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root / src / fftw-3.3.8 / dft / generic.c @ 167:bd3cc4d1df30

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/*
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 * Copyright (c) 2003, 2007-14 Matteo Frigo
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 * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
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 *
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
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 *
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 */
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#include "dft/dft.h"
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typedef struct {
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     solver super;
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} S;
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typedef struct {
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     plan_dft super;
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     twid *td;
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     INT n, is, os;
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} P;
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static void cdot(INT n, const E *x, const R *w, 
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                 R *or0, R *oi0, R *or1, R *oi1)
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{
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     INT i;
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     E rr = x[0], ri = 0, ir = x[1], ii = 0; 
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     x += 2;
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     for (i = 1; i + i < n; ++i) {
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          rr += x[0] * w[0];
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          ir += x[1] * w[0];
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          ri += x[2] * w[1];
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          ii += x[3] * w[1];
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          x += 4; w += 2;
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     }
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     *or0 = rr + ii;
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     *oi0 = ir - ri;
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     *or1 = rr - ii;
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     *oi1 = ir + ri;
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}
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static void hartley(INT n, const R *xr, const R *xi, INT xs, E *o,
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                    R *pr, R *pi)
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{
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     INT i;
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     E sr, si;
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     o[0] = sr = xr[0]; o[1] = si = xi[0]; o += 2;
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     for (i = 1; i + i < n; ++i) {
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          sr += (o[0] = xr[i * xs] + xr[(n - i) * xs]);
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          si += (o[1] = xi[i * xs] + xi[(n - i) * xs]);
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          o[2] = xr[i * xs] - xr[(n - i) * xs];
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          o[3] = xi[i * xs] - xi[(n - i) * xs];
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          o += 4;
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     }
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     *pr = sr;
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     *pi = si;
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}
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static void apply(const plan *ego_, R *ri, R *ii, R *ro, R *io)
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{
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     const P *ego = (const P *) ego_;
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     INT i;
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     INT n = ego->n, is = ego->is, os = ego->os;
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     const R *W = ego->td->W;
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     E *buf;
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     size_t bufsz = n * 2 * sizeof(E);
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     BUF_ALLOC(E *, buf, bufsz);
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     hartley(n, ri, ii, is, buf, ro, io);
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     for (i = 1; i + i < n; ++i) {
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          cdot(n, buf, W,
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               ro + i * os, io + i * os,
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               ro + (n - i) * os, io + (n - i) * os);
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          W += n - 1;
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     }
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     BUF_FREE(buf, bufsz);
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}
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static void awake(plan *ego_, enum wakefulness wakefulness)
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{
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     P *ego = (P *) ego_;
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     static const tw_instr half_tw[] = {
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          { TW_HALF, 1, 0 },
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          { TW_NEXT, 1, 0 }
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     };
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     X(twiddle_awake)(wakefulness, &ego->td, half_tw, ego->n, ego->n,
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                      (ego->n - 1) / 2);
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}
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static void print(const plan *ego_, printer *p)
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{
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     const P *ego = (const P *) ego_;
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     p->print(p, "(dft-generic-%D)", ego->n);
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}
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static int applicable(const solver *ego, const problem *p_, 
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                      const planner *plnr)
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{
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     const problem_dft *p = (const problem_dft *) p_;
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     UNUSED(ego);
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     return (1
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             && p->sz->rnk == 1
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             && p->vecsz->rnk == 0
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             && (p->sz->dims[0].n % 2) == 1 
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             && CIMPLIES(NO_LARGE_GENERICP(plnr), p->sz->dims[0].n < GENERIC_MIN_BAD)
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             && CIMPLIES(NO_SLOWP(plnr), p->sz->dims[0].n > GENERIC_MAX_SLOW)
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             && X(is_prime)(p->sz->dims[0].n)
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          );
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}
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static plan *mkplan(const solver *ego, const problem *p_, planner *plnr)
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{
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     const problem_dft *p;
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     P *pln;
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     INT n;
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     static const plan_adt padt = {
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          X(dft_solve), awake, print, X(plan_null_destroy)
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     };
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     if (!applicable(ego, p_, plnr))
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          return (plan *)0;
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     pln = MKPLAN_DFT(P, &padt, apply);
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     p = (const problem_dft *) p_;
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     pln->n = n = p->sz->dims[0].n;
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     pln->is = p->sz->dims[0].is;
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     pln->os = p->sz->dims[0].os;
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     pln->td = 0;
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     pln->super.super.ops.add = (n-1) * 5;
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     pln->super.super.ops.mul = 0;
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     pln->super.super.ops.fma = (n-1) * (n-1) ;
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#if 0 /* these are nice pipelined sequential loads and should cost nothing */
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     pln->super.super.ops.other = (n-1)*(4 + 1 + 2 * (n-1));  /* approximate */
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#endif
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     return &(pln->super.super);
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}
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static solver *mksolver(void)
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{
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     static const solver_adt sadt = { PROBLEM_DFT, mkplan, 0 };
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     S *slv = MKSOLVER(S, &sadt);
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     return &(slv->super);
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}
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void X(dft_generic_register)(planner *p)
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{
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     REGISTER_SOLVER(p, mksolver());
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}