/*

 * 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;

     twid *td;

     INT n, is, os;

} P;

static void cdot(INT n, const E *x, const R *w, 

     R *or0, R *oi0, R *or1, R *oi1)

{

     INT i;

     E rr = x[0], ri = 0, ir = x[1], ii = 0; 

     x += 2;

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

    rr += x[0] * w[0];

    ir += x[1] * w[0];

    ri += x[2] * w[1];

    ii += x[3] * w[1];

    x += 4; w += 2;

     }

     *or0 = rr + ii;

     *oi0 = ir - ri;

     *or1 = rr - ii;

     *oi1 = ir + ri;

}

static void hartley(INT n, const R *xr, const R *xi, INT xs, E *o,

        R *pr, R *pi)

{

     INT i;

     E sr, si;

     o[0] = sr = xr[0]; o[1] = si = xi[0]; o += 2;

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

    sr += (o[0] = xr[i * xs] + xr[(n - i) * xs]);

    si += (o[1] = xi[i * xs] + xi[(n - i) * xs]);

    o[2] = xr[i * xs] - xr[(n - i) * xs];

    o[3] = xi[i * xs] - xi[(n - i) * xs];

    o += 4;

     }

     *pr = sr;

     *pi = si;

}

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

{

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

     INT i;

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

     const R *W = ego->td->W;

     E *buf;

     size_t bufsz = n * 2 * sizeof(E);

     BUF_ALLOC(E *, buf, bufsz);

     hartley(n, ri, ii, is, buf, ro, io);

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

    cdot(n, buf, W,

         ro + i * os, io + i * os,

         ro + (n - i) * os, io + (n - i) * os);

    W += n - 1;

     }

     BUF_FREE(buf, bufsz);

}

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

{

     P *ego = (P *) ego_;

     static const tw_instr half_tw[] = {

    { TW_HALF, 1, 0 },

    { TW_NEXT, 1, 0 }

     };

     X(twiddle_awake)(wakefulness, &ego->td, half_tw, ego->n, ego->n,

          (ego->n - 1) / 2);

}

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

{

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

     p->print(p, "(dft-generic-%D)", ego->n);

}

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

       && (p->sz->dims[0].n % 2) == 1 

       && CIMPLIES(NO_LARGE_GENERICP(plnr), p->sz->dims[0].n < GENERIC_MIN_BAD)

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

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

    );

}

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

{

     const problem_dft *p;

     P *pln;

     INT n;

     static const plan_adt padt = {

    X(dft_solve), awake, print, X(plan_null_destroy)

     };

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

          return (plan *)0;

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

     p = (const problem_dft *) p_;

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

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

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

     pln->td = 0;

     pln->super.super.ops.add = (n-1) * 5;

     pln->super.super.ops.mul = 0;

     pln->super.super.ops.fma = (n-1) * (n-1) ;

#if 0 /* these are nice pipelined sequential loads and should cost nothing */

     pln->super.super.ops.other = (n-1)*(4 + 1 + 2 * (n-1));  /* approximate */

#endif

     return &(pln->super.super);

}

static solver *mksolver(void)

{

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

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

     return &(slv->super);

}

void X(dft_generic_register)(planner *p)

{

     REGISTER_SOLVER(p, mksolver());

}