dfft2b (3p)

Name

dfft2b - compute a periodic sequence from its Fourier coefficients. 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 DFFT2B(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

CHARACTER*1 PLACE
INTEGER M, N, LDA, LDB, LWORK
DOUBLE PRECISION A(LDA,*), B(2*LDB,*), WORK(*)

SUBROUTINE DFFT2B_64(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

CHARACTER*1 PLACE
INTEGER*8 M, N, LDA, LDB, LWORK
DOUBLE PRECISION A(LDA,*), B(2*LDB,*), WORK(*)




F95 INTERFACE
SUBROUTINE FFT2B(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

CHARACTER(LEN=1) :: PLACE
INTEGER :: M, N, LDA, LDB, LWORK
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A, B

SUBROUTINE FFT2B_64(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

CHARACTER(LEN=1) :: PLACE
INTEGER(8) :: M, N, LDA, LDB, LWORK
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A, B




C INTERFACE
#include <sunperf.h>

void  dfft2b(char  place,  int m, int n, double *a, int lda, double *b,
int ldb, double *work, int lwork);

void dfft2b_64(char place, long m, long n, double *a, long lda,  double
*b, long ldb, double *work, long lwork);

Description

Oracle Solaris Studio Performance Library                           dfft2b(3P)



NAME
       dfft2b  -  compute  a  periodic sequence from its Fourier coefficients.
       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 DFFT2B(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

       CHARACTER*1 PLACE
       INTEGER M, N, LDA, LDB, LWORK
       DOUBLE PRECISION A(LDA,*), B(2*LDB,*), WORK(*)

       SUBROUTINE DFFT2B_64(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

       CHARACTER*1 PLACE
       INTEGER*8 M, N, LDA, LDB, LWORK
       DOUBLE PRECISION A(LDA,*), B(2*LDB,*), WORK(*)




   F95 INTERFACE
       SUBROUTINE FFT2B(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

       CHARACTER(LEN=1) :: PLACE
       INTEGER :: M, N, LDA, LDB, LWORK
       REAL(8), DIMENSION(:) :: WORK
       REAL(8), DIMENSION(:,:) :: A, B

       SUBROUTINE FFT2B_64(PLACE, M, N, A, LDA, B, LDB, WORK, LWORK)

       CHARACTER(LEN=1) :: PLACE
       INTEGER(8) :: M, N, LDA, LDB, LWORK
       REAL(8), DIMENSION(:) :: WORK
       REAL(8), DIMENSION(:,:) :: A, B




   C INTERFACE
       #include <sunperf.h>

       void  dfft2b(char  place,  int m, int n, double *a, int lda, double *b,
                 int ldb, double *work, int lwork);

       void dfft2b_64(char place, 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.


       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)
                 Real array of dimension (LDA,N).  On  entry,  the  two-dimen-
                 sional  array  A(LDA,N)  contains the input data to be trans-
                 formed if an in-place transform is requested.  Otherwise,  it
                 is   not  referenced.   Upon  exit,  results  are  stored  in
                 A(1:M,1:N).


       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) and LDA must be even.


       B (input/output)
                 Real array of dimension (2*LDB, N).  On entry, if an  out-of-
                 place transform is requested B contains the input data.  Oth-
                 erwise, B is not referenced.  B is unchanged upon exit.


       LDB (input)
                 Integer.  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 DFFT2I.


       LWORK (input)
                 Integer.  LWORK >= (M + 2*N + MAX(M, 2*N) + 30)



                                  7 Nov 2015                        dfft2b(3P)