[TOPI] add dilation operators (#316)

* add dilation operators

* fix pylint

* dilate testcases success

* n-D tensor dilation

* support arbitrary dimension

topi/python/topi/nn/__init__.py

@@ -5,3 +5,4 @@
 from .mapping import *
 from .ewise import *
 from .conv import *
+from .dilate import *

topi/python/topi/nn/dilate.py

@@ -0,0 +1,44 @@
+# pylint: disable=invalid-name
+"""Dilation operators"""
+from __future__ import absolute_import as _abs
+import tvm
+
+
+@tvm.tag_scope(tag="dilation")
+def dilate(Input, strides):
+    """Dilate Input with zeros.
+
+    Parameters
+    ----------
+    Input : tvm.Tensor
+        n-D, can be any layout.
+
+    strides : list / tuple of n ints
+        Dilation stride on each dimension, 1 means no dilation.
+
+    Returns
+    -------
+    Output : tvm.Tensor
+        n-D, the same layout as Input.
+    """
+    n = len(Input.shape)
+    assert len(strides) == n, \
+        "Input dimension and strides size dismatch : %d vs %d" %(n, len(strides))
+    output_size = ()
+    for i in range(n):
+        output_size += (tvm.ir_pass.Simplify((Input.shape[i]-1)*strides[i]+1),)
+
+    def _dilate(data, *indices):
+        not_zero = (indices[0]%strides[0]).equal(0)
+        index_tuple = ()
+        for i in range(n):
+            index_tuple += (indices[i]/strides[i],)
+            not_zero = tvm.all(not_zero, (indices[i]%strides[i]).equal(0))
+        return tvm.select(not_zero, data[index_tuple], tvm.const(0.0, data.dtype))
+
+    Output = tvm.compute(
+        (output_size),
+        lambda *indices: _dilate(Input, *indices),
+        name='DilatedInput')
+
+    return Output

topi/python/topi/testing/__init__.py

@@ -6,3 +6,4 @@
 
 from .conv2d_hwcn_python import conv2d_hwcn_python
 from .conv2d_nchw_python import conv2d_nchw_python
+from .dilate_python import dilate_python

topi/python/topi/testing/dilate_python.py

@@ -0,0 +1,33 @@
+# pylint: disable=invalid-name
+"""Dilate operation in python"""
+import numpy as np
+
+
+def dilate_python(input_np, strides):
+    """Dilate operation.
+
+    Parameters
+    ----------
+    input_np : numpy.ndarray
+        n-D, can be any layout.
+
+    strides : list / tuple of n ints
+        Dilation stride on each dimension, 1 means no dilation.
+
+    Returns
+    -------
+    output_np : numpy.ndarray
+        n-D, the same layout as Input.
+    """
+    n = len(input_np.shape)
+    assert len(strides) == n, \
+        "Input dimension and strides size dismatch : %d vs %d" %(n, len(strides))
+    output_size = ()
+    no_zero = ()
+    for i in range(n):
+        output_size += ((input_np.shape[i]-1)*strides[i]+1,)
+        no_zero += ((range(0, output_size[i], strides[i])),)
+    output_np = np.zeros(shape=output_size)
+    output_np[np.ix_(*no_zero)] = input_np
+
+    return output_np

topi/tests/python/test_topi_dilate.py

@@ -0,0 +1,36 @@
+import tvm
+import topi
+import numpy as np
+
+
+def test_dilate():
+    target = 'llvm'
+    ctx = tvm.cpu(0)
+
+    def _test_dilate(input_size, strides):
+        Input = tvm.placeholder((input_size))
+        Output = topi.nn.dilate(Input, strides)
+        schedule = tvm.create_schedule(Output.op)
+        input_np = np.random.uniform(size=input_size).astype(Input.dtype)
+        output_np = topi.testing.dilate_python(input_np, strides)
+        input_tvm = tvm.nd.array(input_np, ctx=ctx)
+        output_size = ()
+        for i in range(len(input_size)):
+            output_size += (tvm.ir_pass.Simplify(Output.shape[i]).value,)
+        output_tvm = tvm.nd.array(np.zeros(shape=output_size).astype(Output.dtype), ctx=ctx)
+        f = tvm.build(schedule, [Input, Output], target)
+        f(input_tvm, output_tvm)
+        np.testing.assert_allclose(output_tvm.asnumpy(), output_np, rtol=1e-5)
+
+    _test_dilate((32,), (2,))
+    _test_dilate((32,32), (2,2))
+    _test_dilate((1,3,32,32), (1,1,1,1))
+    _test_dilate((1,3,32,32), (2,2,2,2))
+    _test_dilate((1,32,32,3,3), (1,1,1,1,1))
+    _test_dilate((1,32,32,3,3), (2,2,2,2,2))
+    _test_dilate((1,32,32,32,3,3), (1,1,1,2,2,2))
+    _test_dilate((1,32,32,32,3,3), (2,2,2,1,1,1))
+
+
+if __name__ == "__main__":
+    test_dilate()