cunumeric.fft.ifft#

cunumeric.fft.ifft(a: ndarray, n: int | None = None, axis: int = -1, norm: str | None = None) → ndarray#

Compute the one-dimensional inverse discrete Fourier Transform.

This function computes the inverse of the one-dimensional n-point discrete Fourier transform computed by fft. In other words, ifft(fft(a)) == a to within numerical accuracy. For a general description of the algorithm and definitions, see numpy.fft.

The input should be ordered in the same way as is returned by fft, i.e.,

a[0] should contain the zero frequency term,
a[1:n//2] should contain the positive-frequency terms,
a[n//2 + 1:] should contain the negative-frequency terms, in increasing order starting from the most negative frequency.

For an even number of input points, A[n//2] represents the sum of the values at the positive and negative Nyquist frequencies, as the two are aliased together. See numpy.fft for details.

Parameters:

a (array_like) – Input array, can be complex.
n (int, optional) – Length of the transformed axis of the output. If n is smaller than the length of the input, the input is cropped. If it is larger, the input is padded with zeros. If n is not given, the length of the input along the axis specified by axis is used. See notes about padding issues.
axis (int, optional) – Axis over which to compute the inverse DFT. If not given, the last axis is used.
norm ({"backward", "ortho", "forward"}, optional) – Normalization mode (see numpy.fft). Default is “backward”. Indicates which direction of the forward/backward pair of transforms is scaled and with what normalization factor.

Returns:

out – The truncated or zero-padded input, transformed along the axis indicated by axis, or the last one if axis is not specified.

Return type:

complex ndarray

Notes

This is really ifftn with different defaults. For more details see ifftn. Multi-GPU usage is limited to data parallel axis-wise batching.