[Relay,Topi][OP] affine_grid and grid_sample

include/tvm/relay/attrs/image.h

@@ -167,6 +167,34 @@ struct Dilation2DAttrs : public tvm::AttrsNode<Dilation2DAttrs> {
   }
 };
 
+/*! \brief Attributes used in image affine_grid operator */
+struct AffineGridAttrs : public tvm::AttrsNode<AffineGridAttrs> {
+  Array<IndexExpr> target_shape;
+
+  TVM_DECLARE_ATTRS(AffineGridAttrs, "relay.attrs.AffineGridAttrs") {
+    TVM_ATTR_FIELD(target_shape).describe("Specifies the output shape (H, W).");
+  }
+};
+
+/*! \brief Attributes used in image grid_sample operator */
+struct GridSampleAttrs : public tvm::AttrsNode<GridSampleAttrs> {
+  String method;
+  String layout;
+
+  TVM_DECLARE_ATTRS(GridSampleAttrs, "relay.attrs.GridSampleAttrs") {
+    TVM_ATTR_FIELD(method)
+        .set_default("bilinear")
+        .describe(
+            "Specify the mode to use for scaling."
+            "bilinear - Bilinear Interpolation");
+    TVM_ATTR_FIELD(layout).set_default("NCHW").describe(
+        "Dimension ordering of input data. Can be 'NCHW', 'NHWC', etc."
+        "'N', 'C', 'H', 'W' stands for batch, channel, height, and width"
+        "dimensions respectively. Resize is applied on the 'H' and"
+        "'W' dimensions.");
+  }
+};
+
 }  // namespace relay
 }  // namespace tvm
 #endif  // TVM_RELAY_ATTRS_IMAGE_H_

python/tvm/relay/frontend/mxnet.py

@@ -757,6 +757,26 @@ def _mx_resize(inputs, attrs):
     return _op.image.resize(inputs[0], size,
                             coordinate_transformation_mode="align_corners")
 
+def _mx_grid_generator(inputs, attrs):
+    transform_type = attrs.get_str("transform_type")
+    if transform_type == 'affine':
+        target_shape = attrs.get_int_tuple("target_shape")
+        return _op.image.affine_grid(_op.reshape(inputs[0], (0, 2, 3)), target_shape)
+    if transform_type == 'warp':
+        checked_type = _infer_type(inputs[0]).checked_type
+        batch, _, height, width = get_const_tuple(checked_type.shape)
+        dtype = checked_type.dtype
+        identity_affine = relay.const(np.array([[[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]], dtype=dtype))
+        identity_affine = _op.broadcast_to(identity_affine, (batch, 2, 3))
+        normalizer = (2.0 / np.array([width - 1, height - 1])).reshape(1, -1, 1, 1).astype(dtype)
+        normalized_flow = inputs[0] * relay.const(normalizer)
+        grid = _op.image.affine_grid(identity_affine, (height, width))
+        return grid + normalized_flow
+    raise ValueError("unknown transform type" + transform_type)
+
+def _mx_bilinear_sampler(inputs, attrs):
+    return _op.image.grid_sample(inputs[0], inputs[1], 'bilinear', 'NCHW')
+
 def _mx_roi_pooling(inputs, attrs):
     new_attrs = {}
     new_attrs["pooled_size"] = attrs.get_int_tuple("pooled_size")
@@ -1996,6 +2016,8 @@ def impl(inputs, input_types):
     "_contrib_box_nms" : _mx_box_nms,
     "_contrib_DeformableConvolution" : _mx_deformable_convolution,
     "_contrib_AdaptiveAvgPooling2D" : _mx_adaptive_avg_pooling,
+    "GridGenerator"                 : _mx_grid_generator,
+    "BilinearSampler"               : _mx_bilinear_sampler,
     # NLP
     "RNN"               : _mx_rnn_layer,
     "_rnn_param_concat" : _mx_rnn_param_concat,

python/tvm/relay/op/image/_image.py

@@ -19,6 +19,7 @@
 from __future__ import absolute_import
 
 import topi
+from topi.util import get_const_tuple
 from .. import op as reg
 from .. import strategy
 from ..op import OpPattern
@@ -67,3 +68,22 @@ def compute_crop_and_resize(attrs, inputs, out_type):
 # dilation2d
 reg.register_strategy("image.dilation2d", strategy.dilation2d_strategy)
 reg.register_pattern("image.dilation2d", OpPattern.OUT_ELEMWISE_FUSABLE)
+
+
+# affine_grid
+@reg.register_compute("image.affine_grid")
+def compute_affine_grid(attrs, inputs, out_dtype):
+    target_shape = get_const_tuple(attrs.target_shape)
+    return [topi.image.affine_grid(inputs[0], target_shape)]
+
+reg.register_injective_schedule("image.affine_grid")
+
+
+# grid_sample
+@reg.register_compute("image.grid_sample")
+def compute_grid_sample(attrs, inputs, out_dtype):
+    method = attrs.method
+    layout = attrs.layout
+    return [topi.image.grid_sample(inputs[0], inputs[1], method, layout)]
+
+reg.register_injective_schedule("image.grid_sample")

python/tvm/relay/op/image/image.py

@@ -215,3 +215,67 @@ def dilation2d(data,
 
     return _make.dilation2d(data, weight, strides, padding, dilations, data_layout,
                             kernel_layout, out_dtype)
+
+
+def affine_grid(data, target_shape=None):
+    """affine_grid operator that generates 2D sampling grid.
+
+    This operation is described in https://arxiv.org/pdf/1506.02025.pdf. It generates a uniform
+    sampling grid within the target shape and normalizes it to [-1, 1]. The provided affine
+    transformation is then applied on the sampling grid.
+
+    Parameters
+    ----------
+    data : tvm.Tensor
+        3-D with shape [batch, 2, 3]. The affine matrix.
+
+    target_shape: list/tuple of two int
+        Specifies the output shape (H, W).
+
+    Returns
+    -------
+    Output : tvm.Tensor
+        4-D with shape [batch, 2, target_height, target_width]
+    """
+    return _make.affine_grid(data, target_shape)
+
+def grid_sample(data, grid, method='bilinear', layout='NCHW'):
+    """Applies bilinear sampling to input feature map.
+
+    Given :math:`data` and :math:`grid`, then the output is computed by
+
+    .. math::
+
+        x_{src} = grid[batch, 0, y_{dst}, x_{dst}] \\
+        y_{src} = grid[batch, 1, y_{dst}, x_{dst}] \\
+        output[batch, channel, y_{dst}, x_{dst}] = G(data[batch, channel, y_{src}, x_{src})
+
+    :math:`x_{dst}`, :math:`y_{dst}` enumerate all spatial locations in :math:`output`, and
+    :math:`G()` denotes the interpolation function.
+    The out-boundary points will be padded with zeros. The shape of the output will be
+    (data.shape[0], data.shape[1], grid.shape[2], grid.shape[3]).
+
+    The operator assumes that :math:`grid` has been normalized to [-1, 1].
+
+    grid_sample often cooperates with affine_grid which generates sampling grids for grid_sample.
+
+    Parameters
+    ----------
+    data : tvm.Tensor
+        4-D with shape [batch, in_channel, in_height, in_width]
+
+    grid : tvm.Tensor
+        4-D with shape [batch, 2, out_height, out_width]
+
+    method : str
+        The interpolation method. Only 'bilinear' is supported.
+
+    layout : str
+        The layout of input data and the output.
+
+    Returns
+    -------
+    Output : tvm.Tensor
+        4-D with shape [batch, 2, out_height, out_width]
+    """
+    return _make.grid_sample(data, grid, method, layout)

src/relay/op/image/grid_sample.cc

@@ -0,0 +1,168 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+/*!
+ * \file grid_sample.cc
+ * \brief affine_grid and grid_sample operator
+ */
+#include <tvm/relay/attrs/image.h>
+#include <tvm/relay/op.h>
+#include <tvm/tir/data_layout.h>
+
+#include "../op_common.h"
+
+namespace tvm {
+namespace relay {
+
+// relay.image.affine_grid
+TVM_REGISTER_NODE_TYPE(AffineGridAttrs);
+
+bool AffineGridRel(const Array<Type>& types, int num_inputs, const Attrs& attrs,
+                   const TypeReporter& reporter) {
+  CHECK_EQ(types.size(), 2);
+  const auto* data = types[0].as<TensorTypeNode>();
+  if (data == nullptr) return false;
+  auto batch_size = data->shape[0];
+
+  const AffineGridAttrs* param = attrs.as<AffineGridAttrs>();
+  CHECK(param != nullptr);
+
+  Array<IndexExpr> oshape;
+
+  CHECK(data->shape.size() == 3U && reporter->AssertEQ(data->shape[1], 2) &&
+        reporter->AssertEQ(data->shape[2], 3))
+      << "data should be an"
+         "affine matrix with shape [batch_size, 2, 3]";
+  CHECK(param->target_shape.defined() && param->target_shape.size() == 2)
+      << "target_shape should be 2D";
+  oshape.push_back(batch_size);
+  oshape.push_back(2);
+  oshape.push_back(param->target_shape[0]);
+  oshape.push_back(param->target_shape[1]);
+
+  // assign output type
+  reporter->Assign(types[1], TensorType(oshape, data->dtype));
+  return true;
+}
+
+// Positional relay function to create affine_grid operator
+// used by frontend FFI.
+Expr MakeAffineGrid(Expr data, Array<IndexExpr> target_shape) {
+  auto attrs = make_object<AffineGridAttrs>();
+  attrs->target_shape = std::move(target_shape);
+  static const Op& op = Op::Get("image.affine_grid");
+  return Call(op, {data}, Attrs(attrs), {});
+}
+
+TVM_REGISTER_GLOBAL("relay.op.image._make.affine_grid").set_body_typed(MakeAffineGrid);
+
+RELAY_REGISTER_OP("image.affine_grid")
+    .describe(R"code(affine_grid operator that generates 2D sampling grid.
+
+This operation is described in https://arxiv.org/pdf/1506.02025.pdf. It generates a uniform
+sampling grid within the target shape and normalizes it to [-1, 1]. The provided affine
+transformation is then applied on the sampling grid.
+
+- **data**: data is 3D array of shape [batch, 2, 3], which defines an affine transformation.
+
+- **out**: out is 4D array of shape [batch, 2, height, width], where each vector
+           :math:`out[b, :, h, w]` represents the coordinate :math:`(x, y)`
+
+)code" TVM_ADD_FILELINE)
+    .set_attrs_type<AffineGridAttrs>()
+    .set_num_inputs(1)
+    .add_argument("data", "Tensor", "The affine matrix.")
+    .set_support_level(5)
+    .add_type_rel("AffineGrid", AffineGridRel)
+    .set_attr<TOpPattern>("TOpPattern", kInjective);
+
+// relay.image.grid_sample
+TVM_REGISTER_NODE_TYPE(GridSampleAttrs);
+
+bool GridSampleRel(const Array<Type>& types, int num_inputs, const Attrs& attrs,
+                   const TypeReporter& reporter) {
+  CHECK_EQ(types.size(), 3);
+  const auto* data = types[0].as<TensorTypeNode>();
+  const auto* grid = types[1].as<TensorTypeNode>();
+  if (!data || !grid) return false;
+  const auto* param = attrs.as<GridSampleAttrs>();
+  CHECK(param);
+  static const Layout kNCHW("NCHW");
+  const Layout in_layout(param->layout);
+  auto layout_converter = tir::BijectiveLayout(in_layout, kNCHW);
+  auto oshape = layout_converter.ForwardShape(data->shape);
+  oshape.Set(2, grid->shape[2]);
+  oshape.Set(3, grid->shape[3]);
+  // assign output type
+  reporter->Assign(types[2], TensorType(layout_converter.BackwardShape(oshape), data->dtype));
+  return true;
+}
+
+// Positional relay function to create affine_grid operator
+// used by frontend FFI.
+Expr MakeGridSample(Expr data, Expr grid, String method, String layout) {
+  auto attrs = make_object<GridSampleAttrs>();
+  attrs->method = std::move(method);
+  attrs->layout = std::move(layout);
+  static const Op& op = Op::Get("image.grid_sample");
+  return Call(op, {data, grid}, Attrs(attrs), {});
+}
+
+TVM_REGISTER_GLOBAL("relay.op.image._make.grid_sample").set_body_typed(MakeGridSample);
+
+RELAY_REGISTER_OP("image.grid_sample")
+    .describe(R"code(Applies grid sampling to input feature map.
+
+Given :math:`data` and :math:`grid`, then the output is computed by
+
+.. math::
+  x_{src} = grid[batch, 0, y_{dst}, x_{dst}] \\
+  y_{src} = grid[batch, 1, y_{dst}, x_{dst}] \\
+  output[batch, channel, y_{dst}, x_{dst}] = G(data[batch, channel, y_{src}, x_{src})
+
+:math:`x_{dst}`, :math:`y_{dst}` enumerate all spatial locations in :math:`output`, and
+:math:`G()` denotes the interpolation function.
+The out-boundary points will be padded with zeros. The shape of the output will be
+(data.shape[0], data.shape[1], grid.shape[2], grid.shape[3]).
+
+The operator assumes that :math:`data` has 'NCHW' layout and :math:`grid` has been normalized to [-1, 1].
+
+grid_sample often cooperates with affine_grid which generates sampling grids for grid_sample.
+
+- **data**: data is 4D array of shape
+            (batch_size, channels, in_height, in_width) for NCHW
+            (batch_size, in_height, in_width, channels) for NHWC
+
+- **grid**: out is 4D array of shape [batch, 2, out_height, out_width], where each vector
+           :math:`out[b, :, h, w]` represents the coordinate :math:`(x, y)`
+
+- **out**: out is 4D array of shape
+           (batch, in_channel, out_height, out_width) for NCHW
+           (batch_size, in_height, in_width, channels) for NHWC
+
+)code" TVM_ADD_FILELINE)
+    .set_num_inputs(2)
+    .set_attrs_type<GridSampleAttrs>()
+    .add_argument("data", "Tensor", "The input tensor.")
+    .set_support_level(5)
+    .add_type_rel("GridSample", GridSampleRel)
+    .set_attr<TOpPattern>("TOpPattern", kInjective);
+
+}  // namespace relay
+}  // namespace tvm

tests/python/frontend/mxnet/test_forward.py

@@ -639,6 +639,42 @@ def test_forward_bilinear_resize():
     mx_sym = mx.sym.contrib.BilinearResize2D(data, height=5, width=10)
     verify_mxnet_frontend_impl(mx_sym, (1, 2, 3, 4), (1, 2, 5, 10))
 
+def test_forward_grid_generator():
+    def verify(shape, transform_type, target_shape):
+        x = np.random.uniform(size=shape).astype("float32")
+        ref_res = mx.nd.GridGenerator(mx.nd.array(x), transform_type, target_shape)
+        mx_sym = mx.sym.GridGenerator(mx.sym.var("x"), transform_type, target_shape)
+        shape_dict = {"x": x.shape}
+        mod, _ = relay.frontend.from_mxnet(mx_sym, shape_dict)
+        for target, ctx in ctx_list():
+            for kind in ["graph", "debug"]:
+                intrp = relay.create_executor(
+                    kind, mod=mod, ctx=ctx, target=target)
+                op_res = intrp.evaluate()(x)
+                tvm.testing.assert_allclose(
+                    op_res.asnumpy(), ref_res.asnumpy(), rtol=1e-5, atol=1e-5)
+    verify((4, 6), 'affine', (16, 32))
+    verify((4, 2, 16, 16), 'warp', None)
+    verify((1, 2, 16, 16), 'warp', None)
+
+def test_forward_bilinear_sampler():
+    def verify(data_shape, grid_shape):
+        data = np.random.uniform(size=data_shape).astype("float32")
+        grid = np.random.uniform(low=-1.5, high=1.5, size=grid_shape).astype("float32")
+        ref_res = mx.nd.BilinearSampler(mx.nd.array(data), mx.nd.array(grid))
+        mx_sym = mx.sym.BilinearSampler(mx.sym.var("data"), mx.sym.var("grid"))
+        shape_dict = {"data": data.shape, "grid": grid.shape}
+        mod, _ = relay.frontend.from_mxnet(mx_sym, shape_dict)
+        for target, ctx in ctx_list():
+            for kind in ["graph", "debug"]:
+                intrp = relay.create_executor(
+                    kind, mod=mod, ctx=ctx, target=target)
+                op_res = intrp.evaluate()(data, grid)
+                tvm.testing.assert_allclose(
+                    op_res.asnumpy(), ref_res.asnumpy(), rtol=1e-5, atol=1e-5)
+    verify((4, 4, 16, 32), (4, 2, 8, 8))
+    verify((4, 4, 16, 32), (4, 2, 32, 32))
+
 def test_forward_rnn_layer():
     def verify(mode, seq_len, input_size, hidden_size, num_layers,
                batch=1, init_states=True, bidirectional=False):
@@ -1211,3 +1247,5 @@ def verify(data_shape, kernel_size, max_displacement, stride1, stride2, pad_size
     test_forward_unravel_index()
     test_forward_swap_axis()
     test_forward_correlation()
+    test_forward_grid_generator()
+    test_forward_bilinear_sampler()