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/*
* Copyright (c) 2003 Matteo Frigo
* Copyright (c) 2003 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/* $Id: rdft-dht.c,v 1.1 2008/10/17 06:11:29 scuri Exp $ */
/* Solve an R2HC/HC2R problem via post/pre processing of a DHT. This
is mainly useful because we can use Rader to compute DHTs of prime
sizes. It also allows us to express hc2r problems in terms of r2hc
(via dht-r2hc), and to do hc2r problems without destroying the input. */
#include "rdft.h"
typedef struct {
solver super;
} S;
typedef struct {
plan_rdft super;
plan *cld;
int is, os;
int n;
} P;
static void apply_r2hc(const plan *ego_, R *I, R *O)
{
const P *ego = (const P *) ego_;
int os;
int i, n;
{
plan_rdft *cld = (plan_rdft *) ego->cld;
cld->apply((plan *) cld, I, O);
}
n = ego->n;
os = ego->os;
for (i = 1; i < n - i; ++i) {
E a, b;
a = K(0.5) * O[os * i];
b = K(0.5) * O[os * (n - i)];
O[os * i] = a + b;
#if FFT_SIGN == -1
O[os * (n - i)] = b - a;
#else
O[os * (n - i)] = a - b;
#endif
}
}
/* hc2r, destroying input as usual */
static void apply_hc2r(const plan *ego_, R *I, R *O)
{
const P *ego = (const P *) ego_;
int is = ego->is;
int i, n = ego->n;
for (i = 1; i < n - i; ++i) {
E a, b;
a = I[is * i];
b = I[is * (n - i)];
#if FFT_SIGN == -1
I[is * i] = a - b;
I[is * (n - i)] = a + b;
#else
I[is * i] = a + b;
I[is * (n - i)] = a - b;
#endif
}
{
plan_rdft *cld = (plan_rdft *) ego->cld;
cld->apply((plan *) cld, I, O);
}
}
/* hc2r, without destroying input */
static void apply_hc2r_save(const plan *ego_, R *I, R *O)
{
const P *ego = (const P *) ego_;
int is = ego->is, os = ego->os;
int i, n = ego->n;
O[0] = I[0];
for (i = 1; i < n - i; ++i) {
E a, b;
a = I[is * i];
b = I[is * (n - i)];
#if FFT_SIGN == -1
O[os * i] = a - b;
O[os * (n - i)] = a + b;
#else
O[os * i] = a + b;
O[os * (n - i)] = a - b;
#endif
}
if (i == n - i)
O[os * i] = I[is * i];
{
plan_rdft *cld = (plan_rdft *) ego->cld;
cld->apply((plan *) cld, O, O);
}
}
static void awake(plan *ego_, int flg)
{
P *ego = (P *) ego_;
AWAKE(ego->cld, flg);
}
static void destroy(plan *ego_)
{
P *ego = (P *) ego_;
X(plan_destroy_internal)(ego->cld);
}
static void print(const plan *ego_, printer *p)
{
const P *ego = (const P *) ego_;
p->print(p, "(%s-dht-%d%(%p%))",
ego->super.apply == apply_r2hc ? "r2hc" : "hc2r",
ego->n, ego->cld);
}
static int applicable0(const solver *ego_, const problem *p_)
{
UNUSED(ego_);
if (RDFTP(p_)) {
const problem_rdft *p = (const problem_rdft *) p_;
return (1
&& p->sz->rnk == 1
&& p->vecsz->rnk == 0
&& (p->kind[0] == R2HC || p->kind[0] == HC2R)
/* hack: size-2 DHT etc. are defined as being equivalent
to size-2 R2HC in problem.c, so we need this to prevent
infinite loops for size 2 in EXHAUSTIVE mode: */
&& p->sz->dims[0].n > 2
);
}
return 0;
}
static int applicable(const solver *ego, const problem *p_,
const planner *plnr)
{
return (!NO_UGLYP(plnr) && applicable0(ego, p_));
}
static plan *mkplan(const solver *ego_, const problem *p_, planner *plnr)
{
P *pln;
const problem_rdft *p;
problem *cldp;
plan *cld;
static const plan_adt padt = {
X(rdft_solve), awake, print, destroy
};
if (!applicable(ego_, p_, plnr))
return (plan *)0;
p = (const problem_rdft *) p_;
if (p->kind[0] == R2HC || DESTROY_INPUTP(plnr))
cldp = X(mkproblem_rdft_1)(p->sz, p->vecsz, p->I, p->O, DHT);
else {
tensor *sz = X(tensor_copy_inplace)(p->sz, INPLACE_OS);
cldp = X(mkproblem_rdft_1)(sz, p->vecsz, p->O, p->O, DHT);
X(tensor_destroy)(sz);
}
cld = X(mkplan_d)(plnr, cldp);
if (!cld) return (plan *)0;
pln = MKPLAN_RDFT(P, &padt, p->kind[0] == R2HC ?
apply_r2hc : (DESTROY_INPUTP(plnr) ?
apply_hc2r : apply_hc2r_save));
pln->n = p->sz->dims[0].n;
pln->is = p->sz->dims[0].is;
pln->os = p->sz->dims[0].os;
pln->cld = cld;
pln->super.super.ops = cld->ops;
pln->super.super.ops.other += 4 * ((pln->n - 1)/2);
pln->super.super.ops.add += 2 * ((pln->n - 1)/2);
if (p->kind[0] == R2HC)
pln->super.super.ops.mul += 2 * ((pln->n - 1)/2);
if (pln->super.apply == apply_hc2r_save)
pln->super.super.ops.other += 2 + (pln->n % 2 ? 0 : 2);
return &(pln->super.super);
}
/* constructor */
static solver *mksolver(void)
{
static const solver_adt sadt = { mkplan };
S *slv = MKSOLVER(S, &sadt);
return &(slv->super);
}
void X(rdft_dht_register)(planner *p)
{
REGISTER_SOLVER(p, mksolver());
}
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