Description

S3L_fft_detailed computes the in-place forward or inverse FFT along a specified axis of a complex or double complex parallel array, a. FFT direction and axis are specified by the arguments iflag and axis, respectively. Both power-of-two and arbitrary radix FFTs are supported. Upon completion, a is overwritten with the FFT result.

A 1D parallel FFT can be used for array sizes that are a multiple of the square of the number of processes. Higher dimensionality FFTs can be used for arbitrary sizes and distributions.

For the 2D FFT, a more efficient transpose algorithm is employed when the blocksizes along each dimension are equal to the extents divided by the number of processes. This yields significant performance benefits.

S3L_fft_detailed can only be used for complex and double complex data types. To compute a real-data forward FFT, use S3L_rc_fft. This performs a forward FFT on the real data, yielding packed representation of the complex results. To compute the corresponding inverse FFT, use S3L_cr_fft, which will perform an inverse FFT on the complex data, overwriting the original real array with real-valued results of the inverse FFT.

The floating-point precision of the result always matches that of the input.

S3L_fft_detailed and S3L_ifft do not perform any scaling. Consequently, when a forward FFT is followed by an inverse FFT, the original data will be scaled by the product of the extents of the array.