I tried two ways for the same issue, one works and the other doesn't. The following version works, returning a value of 4.
int gather_list()
{
mpi::environment env;
mpi::communicator world;
std::srand(time(0) + world.rank());
int my_number = std::rand();
std::vector<int> tmp_vec;
tmp_vec.push_back(my_number);
tmp_vec.push_back(my_number + 1);
if (world.rank() == 0)
{
std::vector<int> all_numbers;
gather(world, &tmp_vec[0], tmp_vec.size(), all_numbers, 0);
std::cout << all_numbers.size() << std::endl;
} else
{
gather(world, &tmp_vec[0], tmp_vec.size(), 0);
}
return 0;
}
The following version doesn't work, returning a value of 2.
class ArchivableVecInt : public std::vector<int>
{
public:
ArchivableVecInt() = default;
explicit ArchivableVecInt(const std::vector<int> &vec)
{
auto base_ptr = static_cast<std::vector<int> *>(this);
*base_ptr = vec;
}
template<class Archiver>
void serialize(Archiver &ar, unsigned int)
{
for (auto i: *this)
{
ar & i;
}
}
protected:
};
int gather_list()
{
mpi::environment env;
mpi::communicator world;
std::srand(time(0) + world.rank());
int my_number = std::rand();
std::vector<int> tmp_vec;
tmp_vec.push_back(my_number);
tmp_vec.push_back(my_number + 1);
ArchivableVecInt my_vec(tmp_vec);
if (world.rank() == 0)
{
std::vector<ArchivableVecInt> all_numbers;
gather(world, my_vec, all_numbers, 0);
for (int proc = 0; proc < world.size(); ++proc)
std::cout << "Process #" << proc << " thought of "
<< all_numbers[proc].size() << std::endl;
} else
{
gather(world, my_vec, 0);
}
return 0;
}
I tried 2 processes, while rank 0 returns a value of 2, rank 1 returns zero. Seems the gather(world, my_vec, 0) didn't work, why?
result as below.
Thanks in advance.
In your second example your receive buffer is a vector<vector<int>> meaning that the data is not contiguous. MPI needs contiguous buffers.
Related
#include <iostream>
#include <vector>
using namespace std;
class House {
public:
//default constructor
House(string = "no-style", double = 0.0);
//destructor
~House();
//set the style
void setStyle(string style);
//set the cost
void setCost(double cost);
//get the style
string getStyle() const;
//get the cost
double getCost() const;
//overloaded operator: = (assignment)
House& operator = (const House &other);
//overloaded operator: == (comparison)
bool operator == (const House &other);
//overloaded operator: = (assignment)
friend ostream& operator<<(ostream& out, const House& other);
private:
string* pStyle;
double* pCost;
};
//default constructor
House::House(string style, double cost)
{
pStyle = new string{style};
pCost = new double{cost};
}
//destructor
House::~House()
{
if(pStyle != nullptr)
delete pStyle;
if(pCost != nullptr)
delete pCost;
}
//set the style
void House::setStyle(string style)
{
*pStyle = style;
}
//set the cost
void House::setCost(double cost)
{
*pCost = cost;
}
//get the style
string House::getStyle() const
{
return *pStyle;
}
//get the cost
double House::getCost() const
{
return *pCost;
}
//overloaded operator: = (assignment)
House& House::operator = (const House &other)
{
if(pStyle != nullptr)
delete pStyle;
if(pCost != nullptr)
delete pCost;
pStyle = new string{*other.pStyle};
pCost = new double{*other.pCost};
return *this;
}
//overloaded operator: == (comparison)
bool House::operator == (const House &other)
{
return (*pStyle == *other.pStyle && *pCost == *other.pCost);
}
ostream& operator<<(ostream& out, const House& other)
{
out<<"House " << other.getStyle() <<" costs:" << other.getCost()<<" dollars."<<endl;
return out;
}
void showHouses(vector<House>& houses, int houseCount) {
cout << endl << "Here are your houses: " << endl;
for(int i=0; i<houseCount; i++)
{
cout << houses.at(i);
}
}
int main() {
vector<House> houses;
House currentHouse;
int houseCount = 0; // number of houses
string style;
double cost;
int num;
cout << "Here is the currentHouse: " << currentHouse << endl;
do{
cout<<"How many houses do you want to build? (must be at least 3) ";
cin >> houseCount;
}while(houseCount<3);
cout << endl;
for(int i=0; i<houseCount; i++)
{
cout<<"What is the style for house "<<i+1<<"? ";
cin >> style;
cout<<"What is the cost for house "<<i+1<<"? ";
cin >> cost;
currentHouse.setStyle(style);
currentHouse.setCost(cost);
houses.push_back(currentHouse);
cout<<houses.at(i);
}
showHouses(houses, houseCount);
cout << endl << "Which house do you want to change? ";
cin >>num;
cout<<"What is the new style? ";
cin >> style;
cout<<"What is the new cost? ";
cin >> cost;
currentHouse = House(style, cost);
if(houses.at(num) == currentHouse)
cout<<"The new house is the same as the old house."<<endl;
else
cout<<"The houses are different."<<endl;
cout << "Copying new house to the old house ..." << endl;
houses.at(num) = currentHouse;
showHouses(houses, houseCount);
return 0;
}
The code is not working when put value of houseCount greater than 1. I have received the following error message while execute the code:
Here is the currentHouse: House no-style costs:0 dollars.
How many houses do you want to build? (must be at least 3) 3
What is the style for house 1? e
What is the cost for house 1? 2
What is the style for house 2? f
What is the cost for house 2? 5
terminate called after throwing an instance of 'std::logic_error'
what(): basic_string::_M_construct null not valid
Aborted (core dumped)
Here is my insert method of a chaining class that I implement, the data type is integer (typedef int TELEM).By displaying the numbers stored, from 16 shows me other values too big
include
typedef int TELEM;
// liste d'éléments de type TELEM
class liste {
public:
liste::liste() : m_nb(0) ,m_tetefile(0)
{
m_tetefile = new TELEM[m_nb+1] ;
}
liste::~liste()
{
m_nb = 0;
delete m_tetefile;
}
bool liste::est_vide() const
{
return m_nb == 0;
}
int liste::taille() const
{
return m_nb;
}
const TELEM& liste::operator[](int i) const
{
assert((i>=1) && (i<=m_nb));
return (m_tetefile[i]);
}
void liste::inserer(const TELEM& e, int i)
{
assert((i>=1) && (i<=m_nb+1));
for (int k = m_nb ; k >= i ; --k)
m_tetefile[k+1] = m_tetefile[k];
m_tetefile[i] = e;
std::cout << e <<std::endl;
std::cout << m_tetefile[i] <<std::endl;
m_nb++;
}
private:
TELEM m_nb ;
TELEM *m_tetefile;
};
std::ostream& operator<<(std::ostream& os, const liste& l)
{
os << '(';
if (!l.est_vide())
os << l[1];
for (int i=2; i<=l.taille(); ++i)
os << ',' << l[i];
os << ')';
return os;
}
from 16 ca gives me this
(2,4,6,8,10,12,14,875311656,942421548,741355820)
instead
(2,4,6,8,10,12,14,16,18,20)
Custom lambda Comparator slower than normal function c++11. I experienced this a few times. But, Still Couldn't figure out the reason why this is so. Does anyone experience this and know the cause behind it?
#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 1;
vector<int> v(N);
vector<int> sorted(N);
map<int, int> counts;
long long start;
void startClock() {
start = clock();
}
void stopClock() {
cout << float( clock () - start ) / CLOCKS_PER_SEC << endl;
}
void copyOriginal() {
for (int i = 0; i < N; ++i)
sorted[i] = v[i];
}
void sortWLambda(map<int, int>& counts) {
cout << "sorting with lambda" << endl;
sort(sorted.begin(), sorted.end(), [counts](const int& a, const int& b) {
if (*counts.find(a) != *counts.find(b)) return *counts.find(a) < *counts.find(b);
return a < b;
});
}
bool comparator(const int& a, const int& b) {
if (*counts.find(a) != *counts.find(b)) return *counts.find(a) < *counts.find(b);
return a < b;
}
void sortWoLambda() {
cout << "sorting w/o lambda" << endl;
sort(sorted.begin(), sorted.end(), comparator);
}
int main() {
for (int i = 0; i < N; ++i) {
int num = rand() % 1234;
counts[num]++;
v[i] = num;
}
copyOriginal();
startClock();
sortWLambda(counts);
stopClock();
copyOriginal();
startClock();
sortWoLambda();
stopClock();
return 0;
}
sorting with lambda 6.28 sec
sorting w/o lambda 0.17 sec
pass by reference made the difference for lambda.
I tried this..
sort(sorted.begin(), sorted.end(), [&counts](const int& a, const int& b) {
if (*counts.find(a) != *counts.find(b)) return *counts.find(a) < *counts.find(b);
return a < b;
});
now this takes same time as normal function
Passing by constant reference in the lambda capture list this helped me too!
I'm having trouble creating a program that will convert infix to postfix. My code is as follows:
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
#define DEFAULT_SIZE 20
/*
*
*/
class Stack {
char *arr;
int tos, capacity;
public:
//Constructors
Stack();
Stack(int size);
//Destructor
~Stack();
//Methods
void push(char a);
char pop();
int get_size();
bool is_empty();
bool is_full();
void display();
char get_top();
};
Stack::Stack() {
arr = new char[DEFAULT_SIZE];
tos = 0;
capacity = DEFAULT_SIZE;
}
Stack::Stack(int size) {
arr = new char[size];
tos = 0;
capacity = size;
}
Stack::~Stack() {
delete[] arr;
}
void Stack::push(char a) {
if (!is_full())
arr[tos++] = a;
else
cout << "Sorry, the stack is full. Push failed!" << endl;
}
char Stack::pop() {
if (!is_empty())
return arr[--tos];
else {
cout << "Sorry, the stack is empty. Pop failed!" << endl;
return -1;
}
}
char Stack::get_top() {
if (!is_empty())
return arr[tos - 1];
else {
cout << "Sorry, the stack is empty. Pop failed!" << endl;
return 'E';
}
}
int Stack::get_size() {
return tos;
}
bool Stack::is_empty() {
if (tos == 0)
return true;
else
return false;
}
bool Stack::is_full() {
if (tos == capacity)
return true;
else
return false;
}
void Stack::display() {
if (tos == 0)
cout << "The stack is empty" << endl;
else {
for (int i = 0; i<tos;i++)
cout << arr[i] << " ";
cout << endl;
}
}
int main() {
Stack stack(50);
string infix = "(1+3)*2/(6-4)^2";
stringstream ss;
for (char c : infix) {
if ('0' <= c && c <= '9') {
ss << c;
}
else if (c == '(') {
continue;
}
else if (c == ')') {
ss << stack.pop();
stack.pop();
}
else if (c == '^' || c == '*' || c == '/' || c == '+' || c == '-') {
stack.push(c);
}
}
string postfix = ss.str();
cout << postfix;
I know what my issue is, I just dont understand or comprehend how to solve it. This code currently outputs 13+264-2. It needs to output 13+2*64-2^/. I know my issues is with my last else if statement in int main(). I dont understand how to rearrange the operators behind the operands.
Anything in parentheses is passed into the stream correctly, because I can wait until the closing parenthesis is hit to add in the operator. I can't visualize how to make that work for things not in parentheses though. Can anyone offer any advice?
I am writing code for an assignment in my college C++ class, the program is meant to create a dynamically allocated array using a class. I am getting a debug assertion failed error when my objects go out of scope, because I am double deleting the pointer to the newly created array. I have no idea where this happens because I only use delete[] twice in the entire class. Here is my source:
#include
using namespace std;
//classes
class IntArray {
private:
int * begin;
int arrSize;
//returns true if n is a valid index inside the array
bool inBounds(int n) {
if (n < 0 || n >= arrSize) {
return false;
}
return true;
}
public:
//default constructor
IntArray() {
begin = new int[1];
begin[0] = 0;
arrSize = 1;
}
//call constructor
IntArray(int n) {
arrSize = n;
begin = new int[n];
for (int i = 0; i < n; i++) {
begin[i] = 0;
}
}
//copy constructor
IntArray(IntArray * in) {
arrSize = in->size();
begin = new int[arrSize];
for (int i = 0; i < arrSize; i++) {
begin[i] = in->begin[i];
}
}
//call constructor for arrays
IntArray(int in[],int s) {
arrSize = s;
begin = new int[arrSize];
for (int i = 0; i < arrSize; i++) {
begin[i] = in[i];
}
}
//method functions
//returns the size of the array
int size() {
return arrSize;
}
//returns the value of the element at position n
int get(int n) {
if (inBounds(n)) {
return begin[n];
}
cout << "Error: Invalid bound entered, returning value at index 0" << endl;
return begin[0];
}
//function that sets the value at position n to the value of input
void put(int n, int input) {
if (inBounds(n)) {
begin[n] = input;
}
else {
cout << "Error: invalid bound entered, no value changed" << endl;
}
}
//overloaded operators
//sets the value at the position n to input value
int & operator[](int n) {
if (inBounds(n)) {
return begin[n];
}
cout << "Error: invalid bound entered, returning index 0" << endl;
return begin[0];
}
//operator = allows copying of one IntArray to another
IntArray & operator=(IntArray source) {
arrSize = source.size();
delete[] begin;
begin = 0;
begin = new int[arrSize];
for (int i = 0; i < arrSize; i++) {
begin[i] = source[i];
}
return *this;
}
//destructor
~IntArray() {
//deallocate memory used by array
if (begin != 0) {
delete[] begin;
}
}
};
int main() {
IntArray arr1(10);
for (int i = 0; i < 10; i++) {
arr1[i] = 11 * i;
cout << arr1[i] << " ";
}
cout << endl;
for (int i = 0; i < 10; i++) {
cout << arr1.get(i) << " ";
}
cout << endl;
arr1.put(6, 16);
arr1.put(4, 10);
IntArray arr2(arr1);
IntArray arr3 = arr1;
for (int i = 0; i < 10; i++) {
cout << arr3.get(i) << " ";
}
cout << endl;
for (int i = 0; i < 10; i++) {
cout << arr2.get(i) << " ";
}
cout << endl;
system("PAUSE");
return 0;
}
And a screenshot of the exact error:
Thanks to #heavyd I realized that the error arose from an improper construction of the class due to a logic error in my class definition. The problem was in the way I was copying data to the new class (improperly) and the way that my copy constructor worked, as well as the return type of one of my member functions.