[CSC 335] ztest (armadillo version)

[Andrew J. Pounds]

I was asked to send out an example of using C++ and Armadillo using 
complex numbers.  I am including here my ztestarma.cpp source, which 
solves the same problem that ztest.f90 and gslztest.c solved.  Basically 
a complex matrix is created, I take the inverse of the matrix, and them 
multiply the inverse and the original matrix.  The solution should be a 
matrix with all 1 along the diagonal -- but due to numerical precision 
errors this is rarely the case.  At the end I sum up the diagonal 
elements to see if it matches the matrix dimension.

#include <iostream>
#include <armadillo>
// Compile with gcc gslztest.c -lgsl -lm

using namespace std;

int main (void)
{

     const int N = 10;
     int i, j;
     double pi, NCUBE, alpha;
     complex<double> sumdiag;


     // Create pointers and allocate space for complex matrices
     arma::cx_dmat A(N,N);
     arma::cx_dmat B(N,N);
     arma::cx_dmat C(N,N);
     arma::cx_dmat INV(N,N);


     pi = acos(-1.0);

     // Set the value of N^3 since we use is a lot

     NCUBE = (double) N * (double) N * (double) N;

     // Now fill the matrices with the same info

     for (i=1; i<=N; i++)
         for (j=1; j<=N; j++) {
             alpha =  sqrt( pow(cos ( (double) (  i*i*j) * pi / NCUBE ),2) +
                            pow(sin ( (double) (2*i*i*j) * pi / NCUBE ),2));
             alpha = (double) 1.0 / alpha;
             A( i-1, j-1) = complex<double>(
                       alpha * cos( (double) (  i*i*j) * pi / NCUBE ),
                       alpha * sin( (double) (2*i*i*j) * pi / NCUBE ));
             B( i-1, j-1) = A( i-1, j-1);
         }

     inv(INV,B);

     C = INV*A;

     sumdiag = complex<double>(0.0,0.0);
     for (i=0;i<N;i++) sumdiag = sumdiag + C(i,i);


     printf("Sum of diagonal is %g + i %g\n", sumdiag);

}

-- 
*Andrew J. Pounds, Ph.D.*
/Professor of Chemistry and Computer Science/
/Director of the Computational Science Program/
/Mercer University, Macon, GA, 31207 (478) 301-5627 /
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