PRACE NPT

#include <stdio.h>

#include <math.h>

void nflops( int m, int *mfli, int *mflt )

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

// --- nflops calculates the number of flops for the complex-to-

//     complex Radix-4 FFT of length 2**m.

//     m should be >= 2.

// --- In the initialisation part it is assumed that the evaluation

//     of a Sine or Cosine function takes 10 flops.

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

{

   int mfl2, mfl3, mdiv, mmod, m2, n, n12, n14, n24, n4;

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

// --- Test input parameter.

   if ( m < 2 ) {

      printf( " *** Error in routine Nflops: m < 2 : m = %d\n", m );

      return;

   }

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

// --- Marginal cases:

   if ( m == 2 ) {

      *mfli = 22; *mflt = 20;

      return;

   }

   if ( m == 3 ) {

      *mfli = 107; *mflt = 86;

      return;

   }

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

// --- Initialisation part.

   m2    = ( m + 1 )/2;

   *mfli = 21* ( (int)pow( 4, m2 ) - 1 )/3  + m2;

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

// --- Transform part:

   n = (int)pow( 2, m );

   if ( n < 64 ) {

      if ( n == 16 ) {

         *mflt = 264;

      }

      else if ( n == 32 ) {

         *mflt = 644;

      }

   }

   else {

      n4   = n/4;

      mfl2 = 54*n4 + 48;

      mmod = m%4;

      mdiv = ( m - 1 )/4;

      n12  = 23*n4;

      n14  = 48*n4;

      n24  = n14 + n14;

      mfl3 = ( mdiv - 1 )*n24;

      switch( mmod ) {

      case 0:

         mfl3 = mfl3 + n24;

         break;

      case 1:

         mfl3 = mfl3 + n12;

         break;

      case 2:

         mfl3 = mfl3 + n14;

         break;

      case 3:

         mfl3 = mfl3 + n14 + n12;

         break;

      }

      *mflt = mfl2 + mfl3;

   }

}