• NAME
• F95 INTERFACE
• C INTERFACE
• ARGUMENTS

NAME

dfft3b - 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. =head1 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(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(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) 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 contains 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).