std::vector<std::vector<int> >

A std::vector can contain a collection of std::vectors. If all std::vectors in this collection are of the same size, one has a matrix.

When using std::vector<std::vector<int> > for a two-dimensional matrix, the choice between x-y-ordering or y-x-ordering must be made. The run-time speed difference does not reside in individual element read/write, but when obtaining a row or collumn: in a y-x-ordered std::vector<std::vector<int> > an individual row can be obtained, in an x-y-ordered std::vector<std::vector<int> > an individual collumn can be obtained.

Below is an example of a y-x-ordered std::vector<std::vector<int> >.


#include <cassert>

#include <vector>



int main()

{

  const int n_rows = 5;

  const int n_cols = 10;

  //Create the y-x-ordered 2D-vector

  std::vector<std::vector<int> > v(n_rows, std::vector<int>(n_cols,0));

  const int y = n_rows - 1;

  const int x = n_cols - 1;

  assert(y < static_cast<int>(v.size()));

  assert(x < static_cast<int>(v[y].size()));

  v[y][x] = 10; //y-x-ordered

}

std::vector<std::vector<int> > code snippets

Note that some of these code snippets also work on other containers.

boost::multi_array

The boost::multi_array (part of the Boost library) is not only support a two-dimensional matrix, but to many more dimensions.

When using C++ Builder 6.0, this does not compile (it results in the compile error borland.hpp: Only member functions may be 'const' or 'volatile').

boost::numeric::ublas::matrix

The boost::numeric::ublas::matrix (part of the Boost library) support a two-dimensional matrix.

When using C++ Builder 6.0, this does not compile (it results in the compile error Your compiler and/or configuration is unsupported by this verions of uBLAS).

blitz::Array

The blitz::Array (part of the Blitz++ library) is not only support a two-dimensional matrix, but to many more dimensions.

When using C++ Builder 6.0, this does not compile (it results in the compile error bzconfig.h: Unknown compiler).

Techsoft's matrix

Techsoft's matrix supports a x-y-ordered two-dimensional matrix.


#include <cassert>

#include <techsoft/matrix.h>



int main()

{

  const int n_rows = 5;

  const int n_cols = 10;

  math::matrix<int> v(n_rows,n_cols);

  const int y = n_rows - 1;

  const int x = n_cols - 1;

  assert(v(x,y)==0);

  v(x,y) = 10;

  assert(v(x,y)==10);

}

Flood::Matrix

The Flood::Matrix (from the Flood library) supports a x-y-ordered two-dimensional matrix.


#include <cassert>

#include <flood/utilities/matrix.h>

 

int main()

{

  const int n_rows = 5;

  const int n_cols = 10;

  Flood::Matrix<int> v(n_rows,n_cols);

  const int y = n_rows - 1;

  const int x = n_cols - 1;

  assert( x < v.getNumberOfRows());

  assert( y < v.getNumberOfColumns());

  assert(v[x][y]==0);

  v[x][y] = 10;

  assert(v[x][y]==10);

}

External links

References

Wikipedia page about matrices

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.

(C++) Matrix