NAME

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. =head1 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(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(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 immediately 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)