SingleSource/UnitTests/Vector/Altivec/alti.stepfft.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <float.h>
#include <altivec.h>
#define N 128
#define N2 N/2

void cfft2(int n, float x[][2], float y[][2], float w[][2], float sign);
void cffti(int n, float w[][2]);
float ggl(float *ds);
void ccopy(int n, float x[][2], float y[][2]);
void step (unsigned int n,unsigned int mj, 
           float a[][2], float b[][2], 
           float c[][2], float d[][2], 
           float w[][2], float sign);

int main(void)
{
/* SSE version of cfft2 - uses Apple intrinsics
   W. Petersen, SAM. Math. ETHZ 2 May, 2002 */
   int first,i,icase,it,n;
   int nits=1000;              /* number of iterations for timing test */
   float error,fnm1,sign,z0,z1;
   static float seed = 331.0;
   float *x,*y,*z,*w;
   float t1,ln2,mflops;
/* allocate storage for x,y,z,w on 4-word bndr. */
   x = (float *)malloc(8*N);
   y = (float *)malloc(8*N);
   z = (float *)malloc(8*N);
   w = (float *)malloc(4*N);
   first = 1;
   for(icase=0;icase<2;icase++){
   if(first){
      for(i=0;i<2*N;i+=2){
         z0 = ggl(&seed);     /* real part of array */
         z1 = ggl(&seed);     /* imaginary part of array */
         x[i] = z0;
         z[i] = z0;           /* copy of initial real data */
         x[i+1] = z1;
         z[i+1] = z1;         /* copy of initial imag. data */
      }
   } else {
      for(i=0;i<2*N;i+=2){
         z0 = 0;              /* real part of array */
         z1 = 0;              /* imaginary part of array */
         x[i] = z0;
         z[i] = z0;           /* copy of initial real data */
         x[i+1] = z1;
         z[i+1] = z1;         /* copy of initial imag. data */
      }
   }
/* initialize sine/cosine tables */
   n = N;
   cffti(n,w);
/* transform forward, back */
   if(first){
      sign = 1.0;
      cfft2(n,x,y,w,sign);
      sign = -1.0;
      cfft2(n,y,x,w,sign);
/* results should be same as initial multiplied by N */
      fnm1 = 1.0/((float) n);
      error = 0.0;
      for(i=0;i<2*N;i+=2){
         error += (z[i] - fnm1*x[i])*(z[i] - fnm1*x[i]) +
                  (z[i+1] - fnm1*x[i+1])*(z[i+1] - fnm1*x[i+1]);
      }
      error = sqrt(fnm1*error);
      printf(" for n=%d, fwd/bck error=%e\n",N,error);
      first = 0;
   } else {
      for(it=0;it<nits;it++){
         sign = +1.0;
         cfft2(n,x,y,w,sign);
         sign = -1.0;
         cfft2(n,y,x,w,sign);
      }
   }
   }
  return 0;
}
void cfft2(int n, float x[][2], float y[][2], float w[][2], float sign)
{
   int jb, m, j, mj, tgle;
   m    = (int) (log((float) n)/log(1.99));
   mj   = 1;
   tgle = 1;  /* toggling switch for work array */
   step(n,mj,&x[0],&x[n/2],&y[0],&y[mj],w,sign);
   for(j=0;j<m-2;j++){
      mj *= 2;
      if(tgle){
         step(n,mj,&y[0],&y[n/2],&x[0],&x[mj],w,sign);
         tgle = 0;
      } else {
         step(n,mj,&x[0],&x[n/2],&y[0],&y[mj],w,sign);
         tgle = 1;
      }
   }
/* last pass thru data: move y to x if needed */
   if(tgle) {
      ccopy(n,y,x);
   }
   mj   = n/2;
   step(n,mj,&x[0],&x[n/2],&y[0],&y[mj],w,sign);
}

// LLVM LOCAL begin
// Implementations of sin() and cos() may vary slightly in the accuracy of
// their results, typically only in the least significant bit.  Round to make
// the results consistent across platforms.
typedef union { double d; unsigned long long ll; } dbl_ll_union;
static double LLVMsin(double d) {
  dbl_ll_union u;
  u.d = sin(d);
  u.ll = (u.ll + 1) & ~1ULL;
  return u.d;
}
static double LLVMcos(double d) {
  dbl_ll_union u;
  u.d = cos(d);
  u.ll = (u.ll + 1) & ~1ULL;
  return u.d;
}
// LLVM LOCAL end

void cffti(int n, float w[][2])
{
   int i,n2;
   float aw,arg,pi;
   pi = 3.141592653589793;
   n2 = n/2;
   aw = 2.0*pi/((float)n);
   for(i=0;i<n2;i++){
      arg   = aw*((float)i);
      w[i][0] = LLVMcos(arg);
      w[i][1] = LLVMsin(arg);
   }
}
void ccopy(int n, float x[][2], float y[][2])
{
   int i;
   for(i=0;i<n;i++){
      y[i][0] = x[i][0];
      y[i][1] = x[i][1];
   }
}
void step (unsigned int n,unsigned int mj, 
           float a[][2], float b[][2], 
           float c[][2], float d[][2], 
           float w[][2], float sign)
{
   int j,k,jc,jw,l,lj,mj2;
   float rp,up;
   float wr[4] __attribute((aligned(16))), wu[4] __attribute((aligned(16)));
   const vector float vminus = (vector float){-0.,0.,-0.,0.};
   const vector float vzero  = (vector float){0.,0.,0.,0.};
   const vector unsigned char pv3201 = 
   (vector unsigned char){4,5,6,7,0,1,2,3,12,13,14,15,8,9,10,11};
   vector float v0,v1,v2,v3,v4,v5,v6,v7;

   mj2 = 2*mj;
   lj  = n/mj2;

   for(j=0; j<lj; j++){
      jw  = j*mj; jc  = j*mj2;
      rp = w[jw][0];
      up = w[jw][1];
      if(sign<0.0) up = -up;
      if(mj<2){
/* special case mj=1 */ 
         d[jc][0] = rp*(a[jw][0] - b[jw][0]) - up*(a[jw][1] - b[jw][1]);
         d[jc][1] = up*(a[jw][0] - b[jw][0]) + rp*(a[jw][1] - b[jw][1]);
         c[jc][0] = a[jw][0] + b[jw][0];
         c[jc][1] = a[jw][1] + b[jw][1];
      } else {
/* mj>=2 case */ 
         wr[0] = rp; wr[1] = rp; wr[2] = rp; wr[3] = rp; 
         wu[0] = up; wu[1] = up; wu[2] = up; wu[3] = up; 
         v6 = vec_ld(0,wr);
         v7 = vec_ld(0,wu);
         v7 = vec_xor(v7,vminus);
         for(k=0; k<mj; k+=2){
            v0 = vec_ld(0,(vector float *) &a[jw+k]); /* read a */
            v1 = vec_ld(0,(vector float *) &b[jw+k]); /* read b */
            v2 = vec_add(v0, v1);
            vec_st(v2,0,(vector float *) &c[jc+k]);   /* store c */
            v3 = vec_sub(v0, v1); 
            v4 = vec_perm(v3,v3,pv3201);
            v0 = vec_madd(v6,v3,vzero);
            v1 = vec_madd(v7,v4,vzero);
            v2 = vec_add(v0,v1);                     /* w*(a - b) */
            vec_st(v2,0,(vector float *) &d[jc+k]);  /* store a */
         }
      }
   }
}
float ggl(float *ds)
{

/* generate u(0,1) distributed random numbers. 
   Seed ds must be saved between calls. ggl is 
   essentially the same as the IMSL routine RNUM. 

   W. Petersen and M. Troyer, 24 Oct. 2002, ETHZ: 
   a modification of a fortran version from 
   I. Vattulainen, Tampere Univ. of Technology, 
   Finland, 1992 */

   double t,d2=0.2147483647e10;
   t   = (float) *ds;
   t   = fmod(0.16807e5*t,d2);
   *ds = (float) t;
   return((float) ((t-1.0e0)/(d2-1.0e0)));
}