Linear Algebra and the C Language/a0ii

Install and compile this file in your working directory.

/* ------------------------------------ */
/*  Save as :   c00c.c                  */
/* ------------------------------------ */
#include "v_a.h"
/* ------------------------------------ */
void fun(int r)
{
double **A      = rdefinite_negative_mR(      i_mR(r,r), 99);
double **invA   =                inv_mR(A,    i_mR(r,r));
double **EValue =               eigs_mR(invA, i_mR(r,C1));

  clrscrn();  
  printf(" A: Definite negative");
  p_mR(A,S12,P6,C6);
  
  printf(" invA:");
  p_mR(invA,S12,P6,C6);
  
  printf(" Eigenvalues: eigs_mR(InvA,EValue);");
  p_mR(EValue,S9,P3,C1);    
  
  f_mR(A);
  f_mR(invA);
  f_mR(EValue);
}
/* ------------------------------------ */
int main(void)
{
time_t t;

  srand(time(&t));

do
{
  fun(RC4);

} while(stop_w());

  return 0;
}

/* ------------------------------------ */
/* ------------------------------------ */

The inverse matrix of a negative-definite matrix is negative definite.

Screen output example:

                                                                                       
 A: Definite negative
  -39.604949    +7.223354   -28.689030   -26.798513 
   +7.223354   -42.959966    -3.018440    -7.520833 
  -28.689030    -3.018440   -56.811738   +14.212596 
  -26.798513    -7.520833   +14.212596   -64.623348 

 invA:
   -0.516185    -0.165366    +0.346903    +0.309595 
   -0.165366    -0.076970    +0.113222    +0.102434 
   +0.346903    +0.113222    -0.251945    -0.212443 
   +0.309595    +0.102434    -0.212443    -0.202503 

 Eigenvalues: eigs_mR(InvA,EValue);
   -1.000 
   -0.022 
   -0.013 
   -0.012 


 Press   return to continue
 Press X return to stop