/*

 * 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

 *

 */

#include "dft/dft.h"

typedef struct {

     solver super;

} S;

typedef struct {

     plan_dft super;

     INT n;     /* problem size */

     INT nb;    /* size of convolution */

     R *w;      /* lambda k . exp(2*pi*i*k^2/(2*n)) */

     R *W;      /* DFT(w) */

     plan *cldf;

     INT is, os;

} P;

static void bluestein_sequence(enum wakefulness wakefulness, INT n, R *w)

{

     INT k, ksq, n2 = 2 * n;

     triggen *t = X(mktriggen)(wakefulness, n2);

     ksq = 0;

     for (k = 0; k < n; ++k) {

    t->cexp(t, ksq, w+2*k);

          /* careful with overflow */

          ksq += 2*k + 1; while (ksq > n2) ksq -= n2;

     }

     X(triggen_destroy)(t);

}

static void mktwiddle(enum wakefulness wakefulness, P *p)

{

     INT i;

     INT n = p->n, nb = p->nb;

     R *w, *W;

     E nbf = (E)nb;

     p->w = w = (R *) MALLOC(2 * n * sizeof(R), TWIDDLES);

     p->W = W = (R *) MALLOC(2 * nb * sizeof(R), TWIDDLES);

     bluestein_sequence(wakefulness, n, w);

     for (i = 0; i < nb; ++i)

          W[2*i] = W[2*i+1] = K(0.0);

     W[0] = w[0] / nbf;

     W[1] = w[1] / nbf;

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

          W[2*i] = W[2*(nb-i)] = w[2*i] / nbf;

          W[2*i+1] = W[2*(nb-i)+1] = w[2*i+1] / nbf;

     }

     {

          plan_dft *cldf = (plan_dft *)p->cldf;

    /* cldf must be awake */

          cldf->apply(p->cldf, W, W+1, W, W+1);

     }

}

static void apply(const plan *ego_, R *ri, R *ii, R *ro, R *io)

{

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

     INT i, n = ego->n, nb = ego->nb, is = ego->is, os = ego->os;

     R *w = ego->w, *W = ego->W;

     R *b = (R *) MALLOC(2 * nb * sizeof(R), BUFFERS);

     /* multiply input by conjugate bluestein sequence */

     for (i = 0; i < n; ++i) {

    E xr = ri[i*is], xi = ii[i*is];

          E wr = w[2*i], wi = w[2*i+1];

          b[2*i] = xr * wr + xi * wi;

          b[2*i+1] = xi * wr - xr * wi;

     }

     for (; i < nb; ++i) b[2*i] = b[2*i+1] = K(0.0);

     /* convolution: FFT */

     {

          plan_dft *cldf = (plan_dft *)ego->cldf;

          cldf->apply(ego->cldf, b, b+1, b, b+1);

     }

     /* convolution: pointwise multiplication */

     for (i = 0; i < nb; ++i) {

    E xr = b[2*i], xi = b[2*i+1];

          E wr = W[2*i], wi = W[2*i+1];

          b[2*i] = xi * wr + xr * wi;

          b[2*i+1] = xr * wr - xi * wi;

     }

     /* convolution: IFFT by FFT with real/imag input/output swapped */

     {

          plan_dft *cldf = (plan_dft *)ego->cldf;

          cldf->apply(ego->cldf, b, b+1, b, b+1);

     }

     /* multiply output by conjugate bluestein sequence */

     for (i = 0; i < n; ++i) {

    E xi = b[2*i], xr = b[2*i+1];

          E wr = w[2*i], wi = w[2*i+1];

          ro[i*os] = xr * wr + xi * wi;

          io[i*os] = xi * wr - xr * wi;

     }

     X(ifree)(b);   

}

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

{

     P *ego = (P *) ego_;

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

     switch (wakefulness) {

   case SLEEPY:

        X(ifree0)(ego->w); ego->w = 0;

        X(ifree0)(ego->W); ego->W = 0;

        break;

   default:

        A(!ego->w);

        mktwiddle(wakefulness, ego);

        break;

     }

}

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

          const planner *plnr)

{

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

     UNUSED(ego);

     return (1

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

       && p->vecsz->rnk == 0

       /* FIXME: allow other sizes */

       && X(is_prime)(p->sz->dims[0].n)

       /* FIXME: avoid infinite recursion of bluestein with itself.

    This works because all factors in child problems are 2, 3, 5 */

       && p->sz->dims[0].n > 16

       && CIMPLIES(NO_SLOWP(plnr), p->sz->dims[0].n > BLUESTEIN_MAX_SLOW)

    );

}

static void destroy(plan *ego_)

{

     P *ego = (P *) ego_;

     X(plan_destroy_internal)(ego->cldf);

}

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

{

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

     p->print(p, "(dft-bluestein-%D/%D%(%p%))",

              ego->n, ego->nb, ego->cldf);

}

static INT choose_transform_size(INT minsz)

{

     while (!X(factors_into_small_primes)(minsz))

    ++minsz;

     return minsz;

}

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

{

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

     P *pln;

     INT n, nb;

     plan *cldf = 0;

     R *buf = (R *) 0;

     static const plan_adt padt = {

    X(dft_solve), awake, print, destroy

     };

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

    return (plan *) 0;

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

     nb = choose_transform_size(2 * n - 1);

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

     cldf = X(mkplan_f_d)(plnr, 

        X(mkproblem_dft_d)(X(mktensor_1d)(nb, 2, 2),

               X(mktensor_1d)(1, 0, 0),

               buf, buf+1, 

               buf, buf+1),

        NO_SLOW, 0, 0);

     if (!cldf) goto nada;

     X(ifree)(buf);

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

     pln->n = n;

     pln->nb = nb;

     pln->w = 0;

     pln->W = 0;

     pln->cldf = cldf;

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

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

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

     pln->super.super.ops.add += 4 * n + 2 * nb;

     pln->super.super.ops.mul += 8 * n + 4 * nb;

     pln->super.super.ops.other += 6 * (n + nb);

     return &(pln->super.super);

 nada:

     X(ifree0)(buf);

     X(plan_destroy_internal)(cldf);

     return (plan *)0;

}

static solver *mksolver(void)

{

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

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

     return &(slv->super);

}

void X(dft_bluestein_register)(planner *p)

{

     REGISTER_SOLVER(p, mksolver());

}