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/* temperton/gpfa.f -- translated by f2c (version 20050501).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "v3p_netlib.h"
/* Table of constant values */
static integer c__2 = 2;
static integer c__3 = 3;
/* SUBROUTINE 'GPFA' */
/* SELF-SORTING IN-PLACE GENERALIZED PRIME FACTOR (COMPLEX) FFT */
/* *** THIS IS THE ALL-FORTRAN VERSION *** */
/* ------------------------------- */
/* CALL GPFA(A,B,TRIGS,INC,JUMP,N,LOT,ISIGN,NPQR) */
/* A IS FIRST REAL INPUT/OUTPUT VECTOR */
/* B IS FIRST IMAGINARY INPUT/OUTPUT VECTOR */
/* TRIGS IS A TABLE OF TWIDDLE FACTORS, PRECALCULATED */
/* BY CALLING SUBROUTINE 'SETGPFA' */
/* INC IS THE INCREMENT WITHIN EACH DATA VECTOR */
/* JUMP IS THE INCREMENT BETWEEN DATA VECTORS */
/* N IS THE LENGTH OF THE TRANSFORMS: */
/* ----------------------------------- */
/* N = (2**IP) * (3**IQ) * (5**IR) */
/* ----------------------------------- */
/* LOT IS THE NUMBER OF TRANSFORMS */
/* ISIGN = +1 FOR FORWARD TRANSFORM */
/* = -1 FOR INVERSE TRANSFORM */
/* NPQR = NPQR OBTAINED FROM SETGPFA */
/* WRITTEN BY CLIVE TEMPERTON */
/* RECHERCHE EN PREVISION NUMERIQUE */
/* ATMOSPHERIC ENVIRONMENT SERVICE, CANADA */
/* MODIFIED FOR VXL PROJECT TO ADD NPQR ARGUMENT */
/* ---------------------------------------------------------------------- */
/* DEFINITION OF TRANSFORM */
/* ----------------------- */
/* X(J) = SUM(K=0,...,N-1)(C(K)*EXP(ISIGN*2*I*J*K*PI/N)) */
/* --------------------------------------------------------------------- */
/* FOR A MATHEMATICAL DEVELOPMENT OF THE ALGORITHM USED, */
/* SEE: */
/* C TEMPERTON : "A GENERALIZED PRIME FACTOR FFT ALGORITHM */
/* FOR ANY N = (2**P)(3**Q)(5**R)", */
/* SIAM J. SCI. STAT. COMP., MAY 1992. */
/* ---------------------------------------------------------------------- */
/*< SUBROUTINE GPFA(A,B,TRIGS,INC,JUMP,N,LOT,ISIGN,NPQR) >*/
/* Subroutine */ int gpfa_(real *a, real *b, real *trigs, integer *inc,
integer *jump, integer *n, integer *lot, integer *isign, integer *
npqr)
{
/* Builtin functions */
integer pow_ii(integer *, integer *);
/* Local variables */
integer i__, ip, iq, ir;
extern /* Subroutine */ int gpfa2f_(real *, real *, real *, integer *,
integer *, integer *, integer *, integer *, integer *), gpfa3f_(
real *, real *, real *, integer *, integer *, integer *, integer *
, integer *, integer *), gpfa5f_(real *, real *, real *, integer *
, integer *, integer *, integer *, integer *, integer *);
/*< REAL A(*), B(*), TRIGS(*) >*/
/*< INTEGER INC, JUMP, N, LOT, ISIGN, NPQR(3) >*/
/*< IP = NPQR(1) >*/
/* Parameter adjustments */
--npqr;
--trigs;
--b;
--a;
/* Function Body */
ip = npqr[1];
/*< IQ = NPQR(2) >*/
iq = npqr[2];
/*< IR = NPQR(3) >*/
ir = npqr[3];
/* COMPUTE THE TRANSFORM */
/* --------------------- */
/*< I = 1 >*/
i__ = 1;
/*< IF (IP.GT.0) THEN >*/
if (ip > 0) {
/*< CALL GPFA2F(A,B,TRIGS,INC,JUMP,N,IP,LOT,ISIGN) >*/
gpfa2f_(&a[1], &b[1], &trigs[1], inc, jump, n, &ip, lot, isign);
/*< I = I + 2 * ( 2**IP) >*/
i__ += pow_ii(&c__2, &ip) << 1;
/*< ENDIF >*/
}
/*< IF (IQ.GT.0) THEN >*/
if (iq > 0) {
/*< CALL GPFA3F(A,B,TRIGS(I),INC,JUMP,N,IQ,LOT,ISIGN) >*/
gpfa3f_(&a[1], &b[1], &trigs[i__], inc, jump, n, &iq, lot, isign);
/*< I = I + 2 * (3**IQ) >*/
i__ += pow_ii(&c__3, &iq) << 1;
/*< ENDIF >*/
}
/*< IF (IR.GT.0) THEN >*/
if (ir > 0) {
/*< CALL GPFA5F(A,B,TRIGS(I),INC,JUMP,N,IR,LOT,ISIGN) >*/
gpfa5f_(&a[1], &b[1], &trigs[i__], inc, jump, n, &ir, lot, isign);
/*< ENDIF >*/
}
/*< RETURN >*/
return 0;
/*< END >*/
} /* gpfa_ */
#ifdef __cplusplus
}
#endif
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