numpy · rgommers · Jan 16, 2024 · Dec 6, 2023 · Jan 10, 2024 · Jan 12, 2024
diff --git a/numpy/array_api/__init__.py b/numpy/array_api/__init__.py
@@ -353,6 +353,9 @@
 
 __all__ += ["matmul", "tensordot", "matrix_transpose", "vecdot"]
 
+from . import fft
+__all__ += ["fft"]
+
 from ._manipulation_functions import (
     concat,
     expand_dims,

diff --git a/numpy/array_api/fft.py b/numpy/array_api/fft.py
@@ -0,0 +1,296 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Union, Optional, Literal
+
+if TYPE_CHECKING:
+    from ._typing import Device
+    from collections.abc import Sequence
+
+from ._dtypes import (
+    _floating_dtypes,
+    _real_floating_dtypes,
+    _complex_floating_dtypes,
+    float32,
+    complex64,
+)
+from ._array_object import Array
+from ._data_type_functions import astype
+
+import numpy as np
+
+def fft(
+    x: Array,
+    /,
+    *,
+    n: Optional[int] = None,
+    axis: int = -1,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.fft <numpy.fft.fft>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in fft")
+    res = Array._new(np.fft.fft(x._array, n=n, axis=axis, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, complex64)
+    return res
+
+def ifft(
+    x: Array,
+    /,
+    *,
+    n: Optional[int] = None,
+    axis: int = -1,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.ifft <numpy.fft.ifft>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in ifft")
+    res = Array._new(np.fft.ifft(x._array, n=n, axis=axis, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, complex64)
+    return res
+
+def fftn(
+    x: Array,
+    /,
+    *,
+    s: Sequence[int] = None,
+    axes: Sequence[int] = None,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.fftn <numpy.fft.fftn>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in fftn")
+    res = Array._new(np.fft.fftn(x._array, s=s, axes=axes, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, complex64)
+    return res
+
+def ifftn(
+    x: Array,
+    /,
+    *,
+    s: Sequence[int] = None,
+    axes: Sequence[int] = None,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.ifftn <numpy.fft.ifftn>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in ifftn")
+    res = Array._new(np.fft.ifftn(x._array, s=s, axes=axes, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, complex64)
+    return res
+
+def rfft(
+    x: Array,
+    /,
+    *,
+    n: Optional[int] = None,
+    axis: int = -1,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.rfft <numpy.fft.rfft>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _real_floating_dtypes:
+        raise TypeError("Only real floating-point dtypes are allowed in rfft")
+    res = Array._new(np.fft.rfft(x._array, n=n, axis=axis, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == float32:
+        return astype(res, complex64)
+    return res
+
+def irfft(
+    x: Array,
+    /,
+    *,
+    n: Optional[int] = None,
+    axis: int = -1,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.irfft <numpy.fft.irfft>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in irfft")
+    res = Array._new(np.fft.irfft(x._array, n=n, axis=axis, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, float32)
+    return res
+
+def rfftn(
+    x: Array,
+    /,
+    *,
+    s: Sequence[int] = None,
+    axes: Sequence[int] = None,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.rfftn <numpy.fft.rfftn>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _real_floating_dtypes:
+        raise TypeError("Only real floating-point dtypes are allowed in rfftn")
+    res = Array._new(np.fft.rfftn(x._array, s=s, axes=axes, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == float32:
+        return astype(res, complex64)
+    return res
+
+def irfftn(
+    x: Array,
+    /,
+    *,
+    s: Sequence[int] = None,
+    axes: Sequence[int] = None,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.irfftn <numpy.fft.irfftn>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in irfftn")
+    res = Array._new(np.fft.irfftn(x._array, s=s, axes=axes, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, float32)
+    return res
+
+def hfft(
+    x: Array,
+    /,
+    *,
+    n: Optional[int] = None,
+    axis: int = -1,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.hfft <numpy.fft.hfft>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _complex_floating_dtypes:
+        raise TypeError("Only complex floating-point dtypes are allowed in hfft")
+    res = Array._new(np.fft.hfft(x._array, n=n, axis=axis, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == complex64:
+        return astype(res, float32)
+    return res
+
+def ihfft(
+    x: Array,
+    /,
+    *,
+    n: Optional[int] = None,
+    axis: int = -1,
+    norm: Literal["backward", "ortho", "forward"] = "backward",
+) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.ihfft <numpy.fft.ihfft>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _real_floating_dtypes:
+        raise TypeError("Only real floating-point dtypes are allowed in ihfft")
+    res = Array._new(np.fft.ihfft(x._array, n=n, axis=axis, norm=norm))
+    # Note: np.fft functions improperly upcast float32 and complex64 to
+    # complex128
+    if x.dtype == float32:
+        return astype(res, complex64)
+    return res
+
+def fftfreq(n: int, /, *, d: float = 1.0, device: Optional[Device] = None) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.fftfreq <numpy.fft.fftfreq>`.
+
+    See its docstring for more information.
+    """
+    if device not in ["cpu", None]:
+        raise ValueError(f"Unsupported device {device!r}")
+    return Array._new(np.fft.fftfreq(n, d=d))
+
+def rfftfreq(n: int, /, *, d: float = 1.0, device: Optional[Device] = None) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.rfftfreq <numpy.fft.rfftfreq>`.
+
+    See its docstring for more information.
+    """
+    if device not in ["cpu", None]:
+        raise ValueError(f"Unsupported device {device!r}")
+    return Array._new(np.fft.rfftfreq(n, d=d))
+
+def fftshift(x: Array, /, *, axes: Union[int, Sequence[int]] = None) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.fftshift <numpy.fft.fftshift>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _floating_dtypes:
+        raise TypeError("Only floating-point dtypes are allowed in fftshift")
+    return Array._new(np.fft.fftshift(x._array, axes=axes))
+
+def ifftshift(x: Array, /, *, axes: Union[int, Sequence[int]] = None) -> Array:
+    """
+    Array API compatible wrapper for :py:func:`np.fft.ifftshift <numpy.fft.ifftshift>`.
+
+    See its docstring for more information.
+    """
+    if x.dtype not in _floating_dtypes:
+        raise TypeError("Only floating-point dtypes are allowed in ifftshift")
+    return Array._new(np.fft.ifftshift(x._array, axes=axes))
+
+__all__ = [
+    "fft",
+    "ifft",
+    "fftn",
+    "ifftn",
+    "rfft",
+    "irfft",
+    "rfftn",
+    "irfftn",
+    "hfft",
+    "ihfft",
+    "fftfreq",
+    "rfftfreq",
+    "fftshift",
+    "ifftshift",
+]
diff --git a/numpy/tests/test_public_api.py b/numpy/tests/test_public_api.py
@@ -109,6 +109,7 @@ def test_NPY_NO_EXPORT():
 # private, to clean up our public API and avoid confusion.
 PUBLIC_MODULES = ['numpy.' + s for s in [
     "array_api",
+    "array_api.fft",
     "array_api.linalg",
     "ctypeslib",
     "dtypes",