/*

 * 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

 *

 */

/* plans for RDFT of rank >= 2 (multidimensional) */

/* FIXME: this solver cannot strictly be applied to multidimensional

   DHTs, since the latter are not separable...up to rnk-1 additional

   post-processing passes may be required.  See also:

   R. N. Bracewell, O. Buneman, H. Hao, and J. Villasenor, "Fast

   two-dimensional Hartley transform," Proc. IEEE 74, 1282-1283 (1986).

   H. Hao and R. N. Bracewell, "A three-dimensional DFT algorithm

   using the fast Hartley transform," Proc. IEEE 75(2), 264-266 (1987).

*/

#include "rdft/rdft.h"

typedef struct {

     solver super;

     int spltrnk;

     const int *buddies;

     size_t nbuddies;

} S;

typedef struct {

     plan_rdft super;

     plan *cld1, *cld2;

     const S *solver;

} P;

/* Compute multi-dimensional RDFT by applying the two cld plans

   (lower-rnk RDFTs). */

static void apply(const plan *ego_, R *I, R *O)

{

     const P *ego = (const P *) ego_;

     plan_rdft *cld1, *cld2;

     cld1 = (plan_rdft *) ego->cld1;

     cld1->apply(ego->cld1, I, O);

     cld2 = (plan_rdft *) ego->cld2;

     cld2->apply(ego->cld2, O, O);

}

static void awake(plan *ego_, enum wakefulness wakefulness)

{

     P *ego = (P *) ego_;

     X(plan_awake)(ego->cld1, wakefulness);

     X(plan_awake)(ego->cld2, wakefulness);

}

static void destroy(plan *ego_)

{

     P *ego = (P *) ego_;

     X(plan_destroy_internal)(ego->cld2);

     X(plan_destroy_internal)(ego->cld1);

}

static void print(const plan *ego_, printer *p)

{

     const P *ego = (const P *) ego_;

     const S *s = ego->solver;

     p->print(p, "(rdft-rank>=2/%d%(%p%)%(%p%))",

        s->spltrnk, ego->cld1, ego->cld2);

}

static int picksplit(const S *ego, const tensor *sz, int *rp)

{

     A(sz->rnk > 1); /* cannot split rnk <= 1 */

     if (!X(pickdim)(ego->spltrnk, ego->buddies, ego->nbuddies, sz, 1, rp))

    return 0;

     *rp += 1; /* convert from dim. index to rank */

     if (*rp >= sz->rnk) /* split must reduce rank */

    return 0;

     return 1;

}

static int applicable0(const solver *ego_, const problem *p_, int *rp)

{

     const problem_rdft *p = (const problem_rdft *) p_;

     const S *ego = (const S *)ego_;

     return (1

       && FINITE_RNK(p->sz->rnk) && FINITE_RNK(p->vecsz->rnk)

       && p->sz->rnk >= 2

       && picksplit(ego, p->sz, rp)

    );

}

/* TODO: revise this. */

static int applicable(const solver *ego_, const problem *p_, 

          const planner *plnr, int *rp)

{

     const S *ego = (const S *)ego_;

     if (!applicable0(ego_, p_, rp)) return 0;

     if (NO_RANK_SPLITSP(plnr) && (ego->spltrnk != ego->buddies[0]))

    return 0;

     if (NO_UGLYP(plnr)) {

    /* Heuristic: if the vector stride is greater than the transform

       sz, don't use (prefer to do the vector loop first with a

       vrank-geq1 plan). */

    const problem_rdft *p = (const problem_rdft *) p_;

    if (p->vecsz->rnk > 0 &&

        X(tensor_min_stride)(p->vecsz) > X(tensor_max_index)(p->sz))

         return 0;

     }

     return 1;

}

static plan *mkplan(const solver *ego_, const problem *p_, planner *plnr)

{

     const S *ego = (const S *) ego_;

     const problem_rdft *p;

     P *pln;

     plan *cld1 = 0, *cld2 = 0;

     tensor *sz1, *sz2, *vecszi, *sz2i;

     int spltrnk;

     static const plan_adt padt = {

    X(rdft_solve), awake, print, destroy

     };

     if (!applicable(ego_, p_, plnr, &spltrnk))

          return (plan *) 0;

     p = (const problem_rdft *) p_;

     X(tensor_split)(p->sz, &sz1, spltrnk, &sz2);

     vecszi = X(tensor_copy_inplace)(p->vecsz, INPLACE_OS);

     sz2i = X(tensor_copy_inplace)(sz2, INPLACE_OS);

     cld1 = X(mkplan_d)(plnr, 

      X(mkproblem_rdft_d)(X(tensor_copy)(sz2),

              X(tensor_append)(p->vecsz, sz1),

              p->I, p->O, p->kind + spltrnk));

     if (!cld1) goto nada;

     cld2 = X(mkplan_d)(plnr, 

      X(mkproblem_rdft_d)(

           X(tensor_copy_inplace)(sz1, INPLACE_OS),

           X(tensor_append)(vecszi, sz2i),

           p->O, p->O, p->kind));

     if (!cld2) goto nada;

     pln = MKPLAN_RDFT(P, &padt, apply);

     pln->cld1 = cld1;

     pln->cld2 = cld2;

     pln->solver = ego;

     X(ops_add)(&cld1->ops, &cld2->ops, &pln->super.super.ops);

     X(tensor_destroy4)(sz2, sz1, vecszi, sz2i);

     return &(pln->super.super);

 nada:

     X(plan_destroy_internal)(cld2);

     X(plan_destroy_internal)(cld1);

     X(tensor_destroy4)(sz2, sz1, vecszi, sz2i);

     return (plan *) 0;

}

static solver *mksolver(int spltrnk, const int *buddies, size_t nbuddies)

{

     static const solver_adt sadt = { PROBLEM_RDFT, mkplan, 0 };

     S *slv = MKSOLVER(S, &sadt);

     slv->spltrnk = spltrnk;

     slv->buddies = buddies;

     slv->nbuddies = nbuddies;

     return &(slv->super);

}

void X(rdft_rank_geq2_register)(planner *p)

{

     static const int buddies[] = { 1, 0, -2 };

     size_t i;

     for (i = 0; i < NELEM(buddies); ++i)

          REGISTER_SOLVER(p, mksolver(buddies[i], buddies, NELEM(buddies)));

     /* FIXME: Should we try more buddies?  See also dft/rank-geq2. */

}