NAME

dfft3f - compute the Fourier coefficients of a real periodic sequence. The DFFT operations are unnormalized, so a call of DFFT3F followed by a call of DFFT3B will multiply the input sequence by M*N*K. =head1 SYNOPSIS

  SUBROUTINE DFFT3F( PLACE, FULL, M, N, K, A, LDA, B, LDB, WORK, 
 *      LWORK)
  CHARACTER * 1 PLACE, FULL
  INTEGER M, N, K, LDA, LDB, LWORK
  DOUBLE PRECISION A(LDA,N,*), B(LDB,N,*), WORK(*)

  SUBROUTINE DFFT3F_64( PLACE, FULL, M, N, K, A, LDA, B, LDB, WORK, 
 *      LWORK)
  CHARACTER * 1 PLACE, FULL
  INTEGER*8 M, N, K, LDA, LDB, LWORK
  DOUBLE PRECISION A(LDA,N,*), B(LDB,N,*), WORK(*)

F95 INTERFACE

  SUBROUTINE FFT3F( PLACE, FULL, [M], [N], [K], A, [LDA], B, [LDB], 
 *       WORK, LWORK)
  CHARACTER(LEN=1) :: PLACE, FULL
  INTEGER :: M, N, K, LDA, LDB, LWORK
  REAL(8), DIMENSION(:) :: WORK
  REAL(8), DIMENSION(:,:,:) :: A, B

  SUBROUTINE FFT3F_64( PLACE, FULL, [M], [N], [K], A, [LDA], B, [LDB], 
 *       WORK, LWORK)
  CHARACTER(LEN=1) :: PLACE, FULL
  INTEGER(8) :: M, N, K, LDA, LDB, LWORK
  REAL(8), DIMENSION(:) :: WORK
  REAL(8), DIMENSION(:,:,:) :: A, B

C INTERFACE

#include <sunperf.h>

void dfft3f(char place, char full, int m, int n, int k, double *a, int lda, double *b, int ldb, double *work, int lwork);

void dfft3f_64(char place, char full, long m, long n, long k, double *a, long lda, double *b, long ldb, double *work, long lwork);

ARGUMENTS

PLACE (input)
Select an in-place ('I' or 'i') or out-of-place ('O' or 'o') transform.
FULL (input)
Select a full ('F' or 'f') or partial (' ') representation of the results. If the caller selects full representation then an MxNxK real array will transform to produce an MxNxK complex array. If the caller does not select full representation then an MxNxK real array will transform to a (M/2+1)xNxK complex array that takes advantage of the symmetry properties of a transformed real sequence.
M (input)
Integer specifying the number of rows to be transformed. It is most efficient when M is a product of small primes. M > = 0; when M = 0, the subroutine returns immediately without changing any data.
N (input)
Integer specifying the number of columns to be transformed. It is most efficient when N is a product of small primes. N > = 0; when N = 0, the subroutine returns immediately without changing any data.
K (input)
Integer specifying the number of planes to be transformed. It is most efficient when K is a product of small primes. K > = 0; when K = 0, the subroutine returns immediately without changing any data.
A (input/output)
On entry, a three-dimensional array A(LDA,N,K) that contains input data to be transformed. On exit, if an in-place transform is done and FULL is not 'F' or 'f', A(1:2*(M/2+1),1:N,1:K) will contain the partial transformed results. If FULL = 'F' or 'f', A(1:2*M,1:N,1:K) will contain the complete transformed results.
LDA (input)
Leading dimension of the array containing the data to be transformed. LDA must be even if the transformed sequences are to be stored in A.
If PLACE = ('O' or 'o') LDA > = M

If PLACE = ('I' or 'i') LDA must be even. If

FULL = ('F' or 'f'), LDA > = 2*M

FULL is not ('F' or 'f'), LDA > = 2*(M/2+1)
B (input/output)
Upon exit, a three-dimensional array B(2*LDB,N,K) that contains the transformed results if an out-of-place transform is done. Otherwise, B is not used.
If an out-of-place transform is done and FULL is not 'F' or 'f', B(1:2*(M/2+1),1:N,1:K) will contain the partial transformed results. If FULL = 'F' or 'f', B(1:2*M,1:N,1:K) will contain the complete transformed results.
LDB (input)
2*LDB is the leading dimension of the array B. If an in-place transform is desired LDB is ignored.
If PLACE is ('O' or 'o') and

FULL is ('F' or 'f'), then LDB > = M

FULL is not ('F' or 'f'), then LDB > = M/2 + 1

Note that even though LDB is used in the argument list, 2*LDB is the actual leading dimension of B.
WORK (input/output)
One-dimensional real array of length at least LWORK. WORK must have been initialized by DFFT3I.
LWORK (input)
Integer. LWORK > = (M + 2*(N + K) + 4*K + 45).