dfft3b(3P) Sun Performance Library dfft3b(3P)NAMEdfft3b - compute a periodic sequence from its Fourier coefficients. 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.
SYNOPSIS
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);
ARGUMENTS
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) con‐
tains 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 contains the data to be trans‐
formed and 2*LDB >= 2*(M/2+1). Otherwise it is not refer‐
enced.
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).
6 Mar 2009 dfft3b(3P)
