(C++) boost::numeric::ublas::matrix example 5: unchop

February 24, 2017 · View on GitHub

(C++) boost::numeric::ublas::matrix example 5: unchop

boost::numeric::ublas::matrix example 5: unchop is a Boost.uBLAS library example.

Download the Qt Creator project 'CppUblasMatrixExample5' (zip)

Technical facts

Application type(s)

Desktop application

Operating system(s) or programming environment(s)

Lubuntu 12.10 (quantal)
Raspbian

Qt Creator 2.5.2

Console application

C++11

G++ 4.7.2

Libraries used:

STL: GNU ISO C++ Library, version 4.7.2

Qt project file: CppUblasMatrixExample5.pro

`TEMPLATE = app CONFIG += console CONFIG -= qt QMAKE_CXXFLAGS += -std=c++11 SOURCES += main.cpp`

main.cpp

#ifdef _WIN32 #undef __STRICT_ANSI__ #endif #include <climits> #include <vector> #include <boost/numeric/ublas/assignment.hpp> #include <boost/numeric/ublas/detail/matrix_assign.hpp> #include <boost/numeric/ublas/matrix.hpp> #include <boost/numeric/ublas/matrix_proxy.hpp> ///Chop returns a std::vector of sub-matrices //[ A at [0] B at [1] ] //[ C at [2] D at [4] ] const std::vector<boost::numeric::ublas::matrix<double> > Chop( const boost::numeric::ublas::matrix<double>& m) { using boost::numeric::ublas::range; using boost::numeric::ublas::matrix; using boost::numeric::ublas::matrix_range; std::vector<matrix<double> > v; v.reserve(4); const int midy = m.size1() / 2; const int midx = m.size2() / 2; const matrix_range<const matrix<double> > top_left( m,range(0 ,midy ),range(0 ,midx )); const matrix_range<const matrix<double> > bottom_left( m,range(midy,m.size1()),range(0 ,midx )); const matrix_range<const matrix<double> > top_right( m,range(0 ,midy ),range(midx,m.size2())); const matrix_range<const matrix<double> > bottom_right(m,range(midy,m.size1()),range(midx,m.size2())); v.push_back(matrix<double>(top_left)); v.push_back(matrix<double>(top_right)); v.push_back(matrix<double>(bottom_left)); v.push_back(matrix<double>(bottom_right)); return v; } ///Unchop merges the 4 std::vector of sub-matrices produced by Chop const boost::numeric::ublas::matrix<double> Unchop( const std::vector<boost::numeric::ublas::matrix<double> >& v) { //Chop returns a std::vector of sub-matrices //[ A at [0] B at [1] ] //[ C at [2] D at [4] ] using boost::numeric::ublas::range; using boost::numeric::ublas::matrix; using boost::numeric::ublas::matrix_range; assert(v.size() == 4); assert(v[0].size1() == v[1].size1()); assert(v[2].size1() == v[3].size1()); assert(v[0].size2() == v[2].size2()); assert(v[1].size2() == v[3].size2()); boost::numeric::ublas::matrix<double> m(v[0].size1() + v[2].size1(),v[0].size2() + v[1].size2()); for (int quadrant=0; quadrant!=4; ++quadrant) { const boost::numeric::ublas::matrix<double>& w = v[quadrant]; const std::size_t n_rows = v[quadrant].size1(); const std::size_t n_cols = v[quadrant].size2(); const int offset_x = quadrant % 2 ? v[0].size2() : 0; const int offset_y = quadrant / 2 ? v[0].size1() : 0; for (std::size_t row=0; row!=n_rows; ++row) { for (std::size_t col=0; col!=n_cols; ++col) { m(offset_y + row, offset_x + col) = w(row,col); } } } assert(v[0].size1() + v[2].size1() == m.size1()); assert(v[1].size1() + v[3].size1() == m.size1()); assert(v[0].size2() + v[1].size2() == m.size2()); assert(v[2].size2() + v[3].size2() == m.size2()); return m; } const boost::numeric::ublas::matrix<double> CreateRandomMatrix(const std::size_t n_rows, const std::size_t n_cols) { boost::numeric::ublas::matrix<double> m(n_rows,n_cols); for (std::size_t row=0; row!=n_rows; ++row) { for (std::size_t col=0; col!=n_cols; ++col) { m(row,col) = static_cast<double>(std::rand()) / static_cast<double>(RAND_MAX); } } return m; } int main() { using boost::numeric::ublas::detail::equals; using boost::numeric::ublas::matrix; //Check 0x0 to and including 9x9 matrices for (std::size_t n_rows = 0; n_rows!=10; ++n_rows) { for (std::size_t n_cols = 0; n_cols!=10; ++n_cols) { //Epsilon is more or less the smallest round-off error const double epsilon = std::numeric_limits<double>::epsilon(); //Create a random matrix const matrix<double> m = CreateRandomMatrix(n_rows,n_cols); //Assume it is found identical to itself assert(equals(m,m,epsilon,epsilon)); //Chop and unchop the input matrix const matrix<double> n = Unchop(Chop(m)); //Assume input matrix and result are identical assert(equals(m,n,epsilon,epsilon)); } } }