Revert vendoring of SciPy functions

mkl_fft/interfaces/_scipy_fft.py

@@ -36,6 +36,7 @@
 
 import mkl
 import numpy as np
+import scipy
 
 import mkl_fft
 
@@ -61,6 +62,10 @@
     "ihfft2",
     "hfftn",
     "ihfftn",
+    "fftshift",
+    "ifftshift",
+    "fftfreq",
+    "rfftfreq",
     "get_workers",
     "set_workers",
 ]
@@ -650,6 +655,51 @@ def ihfftn(
     return result
 
 
+# define thin wrappers for scipy functions to avoid circular dependencies
+def fftfreq(n, d=1.0, *, xp=None, device=None):
+    """
+    Return the Discrete Fourier Transform sample frequencies.
+
+    For full documentation refer to `scipy.fft.fftfreq`.
+
+    """
+    return scipy.fft.fftfreq(n, d=d, xp=xp, device=device)
+
+
+def rfftfreq(n, d=1.0, *, xp=None, device=None):
+    """
+    Return the Discrete Fourier Transform sample frequencies (for usage with
+    `rfft`, `irfft`).
+
+    For full documentation refer to `scipy.fft.rfftfreq`.
+
+    """
+    return scipy.fft.rfftfreq(n, d=d, xp=xp, device=device)
+
+
+def fftshift(x, axes=None):
+    """
+    Shift the zero-frequency component to the center of the spectrum.
+
+    For full documentation refer to `scipy.fft.fftshift`.
+
+    """
+    from scipy.fft import fftshift
+
+    return fftshift(x, axes=axes)
+
+
+def ifftshift(x, axes=None):
+    """
+    The inverse of `fftshift`. Although identical for even-length `x`, the
+    functions differ by one sample for odd-length `x`.
+
+    For full documentation refer to `scipy.fft.ifftshift`.
+
+    """
+    return scipy.fft.ifftshift(x, axes=axes)
+
+
 def get_workers():
     """
     Gets the number of workers used by mkl_fft by default.

mkl_fft/interfaces/scipy_fft.py

@@ -28,14 +28,17 @@
 from ._scipy_fft import (
     fft,
     fft2,
+    fftfreq,
     fftn,
+    fftshift,
     get_workers,
     hfft,
     hfft2,
     hfftn,
     ifft,
     ifft2,
     ifftn,
+    ifftshift,
     ihfft,
     ihfft2,
     ihfftn,
@@ -44,10 +47,10 @@
     irfftn,
     rfft,
     rfft2,
+    rfftfreq,
     rfftn,
     set_workers,
 )
-from ._scipy_helper import fftfreq, fftshift, ifftshift, rfftfreq
 
 __all__ = [
     "fft",