refine rank_loss_op

paddle/operators/rank_loss_op.cc

@@ -28,18 +28,21 @@ class RankLossOp : public framework::OperatorWithKernel {
  protected:
   void InferShape(const framework::InferShapeContext &ctx) const override {
     // input check
-    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("P"), "Input(P) shouldn't be null");
-    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Oi"), "Input(Oi) shouldn't be null");
-    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Oj"), "Input(Oj) shouldn't be null");
-    auto p_dims = ctx.Input<framework::Tensor>("P")->dims();
-    auto oi_dims = ctx.Input<framework::Tensor>("Oi")->dims();
-    auto oj_dims = ctx.Input<framework::Tensor>("Oj")->dims();
-    PADDLE_ENFORCE_EQ(oi_dims, oj_dims,
-                      "Input(Oi) and Input(Oj) must have the same size");
-    PADDLE_ENFORCE_EQ(
-        p_dims, oi_dims,
-        "Input(P) must have the same size with Input(Oi) & Input(Oj)");
-    ctx.Output<framework::Tensor>("Out")->Resize(p_dims);
+    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Label"),
+                            "Input(Label) shouldn't be null");
+    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Left"),
+                            "Input(Left) shouldn't be null");
+    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Right"),
+                            "Input(Right) shouldn't be null");
+    auto label_dims = ctx.Input<framework::Tensor>("Label")->dims();
+    auto left_dims = ctx.Input<framework::Tensor>("Left")->dims();
+    auto right_dims = ctx.Input<framework::Tensor>("Right")->dims();
+    PADDLE_ENFORCE((label_dims.size() == 1) && (left_dims.size() == 1) &&
+                       (right_dims.size() == 1),
+                   "The rank of all inputs must be 1.");
+    PADDLE_ENFORCE((label_dims == left_dims) && (left_dims == right_dims),
+                   "All inputs must have the same size");
+    ctx.Output<framework::LoDTensor>("Out")->Resize(label_dims);
   }
 };
 
@@ -48,14 +51,23 @@ class RankLossOpMaker : public framework::OpProtoAndCheckerMaker {
   RankLossOpMaker(framework::OpProto *proto,
                   framework::OpAttrChecker *op_checker)
       : OpProtoAndCheckerMaker(proto, op_checker) {
-    AddInput("P", "The desired target values for posteriors.");
-    AddInput("Oi", "The model output for item i.");
-    AddInput("Oj", "The model output for item j.");
-    AddOutput("Out", "The output tensor of RankLoss operator.");
+    AddInput("Label",
+             "The label indicating A ranked higher than B or not, 1-D tensor.");
+    AddInput("Left", "The output of RankNet for doc A, 1-D tensor.");
+    AddInput("Right", "The output of RankNet for doc B, 1-D tensor");
+    AddOutput("Out", "The output loss of RankLoss operator, 1-D tensor.");
     AddComment(R"DOC(RankLoss operator
 
-A rank loss operator for learning to rank (LTR) task. This operator contains
-three inputs: P, Oi, and Oj, and the rank cost can be expressed as
+Rank loss operator for RankNet[1]. RankNet is a pairwise ranking model with
+one training sample consisting of a pair of doc A and B, and the label P
+indicating that A is ranked higher than B or not:
+
+P = {0, 1} or {0, 0.5, 1}, where 0.5 means no information about the rank of
+the input pair.
+
+The RankLoss operator contains three inputs: Left (o_i), Right (o_j) and Label
+(P_{i,j}), which represent the output of RankNet for two docs and the label
+respectively, and yields the rank loss C_{i,j} by following the expression
 
 \f[
   C_{i,j} = -\tilde{P_{ij}} * o_{i,j} + log(1 + e^{o_{i,j}}) \\
@@ -63,10 +75,11 @@ three inputs: P, Oi, and Oj, and the rank cost can be expressed as
   \tilde{P_{i,j}} = \left \{0, 0.5, 1 \right \} \ or \ \left \{0, 1 \right \}
 \f]
 
-A detailed explanation about these notations can be found in
+The operator can take inputs of one sample or in batch.
 
 [1]. Chris Burges, Tal Shaked, Erin Renshaw, et al. Learning to
-     Rank useing Gradient Descent.
+     Rank using Gradient Descent.
+     http://icml.cc/2015/wp-content/uploads/2015/06/icml_ranking.pdf
 )DOC");
   }
 };
@@ -81,15 +94,25 @@ class RankLossGradOp : public framework::OperatorWithKernel {
 
  protected:
   void InferShape(const framework::InferShapeContext &ctx) const override {
-    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("P"), "Input(P) shouldn't be null.");
-    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Oi"), "Input(Oi) shouldn't be null.");
-    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Oj"), "Input(Oj) shouldn't be null.");
+    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Label"),
+                            "Input(Label) shouldn't be null.");
+    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Left"),
+                            "Input(Left) shouldn't be null.");
+    PADDLE_ENFORCE_NOT_NULL(ctx.InputVar("Right"),
+                            "Input(Right) shouldn't be null.");
     PADDLE_ENFORCE_NOT_NULL(ctx.InputVar(framework::GradVarName("Out")),
                             "Input(Out@GRAD) shouldn't be null.");
-    auto dims = ctx.Input<framework::Tensor>("P")->dims();
-    ctx.Output<framework::Tensor>(framework::GradVarName("P"))->Resize(dims);
-    ctx.Output<framework::Tensor>(framework::GradVarName("Oi"))->Resize(dims);
-    ctx.Output<framework::Tensor>(framework::GradVarName("Oj"))->Resize(dims);
+    auto dims = ctx.Input<framework::Tensor>("Left")->dims();
+    auto *left_grad =
+        ctx.Output<framework::LoDTensor>(framework::GradVarName("Left"));
+    auto *right_grad =
+        ctx.Output<framework::LoDTensor>(framework::GradVarName("Right"));
+    if (left_grad) {
+      left_grad->Resize(dims);
+    }
+    if (right_grad) {
+      right_grad->Resize(dims);
+    }
   }
 };
 

paddle/operators/rank_loss_op.h

@@ -24,25 +24,20 @@ template <typename Place, typename T>
 class RankLossKernel : public framework::OpKernel {
  public:
   void Compute(const framework::ExecutionContext& ctx) const {
-    auto* out = ctx.Output<framework::Tensor>("Out");
-    auto* p_t = ctx.Input<framework::Tensor>("P");
-    auto* oi_t = ctx.Input<framework::Tensor>("Oi");
-    auto* oj_t = ctx.Input<framework::Tensor>("Oj");
-    out->mutable_data<T>(ctx.GetPlace());
+    auto* out_t = ctx.Output<framework::LoDTensor>("Out");
+    auto* label_t = ctx.Input<framework::Tensor>("Label");
+    auto* left_t = ctx.Input<framework::Tensor>("Left");
+    auto* right_t = ctx.Input<framework::Tensor>("Right");
+    out_t->mutable_data<T>(ctx.GetPlace());
 
-    auto& dev = ctx.GetEigenDevice<Place>();
-    auto out_eig = framework::EigenVector<T>::Flatten(*out);
-    auto p_eig = framework::EigenVector<T>::Flatten(*p_t);
-    auto oi_eig = framework::EigenVector<T>::Flatten(*oi_t);
-    auto oj_eig = framework::EigenVector<T>::Flatten(*oj_t);
-
-    framework::Tensor o_t;
-    o_t.Resize(oi_t->dims());
-    o_t.mutable_data<T>(ctx.GetPlace());
-    auto o_eig = framework::EigenVector<T>::Flatten(o_t);
-    o_eig.device(dev) = oi_eig - oj_eig;
+    auto out = framework::EigenVector<T>::Flatten(*out_t);
+    auto label = framework::EigenVector<T>::Flatten(*label_t);
+    auto left = framework::EigenVector<T>::Flatten(*left_t);
+    auto right = framework::EigenVector<T>::Flatten(*right_t);
 
-    out_eig.device(dev) = (1. + (o_eig).exp()).log() - p_eig * o_eig;
+    auto& dev = ctx.GetEigenDevice<Place>();
+    out.device(dev) =
+        (1. + (left - right).exp()).log() - label * (left - right);
   }
 };
 
@@ -50,40 +45,35 @@ template <typename Place, typename T>
 class RankLossGradKernel : public framework::OpKernel {
  public:
   void Compute(const framework::ExecutionContext& ctx) const {
-    auto* d_oi = ctx.Output<framework::Tensor>(framework::GradVarName("Oi"));
-    auto* d_oj = ctx.Output<framework::Tensor>(framework::GradVarName("Oj"));
-    auto* d_p = ctx.Output<framework::Tensor>(framework::GradVarName("P"));
-
-    auto* d_out = ctx.Input<framework::Tensor>(framework::GradVarName("Out"));
-    auto* p_t = ctx.Input<framework::Tensor>("P");
-    auto* oi_t = ctx.Input<framework::Tensor>("Oi");
-    auto* oj_t = ctx.Input<framework::Tensor>("Oj");
+    auto* d_left_t =
+        ctx.Output<framework::LoDTensor>(framework::GradVarName("Left"));
+    auto* d_right_t =
+        ctx.Output<framework::LoDTensor>(framework::GradVarName("Right"));
 
-    d_oi->mutable_data<T>(ctx.GetPlace());
-    d_oj->mutable_data<T>(ctx.GetPlace());
-    d_p->mutable_data<T>(ctx.GetPlace());
+    auto* d_out_t = ctx.Input<framework::Tensor>(framework::GradVarName("Out"));
+    auto* label_t = ctx.Input<framework::Tensor>("Label");
+    auto* left_t = ctx.Input<framework::Tensor>("Left");
+    auto* right_t = ctx.Input<framework::Tensor>("Right");
 
     auto& dev = ctx.GetEigenDevice<Place>();
-    auto d_out_eig = framework::EigenVector<T>::Flatten(*d_out);
-    auto p_eig = framework::EigenVector<T>::Flatten(*p_t);
-    auto oi_eig = framework::EigenVector<T>::Flatten(*oi_t);
-    auto oj_eig = framework::EigenVector<T>::Flatten(*oj_t);
-
-    auto d_oi_eig = framework::EigenVector<T>::Flatten(*d_oi);
-    auto d_oj_eig = framework::EigenVector<T>::Flatten(*d_oj);
-
-    framework::Tensor o_t;
-    o_t.Resize(oi_t->dims());
-    o_t.mutable_data<T>(ctx.GetPlace());
-    auto o_eig = framework::EigenVector<T>::Flatten(o_t);
-    o_eig.device(dev) = oi_eig - oj_eig;
-
-    // dOi & dOj
-    d_oi_eig.device(dev) =
-        d_out_eig * (o_eig.exp() / (1. + o_eig.exp()) - p_eig);
-    d_oj_eig.device(dev) = -d_oi_eig;
-    // dP
-    framework::EigenVector<T>::Flatten(*d_p).device(dev) = -o_eig;
+    auto d_out = framework::EigenVector<T>::Flatten(*d_out_t);
+    auto label = framework::EigenVector<T>::Flatten(*label_t);
+    auto left = framework::EigenVector<T>::Flatten(*left_t);
+    auto right = framework::EigenVector<T>::Flatten(*right_t);
+
+    // compute d_left
+    if (d_left_t) {
+      d_left_t->mutable_data<T>(ctx.GetPlace());
+      auto d_left = framework::EigenVector<T>::Flatten(*d_left_t);
+      d_left.device(dev) = d_out * (1. / (1. + (right - left).exp()) - label);
+    }
+    // compute d_right
+    if (d_right_t) {
+      d_right_t->mutable_data<T>(ctx.GetPlace());
+      auto d_right = framework::EigenVector<T>::Flatten(*d_right_t);
+      d_right.device(dev) =
+          -d_out * (1.0 / (1. + (right - left).exp()) - label);
+    }
   }
 };
 }  // namespace operators

python/paddle/v2/framework/tests/test_rank_loss_op.py

@@ -3,24 +3,29 @@ import numpy as np
 from op_test import OpTest
 
 
-class TestReshapeOp(OpTest):
+class TestRankLossOp(OpTest):
     def setUp(self):
         self.op_type = "rank_loss"
-        num = 5
-        # P = {0, 1.0} or {0, 0.5, 1.0}
-        P = np.random.randint(0, 2, size=(num, num)).astype("float32")
-        Oi = np.random.random((num, num)).astype("float32")
-        Oj = np.random.random((num, num)).astype("float32")
-        O = Oi - Oj
-        Out = np.log(1.0 + np.exp(O)) - P * O
-        self.inputs = {'P': P, 'Oi': Oi, 'Oj': Oj}
-        self.outputs = {'Out': Out}
+        batch_size = 5
+        # labels_{i} = {0, 1.0} or {0, 0.5, 1.0}
+        label = np.random.randint(0, 2, size=(batch_size, )).astype("float32")
+        left = np.random.random((batch_size, )).astype("float32")
+        right = np.random.random((batch_size, )).astype("float32")
+        loss = np.log(1.0 + np.exp(left - right)) - label * (left - right)
+        self.inputs = {'Label': label, 'Left': left, 'Right': right}
+        self.outputs = {'Out': loss}
 
     def test_check_output(self):
         self.check_output()
 
     def test_check_grad(self):
-        self.check_grad(["Oj"], "Out")
+        self.check_grad(["Left", "Right"], "Out")
+
+    def test_check_grad_ignore_left(self):
+        self.check_grad(["Right"], "Out", no_grad_set=set('Left'))
+
+    def test_check_grad_ignore_right(self):
+        self.check_grad(["Left"], "Out", no_grad_set=set('Right'))
 
 
 if __name__ == '__main__':