Technical facts

Application type(s)

Desktop application

Operating system(s) or programming environment(s)

Lubuntu 12.10 (quantal)

IDE(s):

Qt Creator 2.5.2

Project type:

Console application

C++ standard:

C++98

Compiler(s):

G++ 4.7.2

Libraries used:

STL: GNU ISO C++ Library, version 4.7.2

Qt project file: CppUblasMatrixExample3.pro


TEMPLATE = app


CONFIG += console


CONFIG -= qt


SOURCES += main.cpp

main.cpp


#include <boost/numeric/ublas/matrix.hpp>





const boost::numeric::ublas::matrix<double> Inverse(


  const boost::numeric::ublas::matrix<double>& m)


{


  assert(m.size1() == m.size2() && "Can only calculate the inverse of square matrices");


  assert(m.size1() == 2 && m.size2() == 2 && "Only for 2x2 matrices");


  boost::numeric::ublas::matrix<double> n(2,2);


  const double a = m(0,0);


  const double b = m(0,1);


  const double c = m(1,0);


  const double d = m(1,1);


  assert((a * d) - (b * c) != 0.0 && "Determinant must be nonzero");


  const double determinant = 1.0 / ((a * d) - (b * c));


  n(0,0) =  d * determinant;


  n(0,1) = -b * determinant;


  n(1,0) = -c * determinant;


  n(1,1) =  a * determinant;


  return n;


}





const boost::numeric::ublas::matrix<double> CreateMatrix()


{


  boost::numeric::ublas::matrix<double> m(2,2); //y-x-ordered


  m(0,0) = 4.0;


  m(0,1) = 7.0;


  m(1,0) = 2.0;


  m(1,1) = 6.0;


  return m;


}





bool IsAboutEqual(const double x, const double y) { return std::abs(x-y) < 0.00001; }





int main()


{


  //Create an example matrix


  const boost::numeric::ublas::matrix<double> m = CreateMatrix();





  assert(IsAboutEqual(m(0,0),4.0)); assert(IsAboutEqual(m(0,1),7.0));


  assert(IsAboutEqual(m(1,0),2.0)); assert(IsAboutEqual(m(1,1),6.0));





  //Obtain the inverse of the example matrix


  const boost::numeric::ublas::matrix<double> n = Inverse(m);





  assert(IsAboutEqual(n(0,0), 0.6)); assert(IsAboutEqual(n(0,1),-0.7));


  assert(IsAboutEqual(n(1,0),-0.2)); assert(IsAboutEqual(n(1,1), 0.4));





  //Check that the product of a matrix and its inverse yields an identity matrix


  const boost::numeric::ublas::matrix<double> p = boost::numeric::ublas::prod(m,n);





  assert(IsAboutEqual(p(0,0),1.0)); assert(IsAboutEqual(p(0,1),0.0));


  assert(IsAboutEqual(p(1,0),0.0)); assert(IsAboutEqual(p(1,1),1.0));


}

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(C++) boost::numeric::ublas::matrix example 3: inverse of a 2x2 matrix

Technical facts

Qt project file: CppUblasMatrixExample3.pro

main.cpp