Real transform: status = {S,D}FFT_2D (input_format, output_format, direction, in, out, ni, nj, lda, ni_stride, nj_stride) Complex transforms in complex format: status = {C,Z}FFT_2D (input_format, output_format, direction, in, out, ni, nj, lda, ni_stride, nj_stride) Complex transform in real data format: status = {C,Z}FFT_2D (input_format, output_format, direction, in_real, out_real, in_imag, out_imag, ni, nj, lda, ni_stride, nj_stride)
input_format, output_format character*(*) Identifies the data type of the input and the format to be used to store the data, regardless of the data type. For example, a complex sequence can be stored in real format. The character 'R' specifies the format as real; the character 'C' specifies the format as complex. As convenient, use either upper- or lowercase characters, and either spell out or abbreviate the word. The following table shows the valid values: Subprogram Input Format Output Format Direction {S,D} 'R' 'C' 'F' 'C' 'R' 'B' 'R' 'R' 'F' or 'B' {C,Z} 'R' 'R' 'F' or 'B' 'C' 'C' 'F' or 'B' For complex data, the type of data determines what other arguments are needed. When both the input and output data are real, the complex routines store the data as separate arrays for imaginary and real data so additional arguments are needed. direction character*(*) Specifies the operation as either the forward or inverse transform. Use 'F' or 'f' to specify the forward transform. Use 'B' or 'b' to specify the inverse transform. in, out real*4 | real*8 | complex*8 | complex*16 Both the arguments are two-dimensional arrays. The input and output arrays can be the same array. The IN array contains the data to be transformed. The OUT array contains the transformed data. in_real, out_real, in_imag, out_imag real*4 | real*8 Use these arguments when performing a complex transform on real data format and storing the result in a real data format. ni, nj integer*4 Specifies the size of the first and second dimension of data in the input array; ni > 0, nj > 0. For SFFT_2D and DFFT_2D, ni must be even. lda integer*4 Specifies the number of rows in the IN and OUT arrays; lda >= ni. For {S,D} routines, lda >= ni+2 when the input format is 'R' and the output format is 'C' or the input format is 'C' and the output format is 'R'. ni_stride, nj_stride integer*4 Specifies the distance between consecutive elements in a column and row in the IN and OUT arrays; ni_stride >= 1, nj_stride >= 1.
The _FFT_2D routines compute the fast forward or inverse Fourier transform of two-dimensional data in one step. The SFFT_2D and DFFT_2D functions perform the forward Fourier transform of a real sequence and store the result in either real or complex data format. These functions also perform the inverse Fourier transform of a complex sequence into a real sequence. The CFFT_2D and ZFFT_2D functions perform Fourier transforms on a complex sequence. However, the argument list is different, depending on the data format in which the output data is stored. See the CXML Reference Manual's chapter on "Using the Signal Processing Subprograms" for an explanation of real and complex data format.
0 DXML_SUCCESS() 4 (with real transforms only) DXML_ILL_N_IS_ODD() 8 DXML_ILL_N_RANGE() 11 DXML_ILL_LDA() 12 DXML_INS_RES() 13 DXML_BAD_STRIDE() 15 DXML_BAD_DIRECTION_STRING() 16 DXML_BAD_FORMAT_STRING() 18 DXML_BAD_FORMAT_FOR_DIRECTION()
INCLUDE 'CXMLDEF.FOR' INTEGER*4 N_I, N_J, STATUS, LDA REAL*8 A(1026,512), B(1026,513) N_I = 1024 N_J = 512 LDA = 1024 STATUS = DFFT_2D('R','C','F',A,B,N_I,N_J,LDA,1,1) This FORTRAN code computes the forward, two-dimensional, real FFT of a 1024x512 matrix A. The result of the transform is stored in B in complex form. Note that the leading dimension of B is 1026 in order to hold the extra complex values (see section on data storage). Note also that the input matrix A also requires a leading dimension of at least 1026. INCLUDE 'CXMLDEF.FOR' INTEGER*4 N_I, N_J, STATUS, LDA COMPLEX*8 A(1024,512), B(1024,512) N_I = 1024 N_J = 512 LDA = 1024 STATUS = CFFT_2D('C','C','F',A,B,N_I,N_J,LDA,1,1) This FORTRAN code computes the forward, two-dimensional, complex FFT of a matrix A, of dimension 1024 by 512. The result of the transform is stored in B in complex form.