Contents
dfft3b - compute a periodic sequence from its Fourier coef-
ficients. 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.
SUBROUTINE DFFT3B(PLACE, M, N, K, A, LDA, B, LDB, WORK, LWORK)
CHARACTER * 1 PLACE
INTEGER M, N, K, LDA, LDB, LWORK
DOUBLE PRECISION A(LDA,N,*), B(2*LDB,N,*), WORK(*)
SUBROUTINE DFFT3B_64(PLACE, M, N, K, A, LDA, B, LDB, WORK, LWORK)
CHARACTER * 1 PLACE
INTEGER*8 M, N, K, LDA, LDB, LWORK
DOUBLE PRECISION A(LDA,N,*), B(2*LDB,N,*), WORK(*)
F95 INTERFACE
SUBROUTINE FFT3B(PLACE, [M], [N], [K], A, [LDA], B, [LDB], WORK,
LWORK)
CHARACTER(LEN=1) :: PLACE
INTEGER :: M, N, K, LDA, LDB, LWORK
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:,:) :: A, B
SUBROUTINE FFT3B_64(PLACE, [M], [N], [K], A, [LDA], B, [LDB], WORK,
LWORK)
CHARACTER(LEN=1) :: PLACE
INTEGER(8) :: M, N, K, LDA, LDB, LWORK
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void dfft3b(char place, int m, int n, int k, double *a, int
lda, double *b, int ldb, double *work, int lwork);
void dfft3b_64(char place, long m, long n, long k, double
*a, long lda, double *b, long ldb, double *work,
long lwork);
PLACE (input)
Select an in-place ('I' or 'i') or out-of-place
('O' or 'o') transform.
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, the three-dimensional array A(LDA,N,K)
contains the data to be transformed if an in-place
transform is requested. Otherwise, it is not
referenced. Upon exit, results are stored in
A(1:M,1:N,1:K).
LDA (input)
Integer specifying the leading dimension of A. If
an out-of-place transform is desired LDA >= M.
Else if an in-place transform is desired LDA >=
2*(M/2+1).
B (input/output)
Real array of dimension B(2*LDB,N,K). On entry,
if an out-of-place transform is requested
B(1:2*(M/2+1),1:N,1:K) contains the input data.
Otherwise, B is not referenced. B is unchanged
upon exit.
LDB (input)
If an out-of-place transform is desired, 2*LDB is
the leading dimension of the array B which con-
tains the data to be transformed and 2*LDB >=
2*(M/2+1). Otherwise it is not referenced.
WORK (input/output)
One-dimensional real array of length at least
LWORK. On input, WORK must have been initialized
by DFFT3I.
LWORK (input)
Integer. LWORK >= (M + 2*(N + K) + 4*K + 45).