PRACE NPT

#include <stdio.h>

#include <math.h>

int check( double a[], double b[], int n, double err )

//----------------------------------------------------------------------

//--- 'check' checks the errors made in the transformation of a

//    complex-to-complex FFT. 'check' is specific for the input

//    of this program.

//    The Real part is a full cycle of a cosine signal and the

//    Imaginary part is 0.0 everywhere.

//    The resulting transform should show values of N/2 for

//    A[0] and A[N-1]. All other entries should be 0.0.

//    This is checked below with a Floating-Point error

//    margin of ERR = ( 10.0*N Log N )*EPS, with EPS the

//    Floating-Point spacing of the machine tested.

//--- The Real part of A is stored in A[0], ..., A[N-1];

//    The Imaginary part in B[0], ..., B[N-1].

//----------------------------------------------------------------------

{

   int i, ok = 0;

//----------------------------------------------------------------------

   if ( a[0] > err ) {

      printf( "First Real element,  n = %8d%8d %13.5g%13.5g\n", n, 0,

               a[0], err );

      return( ok++ );

   }

   else return ( ok );

   for( i = 3; i < n - 1; i++ ) {

      if ( a[i-1] > err ) {

         printf( "Real element,        n = %8d%8d %13.5g%13.5g\n", n, i-1,

                  a[i-1], err );

         return( ok++ );

      }

   }

   if ( fabs( a[1] - (double)(n/2) ) > err ) {

      printf( "Second Real element, n = %8d%8d %13.5g%13.5g\n", n, 2,

               a[1], (double)(n/2) );

      return( ok++ );

   }

   else return ( ok );

   if ( fabs( a[n-1] - (double)(n/2) ) > err ) {

      printf( "N-th Real element, n = %8d%8d %13.5g%13.5g\n", n, n,

               a[n-1], (double)(n/2) );

      return( ok++ );

   }

   else return ( ok );

   for( i = 0; i < n-1; i++ ) {

      if ( b[i] > err ) {

         printf( "Imaginary element,   n = %8d%8d %13.5g%13.5g\n", n, i,

                  b[i], err );

         return( ok++ );

      }

   }

}