I have been looking for an error in a code that I am using for finite element methods. The point is that I have to get some data from a file to identify the material of a cell. The type of this material_id is unsigned char
, and here is the problem.
When reading the data from the file, different ways to assign the value to a unsigned char variable gives different result. I have fixed the problem, but I am still wondering why it is working in a different way. Here you have a sample code reproducing the different behavior:
#include <map>
#include <sstream>
#include <fstream>
#include <string>
#include <iostream>
#include <vector>
#include <stdlib.h>
namespace types
{
//typedef unsigned int material_id;
typedef unsigned char material_id;
}
namespace Utilities
{
int string_to_int(const std::string & str)
{
return atoi(str.c_str());
}
}
template<typename Number>
void parseVector_1(std::ifstream & myfile,
std::vector<Number> & mat_id)
{
Number num;
std::string line, bin;
if (myfile.is_open())
{
getline (myfile,line);
std::istringstream iss(line);
while ( iss.good() )
{
iss >> bin; // option 1
num = Utilities::string_to_int(bin); // option 1
mat_id.push_back(num);
}
}
else std::cout << "Unable to open file";
}
template<typename Number>
void parseVector_2(std::ifstream & myfile,
std::vector<Number> & mat_id)
{
Number num;
std::string line, bin;
if (myfile.is_open())
{
getline (myfile,line);
std::istringstream iss(line);
while ( iss.good() )
{
iss >> num; // option 2
mat_id.push_back(num);
}
}
else std::cout << "Unable to open file";
}
int main()
{
unsigned int n_mat;
std::vector<types::material_id> mat_id_1;
std::vector<types::material_id> mat_id_2;
std::map<types::material_id, double> D1v;
D1v[0] = 0.0;
D1v[1] = 1.0;
D1v[2] = 2.0;
D1v[3] = 3.0;
D1v[4] = 4.0;
std::ifstream myfile1 ("materials.dat");
parseVector_1(myfile1, mat_id_1);
myfile1.close();
std::ifstream myfile2 ("materials.dat");
parseVector_2(myfile2, mat_id_2);
myfile2.close();
n_mat = mat_id_1.size();
std::cout << "option 1: ";
for (unsigned int i = 0; i < n_mat; ++i)
std::cout << "mat["<<i<<"]=" << D1v[mat_id_1[i]] << " ";
std::cout << std::endl;
n_mat = mat_id_2.size();
std::cout << "option 2: ";
for (unsigned int i = 0; i < n_mat; ++i)
std::cout << "mat["<<i<<"]=" << D1v[mat_id_2[i]] << " ";
std::cout << std::endl;
return 0;
}
The content of the "materials.dat" file is the following line:
0 1 2 3 4
And here is the output of the execution:
$ unsignedchar_problem.exe
option 1: mat[0]=0 mat[1]=1 mat[2]=2 mat[3]=3 mat[4]=4
option 2: mat[0]=0 mat[1]=0 mat[2]=0 mat[3]=0 mat[4]=0 mat[5]=0
Can anyone give some insight why option 1 is working fine, but option 2 is not? Is it dependent on the compiler/platform of it is always like that?
As an additional information, the problem was because the material_id
type was defined as unsigned int
by the other user in his computer, so it was working without any problem.