I'm trying to condense multiple single page tiffs into single PDF documents. This works fine with a foreach loop or standard iteration but can be very slow for several 100 page documents. I tried the following based on a some examples I found to use multithreading and it has significant performance improvements however it obliterates the page order instead of 1,2,3,4 it will be 1,3,4,2,6,5 on what thread completes first. My question is how would I utilize this technique while maintaining the page order and if I can will it negate the performance benefit of the multithreading? Thank you in advance. PdfDocument doc = new PdfDocument(); string mail = textBox1.Text; string[] split = mail.Split(new string[] { Environment.NewLine }, StringSplitOptions.None); int counter = split.Count(); // Source must be array or IList. var source = Enumerable.Range(0, 100000).ToArray(); // Partition the entire source array. var rangePartitioner = Partitioner.Create(0, counter); double[] results = new double[counter]; // Loop over the partitions in parallel. Parallel.ForEach(rangePartitioner, (range, loopState) => { // Loop over each range element without a delegate invocation. for (int i = range.Item1; i < range.Item2; i++) { f_prime = split[i].Replace(" " , ""); PdfPage page = doc.AddPage(); XGraphics gfx = XGraphics.FromPdfPage(page); XImage image = XImage.FromFile(f_prime); double x = 0; gfx.DrawImage(image, x, 0); } });

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  • Why does reusing arrays increase performance so significantly in c#?

    - by Willem
    In my code, I perform a large number of tasks, each requiring a large array of memory to temporarily store data. I have about 500 tasks. At the beginning of each task, I allocate memory for an array : double[] tempDoubleArray = new double[M]; M is a large number depending on the precise task, typically around 2000000. Now, I do some complex calculations to fill the array, and in the end I use the array to determine the result of this task. After that, the tempDoubleArray goes out of scope. Profiling reveals that the calls to construct the arrays are time consuming. So, I decide to try and reuse the array, by making it static and reusing it. It requires some additional juggling to figure out the minimum size of the array, requiring an extra pass through all tasks, but it works. Now, the program is much faster (from 80 sec to 22 sec for execution of all tasks). double[] tempDoubleArray = staticDoubleArray; However, I'm a bit in the dark of why precisely this works so well. Id say that in the original code, when the tempDoubleArray goes out of scope, it can be collected, so allocating a new array should not be that hard right? I ask this because understanding why it works might help me figuring out other ways to achieve the same effect, and because I would like to know in what cases allocation gives performance issues.

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  • C#: Any faster way of copying arrays?

    - by Yang
    I have three arrays that need to be combined in one three-dimension array. The following code shows slow performance in Performance Explorer. Is there a faster solution? for (int i = 0; i < sortedIndex.Length; i++) { if (i < num_in_left) { // add instance to the left child leftnode[i, 0] = sortedIndex[i]; leftnode[i, 1] = sortedInstances[i]; leftnode[i, 2] = sortedLabels[i]; } else { // add instance to the right child rightnode[i-num_in_left, 0] = sortedIndex[i]; rightnode[i-num_in_left, 1] = sortedInstances[i]; rightnode[i-num_in_left, 2] = sortedLabels[i]; } } Update: I'm actually trying to do the following: //given three 1d arrays double[] sortedIndex, sortedInstances, sortedLabels; // copy them over to a 3d array (forget about the rightnode for now) double[] leftnode = new double[sortedIndex.Length, 3]; // some magic happens here so that leftnode = {sortedIndex, sortedInstances, sortedLabels};

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  • Name lookup for names not dependent on template parameter in VC++2008 Express. Is it a bug?

    - by Maciej H
    While experimenting a bit with C++ templates I managed to produce this simple code, for which the output is different, than I expected according to my understanding of C++ rules. void bar(double d) { std::cout << "bar(double) function called" << std::endl; } template <typename T> void foo(T t) { bar(3); } void bar(int i) { std::cout << "bar(int) function called" << std::endl; } int main() { foo(3); return 0; } When I compile this code is VC++2008 Express function bar(int) gets called. That would be the behaviour I would expect if bar(3);in the template body was dependent on the template parameter. But it's not. The rule I found here says "The C++ standard prescribes that all names that are not dependent on template parameters are bound to their present definitions when parsing a template function or class". Am I wrong, that "present definition" of bar when parsing the template function foo is the definition of void bar(double d);? Why it's not the case if I am wrong. There are no forward declarations of bar in this compilation unit.

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  • switch namespace by if condtion

    - by pascal
    Hi, in my C++ program I have several namespaces that contain several pointers with identical names. I then want a function to choose a namespace according to a parameter. I.e. something like: #include <iostream> namespace ns1{ double x[5]={1,2,3,4,5}; } namespace ns2{ double x[5]={6,7,8,9,10}; } int main(){ int b=1; if(b==1){ using namespace ns1; } if(b==2){ using namespace ns2; } std::cout << x[3] << std::endl; } However, this doesn't work since the compiler complains that x isn't known in that scope. I guess the problem is that "using namespace ..." is only valid within the if-statement. I think that it should be possible to switch namespaces somehow, but cannot find out how... Do you know how to do this without casting all variable separately? int main(){ int b=1; double *x; if(b==1){ x = ns1::x; } if(b==2){ x = ns2::x; } std::cout << x[3] << std::endl; } Cheers, Pascal

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  • Operator overloading in generic struct: can I create overloads for specific kinds(?) of generic?

    - by Carson Myers
    I'm defining physical units in C#, using generic structs, and it was going okay until I got the error: One of the parameters of a binary operator must be the containing type when trying to overload the mathematical operators so that they convert between different units. So, I have something like this: public interface ScalarUnit { } public class Duration : ScalarUnit { } public struct Scalar<T> where T : ScalarUnit { public readonly double Value; public Scalar(double Value) { this.Value = Value; } public static implicit operator double(Scalar<T> Value) { return Value.Value; } } public interface VectorUnit { } public class Displacement : VectorUnit { } public class Velocity : VectorUnit { } public struct Vector<T> where T : VectorUnit { #... public static Vector<Velocity> operator /(Vector<Displacement> v1, Scalar<Duration> v2) { return new Vector<Velocity>(v1.Magnitude / v2, v1.Direction); } } There aren't any errors for the + and - operators, where I'm just working on a Vector<T>, but when I substitute a unit for T, suddenly it doesn't like it. Is there a way to make this work? I figured it would work, since Displacement implements the VectorUnit interface, and I have where T : VectorUnit in the struct header. Am I at least on the right track here? I'm new to C# so I have difficulty understanding what's going on sometimes.

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  • How to create a String Array and link it to a Grade array

    - by user1861544
    I have a project that I need to create 2 Arrays, one to hold Student Names and one to hold Student Scores. The user inputs the size of the array, and the array needs to be sorted using BubbleSort (putting the high scores at the top). I have started the project, created the first array for scores, I have successfully done bubble sort and sorted the grades. Now I can't figure out how to make an array for Names, and once I do how do I make the names array correspond to the Grades array BubbleSort? Here is the code I have so far. import java.util.Scanner; public class Grades { public static void main(String[]args){ { Scanner UserIn = new Scanner(System.in); System.out.print( "How many students are there? " ); int[]GradeArray = new int[UserIn.nextInt()]; for( int i=0 ; i<GradeArray.length ; i++ ) { System.out.print( "Enter Grade for Student " + (i+1) + ": " ); GradeArray[i] = UserIn.nextInt(); } bubbleSort(GradeArray); for( int i : GradeArray ) System.out.println( i ); System.out.println(); } } private static void bubbleSort(int[]GradeArray){ int n = GradeArray.length; int temp = 0; String temp2; for(int i=0; i<n; i++){ for(int j=1; j<(n-i);j++){ if(GradeArray[j-1]<GradeArray[j]){ //swap temp=GradeArray[j-1]; GradeArray[j-1]=GradeArray[j]; GradeArray[j]=temp; } } } } } Also how do I change the grades to Double? I started with Int and when I try to change everything to double I get an error saying "Found Double, expected Int".

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