update fft api path (#36219)

* update fft api path
* add sample code for ihfft2

Co-authored-by: chenfeiyu <chenfeiyu@baidu.com>

python/paddle/__init__.py

@@ -64,7 +64,6 @@
 import paddle.static  # noqa: F401
 import paddle.vision  # noqa: F401
 
-from .tensor import fft
 from .tensor.random import bernoulli  # noqa: F401
 
 from .tensor.attribute import rank  # noqa: F401
@@ -294,6 +293,7 @@
 from .hapi import flops  # noqa: F401
 from . import hub  # noqa: F401
 from . import linalg  # noqa: F401
+from . import fft  # noqa: F401
 
 import paddle.text  # noqa: F401
 import paddle.vision  # noqa: F401

python/paddle/fft.py

@@ -0,0 +1,61 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from .tensor.fft import fft  # noqa: F401
+from .tensor.fft import fft2  # noqa: F401
+from .tensor.fft import fftn  # noqa: F401
+from .tensor.fft import ifft  # noqa: F401
+from .tensor.fft import ifft2  # noqa: F401
+from .tensor.fft import ifftn  # noqa: F401
+from .tensor.fft import rfft  # noqa: F401
+from .tensor.fft import rfft2  # noqa: F401
+from .tensor.fft import rfftn  # noqa: F401
+from .tensor.fft import irfft  # noqa: F401
+from .tensor.fft import irfft2  # noqa: F401
+from .tensor.fft import irfftn  # noqa: F401
+from .tensor.fft import hfft  # noqa: F401
+from .tensor.fft import hfft2  # noqa: F401
+from .tensor.fft import hfftn  # noqa: F401
+from .tensor.fft import ihfft  # noqa: F401
+from .tensor.fft import ihfft2  # noqa: F401
+from .tensor.fft import ihfftn  # noqa: F401
+from .tensor.fft import fftfreq  # noqa: F401
+from .tensor.fft import rfftfreq  # noqa: F401
+from .tensor.fft import fftshift  # noqa: F401
+from .tensor.fft import ifftshift  # noqa: F401
+
+__all__ = [ # noqa
+    'fft',
+    'fft2',
+    'fftn',
+    'ifft',
+    'ifft2',
+    'ifftn',
+    'rfft',
+    'rfft2',
+    'rfftn',
+    'irfft',
+    'irfft2',
+    'irfftn',
+    'hfft',
+    'hfft2',
+    'hfftn',
+    'ihfft',
+    'ihfft2',
+    'ihfftn',
+    'fftfreq',
+    'rfftfreq',
+    'fftshift',
+    'ifftshift'
+]

python/paddle/tensor/fft.py

@@ -21,30 +21,7 @@
 from ..fluid.data_feeder import check_variable_and_dtype
 from ..fluid.layer_helper import LayerHelper
 
-__all__ = [
-    'fft',
-    'fft2',
-    'fftn',
-    'ifft',
-    'ifft2',
-    'ifftn',
-    'rfft',
-    'rfft2',
-    'rfftn',
-    'irfft',
-    'irfft2',
-    'irfftn',
-    'hfft',
-    'hfft2',
-    'hfftn',
-    'ihfft',
-    'ihfft2',
-    'ihfftn',
-    'fftfreq',
-    'rfftfreq',
-    'fftshift',
-    'ifftshift',
-]
+__all__ = []
 
 
 def _check_normalization(norm):
@@ -1135,7 +1112,24 @@ def ihfft2(x, s=None, axes=(-2, -1), norm="backward", name=None):
             refer to :ref:`api_guide_Name` . 
 
     Returns:
-        out(Tensor) : The result of the inverse real 2-D FFT.
+        out(Tensor) : The result of the inverse hermitian 2-D FFT.
+
+    Examples:
+
+        .. code-block:: python
+
+            import numpy as np
+            import paddle
+
+            x = np.mgrid[:5, :5][0].astype(np.float64)
+            xp = paddle.to_tensor(x)
+            ihfft2_xp = paddle.fft.ihfft2(xp).numpy()
+            print(ihfft2_xp)
+            # [[ 2. +0.j          0. +0.j          0. +0.j        ]
+            #  [-0.5-0.68819096j  0. +0.j          0. +0.j        ]
+            #  [-0.5-0.16245985j  0. +0.j          0. +0.j        ]
+            #  [-0.5+0.16245985j  0. +0.j          0. +0.j        ]
+            #  [-0.5+0.68819096j  0. +0.j          0. +0.j        ]]
     """
     _check_at_least_ndim(x, 2)
     if s is not None: