/*
 * Copyright (c) 1997-1999 Massachusetts Institute of Technology
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

/*
 *
 * executor_cilk.cilk -- execute the fft on a parallel machine with Cilk
 */

#include <cilk.h>
#include <cilk-lib.h>

#include <fftw-int.h>
#include "fftw_cilk.cilkh"

static cilk void parallel_twiddle_codelet(int a, int b,
					  fftw_twiddle_codelet *codelet,
					  fftw_complex *W,
					  fftw_complex *out,
					  int ostride,
					  int dist,
					  int ntwiddle)
{
     if (b - a < 32) {
	  (*codelet)(out + dist * a, W + ntwiddle * a, ostride, b - a, dist);
     } else {
	  int ab = (a + b) / 2;
	  spawn parallel_twiddle_codelet(a, ab, codelet, W, out, ostride,
					 dist, ntwiddle);
	  spawn parallel_twiddle_codelet(ab, b, codelet, W, out, ostride,
					 dist, ntwiddle);
	  sync;
     }
}

static cilk void executor_simple_cilk(int n, const fftw_complex *in,
				      fftw_complex *out,
				      fftw_plan_node *p,
				      int istride,
				      int ostride)
{
     switch (p->type) {
	 case FFTW_NOTW:
	      (*p->nodeu.notw.codelet)(in, out, istride, ostride);
	      break;

	 case FFTW_TWIDDLE:
	      {
		   int r = p->nodeu.twiddle.size;
		   int m = n / r;
		   int i;
		   fftw_twiddle_codelet *codelet;
		   fftw_complex *W;

		   if (n < 128) {
			fftw_executor_simple(n, in, out, p,
					     istride, ostride);
			break;
		   }

		   for (i = 0; i < r; ++i)
			spawn executor_simple_cilk(m, in + i * istride,
						   out + i * (m * ostride),
						   p->nodeu.twiddle.recurse,
						   istride * r, ostride);
			
		   sync;
		   codelet = p->nodeu.twiddle.codelet;
		   W = p->nodeu.twiddle.tw->twarray;

		   spawn parallel_twiddle_codelet(0, m,
						  codelet, 
						  W, out, m * ostride,
						  ostride,
				      p->nodeu.twiddle.codelet_desc->ntwiddle);
		   sync;

		   break;
	      }

	 case FFTW_GENERIC:
	      {
		   int r = p->nodeu.generic.size;
		   int m = n / r;
		   int i;
		   fftw_generic_codelet *codelet;
		   fftw_complex *W;

		   for (i = 0; i < r; ++i)
			spawn executor_simple_cilk(m, in + i * istride,
						   out + i * (m * ostride),
						   p->nodeu.generic.recurse,
						   istride * r, ostride);
						   
		   sync;

		   codelet = p->nodeu.generic.codelet;
		   W = p->nodeu.generic.tw->twarray;

		   (*codelet)(out, W, m, r, n, ostride);

		   break;
	      }

	 case FFTW_RADER:
	      {
		   int r = p->nodeu.rader.size;
		   int m = n / r;
		   int i;
		   fftw_rader_codelet *codelet;
		   fftw_complex *W;

		   for (i = 0; i < r; ++i) {
			spawn executor_simple_cilk(m, in + i * istride,
					     out + i * (m * ostride),
					     p->nodeu.rader.recurse,
					     istride * r, ostride);
		   }
		   sync;

		   codelet = p->nodeu.rader.codelet;
		   W = p->nodeu.rader.tw->twarray;
		   (*codelet)(out, W, m, r, ostride,
			      p->nodeu.rader.rader_data);

		   break;
	      }

	 default:
	      fftw_die("BUG in executor: illegal plan\n");
	      break;
     }
}

static cilk void executor_simple_inplace_cilk(int n, fftw_complex *in,
						 fftw_plan_node *p,
						 int istride)
{
     switch (p->type) {
	 case FFTW_NOTW:
	      (*p->nodeu.notw.codelet) (in, in, istride, istride);
	      break;

	 default:
	      {
		   fftw_complex *tmp;

		   tmp = (fftw_complex *)
			Cilk_alloca(n * sizeof(fftw_complex));

		   spawn executor_simple_cilk(n, in, tmp, p, istride, 1);
		   sync;
		   fftw_strided_copy(n, tmp, istride, in);
	      }
     }
}

#define FFTW_CILK_HOWMANY_CODELET_THRESHOLD 16
#define FFTW_CILK_HOWMANY_SIMPLE_THRESHOLD 16

typedef struct {
     int n; fftw_plan_node *p;
     fftw_notw_codelet *codelet;
     const fftw_complex *in,*out;
     int istride, ostride, idist,odist;
} execute_howmany_data;

static cilk void execute_howmany_codelets(
     execute_howmany_data *d,
     int min, int max)
{
     if (max - min > FFTW_CILK_HOWMANY_CODELET_THRESHOLD) {
	  spawn execute_howmany_codelets(d,
					 min,(min+max)/2);
	  spawn execute_howmany_codelets(d,
					 (min+max)/2+1,max);
     }
     else {
	  fftw_notw_codelet *codelet;
	  fftw_complex *in,*out;
	  int istride, ostride, idist,odist;

	  codelet = d->codelet;
	  in = d->in; out = d->out;
	  istride = d->istride; ostride = d->ostride;
	  idist = d->idist; odist = d->odist;

	  for (; min <= max; ++min)
	       (*codelet)(in + min * idist, 
			  out + min * odist,istride,ostride);
     }
}

static cilk void execute_howmany_simple(
     execute_howmany_data *d,
     int min, int max)
{
     if (max - min > FFTW_CILK_HOWMANY_SIMPLE_THRESHOLD) {
	  spawn execute_howmany_simple(d,
				       min,(min+max)/2);
	  spawn execute_howmany_simple(d,
				       (min+max)/2+1,max);
     }
     else {
	  int n;
	  fftw_complex *in, *out;
	  fftw_plan_node *p;
	  int idist, odist, istride, ostride;

	  n = d->n;
	  p = d->p;
	  in = d->in;
	  out = d->out;
	  istride = d->istride;
	  ostride = d->ostride;
	  idist = d->idist;
	  odist = d->odist;

	  for (; min <= max; ++min)
	       fftw_executor_simple(n, in + min*idist, 
				    out + min*odist,
				    p, istride, ostride);
     }
}

static cilk void executor_many_cilk(int n, const fftw_complex *in,
				    fftw_complex *out,
				    fftw_plan_node *p,
				    int istride,
				    int ostride,
				    int howmany, int idist, int odist)
{
     switch (p->type) {
	 case FFTW_NOTW:
	      {
		   execute_howmany_data d;

		   d.codelet = p->nodeu.notw.codelet;
		   d.in = in; d.out = out;
		   d.istride = istride; d.ostride = ostride;
		   d.idist = idist; d.odist = odist;

		   spawn execute_howmany_codelets(&d,0,howmany-1);

		   break;
	      }

	 default:
	      {
		   execute_howmany_data d;

		   d.n = n; d.p = p;
		   d.in = in; d.out = out;
		   d.istride = istride; d.ostride = ostride;
		   d.idist = idist; d.odist = odist;

		   spawn execute_howmany_simple(&d,0,howmany-1);
	      }
     }
}

static cilk void execute_howmany_codelets_in_place(
     execute_howmany_data *d,
     int min, int max)
{
     if (max - min > FFTW_CILK_HOWMANY_CODELET_THRESHOLD) {
	  spawn execute_howmany_codelets_in_place(d,
						  min,(min+max)/2);
	  spawn execute_howmany_codelets_in_place(d,
						  (min+max)/2+1,max);
     }
     else {
	  fftw_notw_codelet *codelet;
	  fftw_complex *in;
	  int istride, idist;

	  codelet = d->codelet;
	  in = d->in;
	  istride = d->istride;
	  idist = d->idist;

	  for (; min <= max; ++min)
	       (*codelet)(in + min * idist, 
			  in + min * idist,istride,istride);
     }
}

static cilk void execute_howmany_simple_in_place(
     execute_howmany_data *d,
     int min, int max)
{
     if (max - min > FFTW_CILK_HOWMANY_SIMPLE_THRESHOLD) {
	  spawn execute_howmany_simple_in_place(d,
						min,(min+max)/2);
	  spawn execute_howmany_simple_in_place(d,
						(min+max)/2+1,max);
     }
     else {
	  int n;
          fftw_complex *in,*tmp;
          int istride,idist;
	  fftw_plan_node *p;
	  
	  n = d->n;
	  p = d->p;
          in = d->in + min * (idist = d->idist);
          istride = d->istride;
	  tmp = d->out + n * Self;

	  for (; min <= max; ++min) {
	       fftw_executor_simple(n, in, tmp, p, istride, 1);
	       fftw_strided_copy(n, tmp, istride, in);
	       in += idist;
	  }
     }
}

static cilk void executor_many_inplace_cilk(int n, fftw_complex *in,
					    fftw_plan_node *p,
					    int istride,
					    int howmany, int idist)
{
     switch (p->type) {
	 case FFTW_NOTW:
	      {
		   execute_howmany_data d;

		   d.codelet = p->nodeu.notw.codelet;
		   d.in = in;
		   d.istride = istride;
		   d.idist = idist;

		   spawn execute_howmany_codelets_in_place(&d,0,howmany-1);

		   break;
	      }

	 default:
	      {
		   execute_howmany_data d;

		   d.n = n;
		   d.p = p;
		   d.in = in;
		   d.istride = istride;
		   d.idist = idist;
		   d.out = (fftw_complex *)
			Cilk_alloca(Cilk_active_size *
				    n * sizeof(fftw_complex));

		   spawn execute_howmany_simple_in_place(&d,0,howmany-1);
	      }
     }
}

/* user interface */
cilk void fftw_cilk(fftw_plan plan, int howmany, fftw_complex *in, int istride,
		    int idist, fftw_complex *out, int ostride, int odist)
{
     int n = plan->n;

     if (plan->flags & FFTW_IN_PLACE) {
	  if (howmany == 1) {
	       spawn executor_simple_inplace_cilk(n, in, 
						  plan->root, istride);
	  } else {
	       spawn executor_many_inplace_cilk(n, in,
						plan->root, istride, howmany,
						idist);
	  }
     } else {
	  if (howmany == 1) {
	       spawn executor_simple_cilk(n, in, out,
					  plan->root, istride, ostride);
	  } else {
	       spawn executor_many_cilk(n, in, out, 
					plan->root, istride, ostride,
					howmany, idist, odist);
	  }
     }
}