feat(imperative): add swapaxes

GitOrigin-RevId: e84014a01169cb8e2dd5c68227531537585d34ce

imperative/python/megengine/functional/tensor.py

@@ -48,6 +48,7 @@ __all__ = [
     "tile",
     "copy",
     "transpose",
+    "swapaxes",
     "where",
     "zeros",
     "zeros_like",
@@ -715,6 +716,32 @@ def transpose(inp: Tensor, pattern: Iterable[int]) -> Tensor:
     return inp.transpose(pattern)
 
 
+def swapaxes(inp: Tensor, axis1: int, axis2: int) -> Tensor:
+    r"""Interchange two axes of a tensor.
+
+    Args:
+        inp: input tensor to swapaxes.
+        axis1: first axis.
+        axis2: second axis.
+
+    Returns:
+        a tensor after swapping the two axes of 'inp'.
+
+    Examples:
+        >>> x = Tensor(np.array([[[0,1],[2,3]],[[4,5],[6,7]]], dtype=np.int32))
+        >>> F.swapaxes(x, 0, 2)
+        Tensor([[[0 4]
+         [2 6]]
+        [[1 5]
+         [3 7]]], dtype=int32, device=xpux:0)
+    """
+    pattern = list(range(inp.ndim))
+    tempAxis = pattern[axis1]
+    pattern[axis1] = pattern[axis2]
+    pattern[axis2] = tempAxis
+    return inp.transpose(pattern)
+
+
 def reshape(inp: Tensor, target_shape: Iterable[int]) -> Tensor:
     r"""Reshapes a tensor without changing its data.
 

imperative/python/test/unit/functional/test_tensor.py

@@ -214,6 +214,18 @@ def test_split(symbolic):
                 np.testing.assert_equal(ref_out[idx], out[idx].numpy())
 
 
+@pytest.mark.parametrize("is_varnode", [True, False])
+def test_swapaxes(is_varnode):
+    if is_varnode:
+        network = Network()
+    else:
+        network = None
+
+    x = tensor(np.array([[1, 2, 3]], dtype=np.int32))
+    y = F.swapaxes(x, 0, 1)
+    np.testing.assert_equal(y.numpy(), np.array([[1], [2], [3]]).astype(np.int32))
+
+
 @pytest.mark.parametrize("is_varnode", [True, False])
 def test_reshape(is_varnode):
     if is_varnode: