/*
 * Copyright (c) 2003, 2007-14 Matteo Frigo
 * Copyright (c) 2003, 2007-14 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

/* express a twiddle problem in terms of dft + multiplication by
   twiddle factors */

#include "dft/ct.h"

typedef ct_solver S;

typedef struct {
     plan_dftw super;

     INT r, rs, m, mb, me, ms, v, vs;

     plan *cld;

     twid *td;

     const S *slv;
     int dec;
} P;

static void mktwiddle(P *ego, enum wakefulness wakefulness)
{
     static const tw_instr tw[] = { { TW_FULL, 0, 0 }, { TW_NEXT, 1, 0 } };

     /* note that R and M are swapped, to allow for sequential
	access both to data and twiddles */
     X(twiddle_awake)(wakefulness, &ego->td, tw,
		      ego->r * ego->m, ego->m, ego->r);
}

static void bytwiddle(const P *ego, R *rio, R *iio)
{
     INT iv, ir, im;
     INT r = ego->r, rs = ego->rs;
     INT m = ego->m, mb = ego->mb, me = ego->me, ms = ego->ms;
     INT v = ego->v, vs = ego->vs;
     const R *W = ego->td->W;

     mb += (mb == 0); /* skip m=0 iteration */
     for (iv = 0; iv < v; ++iv) {
	  for (ir = 1; ir < r; ++ir) {
	       for (im = mb; im < me; ++im) {
		    R *pr = rio + ms * im + rs * ir;
		    R *pi = iio + ms * im + rs * ir;
		    E xr = *pr;
		    E xi = *pi;
		    E wr = W[2 * im + (2 * (m-1)) * ir - 2];
		    E wi = W[2 * im + (2 * (m-1)) * ir - 1];
		    *pr = xr * wr + xi * wi;
		    *pi = xi * wr - xr * wi;
	       }
	  }
	  rio += vs;
	  iio += vs;
     }
}

static int applicable(INT irs, INT ors, INT ivs, INT ovs,
		      const planner *plnr)
{
     return (1
	     && irs == ors
	     && ivs == ovs
	     && !NO_SLOWP(plnr)
	  );
}

static void apply_dit(const plan *ego_, R *rio, R *iio)
{
     const P *ego = (const P *) ego_;
     plan_dft *cld;
     INT dm = ego->ms * ego->mb;

     bytwiddle(ego, rio, iio);

     cld = (plan_dft *) ego->cld;
     cld->apply(ego->cld, rio + dm, iio + dm, rio + dm, iio + dm);
}

static void apply_dif(const plan *ego_, R *rio, R *iio)
{
     const P *ego = (const P *) ego_;
     plan_dft *cld;
     INT dm = ego->ms * ego->mb;

     cld = (plan_dft *) ego->cld;
     cld->apply(ego->cld, rio + dm, iio + dm, rio + dm, iio + dm);

     bytwiddle(ego, rio, iio);
}

static void awake(plan *ego_, enum wakefulness wakefulness)
{
     P *ego = (P *) ego_;
     X(plan_awake)(ego->cld, wakefulness);
     mktwiddle(ego, wakefulness);
}

static void destroy(plan *ego_)
{
     P *ego = (P *) ego_;
     X(plan_destroy_internal)(ego->cld);
}

static void print(const plan *ego_, printer *p)
{
     const P *ego = (const P *) ego_;
     p->print(p, "(dftw-generic-%s-%D-%D%v%(%p%))",
	      ego->dec == DECDIT ? "dit" : "dif",
	      ego->r, ego->m, ego->v, ego->cld);
}

static plan *mkcldw(const ct_solver *ego_,
		    INT r, INT irs, INT ors,
		    INT m, INT ms,
		    INT v, INT ivs, INT ovs,
		    INT mstart, INT mcount,
		    R *rio, R *iio,
		    planner *plnr)
{
     const S *ego = (const S *)ego_;
     P *pln;
     plan *cld = 0;
     INT dm = ms * mstart;

     static const plan_adt padt = {
	  0, awake, print, destroy
     };

     A(mstart >= 0 && mstart + mcount <= m);
     if (!applicable(irs, ors, ivs, ovs, plnr))
          return (plan *)0;

     cld = X(mkplan_d)(plnr,
			X(mkproblem_dft_d)(
			     X(mktensor_1d)(r, irs, irs),
			     X(mktensor_2d)(mcount, ms, ms, v, ivs, ivs),
			     rio + dm, iio + dm, rio + dm, iio + dm)
			);
     if (!cld) goto nada;

     pln = MKPLAN_DFTW(P, &padt, ego->dec == DECDIT ? apply_dit : apply_dif);
     pln->slv = ego;
     pln->cld = cld;
     pln->r = r;
     pln->rs = irs;
     pln->m = m;
     pln->ms = ms;
     pln->v = v;
     pln->vs = ivs;
     pln->mb = mstart;
     pln->me = mstart + mcount;
     pln->dec = ego->dec;
     pln->td = 0;

     {
	  double n0 = (r - 1) * (mcount - 1) * v;
	  pln->super.super.ops = cld->ops;
	  pln->super.super.ops.mul += 8 * n0;
	  pln->super.super.ops.add += 4 * n0;
	  pln->super.super.ops.other += 8 * n0;
     }
     return &(pln->super.super);

 nada:
     X(plan_destroy_internal)(cld);
     return (plan *) 0;
}

static void regsolver(planner *plnr, INT r, int dec)
{
     S *slv = (S *)X(mksolver_ct)(sizeof(S), r, dec, mkcldw, 0);
     REGISTER_SOLVER(plnr, &(slv->super));
     if (X(mksolver_ct_hook)) {
	  slv = (S *)X(mksolver_ct_hook)(sizeof(S), r, dec, mkcldw, 0);
	  REGISTER_SOLVER(plnr, &(slv->super));
     }
}

void X(ct_generic_register)(planner *p)
{
     regsolver(p, 0, DECDIT);
     regsolver(p, 0, DECDIF);
}