• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• ARGUMENTS

NAME

zfft2b - compute a periodic sequence from its Fourier coefficients. The FFT operations are unnormalized, so a call of ZFFT2F followed by a call of ZFFT2B will multiply the input sequence by M*N.

SYNOPSIS

  SUBROUTINE ZFFT2B( M, N, A, LDA, WORK, LWORK)
  DOUBLE COMPLEX A(LDA,*)
  INTEGER M, N, LDA, LWORK
  DOUBLE PRECISION WORK(*)

  SUBROUTINE ZFFT2B_64( M, N, A, LDA, WORK, LWORK)
  DOUBLE COMPLEX A(LDA,*)
  INTEGER*8 M, N, LDA, LWORK
  DOUBLE PRECISION WORK(*)

F95 INTERFACE

  SUBROUTINE FFT2B( [M], [N], A, [LDA], WORK, LWORK)
  COMPLEX(8), DIMENSION(:,:) :: A
  INTEGER :: M, N, LDA, LWORK
  REAL(8), DIMENSION(:) :: WORK

  SUBROUTINE FFT2B_64( [M], [N], A, [LDA], WORK, LWORK)
  COMPLEX(8), DIMENSION(:,:) :: A
  INTEGER(8) :: M, N, LDA, LWORK
  REAL(8), DIMENSION(:) :: WORK

C INTERFACE

#include <sunperf.h>

void zfft2b(int m, int n, doublecomplex *a, int lda, double *work, int lwork);

void zfft2b_64(long m, long n, doublecomplex *a, long lda, double *work, long lwork);

ARGUMENTS

• M (input)
  Number of rows to be transformed. These subroutines are most efficient when M is a product of small primes. M > = 0.

• N (input)
  Number of columns to be transformed. These subroutines are most efficient when N is a product of small primes. N > = 0.

• A (input/output)
  On entry, a two-dimensional array A(M,N) that contains the sequences to be transformed.

• LDA (input)
  Leading dimension of the array containing the data to be transformed. LDA > = M.

• WORK (input)
  On entry, an array with dimension of at least LWORK. WORK must have been initialized by ZFFT2I.

• LWORK (input)
  The dimension of the array WORK. LWORK > = (4 * (M + N) + 30)