[Help-gsl] Please, run the two programms.

[Jo_Jo]

Please, run the two programms.
In both programms vector v is not equal to vector Q*v, or Qtraqnsp * v.



With regards

Andrzej Buczynski
Moosburg,  Germany

/*

  int gsl_linalg_QR_Qvec (const gsl matrix * QR, 
                          const gsl vector * tau,
                          gsl vector * v )

* This function applies the matrix Q encoded in the decomposition
*  (QR,tau) to the vector v, storing the result Qv in v. 
* 
*  Should be :   v = Qv 
*  
*/

#include <stdio.h>
#include <gsl/gsl_linalg.h>

int main (void)
{
  double a_data[] =       {-0.18, 0.60,  0.57, 0.96,
                            0.41, 0.24, -0.99, 0.58,
                           -0.14, 0.30,  0.97, 0.66,
                           -0.51, 0.13,  0.19, 0.85,
                            0.33, 0.44, -0.66, 0.12 };
        
       double b_data[] = { 1.0, 1.0, 1.0, 1.0 };

       int M = 4, N = 4 , i ;

       gsl_vector * tau = gsl_vector_alloc( GSL_MIN_INT ( M, N ) );
       gsl_matrix_view m = gsl_matrix_view_array (a_data, M, N);
       gsl_vector_set_zero ( tau ) ; 
       gsl_vector_view v = gsl_vector_view_array (b_data, N);
 
 printf("-----vector v   ---------\n");
for (i = 0; i < M; i++) {
    printf ("%f ",gsl_vector_get (&v.vector, i ) );
    printf("\n"); };

printf("now, we are calling the function gsl_linalg_QR_Qvec()--\n");

       (void) gsl_linalg_QR_Qvec (&m.matrix, tau, &v.vector ) ;

printf(" and the-vector v should be Q *v , but is't ---------\n");

for (i = 0; i < M; i++) {
    printf ("%f ",gsl_vector_get (&v.vector, i ) );
    
    printf("\n"); };



 printf(" the-vector tau is not chenged too---------\n");
 for (i = 0; i < M; i++) {
    printf ("%f ",gsl_vector_get (tau, i ) );
    printf("\n"); };
 
 
     gsl_vector_free(tau);

       return 0;
  } ;



/*
  int gsl_linalg_QR_QTvec (const gsl_matrix * QR, 
                           const gsl_vector * tau, 
                                  gsl_vector * v )
 
This function applies the matrix QT encoded in the decomposition 
(QR,tau) to the vector v, storing the result QT*v in v. 
The matrix multiplication is carried out directly
using the encoding of the Householder vectors without
needing to form the full matrix  QT .
    
*/

#include <stdio.h>
#include <gsl/gsl_linalg.h>

int main (void)
{
  double a_data[] =       {-0.18, 0.60,  0.57, 0.96,
                            0.41, 0.24, -0.99, 0.58,
                           -0.14, 0.30,  0.97, 0.66,
                           -0.51, 0.13,  0.19, 0.85,
                            0.33, 0.44, -0.66, 0.12 };
        
       double b_data[] = { 1.0, 1.0, 1.0, 1.0 };

       int M = 4, N = 4 , i ;

       gsl_vector * tau = gsl_vector_alloc( GSL_MIN_INT ( M, N ) );
       gsl_matrix_view m = gsl_matrix_view_array (a_data, M, N);
//       gsl_vector_set_zero ( tau ) ; 
       gsl_vector_view v = gsl_vector_view_array (b_data, N);

       (void) gsl_linalg_QR_QTvec (&m.matrix, tau, &v.vector ) ;

   printf("-----vector v = QTrans*v---------\n");

for (i = 0; i < M; i++) {
    printf ("%f ",gsl_vector_get (&v.vector, i ) );
    
    printf("\n"); };

 printf("-----vector tau---------\n");
 for (i = 0; i < M; i++) {
    printf ("%f ",gsl_vector_get (tau, i ) );
    printf("\n"); };

 
 
     gsl_vector_free(tau);
       return 0;
     }