[GitHub] piiswrong commented on a change in pull request #8603: Contrib operators for object-detection bounding box related stuffs

[GitBox <gi...@apache.org>]

piiswrong commented on a change in pull request #8603: Contrib operators for object-detection bounding box related stuffs
URL: https://github.com/apache/incubator-mxnet/pull/8603#discussion_r159511264
 
 

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 File path: src/operator/contrib/bounding_box.cc
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+/*
+ * 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.
+ */
+
+ /*!
+  *  Copyright (c) 2017 by Contributors
+  * \file bounding_box.cc
+  * \brief Bounding box util functions and operators
+  * \author Joshua Zhang
+  */
+
+#include "./bounding_box-inl.h"
+#include "../elemwise_op_common.h"
+
+namespace mxnet {
+namespace op {
+DMLC_REGISTER_PARAMETER(BoxNMSParam);
+DMLC_REGISTER_PARAMETER(BoxOverlapParam);
+DMLC_REGISTER_PARAMETER(BipartiteMatchingParam);
+
+NNVM_REGISTER_OP(_contrib_box_nms)
+.add_alias("_contrib_box_non_maximum_suppression")
+.describe(R"code(Apply non-maximum suppression to input.
+
+The output will be sorted in descending order according to `score`. Boxes with
+overlaps larger than `overlap_thresh` and smaller scores will be removed and
+filled with -1, the corresponding position will be recorded for backward propogation.
+
+During back-propagation, the gradient will be copied to the original
+position according to the input index. For positions that have been suppressed,
+the in_grad will be assigned 0.
+In summary, gradients are sticked to its boxes, will either be moved or discarded
+according to its original index in input.
+
+Input requirements:
+1. Input tensor have at least 2 dimensions, (n, k), any higher dims will be regarded
+as batch, e.g. (a, b, c, d, n, k) == (a*b*c*d, n, k)
+2. n is the number of boxes in each batch
+3. k is the width of each box item.
+
+By default, a box is [id, score, xmin, ymin, xmax, ymax, ...],
+additional elements are allowed.
+- `id_index`: optional, use -1 to ignore, useful if `force_suppress=False`, which means
+we will skip highly overlapped boxes if one is `apple` while the other is `car`.
+- `coord_start`: required, default=2, the starting index of the 4 coordinates.
+Two formats are supported:
+  `corner`: [xmin, ymin, xmax, ymax]
+  `center`: [x, y, width, height]
+- `score_index`: required, default=1, box score/confidence.
+When two boxes overlap IOU > `overlap_thresh`, the one with smaller score will be suppressed.
+- `in_format` and `out_format`: default='corner', specify in/out box formats.
+
+Examples::
+
+  x = [[0, 0.5, 0.1, 0.1, 0.2, 0.2], [1, 0.4, 0.1, 0.1, 0.2, 0.2],
+       [0, 0.3, 0.1, 0.1, 0.14, 0.14], [2, 0.6, 0.5, 0.5, 0.7, 0.8]]
+  box_nms(x, overlap_thresh=0.1, coord_start=2, score_index=1, id_index=0,
+      force_suppress=True, in_format='corner', out_typ='corner') =
+      [[2, 0.6, 0.5, 0.5, 0.7, 0.8], [0, 0.5, 0.1, 0.1, 0.2, 0.2],
+       [-1, -1, -1, -1, -1, -1], [-1, -1, -1, -1, -1, -1]]
+  out_grad = [[0.1, 0.1, 0.1, 0.1, 0.1, 0.1], [0.2, 0.2, 0.2, 0.2, 0.2, 0.2],
+              [0.3, 0.3, 0.3, 0.3, 0.3, 0.3], [0.4, 0.4, 0.4, 0.4, 0.4, 0.4]]
+  # exe.backward
+  in_grad = [[0.2, 0.2, 0.2, 0.2, 0.2, 0.2], [0, 0, 0, 0, 0, 0],
+             [0, 0, 0, 0, 0, 0], [0.1, 0.1, 0.1, 0.1, 0.1, 0.1]]
+
+)code" ADD_FILELINE)
+.set_num_inputs(1)
+.set_num_outputs(2)
+.set_attr_parser(ParamParser<BoxNMSParam>)
+.set_attr<nnvm::FNumVisibleOutputs>("FNumVisibleOutputs", BoxNMSNumVisibleOutputs)
+.set_attr<nnvm::FInferShape>("FInferShape", BoxNMSShape)
+.set_attr<nnvm::FInferType>("FInferType", ElemwiseType<1, 2>)
+.set_attr<FResourceRequest>("FResourceRequest",
+  [](const NodeAttrs& attrs) {
+    return std::vector<ResourceRequest>{ResourceRequest::kTempSpace};
+  })
+.set_attr<FCompute>("FCompute<cpu>", BoxNMSForward<cpu>)
+.set_attr<nnvm::FGradient>("FGradient", ElemwiseGradUseOut{"_backward_contrib_box_nms"})
+.add_argument("data", "NDArray-or-Symbol", "The input")
+.add_arguments(BoxNMSParam::__FIELDS__());
+
+NNVM_REGISTER_OP(_backward_contrib_box_nms)
+.set_num_inputs(3)
+.set_num_outputs(1)
+.set_attr_parser(ParamParser<BoxNMSParam>)
+.set_attr<nnvm::TIsBackward>("TIsBackward", true)
+.set_attr<FCompute>("FCompute<cpu>", BoxNMSBackward<cpu>)
+.add_arguments(BoxNMSParam::__FIELDS__());
+
+NNVM_REGISTER_OP(_contrib_box_iou)
+.describe(R"doc(Bounding box overlap of two arrays.
+  The overlap is defined as Intersection-over-Union, aka, IOU.
+  - lhs: (a_1, a_2, ..., a_n, 4) array
+  - rhs: (b_1, b_2, ..., b_n, 4) array
+  - output: (a_1, a_2, ..., a_n, b_1, b_2, ..., b_n) array
+
+  Note::
+
+    Zero gradients are back-propagated in this op for now.
 
 Review comment:
   Why define gradient at all?

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