dfft2f(3P) Sun Performance Library dfft2f(3P)NAMEdfft2f - 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.
SYNOPSIS
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);
ARGUMENTS
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 immedi‐
ately without changing 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)
6 Mar 2009 dfft2f(3P)
