Problem with vector<double> alocation

[Ivan Paganini]

Hello all.
I'm trying to use a vector<double> to alocate de data that i need, and
I am passing by reference to the function to receive the values. The
code goes like this:
//code


void GenerateRandomPositions(vector<double>& posiX, vector<double>&
posiY, int nbneurons, int* sizespace)
{posiX.clear();
posiY.clear();

for(i=0;i<NbNeurons;i++)
{
posiX.push_back((double)(rand()%sizespace[0]+1));
posiY.push_back((double)(rand()%sizespace[1]+1));
}
}

//end code

where i need the values of posiX and posiY returned to the program.
The size of NbNeurons is about 10, and sizespace is a number that the
program gets from the number of coordinates in my database. When i try
to run the program, i get the segmentation fault. What can be the
problem?

Thanks.

Ivan S>P<M
Grupo de Visão Cibernética - IFSC - USP - Br

 

[Victor Bazarov]

Hello all.
I'm trying to use a vector<double> to alocate de data that i need, and
I am passing by reference to the function to receive the values. The
code goes like this:
//code


void GenerateRandomPositions(vector<double>& posiX, vector<double>&
posiY, int nbneurons, int* sizespace)
{posiX.clear();
posiY.clear();

for(i=0;i<NbNeurons;i++)
{
posiX.push_back((double)(rand()%sizespace[0]+1));
posiY.push_back((double)(rand()%sizespace[1]+1));
}
}

//end code

where i need the values of posiX and posiY returned to the program.
The size of NbNeurons is about 10, and sizespace is a number that the
program gets from the number of coordinates in my database. When i try
to run the program, i get the segmentation fault. What can be the
problem?

The problem is most likely in 'sizespace'. Since you don't show
how you call your 'GenerateRandomPositions' function, there is no
way to tell what specifically is going on.

BTW, using '%' with the result of calling 'rand' is not a good idea.
See comp.lang.c FAQ for the explanation why and what to use instead.

Victor

 

[Rob Williscroft]

Ivan Paganini wrote in @posting.google.com:

Hello all.
I'm trying to use a vector<double> to alocate de data that i need, and
I am passing by reference to the function to receive the values. The
code goes like this:
//code

#include <iostream>
#include <ostream>
#include <vector>
#include <iterator>
#include <algorithm>

using std::vector;

void GenerateRandomPositions(
vector<double>& posiX, vector<double>& posiY,
int nbneurons, int* sizespace
)
{
posiX.clear();
posiY.clear();

for( int i=0; i<nbneurons; i++)
{
posiX.push_back((double)(rand()%sizespace[0]+1));
posiY.push_back((double)(rand()%sizespace[1]+1));
}
}


int main()
{

int ss[2] = { 100, 200 };
vector< double > px, py;

GenerateRandomPositions( px, py, 10, ss );

std::copy(
px.begin(), px.end(),
std:stream_iterator< double >( std::cout, "," )
);
std::cout << "\n";

std::copy(
py.begin(), py.end(),
std:stream_iterator< double >( std::cout, "," )
);
std::cout << std::endl;
}

where i need the values of posiX and posiY returned to the program.
The size of NbNeurons is about 10, and sizespace is a number that the
program gets from the number of coordinates in my database. When i try
to run the program, i get the segmentation fault. What can be the
problem?

After fixing 1 error (spelling) and adding main() the above
compiles and runs.

HTH

Rob.

 

[Kevin Goodsell]

Hello all.
I'm trying to use a vector<double> to alocate de data that i need, and
I am passing by reference to the function to receive the values. The
code goes like this:
//code


void GenerateRandomPositions(vector<double>& posiX, vector<double>&
posiY, int nbneurons, int* sizespace)
{posiX.clear();
posiY.clear();

for(i=0;i<NbNeurons;i++)
{
posiX.push_back((double)(rand()%sizespace[0]+1));
posiY.push_back((double)(rand()%sizespace[1]+1));
}
}

//end code

http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.8

Pay particular attention to items 1 through 3.

-Kevin