Linear Algebra and the C Language/a0gw

Install and compile this file in your working directory.

/* ------------------------------------ */
/*  Save as :   c00d.c                  */
/* ------------------------------------ */
#include "v_a.h"
/* ------------------------------------ */
void fun(int rc)
{
double **A     = rcentrosymmetric_mR( i_mR(rc,rc),9.);
double **invA  =                      i_mR(rc,rc);
double **AinvA =                      i_mR(rc,rc);

  clrscrn();

  printf(" A:");
  p_mR(A, S4,P0,C6);

  printf(" invA:");
  p_mR(inv_mR(A,invA), S4,P5,C6);

  printf(" A * invA:");
  p_mR(mul_mR(A,invA,AinvA), S4,P5,C6);
    
  f_mR(A);
  f_mR(invA);
  f_mR(AinvA);
}
/* ------------------------------------ */
int main(void)
{
time_t t;

  srand(time(&t));
  
   do 
         fun(rp_I(RC2)*RC2 + RC1);
        
    while(stop_w());
        
  return 0;
}
/* ------------------------------------ */
/* ------------------------------------ */

The inverse of a centrosymmetric matrix is a centrosymmetric matrix

Screen output example:

                                                                                       
A:
  -2   +7   -4   -3   +4 
  -9   -9   +9   -1   -4 
  +6   +4   +2   +4   +6 
  -4   -1   +9   -9   -9 
  +4   -3   -4   +7   -2 

 invA:
-0.20054 -0.12046 -0.01389 -0.01842 -0.11891 
+0.25815 +0.05967 +0.11806 +0.12089 +0.20713 
+0.02778 +0.05556 +0.11111 +0.05556 +0.02778 
+0.20713 +0.12089 +0.11806 +0.05967 +0.25815 
-0.11891 -0.01842 -0.01389 -0.12046 -0.20054 

 A * invA:
+1.00000 +0.00000 +0.00000 +0.00000 +0.00000 
-0.00000 +1.00000 -0.00000 +0.00000 -0.00000 
-0.00000 +0.00000 +1.00000 +0.00000 +0.00000 
+0.00000 -0.00000 +0.00000 +1.00000 -0.00000 
-0.00000 +0.00000 -0.00000 -0.00000 +1.00000 


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