Linear Algebra and the C Language/a01f

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/*  Save as : vepivot.h                 */
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double pivotbest_mR(
double **A,
int pv
)
{
int r;
int c;
int     best_r = pv;
int     best_c = pv;

double    sign = 1.;

double pv_best = fabs(A[pv][pv]);           

  for   ( r=pv; r<A[R_SIZE][C0]; r++)
    for ( c=pv; c<A[C_SIZE][C0]; c++)

           if(fabs(A[r][c])>pv_best )           
             {
              pv_best = fabs(A[r][c]);          
               best_r = r;
               best_c = c;
             }

 if(best_r!=pv){ sign*=-1; swapR_mR(A,pv,best_r); }
 if(best_c!=pv){ sign*=-1; swapC_mR(A,pv,best_c); }

 return(sign);
}
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double zero_under_pivot_mR(
double **A,
int pv
)
{
int r;
double pivot = A[pv][pv];

  if(fabs(pivot)>ERROR_E)
    {            
     mulR_mR( A,(1./pivot),pv); 

     for( r=(pv+R1); r<A[R_SIZE][C0]; r++) 

         addR_mR( A,(-A[r][pv]),pv,r);
    }
   else pivot= 0.0;

 return(pivot);
}
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