From 6097b8b3654982745b156d1a7cb3c834f2c8a486 Mon Sep 17 00:00:00 2001
From: Qiao Longfei <qiaolongfei@baidu.com>
Date: Thu, 8 Nov 2018 22:55:05 +0800
Subject: [PATCH] add bilinear_tensor_product layer

---
 python/paddle/fluid/layers/nn.py | 76 ++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/python/paddle/fluid/layers/nn.py b/python/paddle/fluid/layers/nn.py
index b0a8efd5edc..8302a586310 100644
--- a/python/paddle/fluid/layers/nn.py
+++ b/python/paddle/fluid/layers/nn.py
@@ -162,6 +162,7 @@ __all__ = [
     'grid_sampler',
     'log_loss',
     'add_position_encoding',
+    'bilinear_tensor_product',
 ]
 
 
@@ -8046,3 +8047,78 @@ def add_position_encoding(input, alpha, beta, name=None):
         attrs={"alpha": alpha,
                "beta": beta})
     return out
+
+
+def bilinear_tensor_product(x,
+                            y,
+                            size,
+                            act=None,
+                            name=None,
+                            param_attr=None,
+                            bias_attr=None):
+    """
+    **Add Position Encoding Layer**
+
+    This layer performs tensor operation on two inputs.
+    For example:
+
+    .. math::
+       y_{i} = x * W_{i} * {y^\mathrm{T}}, i=0,1,...,K-1
+
+    In this formular:
+      - :math:`x`: the first input contains M elements.
+      - :math:`y`: the second input contains N elements.
+      - :math:`y_{i}`: the i-th element of y.
+      - :math:`W_{i}`: the i-th learned weight, shape is [M, N]
+      - :math:`y^\mathrm{T}`: the transpose of :math:`y_{2}`.
+
+    The simple usage is:
+
+    .. code-block:: python
+
+       tensor = bilinear_tensor_product(x=layer1, y=layer2, size=1000)
+
+    Args:
+        x (Variable): 3-D input tensor with shape [N x M x P]
+        y (Variable): 3-D input tensor with shape [N x M x P]
+        size (int): The dimension of this layer.
+        act (str, default None): Activation to be applied to the output of this layer.
+        name (str, default None): The name of this layer.
+        param_attr (ParamAttr|list of ParamAttr, default None): The parameter attribute for learnable
+            parameters/weights of this layer.
+        bias_attr (ParamAttr|list of ParamAttr, default None): The parameter attribute for the bias
+            of this layer. If it is set to False, no bias will be added to the output units.
+            If it is set to None, the bias is initialized zero. Default: None.
+
+    Returns:
+        Variable: A 3-D Tensor of shape [N x M x P] with positional encoding.
+
+    Examples:
+        .. code-block:: python
+
+          position_tensor = fluid.layers.add_position_encoding(input=tensor)
+    """
+    helper = LayerHelper('bilinear_tensor_product', **locals())
+    dtype = helper.input_dtype()
+
+    param_shape = [size, x.shape[1], y.shape[1]]
+
+    w = helper.create_parameter(
+        attr=param_attr, shape=param_shape, dtype=dtype, is_bias=False)
+
+    if name is None:
+        out = helper.create_variable_for_type_inference(dtype=dtype)
+    else:
+        out = helper.create_variable(name=name, dtype=dtype, persistable=False)
+
+    inputs = {"X": x, "Y": y, "Weight": w}
+    if helper.bias_attr:
+        bias_size = [1, size]
+        bias = helper.create_parameter(
+            attr=helper.bias_attr, shape=bias_size, dtype=dtype, is_bias=True)
+        inputs["Bias"] = bias
+    helper.append_op(
+        type="bilinear_tensor_product", inputs=inputs, outputs={"Out": out})
+
+    # add activation
+    return helper.append_activation(out)
-- 
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