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• Efficient update of SQLite table with many records

  - by blackrim

  I am trying to use sqlite (sqlite3) for a project to store hundreds of thousands of records (would like sqlite so users of the program don't have to run a [my]sql server). I have to update hundreds of thousands of records sometimes to enter left right values (they are hierarchical), but have found the standard update table set left_value = 4, right_value = 5 where id = 12340; to be very slow. I have tried surrounding every thousand or so with begin; .... update... update table set left_value = 4, right_value = 5 where id = 12340; update... .... commit; but again, very slow. Odd, because when I populate it with a few hundred thousand (with inserts), it finishes in seconds. I am currently trying to test the speed in python (the slowness is at the command line and python) before I move it to the C++ implementation, but right now this is way to slow and I need to find a new solution unless I am doing something wrong. Thoughts? (would take open source alternative to SQLite that is portable as well)

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• C++ Loop - Need variable to accumulate sum

  - by user1780064

  I'm writing a program to ask the user to enter a value between 5 and 21 (inclusive). If the number entered is not in this range, it prints, "Please try again". If the number is within the range, I need to take that number, and print the sum of all the numbers from 1 to the value entered. So if the user entered "7", the sum would be "28". I successfully wrote the first loop, in the case of the number not being within the range, but cannot figure out how to run the second loop- whether to use a while, do-while, or for loop. Please advise. #include <iostream> int main () { int uservalue; int count; int sum; //Prompt user for input do { cout << "Enter a value from 5 to 21: "; cin >> uservalue; if (uservalue < 5 || uservalue > 21) cout << "Value out of range. Try again..." << endl; } while (uservalue < 5 || uservalue > 21); cout << endl; //Loop to accumulate sum for (count = 1, count < uservalue, count++;) { sum = uservalue + count; if (uservalue <= 5 || uservalue <= 21) cout << the sum is " << sum << endl; } return 0; }

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• Javascript Graph Layout Engine

  - by GJK

  I'm looking for a Javascript library/engine that can do graph layouts. (And when I say layouts, I mean logically position vertices nicely.) The graphs I'm working with are all m-ary trees. M is usually no more than 5 or 6, but it can be greater in some cases. I do have something that I use now, Graphviz's node program, and it works perfectly. The problem is, when running a web app, I have to send a request to the server every time I want a layout. Preferably, I would like something written in Javascript that can be quickly run on the client side. All it needs to do is provide layout information (relative positioning and whatnot). I don't need it to draw to a canvas or use SVG or anything, all I'm interested in is the layout. Library use like jQuery or RaphaelJS is fine by me. I'll work with it. I'm just looking for something to speed things along a little. Also, I'd consider writing my own if I could find a nice description of an algorithm to do the layouts. But I really don't want to spend too much time. I have something that works now, so getting it on the client side is just a bonus, not a necessity.

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• Creating new image in a loop using OpenCV

  - by user565415

  I am programing some image conversion code with OpenCV and I don't know how can I create image memory buffer to load image on every iteration. I have number of iteration (maxImNumber) and I have an input image. In every loop program must create image that is resized and modified input image. Here is some basic code (concept). for (int imageIndex = 0; imageIndex < maxImNumber; imageIndex++){ cvCopy(inputImage, images[imageIndex], 0); cvReleaseImage(&inputImage); images[imageIndex+1] = cvCreateImage(cvSize((image[imageIndex]->width)/2, image[imageIndex]->height), IPL_DEPTH_8U, 1); for (i=1; i < image[imageIndex]->height; i++) { index = 0; // for(j=0; j < image[imageIndex]->width ; j=j+2){ // doing some basic matematical operation on image content and store it to new image images[imageIndex+1][i][index] = (image[imageIndex][i][j] + image[imageIndex][i][j+2])/2; index++ } } inputImage = cvCreateImage(cvSize((image[imageIndex+1]->width), image[imageIndex]->height), IPL_DEPTH_8U, 1); cvCopy(images[imageIndex+1], inputImage, 0); } Can somebody, please, explain how can I create this image buffer (images[]) and allocate memory for it. Also how can I access any image in this buffer? Thank you very much in advance!

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• std::stringstream GCC Abnormal Behavior

  - by FlorianZ

  I have a very interesting problem with compiling a short little program on a Mac (GCC 4.2). The function below would only stream chars or strings into the stringstream, but not anything else (int, double, float, etc.) In fact, the fail flag is set if I attempt to convert for example an int into a string. However, removing the preprocessor flag: _GLIBCXX_DEBUG=1, which is set by default in XCode for the debug mode, will yield the desired results / correct behavior. Here is the simple function I am talking about. value is template variable of type T. Tested for int, double, float (not working), char and strings (working). template < typename T > const std::string Attribute<T>::getValueAsString() const { std::ostringstream stringValue; stringValue << value; return stringValue.str(); } Any ideas what I am doing wrong, why this doesn't work, or what the preprocessor flag does to make this not work anymore? Thanks!

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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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• How to catch exceptions from processes in C#

  - by kitofr

  I all... I have an acceptance runner program here that looks something like this: public Result Run(CommandParser parser) { var result = new Result(); var watch = new Stopwatch(); watch.Start(); try { _testConsole.Start(); parser.ForEachInput(input => { _testConsole.StandardInput.WriteLine(input); return _testConsole.TotalProcessorTime.TotalSeconds < parser.TimeLimit; }); if (TimeLimitExceeded(parser.TimeLimit)) { watch.Stop(); _testConsole.Kill(); ReportThatTestTimedOut(result); } else { result.Status = GetProgramOutput() == parser.Expected ? ResultStatus.Passed : ResultStatus.Failed; watch.Stop(); } } catch (Exception) { result.Status = ResultStatus.Exception; } result.Elapsed = watch.Elapsed; return result; } the _testConsole is an Process adapter that wraps a regular .net process into something more workable. I do however have a hard time to catch any exceptions from the started process (i.e. the catch statement is pointless here) I'm using something like: _process = new Process { StartInfo = { FileName = pathToProcess, UseShellExecute = false, CreateNoWindow = true, RedirectStandardInput = true, RedirectStandardOutput = true, RedirectStandardError = true, Arguments = arguments } }; to set up the process. Any ideas?

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• 2d Vector with wrong values

  - by Petris Rodrigo Fernandes

  I'm studing STL, then i thought "i'll make a 2d array!" but whatever... a coded this: vector< vector<int> > vetor; vetor.resize(10); vetor[0].resize(10); for(int i = 0; i < vetor.capacity(); i++){ for(int h = 0; h < vetor[0].capacity();h++){ vetor[i][h] = h; } } Until here, ok. But when i try to show the array value a use this: for(int i = 0; i < vetor.capacity(); i++){ cout << "LINE " << i << ": "; for(int h = 0; h < vetor[0].capacity();h++){ cout << vetor[i][h] <<" "; } cout << "\n"; } And the results are really wrong: LINE 0: 4 5 6 7 8 9 6 7 8 9 LINE 1: 0 1 2 3 0 1 2 3 0 1 LINE 2: 0 1 2 3 0 1 2 3 0 1 LINE 3: 0 1 2 3 0 1 2 3 0 1 LINE 4: 0 1 2 3 0 1 2 3 0 1 LINE 5: 0 1 2 3 0 1 2 3 0 1 LINE 6: 0 1 2 3 0 1 2 3 0 1 LINE 7: 0 1 2 3 0 1 2 3 0 1 LINE 8: 0 1 2 3 0 1 2 3 4 5 LINE 9: 0 1 2 3 4 5 6 7 8 9 What's happening with my program? it isn't printing the right values!

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• Reflection and Operator Overloads in C#

  - by TenshiNoK

  Here's the deal. I've got a program that will load a given assembly, parse through all Types and their Members and compile a TreeView (very similar to old MSDN site) and then build HTML pages for each node in the TreeView. It basically takes a given assembly and allows the user to create their own MSDN-like library for it for documentation purposes. Here's the problem I've run into: whenever an operator overload is encounted in a defined class, reflection returns that as a "MethodInfo" with the name set to something like "op_Assign" or "op_Equality". I want to be able to capture these and list them properly, but I can't find anything in the MethodInfo object that is returned to accurately identify that I'm looking at an operator. I definitely don't want to just capture everything that starts with "op_", since that will most certainly (at some point) will pick up a method it's not supposed to. I know that other methods and properties that are "special cases" like this one have the "IsSpecialName" property set, but appearantly that's not the case with operators. I've been scouring the 'net and wracking my brain to two days trying to figure this one out, so any help will be greatly appreciated.

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• Why initialize an object to empty

  - by ProgEnthu

  I am learning windows programming with the help of MSDN.Why would somebody initialize an object like the following? WNDCLASS wc = { }; Will this zero all the memory of the object? Whole source code is following: #ifndef UNICODE #define UNICODE #endif #include <windows.h> LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam); int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR pCmdLine, int nCmdShow) { // Register the window class. const wchar_t CLASS_NAME[] = L"Sample Window Class"; WNDCLASS wc = { }; wc.lpfnWndProc = WindowProc; wc.hInstance = hInstance; wc.lpszClassName = CLASS_NAME; RegisterClass(&wc); // Create the window. HWND hwnd = CreateWindowEx( 0, // Optional window styles. CLASS_NAME, // Window class L"Learn to Program Windows", // Window text WS_OVERLAPPEDWINDOW, // Window style // Size and position CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, // Parent window NULL, // Menu hInstance, // Instance handle NULL // Additional application data ); if (hwnd == NULL) { return 0; } ShowWindow(hwnd, nCmdShow); // Run the message loop. MSG msg = { }; while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return 0; } LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { switch (uMsg) { case WM_DESTROY: PostQuitMessage(0); return 0; case WM_PAINT: { PAINTSTRUCT ps; HDC hdc = BeginPaint(hwnd, &ps); FillRect(hdc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW+1)); EndPaint(hwnd, &ps); } return 0; } return DefWindowProc(hwnd, uMsg, wParam, lParam); }

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• Scientific Data processing(Graph comparison and interpretation)

  - by pinkynobrain

  Hi stackoverflow friends, I'm trying to write a program to automate one of my more boring and repetative work tasks. I have some programming experience but none with processing or interpreting large volumes of data so i am seeking your advice(both suggestions of techneques to try and also things to read to learn more about doing this stuff). I have a piece of equipment that monitors an experiment by taking repeated samples and displays the readings on its screen as a graph. The input of experiment can be altered and one of these changes should produce a change in a section of the graph which i currently identify by eye and is what im looking for in the experiment. I want to automate it so that a computer looks at a set of results and spots the experiment input that causes the change. I can already extract the results from the machine. Currently they results for a run are in the form of an integer array with the index being the sample number and the corresponding value being the measurement. The overall shape of the graph will be similar for each experiment run. The change im looking for will be roughly the same and will occur in approximatly the same place every time for the correct experiment input. Unfortunatly there are a few gotcha's that make this problem more difficult. There is some noise in the measuring process which mean there is some random variation in the measured values between different runs. Although the overall shape of the graph remains the same. The time the experiment takes varies slightly each run causing two effects. First, the a whole graph may be shifted slightly on the x axis relative to another runs graph. Second, individual features may appear slightly wider or narrower in different runs. In both these cases the variation isn't particularly large and you can assume that the only non random variation is caused by the correct input being found. Thank you for your time, Pinky

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• "Forced constness" in std::map<std::vector<int>,double> > ?

  - by Peter Jansson

  Consider this program: #include <map> #include <vector> typedef std::vector<int> IntVector; typedef std::map<IntVector,double> Map; void foo(Map& m,const IntVector& v) { Map::iterator i = m.find(v); i->first.push_back(10); }; int main() { Map m; IntVector v(10,10); foo(m,v); return 0; } Using g++ 4.4.0, I get his compilation error: test.cpp: In function 'void foo(Map&, const IntVector&)': test.cpp:8: error: passing 'const std::vector<int, std::allocator<int> >' as 'this' argument of 'void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = int, _Alloc = std::allocator<int>]' discards qualifiers I would expect this error if I was using Map::const_iterator inside foo but not using a non-const iterator. What am I missing, why do I get this error?

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• Checking if a file is a directory or just a file.

  - by Jookia

  I'm writing a program to check if something is a file or is a directory. Is there a better way to do it than this? #include <stdio.h> #include <sys/types.h> #include <dirent.h> #include <errno.h> int isFile(const char* name) { DIR* directory = opendir(name); if(directory != NULL) { closedir(directory); return 0; } if(errno == ENOTDIR) { return 1; } return -1; } int main(void) { const char* file = "./testFile"; const char* directory = "./"; printf("Is %s a file? %s.\n", file, ((isFile(file) == 1) ? "Yes" : "No")); printf("Is %s a directory? %s.\n", directory, ((isFile(directory) == 0) ? "Yes" : "No")); return 0; }

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• Configure Django project in a subdirectory using mod_python. Admin not working.

  - by David

  HI guys. I was trying to configure my django project in a subdirectory of the root, but didn't get things working.(LOcally it works perfect). I followed the django official django documentarion to deploy a project with mod_python. The real problem is that I am getting "Page not found" errors, whenever I try to go to the admin or any view of my apps. Here is my python.conf file located in /etc/httpd/conf.d/ in Fedora 7 LoadModule python_module modules/mod_python.so SetHandler python-program PythonHandler django.core.handlers.modpython SetEnv DJANGO_SETTINGS_MODULE mysite.settings PythonOption django.root /mysite PythonDebug On PythonPath "['/var/www/vhosts/mysite.com/httpdocs','/var/www/vhosts/mysite.com/httpdocs/mysite'] + sys.path" I know /var/www/ is not the best place to put my django project, but I just want to send a demo of my work in progress to my customer, later I will change the location. For example. If I go to www.domain.com/mysite/ I get the index view I configured in mysite.urls. But I cannot access to my app.urls (www.domain.com/mysite/app/) and any of the admin.urls.(www.domain.com/mysite/admin/) Here is mysite.urls: urlpatterns = patterns('', url(r'^admin/password_reset/$', 'django.contrib.auth.views.password_reset', name='password_reset'), (r'^password_reset/done/$', 'django.contrib.auth.views.password_reset_done'), (r'^reset/(?P<uidb36>[0-9A-Za-z]+)-(?P<token>.+)/$', 'django.contrib.auth.views.password_reset_confirm'), (r'^reset/done/$', 'django.contrib.auth.views.password_reset_complete'), (r'^$', 'app.views.index'), (r'^admin/', include(admin.site.urls)), (r'^app/', include('mysite.app.urls')), (r'^photologue/', include('photologue.urls')), ) I also tried changing admin.site.urls with ''django.contrib.admin.urls' , but it didn't worked. I googled a lot to solve this problem and read how other developers configure their django project, but didn't find too much information to deploy django in a subdirectory. I have the admin enabled in INSTALLED_APPS and the settings.py is ok. Please if you have any guide or telling me what I am doing wrong it will be much appreciated. THanks.

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• Preprocessor #define vs. function pointer - best practice?

  - by Dustin

  I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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• threading and getting COM port of attached phone

  - by I__

  i have the following code: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } public class ThreadWork { public static void DoWork() { } } private void Form1_Load(object sender, EventArgs e) { ThreadStart myThreadDelegate = new ThreadStart(ThreadWork.DoWork); Thread myThread = new Thread(myThreadDelegate); myThread.Start(); // Begin communications serialPort1.Open(); serialPort1.Write("AT+CMGF=1\r\n"); //Thread.Sleep(500); serialPort1.Write("AT+CNMI=2,2\r\n"); //Thread.Sleep(500); serialPort1.Write("AT+CSCA=\"+4790002100\"\r\n"); //Thread.Sleep(500); } private void serialPort1_DataReceived_1(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { string response = serialPort1.ReadLine(); this.BeginInvoke(new MethodInvoker(() => textBox1.AppendText(response + "\r\n"))); } } } what i am trying to do is send AT COMMANDS to my phone which is attached to the computer through USB how do i know how to configure the properties of the serial port? (like which COM is the phone on [it's attached through USB], what about baudrate and databits?) when i run the program nothing really happens, i would like to send AT COMMANDS to my phone and the textbox is there to receive the response from my phone this is my first time using threads. am i using them correctly? what is the purpose of it in the current example? is it to just have a delay between send a response? what am i doing wrong?

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• Where are possible locations of queueing/buffering delays in Linux multicast?

  - by Matt

  We make heavy use of multicasting messaging across many Linux servers on a LAN. We are seeing a lot of delays. We basically send an enormous number of small packages. We are more concerned with latency than throughput. The machines are all modern, multi-core (at least four, generally eight, 16 if you count hyperthreading) machines, always with a load of 2.0 or less, usually with a load less than 1.0. The networking hardware is also under 50% capacity. The delays we see look like queueing delays: the packets will quickly start increasing in latency, until it looks like they jam up, then return back to normal. The messaging structure is basically this: in the "sending thread", pull messages from a queue, add a timestamp (using gettimeofday()), then call send(). The receiving program receives the message, timestamps the receive time, and pushes it in a queue. In a separate thread, the queue is processed, analyzing the difference between sending and receiving timestamps. (Note that our internal queues are not part of the problem, since the timestamps are added outside of our internal queuing.) We don't really know where to start looking for an answer to this problem. We're not familiar with Linux internals. Our suspicion is that the kernel is queuing or buffering the packets, either on the send side or the receive side (or both). But we don't know how to track this down and trace it. For what it's worth, we're using CentOS 4.x (RHEL kernel 2.6.9).

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• GWT + JDO + ArrayList

  - by dvieira

  Hi, I'm getting a Null ArrayList in a program i'm developing. For testing purposes I created this really small example that still has the same problem. I already tried diferent Primary Keys, but the problem persists. Any ideas or suggestions? 1-Employee class @PersistenceCapable(identityType = IdentityType.APPLICATION) public class Employee { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true") private String key; @Persistent private ArrayList<String> nicks; public Employee(ArrayList<String> nicks) { this.setNicks(nicks); } public String getKey() { return key; } public void setNicks(ArrayList<String> nicks) { this.nicks = nicks; } public ArrayList<String> getNicks() { return nicks; } } 2-EmployeeService public class BookServiceImpl extends RemoteServiceServlet implements EmployeeService { public void addEmployee(){ ArrayList<String> nicks = new ArrayList<String>(); nicks.add("name1"); nicks.add("name2"); Employee employee = new Employee(nicks); PersistenceManager pm = PMF.get().getPersistenceManager(); try { pm.makePersistent(employee); } finally { pm.close(); } } /** * @return * @throws NotLoggedInException * @gwt.typeArgs <Employee> */ public Collection<Employee> getEmployees() { PersistenceManager pm = getPersistenceManager(); try { Query q = pm.newQuery("SELECT FROM " + Employee.class.getName()); Collection<Employee> list = pm.detachCopyAll((Collection<Employee>)q.execute()); return list; } finally { pm.close(); } } }

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• Why is short project lifetime and other situation-specific reasons used to excuse crappy code? [clos

  - by sharptooth

  Every now and then (including on SO) people say things implying that "if the project is short lived you can leave obvious defects there" or "that memory leak only accounts for 100 bytes per whole program lifetime and could be left". Now in my practice I always reuse company-owned code to the greatest extent I can. Like if I need something and I can find it in the company codebase I take it from there and reuse or adapt. This means that any crappy code will be reused as well and I might notice or not notice defects therein. So the defect in some "test we only need for a month" can slip into a proram we ship to customers. And a leak that "only accounted for 100 bytes per lifetime" now could account for 100 bytes 10 times per second in a server application intended to run for months. That's why I don't understand why excuses like that are offered. Is our compamy the only one having a source control? Or are we the only company that requires writing human-readable code? Could anyone shed a light on why people seriously offer such excuses?

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• "java.lang.OutOfMemoryError: Java heap space" in image and array storage

  - by totalconscience

  I am currently working on an image processing demonstration in java (Applet). I am running into the problem where my arrays are too large and I am getting the "java.lang.OutOfMemoryError: Java heap space" error. The algorithm I run creates an NxD float array where: N is the number of pixel in the image and D is the coordinates of each pixel plus the colorspace components of each pixel (usually 1 for grayscale or 3 for RGB). For each iteration of the algorithm it creates one of these NxD float arrays and stores it for later use in a vector, so that the user of the applet may look at the individual steps. My client wants the program to be able to load a 500x500 RGB image and run as the upper bound. There are about 12 to 20 iterations per run so that means I need to be able to store a 12x500x500x5 float in some fashion. Is there a way to process all of this data and, if possible, how? Example of the issue: I am loading a 512 by 512 Grayscale image and even before the first iteration completes I run out of heap space. The line it points me to is: Y.add(new float[N][D]) where Y is a Vector and N and D are described as above. This is the second instance of the code using that line.

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• c++ STL vector is not acccepting the copy constructor

  - by prabhakaran

  I wrote a code ( c++,visual studio 2010) which is having a vector, even I though copy const is declared, but is still showing that copy const is not declared Here the code #include<iostream> #include<vector> using namespace std; class A { public: A(){cout << "Default A is acting" << endl ;} A(A &a){cout << "Copy Constructor of A is acting" << endl ;} }; int main() { A a; A b=a; vector<A> nothing; nothing.push_back(a); int n; cin >> n; } The error I got is Error 1 error C2558: class 'A' : no copy constructor available or copy constructor is declared 'explicit' c:\program files\microsoft visual studio 10.0\vc\include\xmemory 48 1 delete Anybody please help me

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• Connecting grouped dots/points on a scatter plot based on distance

  - by ToNoY

  I have 2 sets of depth point measurements, for example: > a depth value 1 2 2 2 4 3 3 6 4 4 8 5 5 16 40 6 18 45 7 20 58 > b depth value 1 10 10 2 12 20 3 14 35 I want to show both groups in one figure plotted with depth and with different symbols as you can see here plot(a$value, a$depth, type='b', col='green', pch=15) points(b$value, b$depth, type='b', col='red', pch=14) The plot seems okay, but the annoying part is that the green symbols are all connected (though I want connected lines also). I want connection only when one group has a continued data points at 2 m interval i.e. the symbols should be connected with a line from 2 to 8 m (green) and then group B symbols should be connected from 10-14 m (red) and again group A symbols should be connected (green), which means I do NOT want to see the connection between 8 m sample with the 16 m for group A. An easy solution may be dividing the group A into two parts (say, A-shallow and A-deep) and then plotting A-shallow, B, and A-deep separately. But this is completely impractical because I have thousands of data points with hundreds of groups i.e. I have to produce many depth profiles. Therefore, there has to be a way to program so that dots are NOT connected beyond a prescribed frequency/depth interval (e.g. 2 m in this case) for a particular group of samples. Any idea?

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• Why strings behave like ValueType

  - by AJP

  I was perplexed after executing this piece of code, where strings seems to behave as if they are value types. I am wondering whether the assignment operator is operating on values like equality operator for strings. Here is the piece of code I did to test this behavior. using System; namespace RefTypeDelimma { class Program { static void Main(string[] args) { string a1, a2; a1 = "ABC"; a2 = a1; //This should assign a1 reference to a2 a2 = "XYZ"; //I expect this should change the a1 value to "XYZ" Console.WriteLine("a1:" + a1 + ", a2:" + a2);//Outputs a1:ABC, a2:XYZ //Expected: a1:XYZ, a2:XYZ (as string being a ref type) Proc(a2); //Altering values of ref types inside a procedure //should reflect in the variable thats being passed into Console.WriteLine("a1: " + a1 + ", a2: " + a2); //Outputs a1:ABC, a2:XYZ //Expected: a1:NEW_VAL, a2:NEW_VAL (as string being a ref type) } static void Proc(string Val) { Val = "NEW_VAL"; } } } In the above code if I use a custom classes instead of strings, I am getting the expected behavior. I doubt is this something to do with the string immutability? welcoming expert views on this.

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• How do you convert bytes of bitmap into x, y location of pixels?

  - by Jon

  I have a win32 program that creates a bitmap screenshot. I am trying to figure out the x and y coordinates of the bmBits. Below is the code I have so far: UINT32 nScreenX = GetSystemMetrics(SM_CXSCREEN); UINT32 nScreenY = GetSystemMetrics(SM_CYSCREEN); HDC hdc = GetDC(NULL); HDC hdcScreen = CreateCompatibleDC(hdc); HBITMAP hbmpScreen = CreateDIBSection( hdcDesk, ( BITMAPINFO* )&bitmapInfo.bmiHeader,DIB_RGB_COLORS, &bitmapDataPtr, NULL, 0 ); SelectObject(hdcScreen, hbmpScreen); BitBlt(hdcScreen, 0, 0, nScreenX , nScreenY , hdc, 0, 0, SRCCOPY); ReleaseDC(NULL, hdc); BITMAP bmpScreen; GetObject(hbmpScreen, sizeof(bmpScreen), &bmpScreen); DWORD *pScreenPixels = (DWORD*)bmpScreen.bmBits, UINT32 x = 0; UINT32 y = 0; UINT32 nCntPixels = nScreenX * nScreenY; for(int n = 0; n < nCntPixels; n++) { x = n % nScreenX; y = n / nScreenX; //do stuff with the x and y vals } The code seem correct to me but, when I use this code the x and y values appear to be off. Where does the first pixel of bmBits start? When x and y are both 0. Is that the top left, bottom left, bottom right or top right? Thanks.

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• Reading lines of data from text files using java

  - by razshan

  I have a text file with x amount of lines. each line holds a integer number. When the user clicks a button, an action is performed via actionlistener where it should list all the values as displayed on the text file. However, right now I have linenum set to 10 implying I already told the code that just work with 10 lines of the text file. So, if my text file has only 3 rows/lines of data...it will list those lines and for rest of the other 7 lines, it will spit out "null". I recall there is a way to use ellipsis to let the program know that you don't know the exact value but at the end it calculates it based on the given information. Where my given information will the number of lines with numbers(data). Below is part of the code. private class thehandler implements ActionListener{ public void actionPerformed(ActionEvent event){ BufferedReader inputFile=null; try { FileReader freader =new FileReader("Data.txt"); inputFile = new BufferedReader(freader); String MAP = ""; int linenum=10; while(linenum > 0) { linenum=linenum-1; MAP = inputFile.readLine();//read the next line until the specfic line is found System.out.println(MAP); } } catch( Exception y ) { y.printStackTrace(); } }}

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