ex03g_permutation_matrix_permute_matrix_symmetric.cpp

 
#include <iostream>
#include <cla3p/dense.hpp>
#include <cla3p/perms.hpp>
#include <cla3p/algebra.hpp>
 
int main()
{
    /*
     * Create a (3x3) random symmetric lower matrix.
     */
 
    cla3p::dns::RdMatrix A(3, 3, cla3p::Property::SymmetricLower());
 
    for(cla3p::uint_t j = 0, icnt = 0; j < 3; j++)
        for(cla3p::uint_t i = j; i < 3; i++)
            A(i,j) = icnt++;
 
    /*
     * Create a (3x3) random permutation matrix.
     */
 
    cla3p::prm::PiMatrix P(3);
 
    P(0) = 1;
    P(1) = 2;
    P(2) = 0;
 
    std::cout << "A:\n" << A;
    std::cout << "P:\n" << P << "\n";
 
    /*
     * Perform the operation (P * A * P') 
     * using operators and the permute member function respectively.
     *
     * Permutation operators are used on general matrices.
     * In order to use operators A needs to be converted from symmetric to general. 
     * Resulting matrix will be general.
     *
     * Using permuteMirror() the resulting matrix will be symmetric.
     */
    cla3p::dns::RdMatrix PAPT1 = P * A.general() * P.inverse();
    std::cout << "PAPT1:\n" << PAPT1;
 
    cla3p::dns::RdMatrix PAPT2 = A.permuteMirror(P);
    std::cout << "PAPT2:\n" << PAPT2;
 
    return 0;
}