Contents
dfft2f - compute the Fourier coefficients of a periodic
sequence. The DFFT operations are unnormalized, so a call
of DFFT2F followed by a call of DFFT2B will multiply the
input sequence by M*N.
SUBROUTINE DFFT2F(PLACE, FULL, M, N, A, LDA, B, LDB, WORK, LWORK)
CHARACTER * 1 PLACE, FULL
INTEGER M, N, LDA, LDB, LWORK
DOUBLE PRECISION A(LDA,*), B(2*LDB,*), WORK(*)
SUBROUTINE DFFT2F_64(PLACE, FULL, M, N, A, LDA, B, LDB, WORK, LWORK)
CHARACTER * 1 PLACE, FULL
INTEGER*8 M, N, LDA, LDB, LWORK
DOUBLE PRECISION A(LDA,*), B(2*LDB,*), WORK(*)
F95 INTERFACE
SUBROUTINE FFT2F(PLACE, FULL, [M], [N], A, [LDA], B, [LDB], WORK,
LWORK)
CHARACTER(LEN=1) :: PLACE, FULL
INTEGER :: M, N, LDA, LDB, LWORK
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A, B
SUBROUTINE FFT2F_64(PLACE, FULL, [M], [N], A, [LDA], B, [LDB], WORK,
LWORK)
CHARACTER(LEN=1) :: PLACE, FULL
INTEGER(8) :: M, N, LDA, LDB, LWORK
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void dfft2f(char place, char full, int m, int n, double *a,
int lda, double *b, int ldb, double *work, int
lwork);
void dfft2f_64(char place, char full, long m, long n, double
*a, long lda, double *b, long ldb, double *work,
long lwork);
PLACE (input)
Character. If PLACE = 'I' or 'i' (for in-place) ,
the input and output data are stored in array A.
If PLACE = 'O' or 'o' (for out-of-place), the
input data is stored in array B while the output
is stored in A.
FULL (input)
Indicates whether or not to generate the full
result matrix. 'F' or 'f' will cause DFFT2F to
generate the full result matrix. Otherwise only a
partial matrix that takes advantage of symmetry
will be generated.
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 most efficient when N is
a product of small primes. N >= 0; when N = 0,
the subroutine returns immediately without chang-
ing any data.
A (input/output)
On entry, a two-dimensional array A(LDA,N) that
contains the data to be transformed. Upon exit, A
is unchanged if an out-of-place transform is done.
If an in-place transform with partial result is
requested, A(1:(M/2+1)*2,1:N) will contain the
transformed results. If an in-place transform
with full result is requested, A(1:2*M,1:N) will
contain 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 >= (M/2+1)*2
B (input/output)
Upon exit, a two-dimensional array B(2*LDB,N) 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:(M/2+1)*2,1:N) will contain
the partial transformed results. If FULL = 'F' or
'f', B(1:2*M,1:N) 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'), LDB >= M
FULL is not ('F' or 'f'), 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. On input, WORK must have been initialized
by DFFT2I.
LWORK (input)
Integer. LWORK >= (M + 2*N + MAX(M, 2*N) + 30)