add embedding 2.0 (#26649)

* add embedding 2.0

* add embedding support input int32

paddle/fluid/operators/lookup_table_v2_op.cc

@@ -15,8 +15,8 @@ limitations under the License. */
 #include "paddle/fluid/operators/lookup_table_v2_op.h"
 
 #include <memory>
-
 #include "paddle/fluid/framework/no_need_buffer_vars_inference.h"
+#include "paddle/fluid/framework/op_version_registry.h"
 #include "paddle/fluid/framework/var_type_inference.h"
 
 namespace paddle {
@@ -196,3 +196,14 @@ REGISTER_OP_CPU_KERNEL(lookup_table_v2, ops::LookupTableV2Kernel<float>,
 REGISTER_OP_CPU_KERNEL(lookup_table_v2_grad,
                        ops::LookupTableV2GradKernel<float>,
                        ops::LookupTableV2GradKernel<double>);
+
+/* ==========================  register checkpoint ===========================*/
+REGISTER_OP_VERSION(lookup_table_v2)
+    .AddCheckpoint(
+        R"ROC(fix lookup_table_v2, add input type `int32`)ROC",
+        paddle::framework::compatible::OpVersionDesc()
+            .BugfixWithBehaviorChanged("lookup_table_v2 support input type "
+                                       "`int64`; after support input type "
+                                       "`int32/int64`"));
+
+/* ========================================================================== */

paddle/fluid/operators/lookup_table_v2_op.cu

@@ -85,6 +85,14 @@ __global__ void LookupTableV2Grad(T *table, const T *output, const int64_t *ids,
   }
 }
 
+template <typename T>
+__global__ void InputTypeCovert(const T *in_ids, const int64_t K,
+                                int64_t *out_ids) {
+  for (int i = 0; i < K; i++) {
+    out_ids[i] = (int64_t)(in_ids[i]);
+  }
+}
+
 template <typename T>
 class LookupTableV2CUDAKernel : public framework::OpKernel<T> {
  public:
@@ -101,23 +109,37 @@ class LookupTableV2CUDAKernel : public framework::OpKernel<T> {
     size_t D = table_t->dims()[1];
     size_t K = ids_t->numel();
 
-    auto *ids = ids_t->data<int64_t>();
-    auto *table = table_t->data<T>();
-    auto *output = output_t->mutable_data<T>(context.GetPlace());
-
     dim3 threads(256, 4);
     dim3 grids(80, 1);
 
+    // copy GPU memory to CPU pinned memory
+    framework::Vector<int64_t> ids;
+    ids.resize(K);
+
+    const int64_t *ids_p = nullptr;
+
+    if (ids_t->type() == framework::proto::VarType::INT32) {
+      InputTypeCovert<
+          int><<<grids, threads, 0, context.cuda_device_context().stream()>>>(
+          ids_t->data<int>(), K, ids.MutableData(context.GetPlace()));
+      ids_p = ids.MutableData(context.GetPlace());
+    } else {
+      ids_p = ids_t->data<int64_t>();
+    }
+
+    auto *table = table_t->data<T>();
+    auto *output = output_t->mutable_data<T>(context.GetPlace());
+
     if (padding_idx == -1)
       LookupTableV2<
           T, 256, 4, 80,
           false><<<grids, threads, 0, context.cuda_device_context().stream()>>>(
-          output, table, ids, N, K, D, padding_idx);
+          output, table, ids_p, N, K, D, padding_idx);
     else
       LookupTableV2<
           T, 256, 4, 80,
           true><<<grids, threads, 0, context.cuda_device_context().stream()>>>(
-          output, table, ids, N, K, D, padding_idx);
+          output, table, ids_p, N, K, D, padding_idx);
   }
 };
 
@@ -139,16 +161,24 @@ class LookupTableV2GradCUDAKernel : public framework::OpKernel<T> {
 
       auto *ids_data = ids->data<int64_t>();
       int64_t ids_num = ids->numel();
-
+      dim3 threads(128, 8);
+      dim3 grids(8, 1);
       auto stream = dev_ctx.stream();
       // copy GPU memory to CPU pinned memory
       framework::Vector<int64_t> new_rows;
       new_rows.resize(ids_num);
       auto gpu_place = BOOST_GET_CONST(platform::CUDAPlace, context.GetPlace());
 
-      // TODO(yuyang18): Strange code here.
+      if (ids->type() == framework::proto::VarType::INT32) {
+        InputTypeCovert<
+            int><<<grids, threads, 0, context.cuda_device_context().stream()>>>(
+            ids->data<int>(), ids_num,
+            new_rows.MutableData(context.GetPlace()));
+      } else {
         memory::Copy(gpu_place, new_rows.CUDAMutableData(context.GetPlace()),
                      gpu_place, ids_data, ids_num * sizeof(int64_t), stream);
+      }
+
       d_table->set_rows(new_rows);
 
       auto *d_table_value = d_table->mutable_value();
@@ -177,17 +207,32 @@ class LookupTableV2GradCUDAKernel : public framework::OpKernel<T> {
       int N = d_table_t->dims()[0];
       int D = d_table_t->dims()[1];
       int K = ids_t->numel();
-      const int64_t *ids = ids_t->data<int64_t>();
+
+      dim3 threads(128, 8);
+      dim3 grids(8, 1);
+      // copy GPU memory to CPU pinned memory
+      framework::Vector<int64_t> ids;
+      ids.resize(K);
+
+      const int64_t *ids_p = nullptr;
+
+      if (ids_t->type() == framework::proto::VarType::INT32) {
+        InputTypeCovert<
+            int><<<grids, threads, 0, context.cuda_device_context().stream()>>>(
+            ids_t->data<int>(), K, ids.MutableData(context.GetPlace()));
+        ids_p = ids.MutableData(context.GetPlace());
+      } else {
+        ids_p = ids_t->data<int64_t>();
+      }
+
       const T *d_output = d_output_t->data<T>();
       T *d_table = d_table_t->mutable_data<T>(context.GetPlace());
 
       auto t = framework::EigenVector<T>::Flatten(*d_table_t);
       t.device(*dev_ctx.eigen_device()) = t.constant(static_cast<T>(0));
 
-      dim3 threads(128, 8);
-      dim3 grids(8, 1);
       LookupTableV2Grad<T, 128, 8, 8><<<grids, threads, 0, dev_ctx.stream()>>>(
-          d_table, d_output, ids, N, K, D);
+          d_table, d_output, ids_p, N, K, D);
     }
   }
 };

paddle/fluid/operators/lookup_table_v2_op.h

@@ -14,6 +14,7 @@ limitations under the License. */
 
 #pragma once
 
+#include <algorithm>
 #include <string>
 #include <vector>
 
@@ -45,32 +46,19 @@ class LookupTableV2Kernel : public framework::OpKernel<T> {
     auto *output_t = context.Output<LoDTensor>("Out");  // float tensor
     auto *table_var = context.InputVar("W");
 
-    auto id_name = context.InputNames("Ids").front();
-    auto embedding_name = context.InputNames("W").front();
-    auto out_name = context.OutputNames("Out").front();
-
-    // for remote prefetch
-    auto epmap = context.Attr<std::vector<std::string>>("epmap");
-    auto remote_prefetch = context.Attr<bool>("remote_prefetch");
-    auto table_names = context.Attr<std::vector<std::string>>("table_names");
+    int64_t padding_idx = context.Attr<int64_t>("padding_idx");
+    int64_t ids_numel = ids_t->numel();
 
-    if (remote_prefetch && !epmap.empty()) {
-// if epmap is not empty, then the parameter will be fetched from remote
-// parameter server
+    std::vector<int64_t> ids;
+    ids.reserve(ids_numel);
 
-#ifdef PADDLE_WITH_DISTRIBUTE
-      operators::distributed::prefetch(id_name, out_name, embedding_name, false,
-                                       table_names, epmap, context,
-                                       context.scope());
-#else
-      PADDLE_THROW(
-          "paddle is not compiled with distribute support, can not do "
-          "parameter prefetch!");
-#endif
+    if (ids_t->type() == framework::proto::VarType::INT32) {
+      std::transform(ids_t->data<int>(), ids_t->data<int>() + ids_numel,
+                     std::back_inserter(ids),
+                     [&](int id) { return static_cast<int64_t>(id); });
     } else {
-      int64_t padding_idx = context.Attr<int64_t>("padding_idx");
-      int64_t *ids = const_cast<int64_t *>(ids_t->data<int64_t>());
-      int64_t ids_numel = ids_t->numel();
+      framework::TensorToVector(*ids_t, &ids);
+    }
 
     if (table_var->IsType<LoDTensor>()) {
       auto *table_t = context.Input<LoDTensor>("W");
@@ -117,8 +105,8 @@ class LookupTableV2Kernel : public framework::OpKernel<T> {
               "expected >= 0. But received %ld",
               ids[i]);
           auto id_index = table_t.Index(ids[i]);
-            PADDLE_ENFORCE_GE(
-                id_index, 0, "the input key should be exists. But received %d.",
+          PADDLE_ENFORCE_GE(id_index, 0,
+                            "the input key should be exists. But received %d.",
                             id_index);
           blas.VCOPY(row_width, table + id_index * row_width,
                      output + i * row_width);
@@ -126,7 +114,6 @@ class LookupTableV2Kernel : public framework::OpKernel<T> {
       }
     }
   }
-  }
 };
 
 template <typename T>
@@ -151,17 +138,23 @@ class LookupTableV2GradKernel : public framework::OpKernel<T> {
     // Since paddings are not trainable and fixed in forward, the gradient of
     // paddings makes no sense and we don't deal with it in backward.
     if (is_sparse) {
-      auto *ids = context.Input<LoDTensor>("Ids");
+      auto *ids_t = context.Input<LoDTensor>("Ids");
       auto *d_output = context.Input<LoDTensor>(framework::GradVarName("Out"));
       auto *d_table = context.Output<SelectedRows>(framework::GradVarName("W"));
+      int64_t ids_num = ids_t->numel();
+
+      std::vector<int64_t> ids;
+      ids.reserve(ids_num);
 
-      auto *ids_data = ids->data<int64_t>();
-      int64_t ids_num = ids->numel();
+      if (ids_t->type() == framework::proto::VarType::INT32) {
+        std::transform(ids_t->data<int>(), ids_t->data<int>() + ids_num,
+                       std::back_inserter(ids),
+                       [&](int id) { return static_cast<int64_t>(id); });
+      } else {
+        framework::TensorToVector(*ids_t, &ids);
+      }
 
-      std::vector<int64_t> new_rows;
-      new_rows.resize(ids_num);
-      std::memcpy(&new_rows[0], ids_data, ids_num * sizeof(int64_t));
-      d_table->set_rows(new_rows);
+      d_table->set_rows(ids);
 
       auto *d_table_value = d_table->mutable_value();
       d_table_value->Resize({ids_num, table_dim[1]});
@@ -185,11 +178,23 @@ class LookupTableV2GradKernel : public framework::OpKernel<T> {
       memcpy(d_table_data, d_output_data, sizeof(T) * d_output->numel());
 
     } else {
-      auto *ids = context.Input<LoDTensor>("Ids");
+      auto *ids_t = context.Input<LoDTensor>("Ids");
       auto *d_output = context.Input<LoDTensor>(framework::GradVarName("Out"));
       auto *d_table = context.Output<LoDTensor>(framework::GradVarName("W"));
+      int64_t ids_num = ids_t->numel();
+
+      std::vector<int64_t> ids;
+      ids.reserve(ids_num);
+
+      if (ids_t->type() == framework::proto::VarType::INT32) {
+        std::transform(ids_t->data<int>(), ids_t->data<int>() + ids_num,
+                       std::back_inserter(ids),
+                       [&](int id) { return static_cast<int64_t>(id); });
+      } else {
+        framework::TensorToVector(*ids_t, &ids);
+      }
 
-      auto *ids_data = ids->data<int64_t>();
+      auto *ids_data = ids.data();
 
       int64_t N = table_dim[0];
       int64_t D = table_dim[1];
@@ -199,7 +204,7 @@ class LookupTableV2GradKernel : public framework::OpKernel<T> {
 
       memset(d_table_data, 0, d_table->numel() * sizeof(T));
 
-      for (int64_t i = 0; i < ids->numel(); ++i) {
+      for (int64_t i = 0; i < ids_num; ++i) {
         if (padding_idx != kNoPadding && ids_data[i] == padding_idx) {
           // the gradient of padding_idx should be 0, already done by memset, so
           // do nothing.

python/paddle/fluid/input.py

@@ -129,6 +129,7 @@ def one_hot(input, depth, allow_out_of_range=False):
     return one_hot_out
 
 
+@deprecated(since='2.0.0', update_to='paddle.nn.functional.embedding')
 def embedding(input,
               size,
               is_sparse=False,

python/paddle/fluid/layers/nn.py

@@ -367,6 +367,7 @@ def fc(input,
     return helper.append_activation(pre_activation)
 
 
+@deprecated(since="2.0.0", update_to="paddle.nn.functional.embedding")
 def embedding(input,
               size,
               is_sparse=False,

python/paddle/fluid/tests/unittests/test_adam_op.py

@@ -450,7 +450,7 @@ class TestAdamOpV2(unittest.TestCase):
 
         import paddle
         paddle.disable_static()
-        emb = paddle.nn.Embedding([10, 10])
+        emb = paddle.nn.Embedding(10, 10)
 
         adam = paddle.optimizer.Adam(0.001, parameters=emb.parameters())
         state_dict = adam.state_dict()

python/paddle/fluid/tests/unittests/test_lookup_table_v2_op.py

@@ -59,7 +59,7 @@ class TestLookupTableOpWithTensorIds(OpTest):
     def setUp(self):
         self.op_type = "lookup_table_v2"
         table = np.random.random((17, 31)).astype("float64")
-        ids = np.random.randint(low=0, high=17, size=(2, 4, 5)).astype("int64")
+        ids = np.random.randint(low=0, high=17, size=(2, 4, 5)).astype("int32")
         self.inputs = {'W': table, 'Ids': ids}
         self.outputs = {'Out': table[ids.flatten()].reshape((2, 4, 5, 31))}
 
@@ -100,7 +100,7 @@ class TestLookupTableOpWithTensorIdsAndPadding(TestLookupTableOpWithTensorIds):
 class TestLookupTableWIsSelectedRows(unittest.TestCase):
     def prepare_ids(self, scope, place):
         ids_tensor = scope.var('Ids').get_tensor()
-        ids_array = np.array([0, 4, 3, 5]).astype("int64")
+        ids_array = np.array([0, 4, 3, 5]).astype("int32")
         ids_tensor.set(ids_array, place)
         return ids_array
 

python/paddle/fluid/tests/unittests/test_nn_functional_embedding_dygraph.py

+#   Copyright (c) 2020 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 __future__ import print_function
+
+import unittest
+
+
+class EmbeddingDygraph(unittest.TestCase):
+    def test_1(self):
+        import paddle
+        import paddle.nn as nn
+        import numpy as np
+        paddle.disable_static()
+
+        # example 1
+        inp_word = np.array([[2, 3, 5], [4, 2, 1]]).astype('int64')
+        inp_word.shape  # [2, 3]
+        dict_size = 20
+
+        emb = nn.Embedding(dict_size, 32, weight_attr='emb.w', sparse=False)
+
+
+if __name__ == '__main__':
+    unittest.main()

python/paddle/fluid/tests/unittests/test_nn_functional_embedding_static.py

+#   Copyright (c) 2020 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 __future__ import print_function
+
+import unittest
+import numpy as np
+import paddle.fluid as fluid
+import paddle.nn.functional as functional
+
+
+class EmbeddingStatic(unittest.TestCase):
+    def test_1(self):
+        prog = fluid.Program()
+        with fluid.program_guard(prog):
+
+            def test_bad_x():
+                initializer = fluid.initializer.NumpyArrayInitializer(
+                    np.random.random(size=(128, 100)))
+
+                param_attr = fluid.ParamAttr(
+                    name="emb_weight",
+                    learning_rate=0.5,
+                    initializer=initializer,
+                    trainable=True)
+
+                weight = prog.global_block().create_parameter(
+                    (128, 100), attr=param_attr, dtype="float32")
+
+                label = fluid.layers.data(
+                    name="label",
+                    shape=[4],
+                    append_batch_size=False,
+                    dtype="int64")
+
+                emb = functional.embedding(
+                    x=label, weight=weight, sparse=True, name="embedding")
+
+            test_bad_x()
+
+    def test_2(self):
+        prog = fluid.Program()
+        with fluid.program_guard(prog):
+
+            def test_bad_x():
+                initializer = fluid.initializer.NumpyArrayInitializer(
+                    np.random.random(size=(128, 100)))
+
+                param_attr = fluid.ParamAttr(
+                    name="emb_weight",
+                    learning_rate=0.5,
+                    initializer=initializer,
+                    trainable=True)
+
+                weight = prog.global_block().create_parameter(
+                    (128, 100), attr=param_attr, dtype="float32")
+
+                label = fluid.layers.data(
+                    name="label",
+                    shape=[4],
+                    append_batch_size=False,
+                    dtype="int32")
+
+                emb = functional.embedding(
+                    x=label, weight=weight, sparse=True, name="embedding")
+
+            test_bad_x()
+
+
+if __name__ == '__main__':
+    unittest.main()

python/paddle/nn/functional/__init__.py

@@ -233,3 +233,4 @@ from .vision import space_to_depth  #DEFINE_ALIAS
 from .vision import yolo_box  #DEFINE_ALIAS
 from .vision import yolov3_loss  #DEFINE_ALIAS
 from .input import one_hot  #DEFINE_ALIAS
+from .input import embedding  #DEFINE_ALIAS

python/paddle/nn/functional/input.py

@@ -19,7 +19,7 @@ from ...fluid.layer_helper import LayerHelper
 from ...fluid.layers import core
 from ...fluid.data_feeder import check_variable_and_dtype, check_dtype
 
-__all__ = ['one_hot']
+__all__ = ['one_hot', 'embedding']
 
 
 def one_hot(x, num_classes, name=None):
@@ -83,6 +83,7 @@ def one_hot(x, num_classes, name=None):
             #                       [0., 1., 0., 0.],
             #                       [0., 0., 0., 1.],
             #                       [1., 0., 0., 0.]]
+
     """
 
     if in_dygraph_mode():
@@ -108,3 +109,115 @@ def one_hot(x, num_classes, name=None):
             outputs={'Out': one_hot_out},
             stop_gradient=True)
         return one_hot_out
+
+
+def embedding(x, weight, padding_idx=None, sparse=False, name=None):
+    """
+    The operator is used to lookup embeddings vector of ids provided by :attr:`input` .
+
+    The shape of output Tensor is generated by appending the last dimension of the input Tensor shape
+    with embedding size.
+    **Note:** The id in :attr:`input` must satisfy :math:`0 =< id < weight.shape[0]` ,
+    otherwise the program will throw an exception and exit.
+
+    .. code-block:: text
+
+        Case 1:
+            input is a Tensor. 
+                padding_idx = -1
+                x.data = [[1, 3], [2, 4], [4, 127]]
+                x.shape = [3, 2]
+                weight.shape = [128, 16]
+            output is a Tensor:
+                out.shape = [3, 2, 16]
+                out.data = [[[0.129435295, 0.244512452, ..., 0.436322452],
+                            [0.345421456, 0.524563927, ..., 0.144534654]],
+                            [[0.345249859, 0.124939536, ..., 0.194353745],
+                            [0.945345345, 0.435394634, ..., 0.435345365]],
+                            [[0.945345345, 0.435394634, ..., 0.435345365],
+                            [0.0,         0.0,         ..., 0.0        ]]]  # padding data
+
+            The input padding_idx is less than 0, it is automatically converted to padding_idx = -1 + 128 = 127
+            It will pad all-zero data when ids is 127.
+
+    Args:
+        x(Tensor): A Tensor with type int32/int64, which contains the id information. The value of the input id should
+            satisfy :math:`0<= id < weight.shape[0]` .
+        weight (Tensor): The weight. A Tensor with shape of lookup table parameter. It should have two elements which
+            indicates the size of the dictionary of embeddings and the size of each embedding vector respectively.
+        sparse(bool): The flag indicating whether to use sparse update. This parameter only
+            affects the performance of the backwards gradient update. It is recommended to set
+            True because sparse update is faster. But some optimizers does not support sparse update,
+            such as :ref:`api_optimizer_AdadeltaOptimizer` , :ref:`api_optimizer_AdamaxOptimizer` ,
+            :ref:`api_optimizer_DecayedAdagradOptimizer` , :ref:`api_optimizer_FtrlOptimizer` ,
+            :ref:`api_optimizer_LambOptimizer` and :ref:`api_optimizer_LarsMomentumOptimizer` .
+            In these cases, is_sparse must be False. Default: False.
+        padding_idx(int|long|None): padding_idx needs to be in the interval [-vocab_size, vocab_size).
+            If :math:`padding\_idx < 0`, the :math:`padding\_idx` will automatically be converted
+            to :math:`vocab\_size + padding\_idx` . It will output all-zero padding data whenever lookup
+            encounters :math:`padding\_idx` in id. And the padding data will not be updated while training.
+            If set None, it makes no effect to output. Default: None.
+        name(str|None): For detailed information, please refer
+           to :ref:`api_guide_Name`. Usually name is no need to set and
+           None by default.
+
+    Returns:
+        Tensor: Embedding Tensor  mapped by input. The data type is the same as :attr:`weight`.
+
+    Examples:
+
+        .. code-block:: python
+
+            import paddle
+            import paddle.nn as nn
+
+            weight = prog.global_block().create_parameter(
+                attr=self._param_attr,
+                shape=param_shape,
+                dtype=self._dtype,
+                default_initializer=Constant(1.0))
+
+            prog = paddle.static.Program()
+
+            weight = prog.global_block().create_parameter(
+                    (128, 100), dtype="float32", default_initializer=Constant(1.0))
+
+            label = paddle.data(
+                    name="label",
+                    shape=[4],
+                    append_batch_size=False,
+                    dtype="int64")
+
+            emb = nn.embedding(
+                    x=label, weight=weight, sparse=True, name="embedding")
+
+    """
+    if in_dygraph_mode():
+        return core.ops.lookup_table_v2(
+            weight, x, 'is_sparse', sparse, 'is_distributed', False,
+            'remote_prefetch', False, 'padding_idx', padding_idx)
+    else:
+        helper = LayerHelper('embedding', **locals())
+        dtype = helper.input_dtype()
+
+        check_variable_and_dtype(x, 'input', ['int32', 'int64'], 'embedding')
+
+        is_distributed = False
+        remote_prefetch = sparse and (not is_distributed)
+
+        tmp = helper.create_variable_for_type_inference(dtype)
+        padding_idx = -1 if padding_idx is None else padding_idx if padding_idx >= 0 else (
+            weight.shape[0] + padding_idx)
+
+        helper.append_op(
+            type='lookup_table_v2',
+            inputs={'Ids': x,
+                    'W': weight},
+            outputs={'Out': tmp},
+            attrs={
+                'is_sparse': sparse,
+                'is_distributed': is_distributed,
+                'remote_prefetch': remote_prefetch,
+                'padding_idx': padding_idx
+            })
+        return tmp

python/paddle/nn/layer/common.py

@@ -15,7 +15,7 @@
 # TODO: define the common classes to build a neural network
 from ...fluid.dygraph import BilinearTensorProduct  #DEFINE_ALIAS
 from ...fluid.dygraph import Pool2D  #DEFINE_ALIAS
-from ...fluid.dygraph import Embedding  #DEFINE_ALIAS
+from ...fluid.dygraph import Linear  #DEFINE_ALIAS
 from ...fluid.dygraph import Flatten  #DEFINE_ALIAS
 from ...fluid.dygraph import layers
 from .. import functional as F
@@ -1547,3 +1547,131 @@ class CosineSimilarity(layers.Layer):
 
     def forward(self, x1, x2):
         return F.cosine_similarity(x1, x2, axis=self._axis, eps=self._eps)
+
+
+class Embedding(layers.Layer):
+    """
+    :alias_main: paddle.nn.Embedding
+	:alias: paddle.nn.Embedding,paddle.nn.layer.Embedding,paddle.nn.layer.common.Embedding
+	:old_api: paddle.fluid.dygraph.Embedding
+
+    **Embedding Layer**
+
+    This interface is used to construct a callable object of the ``Embedding`` class.
+    For specific usage, refer to code examples. It implements the function of the Embedding Layer.
+    This layer is used to lookup embeddings vector of ids provided by :attr:`input` .
+    It automatically constructs a 2D embedding matrix based on the
+    input :attr:`size` (vocab_size, emb_size) and :attr:`dtype` .
+
+    The shape of output Tensor is generated by appending an emb_size dimension to the
+    last dimension of the input Tensor shape.
+
+    **Note:** The id in :attr:`input` must satisfy :math:`0 =< id < size[0]` ,
+    otherwise the program will throw an exception and exit.
+
+    .. code-block:: text
+
+        Case 1:
+
+        input is a Tensor. padding_idx = -1
+            input.data = [[1, 3], [2, 4], [4, 127]
+            input.shape = [3, 2]
+        Given size = [128, 16]
+        output is a Tensor:
+            out.shape = [3, 2, 16]
+            out.data = [[[0.129435295, 0.244512452, ..., 0.436322452],
+                        [0.345421456, 0.524563927, ..., 0.144534654]],
+
+                        [[0.345249859, 0.124939536, ..., 0.194353745],
+                        [0.945345345, 0.435394634, ..., 0.435345365]],
+
+                        [[0.945345345, 0.435394634, ..., 0.435345365],
+                        [0.0,         0.0,         ..., 0.0        ]]]  # padding data
+        The input padding_idx is less than 0, it is automatically converted to padding_idx = -1 + 128 = 127
+        It will pad all-zero data when ids is 127.
+
+    Parameters:
+        num_embeddings (int): Just one element which indicate the size
+            of the dictionary of embeddings.
+        embedding_dim:  Just one element which indicate the size of each embedding vector respectively.
+        padding_idx(int|long|None): padding_idx needs to be in the interval [-vocab_size, vocab_size).
+            If :math:`padding\_idx < 0`, the :math:`padding\_idx` will automatically be converted
+            to :math:`vocab\_size + padding\_idx` . It will output all-zero padding data whenever lookup
+            encounters :math:`padding\_idx` in id. And the padding data will not be updated while training.
+            If set None, it makes no effect to output. Default: None.
+        sparse(bool): The flag indicating whether to use sparse update. This parameter only
+            affects the performance of the backwards gradient update. It is recommended to set
+            True because sparse update is faster. But some optimizer does not support sparse update,
+            such as :ref:`api_optimizer_AdadeltaOptimizer` , :ref:`api_optimizer_AdamaxOptimizer` ,
+            :ref:`api_optimizer_DecayedAdagradOptimizer` , :ref:`api_optimizer_FtrlOptimizer` ,
+            :ref:`api_optimizer_LambOptimizer` and :ref:`api_optimizer_LarsMomentumOptimizer` .
+            In these case, is_sparse must be False. Default: False.
+        weight_attr(ParamAttr): To specify the weight parameter property. Default: None, which means the
+            default weight parameter property is used. See usage for details in :ref:`api_fluid_ParamAttr` . In addition,
+            user-defined or pre-trained word vectors can be loaded with the :attr:`param_attr` parameter.
+            The local word vector needs to be transformed into numpy format, and the shape of local word
+            vector should be consistent with :attr:`size` . Then :ref:`api_fluid_initializer_NumpyArrayInitializer`
+            is used to load custom or pre-trained word vectors. See code example 2 for details.
+        name(str|None): For detailed information, please refer
+               to :ref:`api_guide_Name`. Usually name is no need to set and
+               None by default.
+
+    Attribute:
+        **weight** (Parameter): the learnable weights of this layer.
+
+    Returns:
+        None
+
+    Examples:
+
+        .. code-block:: python
+
+          import paddle
+          import paddle.nn as nn
+          import numpy as np
+          paddle.disable_static()
+
+          # example 1
+          inp_word = np.array([[2, 3, 5], [4, 2, 1]]).astype('int64')
+          inp_word.shape  # [2, 3]
+          dict_size = 20
+
+          emb = nn.Embedding(
+                    dict_size,
+                    32,
+                    sparse=False)
+    """
+
+    def __init__(self,
+                 num_embeddings,
+                 embedding_dim,
+                 padding_idx=None,
+                 sparse=False,
+                 weight_attr=None,
+                 name=None):
+        super(Embedding, self).__init__()
+        self._num_embeddings = num_embeddings
+        self._embedding_dim = embedding_dim
+        self._sparse = sparse
+        self._is_distributed = False
+        self._padding_idx = -1 if padding_idx is None else padding_idx if padding_idx >= 0 else (
+            num_embeddings + padding_idx)
+        self._dtype = self._helper.get_default_dtype()
+        self._size = [self._num_embeddings, self._embedding_dim]
+
+        self._weight_attr = weight_attr
+        self._remote_prefetch = False
+        self._name = name
+        self._weight = self.create_parameter(
+            attr=self._weight_attr,
+            shape=self._size,
+            dtype=self._dtype,
+            is_bias=False)
+
+    def forward(self, x):
+        return F.embedding(
+            x,
+            weight=self._weight,
+            padding_idx=self._padding_idx,
+            sparse=self._sparse,
+            name=self._name)