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  • how to write floating value accurately to a bin file.

    - by user319873
    Hi I am trying to dump the floating point values from my program to a bin file. Since I can't use any stdlib function, I am thinking of writting it char by char to a big char array which I am dumping in my test application to a file. It's like float a=3132.000001; I will be dumping this to a char array in 4 bytes. Code example would be:- if((a < 1.0) && (a > 1.0) || (a > -1.0 && a < 0.0)) a = a*1000000 // 6 bit fraction part. Can you please help me writting this in a better way.

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  • Out-of-memory algorithms for addressing large arrays

    - by reve_etrange
    I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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  • Changing brightness in bufferedImage with DataBufferInt

    - by user2958025
    I must read some image and then I have to change brightness and contrast of this image I create main class and constructor where are panels, sliders and other stuff, I added changeListener to slider to take current value. My imagePanel is new Object of that class: public class Obrazek extends JPanel{ public static BufferedImage img = null; public Obrazek() { super(); try { img = ImageIO.read(new File("D:\\ja.jpg")); } catch (IOException e) {} } @Override public void paint(Graphics g) { g.drawImage(img, 0, 0, null); } } This is my load button private void przyciskWczytaj(java.awt.event.ActionEvent evt) { int odpowiedz = jFileChooser1.showOpenDialog(this); if (odpowiedz == jFileChooser1.APPROVE_OPTION) { File file = jFileChooser1.getSelectedFile(); try { BufferedImage im = ImageIO.read(new File(file.getAbsolutePath())); Obrazek.img = im; } catch (IOException ex) { System.out.println("Error"); } } } And now I want to create class where I will change that brightness. I have to use but I don't know how to use that thing: BufferedImage(256, 256, Bufferedmage.TYPE_INT_RGB) and to get each pixel of image I need to do something like: int rgb []=((DataBufferInt)img.getRaster().getDataBuffer()).getData(); And here I is next problem: How can I change the value of each r,g,b and show that new image on my panel

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  • Java file searching problem

    - by Infinity
    Hello guys! I need to search a file for a word and return the whole line and the line number with this word, then edit the line and write back to the file. Maybe the line number isn't necesary to edit a line in a file. I `was reading after seraching with regexp and opening the filechannel of the file, but I can't get the line number. Maybe there are other better ways to do this. Can you help me how to start this?

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  • C Remove the first line from a text file without rewriting file

    - by Tom Van den Bon
    Hi, I've got a service which runs all the time and also keeps a log file. It basically adds new lines to the log file every few seconds. I'm written a small file which reads these lines and then parses them to various actions. The question I have is how can I delete the lines which I have already parsed from the log file without disrupting the writing of the log file by the service? Usually when I need to delete a line in a file then I open the original one and a temporary one and then I just write all the lines to the temp file except the original which I want to delete. Obviously this method will not word here. So how do I go about deleting them ?

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  • Write file need to optimised for heavy traffic part 2

    - by Clayton Leung
    For anyone interest to see where I come from you can refer to part 1, but it is not necessary. write file need to optimised for heavy traffic Below is a snippet of code I have written to capture some financial tick data from the broker API. The code will run without error. I need to optimize the code, because in peak hours the zf_TickEvent method will be call more than 10000 times a second. I use a memorystream to hold the data until it reaches a certain size, then I output it into a text file. The broker API is only single threaded. void zf_TickEvent(object sender, ZenFire.TickEventArgs e) { outputString = string.Format("{0},{1},{2},{3},{4}\r\n", e.TimeStamp.ToString(timeFmt), e.Product.ToString(), Enum.GetName(typeof(ZenFire.TickType), e.Type), e.Price, e.Volume); fillBuffer(outputString); } public class memoryStreamClass { public static MemoryStream ms = new MemoryStream(); } void fillBuffer(string outputString) { byte[] outputByte = Encoding.ASCII.GetBytes(outputString); memoryStreamClass.ms.Write(outputByte, 0, outputByte.Length); if (memoryStreamClass.ms.Length > 8192) { emptyBuffer(memoryStreamClass.ms); memoryStreamClass.ms.SetLength(0); memoryStreamClass.ms.Position = 0; } } void emptyBuffer(MemoryStream ms) { FileStream outStream = new FileStream("c:\\test.txt", FileMode.Append); ms.WriteTo(outStream); outStream.Flush(); outStream.Close(); } Question: Any suggestion to make this even faster? I will try to vary the buffer length but in terms of code structure, is this (almost) the fastest? When memorystream is filled up and I am emptying it to the file, what would happen to the new data coming in? Do I need to implement a second buffer to hold that data while I am emptying my first buffer? Or is c# smart enough to figure it out? Thanks for any advice

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  • [FIXED] Scan file contents into an array of a structure.

    - by ZaZu
    Hello, I have a structure in my program that contains a particular array. I want to scan a random file with numbers and put the contents into that array. This is my code : ( NOTE : This is a sample from a bigger program, so I need the structure and arrays as declared ) The contents of the file are basically : 5 4 3 2 5 3 4 2 #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; FILE *fin; fin=fopen("randomfile.txt","r"); for(i=0;i<5;i++){ fscanf(fin,"%5.2f\t",(*test).what[z][x]); } fclose(fin); return 0; } But the problem is, whenever this I run this code, I get this error : (25) : warning 508 - Data of type 'double' supplied where a pointer is required I tried adding do{ for(i=0;i<5;i++){ q=fscanf(fin,"%5.2f\t",(*test).what[z][x]); } }while(q!=EOF); But that didnt work either, it gives the same error. Does anyone have a solution to this problem ?

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  • Using scanf() in C++ programs is faster than using cin ?

    - by zeroDivisible
    Hello, I don't know if this is true, but when I was reading FAQ on one of the problem providing sites, I found something, that poke my attention: Check your input/output methods. In C++, using cin and cout is too slow. Use these, and you will guarantee not being able to solve any problem with a decent amount of input or output. Use printf and scanf instead. Can someone please clarify this? Is really using scanf() in C++ programs faster than using cin something ? If yes, that is it a good practice to use it in C++ programs? I thought that it was C specific, though I am just learning C++...

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  • R problem with apply + rbind

    - by Carl
    I cannot seem to get the following to work directory <- "./" files.15x16 <- c("15x16-70d.out", "15x16-71d.out") data.15x16<-rbind( lapply( as.array(paste(directory, files.15x16, sep="")), FUN=read.csv, sep=" ", header=F) ) What it should be doing is pretty straightforward - I have a directory name, some file names, and actual files of data. I paste the directory and file names together, read the data from the files in, and then rbind them all together into a single chunk of data. Except the result of the lapply has the data in [[]] - i.e., accessing it occurs via a[[1]], a[[2]], etc which rbind doesn't seem to accept. Suggestions?

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  • StreamReader not working as expected

    - by Jon Preece
    Hi, I have written a simple utility that loops through all C# files in my project and updates the copyright text at the top. For example, a file may look like this; //Copyright My Company, © 2009-2010 The program should update the text to look like this; //Copyright My Company, © 2009-2010 However, the code I have written results in this; //Copyright My Company, � 2009-2011 Here is the code I am using; public bool ModifyFile(string filePath, List<string> targetText, string replacementText) { if (!File.Exists(filePath)) return false; if (targetText == null || targetText.Count == 0) return false; if (string.IsNullOrEmpty(replacementText)) return false; string modifiedFileContent = string.Empty; bool hasContentChanged = false; //Read in the file content using (StreamReader reader = File.OpenText(filePath)) { string file = reader.ReadToEnd(); //Replace any target text with the replacement text foreach (string text in targetText) modifiedFileContent = file.Replace(text, replacementText); if (!file.Equals(modifiedFileContent)) hasContentChanged = true; } //If we haven't modified the file, dont bother saving it if (!hasContentChanged) return false; //Write the modifications back to the file using (StreamWriter writer = new StreamWriter(filePath)) { writer.Write(modifiedFileContent); } return true; } Any help/suggestions are appreciated. Thanks!

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  • write 2d array to a file in C (Operating system)

    - by Bobj-C
    Hello All, I used to use the code below to Write an 1D array to a File: FILE *fp; float floatValue[5] = { 1.1F, 2.2F, 3.3F, 4.4F, 5.5F }; int i; if((fp=fopen("test", "wb"))==NULL) { printf("Cannot open file.\n"); } if(fwrite(floatValue, sizeof(float), 5, fp) != 5) printf("File read error."); fclose(fp); /* read the values */ if((fp=fopen("test", "rb"))==NULL) { printf("Cannot open file.\n"); } if(fread(floatValue, sizeof(float), 5, fp) != 5) { if(feof(fp)) printf("Premature end of file."); else printf("File read error."); } fclose(fp); for(i=0; i<5; i++) printf("%f ", floatValue[i]); My question is if i want to write and read 2D array ??

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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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  • Fastest Way To Format a Plain Text Using Javascript

    - by Nathan Campos
    I have a huge plain text document, about 700kb which is very big for plain texts and I need to format it on cloud converting it to HTML, but the only things that I need to replace, format to HTML so it can be displayed by the browser, are bold and italic. For bold at the plain text they are like this: Not on bold... **bold text here** not bold here And italic like this: Not italic... *italic text* no italic Just like StackOverflow does for their formatting, but the problem is that I need to make it a lot faster, since the text is so big... One of my ideas was to add a page slide, so I the script just need to format some part of the text, not it all, then after the user changes the page the script would be called again, but the problem is how I can make the code for this all?

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  • Read char from txt file in C++

    - by Jack in the Box
    I have a program that will read the number of rows and columns from a txt file. Also, the program has to read the contents of a 2D array from the same file. Here is the txt file 8 20 * * *** *** 8 and 20 are the number of rows and columns respectively. The spaces and asterisks are the contents of the array, Array[8][20] For example, Array[0][1] = '*' I did make the program reading 8 and 20 as follow: ifstream myFile; myFile.open("life.txt"); if(!myFile) { cout << endl << "Failed to open file"; return 1; } myFile >> rows >> cols; myFile.close(); grid = new char*[rows]; for (int i = 0; i < rows; i++) { grid[i] = new char[cols]; } Now, how to assign the spaces and the asterisks to to the fields in the array? I hope you got the point.

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  • Scanner's Read Line returning NoSuchElementException

    - by Brian
    This is my first time using StackOverflow. I am trying to read a text file which consists of a single number one the first line. try { Scanner s = new Scanner(new File("HighScores.txt")); int temp =Integer.parseInt(s.nextLine()); s.close(); return temp; } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } However, I get an error: java.util.NoSuchElementException: No line found at java.util.Scanner.nextLine(Unknown Source) at GameStart.getHighScore(GameStart.java:334) at GameStart.init(GameStart.java:82) at sun.applet.AppletPanel.run(Unknown Source) at java.lang.Thread.run(Unknown Source) I know that HighScores.txt is not empty, so why is this problem occuring? I tried using BufferedReader, and BufferReader.readLine() return null.

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  • FileNotFound exception

    - by Pratik
    I am trying to read a file in a servlet. I am using eclipse IDE. I get a FileNotFoundException if I provide relative file name. List<String> ls=new ArrayList<String>(); Scanner input = new Scanner(new File("Input.txt")); while(input.hasNextLine()) { ls.add(input.nextLine()); } The same code works if I put the absolute path like this: Scanner input = new Scanner(new File("F:/Spring and other stuff/AjaxDemo/src/com/pdd/ajax/Input.txt")); The Java file and text file are there in the same folder. Does it searches text file in some other folder ?

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  • best practices question: How to save a collection of images and a java object in a single file? File

    - by Richard
    Hi all, I am making a java program that has a collection of flash-card like objects. I store the objects in a jtree composed of defaultmutabletreenodes. Each node has a user object attached to it with has a few string/native data type parameters. However, i also want each of these objects to have an image (typical formats, jpg, png etc). I would like to be able to store all of this information, including the images and the tree data to the disk in a single file so the file can be transferred between users and the entire tree, including the images and parameters for each object, can be reconstructed. I had not approached a problem like this before so I was not sure what the best practices were. I found XLMEncoder (http://java.sun.com/j2se/1.4.2/docs/api/java/beans/XMLEncoder.html) to be a very effective way of storing my tree and the native data type information. However I couldn't figure out how to save the image data itself inside of the XML file, and I'm not sure it is possible since the data is binary (so restricted characters would be invalid). My next thought was to associate a hash string instead of an image within each user object, and then gzip together all of the images, with the hash strings as the names and the XMLencoded tree in the same compmressed file. That seemed really contrived though. Does anyone know a good approach for this type of issue? THanks! Thanks!

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  • Write to the second line of a PHP file

    - by Woz
    I have a php file that I want to add an include path to on the second line. I need to open the file and inset a line of code on line 2. I have tried a few techniques none of which are working but I think it has something to do with the text I am trying to write and possibly not escaping character correctly as I am not too familiar with file writing. So here is the file I want to write to: $file = $_SERVER['DOCUMENT_ROOT'].'/'.$domaindir.'/test.php'; Here is the piece of text I want to insert into the file: $dbfile = "include('".$_SERVER['DOCUMENT_ROOT']."/".$domaindir."/web_".$dbname.".inc.php');"; Then what I was doing was a string replace but all it did was bump the "session_start();" bit to a newline! Can anyone point me in the direction of a tutorial that might tell me how to insert this into the second line of my php file or indeed if anyone has any ideas? I can say for sure that the path to the PHP file is fully tested so i know its not that the file is not being open or written to. Any ideas would be much appreciated. Thanks in advance.

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