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  • Help me with this java program

    - by aser
    The question : Input file: customer’s account number, account balance at beginning of month, transaction type (withdrawal, deposit, interest), transaction amount Output: account number, beginning balance, ending balance, total interest paid, total amount deposited, number of deposits, total amount withdrawn, number of withdrawals package sentinel; import java.io.*; import java.util.*; public class Ex7 { /** * @param args the command line arguments */ public static void main(String[] args) throws FileNotFoundException { int AccountNum; double BeginningBalance; double TransactionAmount; int TransactionType; double AmountDeposited=0; int NumberOfDeposits=0; double InterestPaid=0.0; double AmountWithdrawn=0.0; int NumberOfWithdrawals=0; boolean found= false; Scanner inFile = new Scanner(new FileReader("Account.in")); PrintWriter outFile = new PrintWriter("Account.out"); AccountNum = inFile.nextInt(); BeginningBalance= inFile.nextDouble(); while (inFile.hasNext()) { TransactionAmount=inFile.nextDouble(); TransactionType=inFile.nextInt(); outFile.printf("Account Number: %d%n", AccountNum); outFile.printf("Beginning Balance: $%.2f %n",BeginningBalance); outFile.printf("Ending Balance: $%.2f %n",BeginningBalance); outFile.println(); switch (TransactionType) { case '1': // case 1 if we have a Deposite BeginningBalance = BeginningBalance + TransactionAmount; AmountDeposited = AmountDeposited + TransactionAmount; NumberOfDeposits++; outFile.printf("Amount Deposited: $%.2f %n",AmountDeposited); outFile.printf("Number of Deposits: %d%n",NumberOfDeposits); outFile.println(); break; case '2':// case 2 if we have an Interest BeginningBalance = BeginningBalance + TransactionAmount; InterestPaid = InterestPaid + TransactionAmount; outFile.printf("Interest Paid: $%.2f %n",InterestPaid); outFile.println(); break; case '3':// case 3 if we have a Withdraw BeginningBalance = BeginningBalance - TransactionAmount; AmountWithdrawn = AmountWithdrawn + TransactionAmount; NumberOfWithdrawals++; outFile.printf("Amount Withdrawn: $%.2f %n",AmountWithdrawn); outFile.printf("Number of Withdrawals: %d%n",NumberOfWithdrawals); outFile.println(); break; default: System.out.println("Invalid transaction Tybe: " + TransactionType + TransactionAmount); } } inFile.close(); outFile.close(); } } But is gives me this : Exception in thread "main" java.util.InputMismatchException at java.util.Scanner.throwFor(Scanner.java:840) at java.util.Scanner.next(Scanner.java:1461) at java.util.Scanner.nextInt(Scanner.java:2091) at java.util.Scanner.nextInt(Scanner.java:2050) at sentinel.Ex7.main(Ex7.java:36) Java Result: 1

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  • Copy constructor bug

    - by user168715
    I'm writing a simple nD-vector class, but am encountering a strange bug. I've stripped out the class to the bare minimum that still reproduces the bug: #include <iostream> using namespace std; template<unsigned int size> class nvector { public: nvector() {data_ = new double[size];} ~nvector() {delete[] data_;} template<unsigned int size2> nvector(const nvector<size2> &other) { data_ = new double[size]; int i=0; for(; i<size && i < size2; i++) data_[i] = other[i]; for(; i<size; i++) data_[i] = 0; } double &operator[](int i) {return data_[i];} const double&operator[](int i) const {return data_[i];} private: const nvector<size> &operator=(const nvector<size> &other); //Intentionally unimplemented for now double *data_; }; int main() { nvector<2> vector2d; vector2d[0] = 1; vector2d[1] = 2; nvector<3> vector3d(vector2d); for(int i=0; i<3; i++) cout << vector3d[i] << " "; cout << endl; //Prints 1 2 0 nvector<3> other3d(vector3d); for(int i=0; i<3; i++) cout << other3d[i] << " "; cout << endl; //Prints 1 2 0 } //Segfault??? On the surface this seems to work fine, and both tests print out the correct values. However, at the end of main the program crashes with a segfault, which I've traced to nvector's destructor. At first I thought the (incorrect) default assignment operator was somehow being called, which is why I added the (currently) unimplemented explicit assignment operator to rule this possibility out. So my copy constructor must be buggy, but I'm having one of those days where I'm staring at extremely simple code and just can't see it. Do you guys have any ideas?

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  • C++ include statement required if defining a map in a headerfile.

    - by Justin
    I was doing a project for computer course on programming concepts. This project was to be completed in C++ using Object Oriented designs we learned throughout the course. Anyhow, I have two files symboltable.h and symboltable.cpp. I want to use a map as the data structure so I define it in the private section of the header file. I #include <map> in the cpp file before I #include "symboltable.h". I get several errors from the compiler (MS VS 2008 Pro) when I go to debug/run the program the first of which is: Error 1 error C2146: syntax error : missing ';' before identifier 'table' c:\users\jsmith\documents\visual studio 2008\projects\project2\project2\symboltable.h 22 Project2 To fix this I had to #include <map> in the header file, which to me seems strange. Here are the relevant code files: // symboltable.h #include <map> class SymbolTable { public: SymbolTable() {} void insert(string variable, double value); double lookUp(string variable); void init(); // Added as part of the spec given in the conference area. private: map<string, double> table; // Our container for variables and their values. }; and // symboltable.cpp #include <map> #include <string> #include <iostream> using namespace std; #include "symboltable.h" void SymbolTable::insert(string variable, double value) { table[variable] = value; // Creates a new map entry, if variable name already exist it overwrites last value. } double SymbolTable::lookUp(string variable) { if(table.find(variable) == table.end()) // Search for the variable, find() returns a position, if thats the end then we didnt find it. throw exception("Error: Uninitialized variable"); else return table[variable]; } void SymbolTable::init() { table.clear(); // Clears the map, removes all elements. }

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  • how to avoid clutch billiard balls?

    - by Nait87
    I'm working on the simple behaviour of billiard balls in a collision with each other. All works normal, but there was a problem when facing a few easy balls is the effect of coupling balls and they're cool with each other. Tell me how to prevent this. bool MGBilliard::CollisingBall(CCPoint curr_point, CCPoint next_point) { float dx = next_point.x - (curr_point.x + dvdt.x); float dy = next_point.y - (curr_point.y - dvdt.y); float d = dx*dx+dy*dy; return d <= BALL_RADIUS * BALL_RADIUS; } double MGBilliard::angleCollisionBalls(Ball* current, Ball* next) { double na; double dx = fabs(next->location.x - current->location.x); double dy = fabs(next->location.y - current->location.y); na = atan(fabs(dy/dx)); if(atan(fabs(current->location.y/current->location.x)) < atan(fabs(next->location.y/next->location.x))) na = current->angle - na; else if(atan(fabs(current->location.y/current->location.x)) > atan(fabs(next->location.y/next->location.x))) na = current->angle + na; return na; } for(unsigned int i = 0;i<BALL_COUNT;++i) { if(vBalls[i]->speed > 0){ vBalls[i]->speed += vBalls[i]->acceleration; float dsdt = vBalls[i]->speed*dt; dvdt.x = dsdt*cos(vBalls[i]->angle); dvdt.y = dsdt*sin(vBalls[i]->angle); vBalls[i]->location.x += dvdt.x; vBalls[i]->location.y += dvdt.y; for(unsigned int j = 1; j < BALL_COUNT; ++j) { if(i == j) continue; if(CollisingBall(vBalls[i]->spriteBall->getPosition(),vBalls[j]->spriteBall->getPosition())) { vBalls[j]->speed = 600; double angle; angle = angleCollisionBalls(vBalls[i],vBalls[j]); vBalls[i]->angle = (float)-angle; vBalls[j]->angle = (float)angle; } } } }

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  • Optimizing collision engine bottleneck

    - by Vittorio Romeo
    Foreword: I'm aware that optimizing this bottleneck is not a necessity - the engine is already very fast. I, however, for fun and educational purposes, would love to find a way to make the engine even faster. I'm creating a general-purpose C++ 2D collision detection/response engine, with an emphasis on flexibility and speed. Here's a very basic diagram of its architecture: Basically, the main class is World, which owns (manages memory) of a ResolverBase*, a SpatialBase* and a vector<Body*>. SpatialBase is a pure virtual class which deals with broad-phase collision detection. ResolverBase is a pure virtual class which deals with collision resolution. The bodies communicate to the World::SpatialBase* with SpatialInfo objects, owned by the bodies themselves. There currenly is one spatial class: Grid : SpatialBase, which is a basic fixed 2D grid. It has it's own info class, GridInfo : SpatialInfo. Here's how its architecture looks: The Grid class owns a 2D array of Cell*. The Cell class contains two collection of (not owned) Body*: a vector<Body*> which contains all the bodies that are in the cell, and a map<int, vector<Body*>> which contains all the bodies that are in the cell, divided in groups. Bodies, in fact, have a groupId int that is used for collision groups. GridInfo objects also contain non-owning pointers to the cells the body is in. As I previously said, the engine is based on groups. Body::getGroups() returns a vector<int> of all the groups the body is part of. Body::getGroupsToCheck() returns a vector<int> of all the groups the body has to check collision against. Bodies can occupy more than a single cell. GridInfo always stores non-owning pointers to the occupied cells. After the bodies move, collision detection happens. We assume that all bodies are axis-aligned bounding boxes. How broad-phase collision detection works: Part 1: spatial info update For each Body body: Top-leftmost occupied cell and bottom-rightmost occupied cells are calculated. If they differ from the previous cells, body.gridInfo.cells is cleared, and filled with all the cells the body occupies (2D for loop from the top-leftmost cell to the bottom-rightmost cell). body is now guaranteed to know what cells it occupies. For a performance boost, it stores a pointer to every map<int, vector<Body*>> of every cell it occupies where the int is a group of body->getGroupsToCheck(). These pointers get stored in gridInfo->queries, which is simply a vector<map<int, vector<Body*>>*>. body is now guaranteed to have a pointer to every vector<Body*> of bodies of groups it needs to check collision against. These pointers are stored in gridInfo->queries. Part 2: actual collision checks For each Body body: body clears and fills a vector<Body*> bodiesToCheck, which contains all the bodies it needs to check against. Duplicates are avoided (bodies can belong to more than one group) by checking if bodiesToCheck already contains the body we're trying to add. const vector<Body*>& GridInfo::getBodiesToCheck() { bodiesToCheck.clear(); for(const auto& q : queries) for(const auto& b : *q) if(!contains(bodiesToCheck, b)) bodiesToCheck.push_back(b); return bodiesToCheck; } The GridInfo::getBodiesToCheck() method IS THE BOTTLENECK. The bodiesToCheck vector must be filled for every body update because bodies could have moved meanwhile. It also needs to prevent duplicate collision checks. The contains function simply checks if the vector already contains a body with std::find. Collision is checked and resolved for every body in bodiesToCheck. That's it. So, I've been trying to optimize this broad-phase collision detection for quite a while now. Every time I try something else than the current architecture/setup, something doesn't go as planned or I make assumption about the simulation that later are proven to be false. My question is: how can I optimize the broad-phase of my collision engine maintaining the grouped bodies approach? Is there some kind of magic C++ optimization that can be applied here? Can the architecture be redesigned in order to allow for more performance? Actual implementation: SSVSCollsion Body.h, Body.cpp World.h, World.cpp Grid.h, Grid.cpp Cell.h, Cell.cpp GridInfo.h, GridInfo.cpp

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  • New Whitepaper: Oracle E-Business Suite on Exadata

    - by Steven Chan
    Our Maximum Availability Architecture (MAA) team has quietly been amassing a formidable set of whitepapers about the Oracle Exadata Database Machine.  They're available here:MAA Best Practices - Exadata Database MachineIf you're one of the lucky ones with access to this hardware platform, you'll be pleased to hear that the MAA team has just published a new whitepaper with best practices for EBS environments:Oracle E-Business Suite on ExadataThis whitepaper covers the following topics:Getting to Exadata -- a high level overview of fresh installation on, and migration to, Exadata Database Machine with pointers to more detailed documentation High Availability and Disaster Recovery -- an overview of our MAA best practices with pointers to our detailed MAA Best Practices documentation Performance and Scalability -- best practices for running Oracle E-Business Suite on Exadata Database Machine based on our internal testing

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  • Linked List is now Patented?

    - by John Isaiah Carmona
    Linked list Ming-Jen Wang Patent number: 7028023 Filing date: Sep 26, 2002 Issue date: Apr 11, 2006 Application number: 10/260,471 A computerized list is provided with auxiliary pointers for traversing the list in different sequences. One or more auxiliary pointers enable a fast, sequential traversal of the list with a minimum of computational time. Such lists may be used in any application where lists may be reordered for various purposes. Does this mean that I need to acquire permission before using a linked list in my codes? What about the codes I write from my previous apps that uses a linked list? What about the framework that implements the linked list?

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  • How to fix OpenGL Co-ordinate System in SFML?

    - by Marc Alexander Reed
    My OpenGL setup is somehow configured to work like so: (-1, 1) (0, 1) (1, 1) (-1, 0) (0, 0) (1, 0) (-1, -1) (0, -1) (1, -1) How do I configure it so that it works like so: (0, 0) (SW/2, 0) (SW, 0) (0, SH/2) (SW/2, SH/2) (SW, SH/2) (0, SH) (SW/2, SH) (SW/2, SH) SW as Screen Width. SH as Screen Height. This solution would have to fix the problem of I can't translate significantly(1) on the Z axis. Depth doesn't seem to be working either. The Perspective code I'm using is that of my WORKING GLUT OpenGL code which has a cool 3d grid and camera system etc. But my OpenGL setup doesn't seem to work with SFML. Help me guys. :( Thanks in advance. :) #include <SFML/Window.hpp> #include <SFML/Graphics.hpp> #include <SFML/Audio.hpp> #include <SFML/Network.hpp> #include <SFML/OpenGL.hpp> #include "ResourcePath.hpp" //Mac-only #define _USE_MATH_DEFINES #include <cmath> double screen_width = 640.f; double screen_height = 480.f; int main (int argc, const char **argv) { sf::ContextSettings settings; settings.depthBits = 24; settings.stencilBits = 8; settings.antialiasingLevel = 2; sf::Window window(sf::VideoMode(screen_width, screen_height, 32), "SFML OpenGL", sf::Style::Close, settings); window.setActive(); glEnable(GL_DEPTH_TEST); glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glEnable(GL_NORMALIZE); glEnable(GL_COLOR_MATERIAL); glShadeModel(GL_SMOOTH); glViewport(0, 0, screen_width, screen_height); glMatrixMode(GL_PROJECTION); glLoadIdentity(); //glOrtho(0.0f, screen_width, screen_height, 0.0f, -100.0f, 100.0f); gluPerspective(45.0f, (double) screen_width / (double) screen_height , 0.f, 100.f); glClearColor(0.f, 0.f, 1.f, 0.f); //blue while (window.isOpen()) { sf::Event event; while (window.pollEvent(event)) { switch (event.type) { case sf::Event::Closed: window.close(); break; } switch (event.key.code) { case sf::Keyboard::Escape: window.close(); break; case 'W': break; case 'S': break; case 'A': break; case 'D': break; } } glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.f, 0.f, 0.f); glPushMatrix(); glBegin(GL_QUADS); glColor3f(1.f, 0.f, 0.f); glVertex3f(-1.f, 1.f, 0.f); glColor3f(0.f, 1.f, 0.f); glVertex3f(1.f, 1.f, 0.f); glColor3f(1.f, 0.f, 1.f); glVertex3f(1.f, -1.f, 0.f); glColor3f(0.f, 0.f, 1.f); glVertex3f(-1.f, -1.f, 0.f); glEnd(); glPopMatrix(); window.display(); } return EXIT_SUCCESS; }

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  • [Silverlight] How to watermark a WriteableBitmap with a text

    - by Benjamin Roux
    Hello, In my current project, I needed to watermark a WriteableBitmap with a text. As I couldn’t find anything I decided to create a small extension method to do so. public static class WriteableBitmapEx { /// <summary> /// Creates a watermark on the specified image /// </summary> /// <param name="input">The image to create the watermark from</param> /// <param name="watermark">The text to watermark</param> /// <param name="color">The color - default is White</param> /// <param name="fontSize">The font size - default is 50</param> /// <param name="opacity">The opacity - default is 0.25</param> /// <param name="hasDropShadow">Specifies if a drop shadow effect must be added - default is true</param> /// <returns>The watermarked image</returns> public static WriteableBitmap Watermark(this WriteableBitmap input, string watermark, Color color = default(Color), double fontSize = 50, double opacity = 0.25, bool hasDropShadow = true) { var watermarked = GetTextBitmap(watermark, fontSize, color == default(Color) ? Colors.White : color, opacity, hasDropShadow); var width = watermarked.PixelWidth; var height = watermarked.PixelHeight; var result = input.Clone(); var position = new Rect(input.PixelWidth - width - 20 /* right margin */, input.PixelHeight - height, width, height); result.Blit(position, watermarked, new Rect(0, 0, width, height)); return result; } /// <summary> /// Creates a WriteableBitmap from a text /// </summary> /// <param name="text"></param> /// <param name="fontSize"></param> /// <param name="color"></param> /// <param name="opacity"></param> /// <param name="hasDropShadow"></param> /// <returns></returns> private static WriteableBitmap GetTextBitmap(string text, double fontSize, Color color, double opacity, bool hasDropShadow) { TextBlock txt = new TextBlock(); txt.Text = text; txt.FontSize = fontSize; txt.Foreground = new SolidColorBrush(color); txt.Opacity = opacity; if (hasDropShadow) txt.Effect = new DropShadowEffect(); WriteableBitmap bitmap = new WriteableBitmap((int)txt.ActualWidth, (int)txt.ActualHeight); bitmap.Render(txt, null); bitmap.Invalidate(); return bitmap; } } For this code to run, you need the WritableBitmapEx library. As you can see, it’s quite simple. You just need to call the Watermark method and pass it the text you want to add in your image. You can also pass optional parameters like the color, the opacity, the fontsize or if you want a drop shadow effect. I could have specify other parameters like the position or the the font family but you can change the code if you need to. Here’s what it can give Hope this helps.

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  • Silverlight ProgressBar issues with Binding

    - by Chris Skardon
    The ProgressBar pretty much does what it says on the tin, displays progress, in a bar form (well, by default anyhow). It’s pretty simple to use: <ProgressBar Minimum="0" Maximum="100" Value="50"/> Gives you a progress bar with 50% of it filled: Easy! But of course, we’re wanting to use binding to change the value, again, pretty easy, have a ViewModel with a ‘Value’ in it, and bind: <ProgressBar Minimum="0" Maximum="100" Value="{Binding Value}"/> Spiffy, and whilst we’re at it, why not bind the Maximum value as well – after all, we can’t be sure of the size of the progress, and it’s a pain to have to work out the percentage (when the progress bar can do it for us): <ProgressBar Minimum="0" Maximum="MaximumValue" Value="{Binding Value}"/> Right, this will work absolutely fine. Or will it??? On the face of it, it looks good, and testing it shows no issues, until at one point we go from: Maximum = 100; Value = 90; to Maximum=60; Value=50; On the face of it not unreasonable. The problem is more obvious if we look at the states of the properties after each set (initially Maximum is set at 1, Value = 0): Code Maximum Value Value < Maximum Maximum = 100; 100 0 True Value = 90; 100 90 True Maximum = 60; 60 90 False Value = 50; 60 50 True Everything is good until the Value is less than the Maximum, at this point the Progress Bar breaks. That’s right, it no longer updates itself, it will always look 100% full. The simple solution – always ensuring you set Value before Maximum is fine unless you’re using a ProgressBar in a less controlled environment – where for example you’re setting a ‘container’ with both values at the same time. The example I have is in a DataTemplate, I have a DataTemplate for a BusyIndicator, (specifically the BusyContentTemplate). The binding works this way: <BusyIndicator BusyContent="{Binding BusyContent}" BusyContentTemplate="{Binding ProgressTemplate}"/> With the template as the ProgressBar defined above… I was setting my BusyContent like this: BusyContent = content; aaaaaand finally, ‘content’ is a class: public class ContentClass : INotifyPropertyChanged { //Obviously this is properly implemented… public double Maximum { get;set;} public double Value { get;set;} } Soooo… As I was replacing the BusyContent wholesale, the order of the binding being set was outside of my control, so – how to go about it? Basically? Fudge it. Modify the ContentClass to include a method: public void Update(double value, double max) { Value = value; Maximum = max; } and change where the setting is to be: BusyContent.Update(content.Value, content.Maximum); Thereby getting the order correct.. Obvious really. Meh :|

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  • What's wrong with this turn to face algorithm?

    - by Chan
    I implement a torpedo object that chases a rotating planet. Specifically, it will turn toward the planet each update. Initially my implement was: void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (to_target * speed); } which works perfectly for torpedo that is a solid sphere. Now my torpedo is actually a model, which has a forward vector, so using this method looks odd because it doesn't actually turn toward but jump toward. So I revised it a bit to get, double get_rotation_angle(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); double cosine_theta = u.dot(v); // domain of arccosine is [-1, 1] if (cosine_theta > 1) { cosine_theta = 1; } if (cosine_theta < -1) { cosine_theta = -1; } return math3d::to_degree(acos(cosine_theta)); } vector3<float> get_rotation_axis(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); // fix linear case if (u == v || u == -v) { v[0] += 0.05; v[1] += 0.0; v[2] += 0.05; v.normalize(); } vector3<float> axis = u.cross(v); return axis.normal(); } void turn_to_face() { vector3<float> to_target = (target - position); vector3<float> axis = get_rotation_axis(get_forward(), to_target); double angle = get_rotation_angle(get_forward(), to_target); double distance = math3d::distance(position, target); gl_matrix_mode(GL_MODELVIEW); gl_push_matrix(); { gl_load_identity(); gl_translate_f(position.get_x(), position.get_y(), position.get_z()); gl_rotate_f(angle, axis.get_x(), axis.get_y(), axis.get_z()); gl_get_float_v(GL_MODELVIEW_MATRIX, OM); } gl_pop_matrix(); move(); } void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (get_forward() * speed); } The logic is simple, I find the rotation axis by cross product, the angle to rotate by dot product, then turn toward the target position each update. Unfortunately, it looks extremely odds since the rotation happens too fast that it always turns back and forth. The forward vector for torpedo is from the ModelView matrix, the third column A: MODELVIEW MATRIX -------------------------------------------------- R U A T -------------------------------------------------- 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 -------------------------------------------------- Any suggestion or idea would be greatly appreciated.

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  • Using multiple indexes with buffer objects in OpenTK

    - by Rushyo
    I've got multiple buffers in OpenGL holding data on position, normals and texcoords. I also have an equal number of buffers holding distinct index data for each of those buffers. I quite like this format (indvidual indexes for each buffer) utilised by COLLADA since it strikes me as optimally efficient at accessing each buffer. I've set up pointers to the relevant data arrays using VertexPointer, NormalPointer, etc however I have no way to assign pointers to the index buffers since DrawElements appear to only look at one ElementArrayBuffer. Can I utilise multiple indices some way or will I be better off using a different technique which can support this? I'd prefer to keep the distinct indices if at all possible.

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  • What are some good resources for learning about file systems? [closed]

    - by Daniel
    I'd like to learn about file system design at a very detailed level. I'm currently in a graduate level operating systems course, and we're currently going over file systems. We mostly discuss papers and such, but our semester long project is to implement a log-structured file system using fuse and a virtual disk. Are there any good books that focus heavily on file system design and implementation? I have some conceptual clouding on things that seem very basic such as "when we say that an inode has pointers to blocks, do we mean anything besides the inode keeping track of block numbers? Is there any other format for 'disk pointers'?" I'm actually looking at file system design to start my career, so I'm probably going to try to implement a more traditional file system with fuse and our virtual disk format after this course is over.

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  • Memory Management/Embedded Management in C

    - by Sauron
    Im wondering if there is a set or a few good books/Tutorials/Etc.. that go into Memory Management/Allocation Specifically (or at least have a good dedicated section to it) when it comes to C. This is more for me learning Embedded and trying to keep Size down. I've read and Learned C fine, and the "standard" Learning books. However most of the books don't spend a huge amount of time (Understandably since C is pretty huge in general) going into the Finer details about whats going on Down Under. I saw a few on Amazon: http://www.amazon.com/C-Pointers-Dynamic-Memory-Management/dp/0471561525 http://www.amazon.com/Understanding-Pointers-C-Yashavant-Kanetkar/dp/8176563587/ref=pd_sim_b_1 (Not sure how relevant this would be) A specific Book for Embedded that has to do with this would be nice. But Code Samples or...Heck tutorials or anything about this topic would be helpful!

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  • Motivation and use of move constructors in C++

    - by Giorgio
    I recently have been reading about move constructors in C++ (see e.g. here) and I am trying to understand how they work and when I should use them. As far as I understand, a move constructor is used to alleviate the performance problems caused by copying large objects. The wikipedia page says: "A chronic performance problem with C++03 is the costly and unnecessary deep copies that can happen implicitly when objects are passed by value." I normally address such situations by passing the objects by reference, or by using smart pointers (e.g. boost::shared_ptr) to pass around the object (the smart pointers get copied instead of the object). What are the situations in which the above two techniques are not sufficient and using a move constructor is more convenient?

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  • Why is a linked list implementation considered linear?

    - by VeeKay
    My apologies for asking such a simple question. Instead of posting such basic question in SO, I felt that this is more apt a question here. I tried finding an answer for this but none of them are logically appealing or convincing to my understanding. Typically, computer memory is always linear. So is the term non linear used for a data structure in a logical sense? If so, to logically achieve non linearity in a linear computer memory, we use pointers. Right? In that case, if pointers are virtual implementations for achieving non linearity, Why would a data structure like linked list be considered linear if in reality the nodes are never physically adjacent?

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  • SQL 2014 does data the way developers want

    - by Rob Farley
    A post I’ve been meaning to write for a while, good that it fits with this month’s T-SQL Tuesday, hosted by Joey D’Antoni (@jdanton) Ever since I got into databases, I’ve been a fan. I studied Pure Maths at university (as well as Computer Science), and am very comfortable with Set Theory, which undergirds relational database concepts. But I’ve also spent a long time as a developer, and appreciate that that databases don’t exactly fit within the stuff I learned in my first year of uni, particularly the “Algorithms and Data Structures” subject, in which we studied concepts like linked lists. Writing in languages like C, we used pointers to quickly move around data, without a database in sight. Of course, if we had a power failure all this data was lost, as it was only persisted in RAM. Perhaps it’s why I’m a fan of database internals, of indexes, latches, execution plans, and so on – the developer in me wants to be reassured that we’re getting to the data as efficiently as possible. Back when SQL Server 2005 was approaching, one of the big stories was around CLR. Many were saying that T-SQL stored procedures would be a thing of the past because we now had CLR, and that obviously going to be much faster than using the abstracted T-SQL. Around the same time, we were seeing technologies like Linq-to-SQL produce poor T-SQL equivalents, and developers had had a gutful. They wanted to move away from T-SQL, having lost trust in it. I was never one of those developers, because I’d looked under the covers and knew that despite being abstracted, T-SQL was still a good way of getting to data. It worked for me, appealing to both my Set Theory side and my Developer side. CLR hasn’t exactly become the default option for stored procedures, although there are plenty of situations where it can be useful for getting faster performance. SQL Server 2014 is different though, through Hekaton – its In-Memory OLTP environment. When you create a table using Hekaton (that is, a memory-optimized one), the table you create is the kind of thing you’d’ve made as a developer. It creates code in C leveraging structs and pointers and arrays, which it compiles into fast code. When you insert data into it, it creates a new instance of a struct in memory, and adds it to an array. When the insert is committed, a small write is made to the transaction to make sure it’s durable, but none of the locking and latching behaviour that typifies transactional systems is needed. Indexes are done using hashes and using bw-trees (which avoid locking through the use of pointers) and by handling each updates as a delete-and-insert. This is data the way that developers do it when they’re coding for performance – the way I was taught at university before I learned about databases. Being done in C, it compiles to very quick code, and although these tables don’t support every feature that regular SQL tables do, this is still an excellent direction that has been taken. @rob_farley

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  • writing an autopilot for a 2d game with newtonian physics

    - by Jargo
    The subject says it all. I am making a 2d space game with newtonian physics and I need pointers on how to write an autopilot for it. The requirements are best explained by an example. There is a target object which has speed- and position-vectors and there a spaceship that is controlled by the autopilot. This spaceship also have speed, position and maximum acceleration. The autopilot needs to control the ship that it either collides with the target, Or intercepts the target so that the ship has matching speed and position with the target. Could someone give me some pointers how to achieve this behavior or perhaps even an ready implementation? I am sure someone has written something like this before and there is no point in reinventing the wheel.

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  • MSAcpi_ThermalZoneTemperature class not showing actual temperature

    - by jchoudhury
    i want to fetch CPU Performance data in real time including temperature. i used the following code to get CPU Temperature: try { ManagementObjectSearcher searcher = new ManagementObjectSearcher("root\\WMI", "SELECT * FROM MSAcpi_ThermalZoneTemperature"); foreach (ManagementObject queryObj in searcher.Get()) { double temp = Convert.ToDouble(queryObj["CurrentTemperature"].ToString()); double temp_critical = Convert.ToDouble(queryObj["CriticalTripPoint"].ToString()); double temp_cel = (temp/10 - 273.15); double temp_critical_cel = temp_critical / 10 - 273.15; lblCurrentTemp.Text = temp_cel.ToString(); lblCriticalTemp.Text = temp_critical_cel.ToString(); } } catch (ManagementException e) { MessageBox.Show("An error occurred while querying for WMI data: " + e.Message); } but this code shows the temperature that is not the correct temperature. It ususally shows 49.5-50.5 degrees centigrade. But I used "OpenHardwareMonitor" that report CPU temperature over 71 degree centigrade and changing fractions along with time fractions. is there anything I am missing in the code? I used the above code in timer_click event for every 500ms interval to refresh the temperature reading but it's always showing the same temperature from the beginning of execution. That implies if you run this application and if it shows 49 degree then after 1 hour session, it'll constantly show 49 degree. Where is the problem? please help. Thanks in advance.

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  • Wpf binding to a function

    - by carlopenid
    I've a created a simple scrollviewer (pnlDayScroller) and want to have a separate horizontal scrollbar (associated scroller) to do the horizontal scrolling. All works with the below code accept I need to bind the visibility of the associated scroller. I can't simply bind this to the visibility property of the horizontal template part of the scroll viewer as I've set this to be always hidden. The only way I can think to do this is to bind the visibility of the associated scroller to a function such that If associatedScroller.scrollableWidth > 0 then associatedScroller.visibility = visibility.visible else associatedScroller.visibility = visibility.collapsed end if Is this possible to do and if so how do I do it? Private Sub pnlDayScroller_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles pnlDayScroller.Loaded Dim binViewport, binMax, binMin, binSChange, binLChange As Binding Dim horizontalScrollBar As Primitives.ScrollBar = CType(pnlDayScroller.Template.FindName("PART_HorizontalScrollBar", pnlDayScroller), Primitives.ScrollBar) binViewport = New Binding("ViewportSize") binViewport.Mode = BindingMode.OneWay binViewport.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.ViewportSizeProperty, binViewport) binMax = New Binding("Maximum") binMax.Mode = BindingMode.OneWay binMax.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.MaximumProperty, binMax) binMin = New Binding("Minimum") binMin.Mode = BindingMode.OneWay binMin.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.MinimumProperty, binMin) binSChange = New Binding("SmallChange") binSChange.Mode = BindingMode.OneWay binSChange.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.SmallChangeProperty, binSChange) binLChange = New Binding("LargeChange") binLChange.Mode = BindingMode.OneWay binLChange.Source = horizontalScrollBar associatedScroller.SetBinding(Primitives.ScrollBar.LargeChangeProperty, binLChange) End Sub Private Sub associatedScroller_Scroll(ByVal sender As System.Object, ByVal e As System.Windows.RoutedPropertyChangedEventArgs(Of Double)) Handles associatedScroller.ValueChanged pnlDayScroller.ScrollToHorizontalOffset(e.NewValue) end sub FOLLOW UP (thanks to JustABill) : I've add this code into the pnlDayScroller sub above (I've discovered scrollableWidth is a property of scrollviewer not scrollbar, but the maximum property gives a result I can use instead) binVisibility = New Binding("Maximum") binVisibility.Mode = BindingMode.OneWay binVisibility.Source = horizontalScrollBar binVisibility.Converter = New ScrollableConverter associatedScroller.SetBinding(Primitives.ScrollBar.VisibilityProperty, binVisibility) and I've created this class Public Class ScrollableConverter Implements IValueConverter Public Function Convert(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.Convert Dim dblMaximum As Double If targetType IsNot GetType(Visibility) Then Throw New InvalidOperationException("The target must be a visibility") Else dblMaximum = CType(value, Double) Debug.WriteLine("Value of double is " & dblMaximum) If dblMaximum > 0 Then Return Visibility.Visible Else Return Visibility.Collapsed End If End If End Function Public Function ConvertBack(ByVal value As Object, ByVal targetType As Type, ByVal parameter As Object, ByVal culture As System.Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack Throw New NotSupportedException() End Function End Class And the problem is resolved.

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  • c# find nearest match to array of doubles

    - by Scott
    Given the code below, how do I compare a List of objects's values with a test value? I'm building a geolocation application. I'll be passing in longitude and latitude and would like to have the service answer back with the location closest to those values. I started down the path of converting to a string, and formatting the values down to two decimal places, but that seemed a bit too ghetto, and I'm looking for a more elegant solution. Any help would be great. Thanks, Scott public class Location : IEnumerable { public string label { get; set; } public double lat { get; set; } public double lon { get; set; } //Implement IEnumerable public IEnumerator GetEnumerator() { return (IEnumerator)this; } } [HandleError] public class HomeController : Controller { private List<Location> myList = new List<Location> { new Location { label="Atlanta Midtown", lon=33.657674, lat=-84.423130}, new Location { label="Atlanta Airport", lon=33.794151, lat=-84.387228}, new Location { label="Stamford, CT", lon=41.053758, lat=-73.530979}, ... } public static int Main(String[] args) { string inLat = "-80.987654"; double dblInLat = double.Parse(inLat); // here's where I would like to find the closest location to the inLat // once I figure out this, I'll implement the Longitude, and I'll be set }

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  • Linq-To-Objects group by

    - by Oskar Kjellin
    Hey, I'm building a software for timereporting I have a Dictionary<string, Dictionary<string, double>>. The key in the main dictionary is a users name and their value is a dictionary of . I have a function GetDepartment(string UserName) which returns a string with the users department. What I want is to crate a new dictionary, of the same type, that has the department as the main key and in the subdictionary a where hours is the total for that department. I have been trying to do this with linq but did not succeed. Would be very glad for some help here! EDIT: This code does exactly what I want. But I want it in LINQ Dictionary<string, Dictionary<string, double>> temphours = new Dictionary<string, Dictionary<string, double>>(); ; foreach (var user in hours) { string department = GetDepartment(user.Key); if (!temphours.ContainsKey(department)) { temphours.Add(department, new Dictionary<string, double>()); } foreach (var customerReport in user.Value) { if (!temphours[department].ContainsKey(customerReport.Key)) { temphours[department].Add(customerReport.Key, 0); } temphours[department][customerReport.Key] += customerReport.Value; } }

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  • the problem of "cvEigenVV"

    - by gg-anny
    Hi!When I compile the program,VC2005 always tell :"error C2198: 'cvEigenVV' : too few arguments for call". Part of the code below: void draw_oxfd_feature( IplImage* img, struct feature* feat, CvScalar color ) { double m[4] = { feat-a, feat-b, feat-b, feat-c }; double v[4] = { 0 }; double e[2] = { 0 }; CvMat M; CvMat V; CvMat E; double alpha, l1, l2; /* compute axes and orientation of ellipse surrounding affine region */ cvInitMatHeader( &M, 2, 2, CV_64FC1, m, CV_AUTOSTEP ); cvInitMatHeader( &V, 2, 2, CV_64FC1, v, CV_AUTOSTEP ); cvInitMatHeader( &E, 2, 1, CV_64FC1, e, CV_AUTOSTEP ); cvEigenVV( &M, &V, &E, DBL_EPSILON ); l1 = 1 / sqrt( e[1] ); l2 = 1 / sqrt( e[0] ); alpha = -atan2( v[1], v[0] ); alpha *= 180 / CV_PI; cvEllipse( img, cvPoint( feat-x, feat-y ), cvSize( l2, l1 ), alpha, 0, 360, CV_RGB(0,0,0), 3, 8, 0 ); cvEllipse( img, cvPoint( feat-x, feat-y ), cvSize( l2, l1 ), alpha, 0, 360, color, 1, 8, 0 ); cvLine( img, cvPoint( feat-x+2, feat-y ), cvPoint( feat-x-2, feat-y ), color, 1, 8, 0 ); cvLine( img, cvPoint( feat-x, feat-y+2 ), cvPoint( feat-x, feat-y-2 ), color, 1, 8, 0 ); // cvCircle(img,cvPoint(cvRound( feat-x ),cvRound( feat-y )),2, color, CV_FILLED, 8, 0); cvCircle(img,cvPoint( cvRound( feat-x ), cvRound( feat-y )), 2,CV_RGB(0,255,0), CV_FILLED, 8, 0 ); } How to solve the problem?Thank you!

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  • Efficient Multiple Linear Regression in C# / .Net

    - by mrnye
    Does anyone know of an efficient way to do multiple linear regression in C#, where the number of simultaneous equations may be in the 1000's (with 3 or 4 different inputs). After reading this article on multiple linear regression I tried implementing it with a matrix equation: Matrix y = new Matrix( new double[,]{{745}, {895}, {442}, {440}, {1598}}); Matrix x = new Matrix( new double[,]{{1, 36, 66}, {1, 37, 68}, {1, 47, 64}, {1, 32, 53}, {1, 1, 101}}); Matrix b = (x.Transpose() * x).Inverse() * x.Transpose() * y; for (int i = 0; i < b.Rows; i++) { Trace.WriteLine("INFO: " + b[i, 0].ToDouble()); } However it does not scale well to the scale of 1000's of equations due to the matrix inversion operation. I can call the R language and use that, however I was hoping there would be a pure .Net solution which will scale to these large sets. Any suggestions? EDIT #1: I have settled using R for the time being. By using statconn (downloaded here) I have found it to be both fast & relatively easy to use this method. I.e. here is a small code snippet, it really isn't much code at all to use the R statconn library (note: this is not all the code!). _StatConn.EvaluateNoReturn(string.Format("output <- lm({0})", equation)); object intercept = _StatConn.Evaluate("coefficients(output)['(Intercept)']"); parameters[0] = (double)intercept; for (int i = 0; i < xColCount; i++) { object parameter = _StatConn.Evaluate(string.Format("coefficients(output)['x{0}']", i)); parameters[i + 1] = (double)parameter; }

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