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  • How do virtual destructors work?

    - by Prabhu
    Few hours back I was fiddling with a Memory Leak issue and it turned out that I really got some basic stuff about virtual destructors wrong! Let me put explain my class design. class Base { virtual push_elements() {} }; class Derived:public Base { vector<int> x; public: void push_elements(){ for(int i=0;i <5;i++) x.push_back(i); } }; void main() { Base* b = new Derived(); b->push_elements(); delete b; } The bounds checker tool reported a memory leak in the derived class vector. And I figured out that the destructor is not virtual and the derived class destructor is not called. And it surprisingly got fixed when I made the destructor virtual. Isn't the vector deallocated automatically even if the derived class destructor is not called? Is that a quirk in BoundsChecker tool or is my understanding of virtual destructor wrong?

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  • Virtual destructor - How does it work?

    - by Prabhu
    Hello All, Few hours back I was fiddling with a Memory Leak issue and it turned out that I really got some basic stuff about virtual destructor wrong!! Let me put explain my class design. class Base { virtual push_elements()<br>{}<br> }; class Derived:public Base { vector<int> x; public: void push_elements(){ for(int i=0;i <5;i++) x.push_back(i); } }; void main() { Base* b = new Derived(); b->push_elements(); delete b; } The bounds checker tool reported a memory leak in the derived class vector. And I figured out that the destructor is not virtual and the derived class destructor is not called.And it surprisingly got fixed when I made the destructor virtual. But my question is "isn't the vector deallocated automatically even if the derived class destructor is not called"? Is that a quirk in BoundsChecker tool or is my understanding of virtual destructor is wrong:)

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  • Execute a function to affect different template class instances

    - by Samer Afach
    I have a complicated problem, and I need help. I have a base case, class ParamBase { string paramValue; //... } and a bunch of class templates with different template parameters. template <typename T> class Param : public ParamBase { T value; //... } Now, each instance of Param has different template parameter, double, int, string... etc. To make it easier, I have a vector to their base class pointers that contains all the instances that have been created: vector<ParamBase*> allParamsObjects; The question is: How can I run a single function (global or member or anything, your choice), that converts all of those different instances' strings paramValue with different templates arguments and save the conversion result to the appropriate type in Param::value. This has to be run over all objects that are saved in the vector allParamsObjects. So if the template argument of the first Param is double, paramValue has to be converted to double and saved in value; and if the second Param's argument is int, then the paramValue of the second has to be converted to int and saved in value... etc. I feel it's almost impossible... Any help would be highly appreciated :-)

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  • Efficiency of manually written loops vs operator overloads (C++)

    - by Sagekilla
    Hi all, in the program I'm working on I have 3-element arrays, which I use as mathematical vectors for all intents and purposes. Through the course of writing my code, I was tempted to just roll my own Vector class with simple +, -, *, /, etc overloads so I can simplify statements like: for (int i = 0; i < 3; i++) r[i] = r1[i] - r2[i]; // becomes: r = r1 - r2; Which should be more or less identical in generated code. But when it comes to more complicated things, could this really impact my performance heavily? One example that I have in my code is this: Manually written version: for (int j = 0; j < 3; j++) { p.vel[j] = p.oldVel[j] + (p.oldAcc[j] + p.acc[j]) * dt2 + (p.oldJerk[j] - p.jerk[j]) * dt12; p.pos[j] = p.oldPos[j] + (p.oldVel[j] + p.vel[j]) * dt2 + (p.oldAcc[j] - p.acc[j]) * dt12; } Using a Vector class with operator overloads: p.vel = p.oldVel + (p.oldAcc + p.acc) * dt2 + (p.oldJerk - p.jerk) * dt12; p.pos = p.oldPos + (p.oldVel + p.vel) * dt2 + (p.oldAcc - p.acc) * dt12; I am compiling my code for maximum possible speed, as it's extremely important that this code runs quickly and calculates accurately. So will me relying on my Vector's for these sorts of things really affect me? For those curious, this is part of some numerical integration code which is not trivial to run in my program. Any insight would be appreciated, as would any idioms or tricks I'm unaware of.

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  • Building static (but complicated) lookup table using templates.

    - by MarkD
    I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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  • Creating an object in the loop

    - by Jacob
    std::vector<double> C(4); for(int i = 0; i < 1000;++i) for(int j = 0; j < 2000; ++j) { C[0] = 1.0; C[1] = 1.0; C[2] = 1.0; C[3] = 1.0; } is much faster than for(int i = 0; i < 1000;++i) for(int j = 0; j < 2000; ++j) { std::vector<double> C(4); C[0] = 1.0; C[1] = 1.0; C[2] = 1.0; C[3] = 1.0; } I realize this happens because std::vector is repeatedly being created and instantiated in the loop, but I was under the impression this would be optimized away. Is it completely wrong to keep variables local in a loop whenever possible? I was under the (perhaps false) impression that this would provide optimization opportunities for the compiler. EDIT: I use VC++2005 (release mode) with full optimization (/Ox)

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  • Link compatibility between C++ and D

    - by Caspin
    D easily interfaces with C. D just as easily interfaces with C++, but (and it's a big but) the C++ needs to be extremely trivial. The code cannot use: namespaces templates multiple inheritance mix virtual with non-virtual methods more? I completely understand the inheritance restriction. The rest however, feel like artificial limitations. Now I don't want to be able to use std::vector<T> directly, but I would really like to be able to link with std::vector<int> as an externed template. The C++ interfacing page has this particularly depressing comment. D templates have little in common with C++ templates, and it is very unlikely that any sort of reasonable method could be found to express C++ templates in a link-compatible way with D. This means that the C++ STL, and C++ Boost, likely will never be accessible from D. Admittedly I'll probably never need std::vector while coding in D, but I'd love to use QT or boost. So what's the deal. Why is it so hard to express non-trivial C++ classes in D? Would it not be worth it to add some special annotations or something to express at least namespaces?

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  • C++ trouble with pointers to objects

    - by Zibd
    I have a class with a vector of pointers to objects. I've introduced some elements on this vector, and on my main file I've managed to print them and add others with no problems. Now I'm trying to remove an element from that vector and check to see if it's not NULL but it is not working. I'm filling it with on class Test: Other *a = new Other(1,1); Other *b = new Other(2,2); Other *c = new Other(3,3); v->push_back(a); v->push_back(b); v->push_back(c); And on my main file I have: Test t; (...) Other *pointer = t.vect->at(0); delete t.vect->at(0); t.vect->erase(t.vect->begin()); if (pointer == NULL) { cout << "Nothing here.."; } // Never enters here..

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  • Creating a new object destroys an older object with different name in C++

    - by Mikael
    First question here! So, I am having some problems with pointers in Visual C++ 2008. I'm writing a program which will control six cameras and do some processing on them so to clean things up I have created a Camera Manager class. This class handles all operations which will be carried out on all the cameras. Below this is a Camera class which interacts with each individual camera driver and does some basic image processing. Now, the idea is that when the manager is initialised it creates two cameras and adds them to a vector so that I can access them later. The catch here is that when I create the second camera (camera2) the first camera's destructor is called for some reason, which then disconnects the camera. Normally I'd assume that the problem is somewhere in the Camera class, but in this case everything works perfectly as long as I don't create the camera2 object. What's gone wrong? CameraManager.h: #include "stdafx.h" #include <vector> #include "Camera.h" class CameraManager{ std::vector<Camera> cameras; public: CameraManager(); ~CameraManager(); void CaptureAll(); void ShowAll(); }; CameraManager.cpp: #include "stdafx.h" #include "CameraManager.h" CameraManager::CameraManager() { printf("Camera Manager: Initializing\n"); [...] Camera *camera1 = new Camera(NodeInfo,1, -44,0,0); cameras.push_back(*camera1); // Adding the following two lines causes camera1's destructor to be called. Why? Camera *camera2 = new Camera(NodeInfo,0, 44,0,0); cameras.push_back(*camera2); printf("Camera Manager: Ready\n"); }

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  • Getting functions of inherited functions to be called

    - by wrongusername
    Let's say I have a base class Animal from which a class Cow inherits, and a Barn class containing an Animal vector, and let's say the Animal class has a virtual function scream(), which Cow overrides. With the following code: Animal.h #ifndef _ANIMAL_H #define _ANIMAL_H #include <iostream> using namespace std; class Animal { public: Animal() {}; virtual void scream() {cout << "aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh..." << endl;} }; #endif /* _ANIMAL_H */ Cow.h #ifndef _COW_H #define _COW_H #include "Animal.h" class Cow: public Animal { public: Cow() {} void scream() {cout << "MOOooooOOOOOOOO!!!" << endl;} }; #endif /* _COW_H */ Barn.h #ifndef _BARN_H #define _BARN_H #include "Animal.h" #include <vector> class Barn { std::vector<Animal> animals; public: Barn() {} void insertAnimal(Animal animal) {animals.push_back(animal);} void tortureAnimals() { for(int a = 0; a < animals.size(); a++) animals[a].scream(); } }; #endif /* _BARN_H */ and finally main.cpp #include <stdlib.h> #include "Barn.h" #include "Cow.h" #include "Chicken.h" /* * */ int main(int argc, char** argv) { Barn barn; barn.insertAnimal(Cow()); barn.tortureAnimals(); return (EXIT_SUCCESS); } I get this output: aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh... How should I code this to get MOOooooOOOOOOOO!!! (and whatever other classes inheriting Animal wants scream() to be) instead?

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  • "end()" iterator for back inserters?

    - by Thanatos
    For iterators such as those returned from std::back_inserter(), is there something that can be used as an "end" iterator? This seems a little nonsensical at first, but I have an API which is: template<typename InputIterator, typename OutputIterator> void foo( InputIterator input_begin, InputIterator input_end, OutputIterator output_begin, OutputIterator output_end ); foo performs some operation on the input sequence, generating an output sequence. (Who's length is known to foo but may or may not be equal to the input sequence's length.) The taking of the output_end parameter is the odd part: std::copy doesn't do this, for example, and assumes you're not going to pass it garbage. foo does it to provide range checking: if you pass a range too small, it throws an exception, in the name of defensive programming. (Instead of potentially overwriting random bits in memory.) Now, say I want to pass foo a back inserter, specifically one from a std::vector which has no limit outside of memory constraints. I still need a "end" iterator - in this case, something that will never compare equal. (Or, if I had a std::vector but with a restriction on length, perhaps it might sometimes compare equal?) How do I go about doing this? I do have the ability to change foo's API - is it better to not check the range, and instead provide an alternate means to get the required output range? (Which would be needed anyways for raw arrays, but not required for back inserters into a vector.) This would seem less robust, but I'm struggling to make the "robust" (above) work.

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  • SSE (SIMD extensions) support in gcc

    - by goldenmean
    Hi, I see a code as below: include "stdio.h" #define VECTOR_SIZE 4 typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE))); // vector of four single floats typedef union f4vector { v4sf v; float f[VECTOR_SIZE]; } f4vector; void print_vector (f4vector *v) { printf("%f,%f,%f,%f\n", v->f[0], v->f[1], v->f[2], v->f[3]); } int main() { union f4vector a, b, c; a.v = (v4sf){1.2, 2.3, 3.4, 4.5}; b.v = (v4sf){5., 6., 7., 8.}; c.v = a.v + b.v; print_vector(&a); print_vector(&b); print_vector(&c); } This code builds fine and works expectedly using gcc (it's inbuild SSE / MMX extensions and vector data types. this code is doing a SIMD vector addition using 4 single floats. I want to understand in detail what does each keyword/function call on this typedef line means and does: typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE))); What is the vector_size() function return; What is the __attribute__ keyword for Here is the float data type being type defined to vfsf type? I understand the rest part. thanks, -AD

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  • Java constructor using generic types

    - by Beer Me
    I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method breweryMethod() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // breweryMethod() is an instance method // of Brewery, of which <T> is a subclass (right?) c.breweryMethod(); // "The method breweryMethod() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void brewerySubClassMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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  • Matrix multiplication using pairs

    - by sc_ray
    Hi, I am looking into alternate ways to do a Matrix Multiplication. Instead of storing my matrix as a two-dimensional array, I am using a vector such as vector<pair<pair<int,int >,int > > to store my matrix. The pair within my pair (pair) stores my indices (i,j) and the other int stores the value for the given (i,j) pair. I thought I might have some luck implementing my sparse array this way. The problem is when I try to multiply this matrix with itself. If this was a 2-d array implementation, I would have multiplied the matrix as follows: for(i=0; i<row1; i++) { for(j=0; j<col1; j++) { C[i][j] = 0; for(k=0; k<col2; k++) C[i][j] += A[i][j] * A[j][k]; } } Can somebody point out a way to achieve the same result using my vector of 'pair of pairs'? Thanks

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  • Java constructor using generic types

    - by user37903
    I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method initBreweryFromObject() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // initBreweryFromObject() is an instance method // of Brewery, of which <T> is a subclass (right?) c.initBreweryFromObject(); // "The method initBreweryFromObject() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void androidMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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  • Optimizing a "set in a string list" to a "set as a matrix" operation

    - by Eric Fournier
    I have a set of strings which contain space-separated elements. I want to build a matrix which will tell me which elements were part of which strings. For example: "" "A B C" "D" "B D" Should give something like: A B C D 1 2 1 1 1 3 1 4 1 1 Now I've got a solution, but it runs slow as molasse, and I've run out of ideas on how to make it faster: reverseIn <- function(vector, value) { return(value %in% vector) } buildCategoryMatrix <- function(valueVector) { allClasses <- c() for(classVec in unique(valueVector)) { allClasses <- unique(c(allClasses, strsplit(classVec, " ", fixed=TRUE)[[1]])) } resMatrix <- matrix(ncol=0, nrow=length(valueVector)) splitValues <- strsplit(valueVector, " ", fixed=TRUE) for(cat in allClasses) { if(cat=="") { catIsPart <- (valueVector == "") } else { catIsPart <- sapply(splitValues, reverseIn, cat) } resMatrix <- cbind(resMatrix, catIsPart) } colnames(resMatrix) <- allClasses return(resMatrix) } Profiling the function gives me this: $by.self self.time self.pct total.time total.pct "match" 31.20 34.74 31.24 34.79 "FUN" 30.26 33.70 74.30 82.74 "lapply" 13.56 15.10 87.86 97.84 "%in%" 12.92 14.39 44.10 49.11 So my actual questions would be: - Where are the 33% spent in "FUN" coming from? - Would there be any way to speed up the %in% call? I tried turning the strings into factors prior to going into the loop so that I'd be matching numbers instead of strings, but that actually makes R crash. I've also tried going for partial matrix assignment (IE, resMatrix[i,x] <- 1) where i is the number of the string and x is the vector of factors. No dice there either, as it seems to keep on running infinitely.

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  • Another boost error

    - by user1676605
    On this code I get the enourmous error static void ParseTheCommandLine(int argc, char *argv[]) { int count; int seqNumber; namespace po = boost::program_options; std::string appName = boost::filesystem::basename(argv[0]); po::options_description desc("Generic options"); desc.add_options() ("version,v", "print version string") ("help", "produce help message") ("sequence-number", po::value<int>(&seqNumber)->default_value(0), "sequence number") ("pem-file", po::value< vector<string> >(), "pem file") ; po::positional_options_description p; p.add("pem-file", -1); po::variables_map vm; po::store(po::command_line_parser(argc, argv). options(desc).positional(p).run(), vm); po::notify(vm); if (vm.count("pem file")) { cout << "Pem files are: " << vm["pem-file"].as< vector<string> >() << "\n"; } cout << "Sequence number is " << seqNumber << "\n"; exit(1); ../../../FIXMarketDataCommandLineParameters/FIXMarketDataCommandLineParameters.hpp|98|error: no match for ‘operator<<’ in ‘std::operator<< [with _Traits = std::char_traits](((std::basic_ostream &)(& std::cout)), ((const char*)"Pem files are: ")) << ((const boost::program_options::variable_value*)vm.boost::program_options::variables_map::operator[](((const std::string&)(& std::basic_string, std::allocator (((const char*)"pem-file"), ((const std::allocator&)((const std::allocator*)(& std::allocator()))))))))-boost::program_options::variable_value::as with T = std::vector, std::allocator , std::allocator, std::allocator ’|

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  • sending address of a variable declared on the stack?

    - by kobac
    I have a doubt concerning declaring variables, their scope, and if their address could be sent to other functions even if they are declared on the stack? class A{ AA a; void f1(){ B b; aa.f2(&b); } }; class AA{ B* mb; f2(B* b){ mb = b; //... } }; Afterwards, I use my AA::mb pointer in the code. So things I would like to know are following. When the program exits A::f1() function, b variable since declared as a local variable and placed on the stack, can't be used anymore afterwards. What happens with the validity of the AA::mb pointer? It contains the address of the local variable which could not be available anymore, so the pointer isn't valid anymore? If B class is a std::<vector>, and AA::mb is not a pointer anymore to that vector, but a vector collection itself for example. I would like to avoid copying all of it's contents in AA::f2() to a member AA::mb in line mb = b. Which solution would you recommend since I can't assign a pointer to it, because it'll be destroyed when the program exits AA::f2()

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  • Could this C cast to avoid a signed/unsigned comparison make any sense?

    - by sharptooth
    I'm reviewing a C++ project and see effectively the following: std::vector<SomeType> objects; //then later int size = (int)objects.size(); for( int i = 0; i < size; ++i ) { process( objects[i] ); } Here's what I see. std::vector::size() returns size_t that can be of some size not related to the size of int. Even if sizeof(int) == sizeof(size_t) int is signed and can't hold all possible values of size_t. So the code above could only process the lower part of a very long vector and contains a bug. That said I'm curious of why the author might have written this? My only guess is that first he omitted the (int) cast and the compiler emitted something like Visual C++ C4018 warning: warning C4018: '<' : signed/unsigned mismatch so the author though that the best way to avoid the compiler warning would be to simply cast the size_t to int thus making the compiler shut up. Is there any other possible sane reason for that C cast?

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  • optimization math computation (multiplication and summing)

    - by wiso
    Suppose you want to compute the sum of the square of the differences of items: $\sum_{i=1}^{N-1} (x_i - x_{i+1})^2$, the simplest code (the input is std::vector<double> xs, the ouput sum2) is: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (prev - (*i)) * (prev - (*i)); // only 1 - with compiler optimization prev = (*i); } I hope that the compiler do the optimization in the comment above. If N is the length of xs you have N-1 multiplications and 2N-3 sums (sums means + or -). Now suppose you know this variable: sum = $x_1^2 + x_N^2 + 2 sum_{i=2}^{N-1} x_i^2$ Expanding the binomial square: $sum_i^{N-1} (x_i-x_{i+1})^2 = sum - 2\sum_{i=1}^{N-1} x_i x_{i+1}$ so the code becomes: double sum2 = 0.; double prev = xs[0]; for (vector::const_iterator i = xs.begin() + 1; i != xs.end(); ++i) { sum2 += (*i) * prev; prev = (*i); } sum2 = -sum2 * 2. + sum; Here I have N multiplications and N-1 additions. In my case N is about 100. Well, compiling with g++ -O2 I got no speed up (I try calling the inlined function 2M times), why?

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  • Python - creating a list with 2 characteristics bug

    - by user2733911
    The goal is to create a list of 99 elements. All elements must be 1s or 0s. The first element must be a 1. There must be 7 1s in total. import random import math import time # constants determined through testing generation_constant = 0.96 def generate_candidate(): coin_vector = [] coin_vector.append(1) for i in range(0, 99): random_value = random.random() if (random_value > generation_constant): coin_vector.append(1) else: coin_vector.append(0) return coin_vector def validate_candidate(vector): vector_sum = sum(vector) sum_test = False if (vector_sum == 7): sum_test = True first_slot = vector[0] first_test = False if (first_slot == 1): first_test = True return (sum_test and first_test) vector1 = generate_candidate() while (validate_candidate(vector1) == False): vector1 = generate_candidate() print vector1, sum(vector1), validate_candidate(vector1) Most of the time, the output is correct, saying something like [1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0] 7 True but sometimes, the output is: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 2 False What exactly am I doing wrong?

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  • Does the .NET Framework need to be reoptimized after upgrading to a new CPU microarchitecture?

    - by Louis
    I believe that the .NET Framework will optimize certain binaries targeting features specific to the machine it's installed on. After changing the CPU from an Intel Nehalem to a Haswell chip, should the optimization be run again manually? If so, what is the process for that? Between generations here are some notable additions: Westmere: AES instruction set Sandy Bridge: Advanced Vector Extensions Ivy Bridge: RdRand (hardware random number generator), F16C (16-bit Floating-point conversion instructions) Haswell: Haswell New Instructions (includes Advanced Vector Extensions 2 (AVX2), gather, BMI1, BMI2, ABM and FMA3 support) So my, albeit naive, thought process was that the optimizations could take advantage of these in general cases. For example, perhaps calls to the Random library could utilize the hardware-RNG on Ivy Bridge and later models.

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  • How do you traverse and store XML in Blackberry Java app?

    - by Greg
    I'm having a problem accessing the contents of an XML document. My goal is this: Take an XML source and parse it into a fair equivalent of an associative array, then store it as a persistable object. the xml is pretty simple: <root> <element> <category_id>1</category_id> <name>Cars</name> </element> <element> <category_id>2</category_id> <name>Boats</name> </element> </root> Basic java class below. I'm pretty much just calling save(xml) after http response above. Yes, the xml is properly formatted. import java.io.IOException; import java.util.Hashtable; import org.w3c.dom.Document; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import java.util.Vector; import net.rim.device.api.system.PersistentObject; import net.rim.device.api.system.PersistentStore; import net.rim.device.api.xml.parsers.DocumentBuilder; import net.rim.device.api.xml.parsers.DocumentBuilderFactory; public class database{ private static PersistentObject storeVenue; static final long key = 0x2ba5f8081f7ef332L; public Hashtable hashtable; public Vector venue_list; String _node,_element; public database() { storeVenue = PersistentStore.getPersistentObject(key); } public void save(Document xml) { venue_list = new Vector(); storeVenue.setContents(venue_list); Hashtable categories = new Hashtable(); try{ DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory. newInstance(); DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder(); docBuilder.isValidating(); xml.getDocumentElement ().normalize (); NodeList list=xml.getElementsByTagName("*"); _node=new String(); _element = new String(); for (int i=0;i<list.getLength();i++){ Node value=list.item(i).getChildNodes().item(0); _node=list.item(i).getNodeName(); _element=value.getNodeValue(); categories.put(_element, _node); } } catch (Exception e){ System.out.println(e.toString()); } venue_list.addElement(categories); storeVenue.commit(); } The code above is the work in progress, and is most likely heavily flawed. However, I have been at this for days now. I can never seem to get all child nodes, or the name / value pair. When I print out the vector as a string, I usually end up with results like this: [{ = root, = element}] and that's it. No "category_id", no "name" Ideally, I would end up with something like [{1 = cars, 2 = boats}] Any help is appreciated. Thanks

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  • Identifier is undefined

    - by hawk
    I wrote the following code in C++ using VS2012 Express. void ac_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Irrelevant code omitted. } vector<int> ac_benchmark_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, double &time) { // Prepare the container for the results vector<int> matches(num_records * num_patterns); Trie T; Node* trie = T.addWord(records, num_records, record_length); // error line ac_search(num_patterns, pattern_length, patterns, num_records, record_length, records, matches.data(), trie); // Irrelevant code omitted. return matches; } I get the error identifier "ac_search" is undefined at the function invoking line. I am a bit confused here. because the function ac_search is declared as a global (not inside any container). Why can't I call it at this place? Am I missing something? Update I tried ignore irrelevant code and then included it gradually and found that everything is fine until I include the outer loop of ac_search I get the aforementioned error. here is updated code of the function ac_search: void ac_cpu_string_search(uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Loop over all records //for (uint record_number = 0; record_number < num_records; ++record_number) //{ // // Loop over all patterns for (uint pattern_number = 0; pattern_number < num_patterns; ++pattern_number) { // Execute string search const char *ptr_record = &records[record_number * record_length]; const char *ptr_match = std::strstr(ptr_record, &patterns[pattern_number * pattern_length]); // If pattern was found, then calculate offset, otherwise result is -1 if (ptr_match) { matches[record_number * num_patterns + pattern_number] = static_cast<int>(std::distance(ptr_record, ptr_match)); } else { matches[record_number * num_patterns + pattern_number] = -1; } // } //} } Update 2 I think the error has something to do with the function addWord which belongs to the class Trie. When I commented out this function, I did not get the error anymore. Node* Trie::addWord(const char *records, uint num_records, uint record_length) { // Loop over all records for (uint record_number = 0; record_number < num_records; ++record_number) { const char *ptr_record = &records[record_number * record_length]; string s = ptr_record; Node* current = root; if ( s.length() == 0 ) { current->setWordMarker(); // an empty word return; } for ( int i = 0; i < s.length(); i++ ) { Node* child = current->findChild(s[i]); if ( child != NULL ) { current = child; } else { Node* tmp = new Node(); tmp->setContent(s[i]); current->appendChild(tmp); current = tmp; } if ( i == s.length() - 1 ) current->setWordMarker(); } return current; } void ac_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Irrelevant code omitted. } vector<int> ac_benchmark_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, double &time) { // Prepare the container for the results vector<int> matches(num_records * num_patterns); Trie T; Node* trie = T.addWord(records, num_records, record_length); // error line ac_search(num_patterns, pattern_length, patterns, num_records, record_length, records, matches.data(), trie); // Irrelevant code omitted. return matches; }

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  • STL find performs bettern than hand-crafter loop

    - by dusha
    Hello all, I have some question. Given the following C++ code fragment: #include <boost/progress.hpp> #include <vector> #include <algorithm> #include <numeric> #include <iostream> struct incrementor { incrementor() : curr_() {} unsigned int operator()() { return curr_++; } private: unsigned int curr_; }; template<class Vec> char const* value_found(Vec const& v, typename Vec::const_iterator i) { return i==v.end() ? "no" : "yes"; } template<class Vec> typename Vec::const_iterator find1(Vec const& v, typename Vec::value_type val) { return find(v.begin(), v.end(), val); } template<class Vec> typename Vec::const_iterator find2(Vec const& v, typename Vec::value_type val) { for(typename Vec::const_iterator i=v.begin(), end=v.end(); i<end; ++i) if(*i==val) return i; return v.end(); } int main() { using namespace std; typedef vector<unsigned int>::const_iterator iter; vector<unsigned int> vec; vec.reserve(10000000); boost::progress_timer pt; generate_n(back_inserter(vec), vec.capacity(), incrementor()); //added this line, to avoid any doubts, that compiler is able to // guess the data is sorted random_shuffle(vec.begin(), vec.end()); cout << "value generation required: " << pt.elapsed() << endl; double d; pt.restart(); iter found=find1(vec, vec.capacity()); d=pt.elapsed(); cout << "first search required: " << d << endl; cout << "first search found value: " << value_found(vec, found)<< endl; pt.restart(); found=find2(vec, vec.capacity()); d=pt.elapsed(); cout << "second search required: " << d << endl; cout << "second search found value: " << value_found(vec, found)<< endl; return 0; } On my machine (Intel i7, Windows Vista) STL find (call via find1) runs about 10 times faster than the hand-crafted loop (call via find2). I first thought that Visual C++ performs some kind of vectorization (may be I am mistaken here), but as far as I can see assembly does not look the way it uses vectorization. Why is STL loop faster? Hand-crafted loop is identical to the loop from the STL-find body. I was asked to post program's output. Without shuffle: value generation required: 0.078 first search required: 0.008 first search found value: no second search required: 0.098 second search found value: no With shuffle (caching effects): value generation required: 1.454 first search required: 0.009 first search found value: no second search required: 0.044 second search found value: no Many thanks, dusha. P.S. I return the iterator and write out the result (found or not), because I would like to prevent compiler optimization, that it thinks the loop is not required at all. The searched value is obviously not in the vector.

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