/******************************************************************************
*									      *
*  COMPUTE GAUSS SUM							      *
*  04/02/10 (dkc)							      *
*									      *
******************************************************************************/
#include <math.h>
void gauss(unsigned int n, unsigned int k, double *xi, double *out) {
unsigned int i;
double pi,sumre,sumim,tempre,tempim;
pi=3.141592654;
sumre=0.0;
sumim=0.0;
for (i=1; i<=k; i++) {
   tempre=cos(2.0*pi*(double)i*(double)n/(double)k);
   tempim=sin(2.0*pi*(double)i*(double)n/(double)k);
   sumre=sumre+xi[2*i-2]*tempre-xi[2*i-1]*tempim;
   sumim=sumim+xi[2*i-2]*tempim+xi[2*i-1]*tempre;
   }
out[0]=sumre;
out[1]=sumim;
return;
}