Real transform: status = {S,D}FFT_APPLY_2D (input_format, output_format, direction, in, out, lda, fft_struct, ni_stride, nj_stride) Complex transform in complex data format: status = {C,Z}FFT_APPLY_2D (input_format, output_format, direction, in, out, lda, fft_struct, ni_stride, nj_stride) Complex transform in real data format: status = {C,Z}FFT_APPLY_2D (input_format, output_format, direction, in_real, in_imag, out_real, out_imag, lda, fft_struct, 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' of '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. 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'. fft_struct record /dxml_s_fft_structure_2d/ for single-precision real operations record /dxml_d_fft_structure_2d/ for double-precision real operations record /dxml_c_fft_structure_2d/ for single-precision complex operations record /dxml_z_fft_structure_2d/ for double-precision complex operations The argument refers to the structure created by the _2D_INIT routine. ni_stride, nj_stride integer*4 Specifies the distance between consecutive elements in a column and row in the IN and OUT arrays; the valid stride depends on the _INIT routine; ni_stride >= 1, nj_stride >= 1.
The _FFT_APPLY_2D routines compute the fast Fourier transform of two- dimensional data in either the forward or backward direction. These routines are the second step of the three-step procedure. They compute the fast forward or inverse Fourier transform, using the internal data structures created by the _FFT_2D_INIT subroutine. Use the _APPLY_2D routines with their corresponding _INIT_2D and _EXIT_2D routines. For example, use SFFT_APPLY after the SFFT_INIT and end with the SFFT_EXIT routine. 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() 11 DXML_ILL_LDA() 12 DXML_INS_RES() 13 DXML_BAD_STRIDE() 15 DXML_BAD_DIRECTION_STRING() 16 DXML_BAD_FORMAT_STRING() 18 (for real transform only) DXML_BAD_FORMAT_FOR_DIRECTION()
INCLUDE 'CXMLDEF.FOR' INTEGER*4 N_I, N_J, STATUS, LDA REAL*8 A(1026,512), B(1026,513) RECORD /CXML_D_FFT_STRUCTURE_2D/ FFT_STRUCT N_I = 1024 N_J = 512 LDA = 1024 STATUS = DFFT_INIT_2D(N_I,N_J,FFT_STRUCT,.TRUE.) STATUS = DFFT_APPLY_2D('R','C','F',A,B,LDA,FFT_STRUCT,1,1) STATUS = DFFT_EXIT_2D(FFT_STRUCT) 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*16 A(1024,512), B(1024,512) RECORD /CXML_Z_FFT_STRUCTURE_2D/ FFT_STRUCT N_I = 1024 N_J = 512 LDA = 1024 STATUS = ZFFT_INIT_2D(N_I,N_J,FFT_STRUCT,.TRUE.) STATUS = ZFFT_APPLY_2D('C','C','F',A,B,LDA,FFT_STRUCT,1,1) STATUS = ZFFT_EXIT_2D(FFT_STRUCT) 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.