/*

 * 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

 *

 */

/* Do a REDFT00 problem via an R2HC problem, padded symmetrically to

   twice the size.  This is asymptotically a factor of ~2 worse than

   redft00e-r2hc.c (the algorithm used in e.g. FFTPACK and Numerical

   Recipes), but we abandoned the latter after we discovered that it

   has intrinsic accuracy problems. */

#include "reodft/reodft.h"

typedef struct {

     solver super;

} S;

typedef struct {

     plan_rdft super;

     plan *cld, *cldcpy;

     INT is;

     INT n;

     INT vl;

     INT ivs, ovs;

} P;

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

{

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

     INT is = ego->is;

     INT i, n = ego->n;

     INT iv, vl = ego->vl;

     INT ivs = ego->ivs, ovs = ego->ovs;

     R *buf;

     buf = (R *) MALLOC(sizeof(R) * (2*n), BUFFERS);

     for (iv = 0; iv < vl; ++iv, I += ivs, O += ovs) {

    buf[0] = I[0];

    for (i = 1; i < n; ++i) {

         R a = I[i * is];

         buf[i] = a;

         buf[2*n - i] = a;

    }

    buf[i] = I[i * is]; /* i == n, Nyquist */

    /* r2hc transform of size 2*n */

    {

         plan_rdft *cld = (plan_rdft *) ego->cld;

         cld->apply((plan *) cld, buf, buf);

    }

    /* copy n+1 real numbers (real parts of hc array) from buf to O */

    {

         plan_rdft *cldcpy = (plan_rdft *) ego->cldcpy;

         cldcpy->apply((plan *) cldcpy, buf, O);

    }

     }

     X(ifree)(buf);

}

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

{

     P *ego = (P *) ego_;

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

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

}

static void destroy(plan *ego_)

{

     P *ego = (P *) ego_;

     X(plan_destroy_internal)(ego->cldcpy);

     X(plan_destroy_internal)(ego->cld);

}

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

{

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

     p->print(p, "(redft00e-r2hc-pad-%D%v%(%p%)%(%p%))", 

        ego->n + 1, ego->vl, ego->cld, ego->cldcpy);

}

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

{

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

     UNUSED(ego_);

     return (1

       && p->sz->rnk == 1

       && p->vecsz->rnk <= 1

       && p->kind[0] == REDFT00

       && p->sz->dims[0].n > 1  /* n == 1 is not well-defined */

    );

}

static int applicable(const solver *ego, const problem *p, const planner *plnr)

{

     return (!NO_SLOWP(plnr) && applicable0(ego, p));

}

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

{

     P *pln;

     const problem_rdft *p;

     plan *cld = (plan *) 0, *cldcpy;

     R *buf = (R *) 0;

     INT n;

     INT vl, ivs, ovs;

     opcnt ops;

     static const plan_adt padt = {

    X(rdft_solve), awake, print, destroy

     };

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

    goto nada;

     p = (const problem_rdft *) p_;

     n = p->sz->dims[0].n - 1;

     A(n > 0);

     buf = (R *) MALLOC(sizeof(R) * (2*n), BUFFERS);

     cld = X(mkplan_d)(plnr,X(mkproblem_rdft_1_d)(X(mktensor_1d)(2*n,1,1), 

              X(mktensor_0d)(), 

              buf, buf, R2HC));

     if (!cld)

    goto nada;

     X(tensor_tornk1)(p->vecsz, &vl, &ivs, &ovs);

     cldcpy =

    X(mkplan_d)(plnr,

          X(mkproblem_rdft_1_d)(X(mktensor_0d)(),

              X(mktensor_1d)(n+1,1,

                 p->sz->dims[0].os), 

              buf, TAINT(p->O, ovs), R2HC));

     if (!cldcpy)

    goto nada;

     X(ifree)(buf);

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

     pln->n = n;

     pln->is = p->sz->dims[0].is;

     pln->cld = cld;

     pln->cldcpy = cldcpy;

     pln->vl = vl;

     pln->ivs = ivs;

     pln->ovs = ovs;

     X(ops_zero)(&ops);

     ops.other = n + 2*n; /* loads + stores (input -> buf) */

     X(ops_zero)(&pln->super.super.ops);

     X(ops_madd2)(pln->vl, &ops, &pln->super.super.ops);

     X(ops_madd2)(pln->vl, &cld->ops, &pln->super.super.ops);

     X(ops_madd2)(pln->vl, &cldcpy->ops, &pln->super.super.ops);

     return &(pln->super.super);

 nada:

     X(ifree0)(buf);

     if (cld)

    X(plan_destroy_internal)(cld);  

     return (plan *)0;

}

/* constructor */

static solver *mksolver(void)

{

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

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

     return &(slv->super);

}

void X(redft00e_r2hc_pad_register)(planner *p)

{

     REGISTER_SOLVER(p, mksolver());

}