Add python API for appending LoD level (#18702)

* Make lod reset op support for append lod level.

* Fix API.spec
test=develop

* Fix unitest.
test=develop

* Add python api for lod append.
test=develop

* Fix API.spec
test=develop

* Fix format of doc.
test=develop

* Fix unitest.
test=develop

* Fix doc.
test=develop

paddle/fluid/API.spec

@@ -163,7 +163,8 @@ paddle.fluid.layers.autoincreased_step_counter (ArgSpec(args=['counter_name', 'b
 paddle.fluid.layers.reshape (ArgSpec(args=['x', 'shape', 'actual_shape', 'act', 'inplace', 'name'], varargs=None, keywords=None, defaults=(None, None, False, None)), ('document', '6196c9ec3075ca5a9c058ea1f8492256'))
 paddle.fluid.layers.squeeze (ArgSpec(args=['input', 'axes', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', 'ebbac07662a6e22e8e299ced880c7775'))
 paddle.fluid.layers.unsqueeze (ArgSpec(args=['input', 'axes', 'name'], varargs=None, keywords=None, defaults=(None,)), ('document', 'b9bd3129d36a70e7c4385df51ff71c62'))
-paddle.fluid.layers.lod_reset (ArgSpec(args=['x', 'y', 'target_lod'], varargs=None, keywords=None, defaults=(None, None)), ('document', '9a72a7c8c80926150ea826e94efd7e9b'))
+paddle.fluid.layers.lod_reset (ArgSpec(args=['x', 'y', 'target_lod'], varargs=None, keywords=None, defaults=(None, None)), ('document', '74498d37dd622ac472cb36887fce09ea'))
+paddle.fluid.layers.lod_append (ArgSpec(args=['x', 'level'], varargs=None, keywords=None, defaults=None), ('document', '527cc61c20a8fa83008115440419f92b'))
 paddle.fluid.layers.lrn (ArgSpec(args=['input', 'n', 'k', 'alpha', 'beta', 'name'], varargs=None, keywords=None, defaults=(5, 1.0, 0.0001, 0.75, None)), ('document', '73d297256da8954617996958d26ee93d'))
 paddle.fluid.layers.pad (ArgSpec(args=['x', 'paddings', 'pad_value', 'name'], varargs=None, keywords=None, defaults=(0.0, None)), ('document', '2f189f8ef61f1c23779e1593b78755c0'))
 paddle.fluid.layers.pad_constant_like (ArgSpec(args=['x', 'y', 'pad_value', 'name'], varargs=None, keywords=None, defaults=(0.0, None)), ('document', '95aa1972983f30fe9b5a3713e523e20f'))

paddle/fluid/operators/lod_reset_op.cc

@@ -36,7 +36,10 @@ class LoDResetOp : public framework::OperatorWithKernel {
     } else if (ctx->IsRuntime()) {
       ctx->ShareLoD("Y", "Out");
     }
-
+    auto append = ctx->Attrs().Get<bool>("append");
+    if (append) {
+      ctx->ShareLoD("X", /*->*/ "Out");
+    }
     ctx->SetOutputDim("Out", ctx->GetInputDim("X"));
   }
 
@@ -53,10 +56,14 @@ class LoDResetOpVarTypeInference : public framework::VarTypeInference {
   void operator()(framework::InferVarTypeContext *ctx) const override {
     auto x_var_name = ctx->Input("X").front();
     auto out_var_name = ctx->Output("Out").front();
+    bool append = boost::get<bool>(ctx->GetAttr("append"));
     if (ctx->HasInput("Y")) {
       auto y_var_name = ctx->Input("Y").front();
       auto y_lod_level = std::max(ctx->GetLoDLevel(y_var_name), 1);
       ctx->SetLoDLevel(out_var_name, y_lod_level);
+    } else if (append) {
+      auto x_lod_level = std::max(ctx->GetLoDLevel(x_var_name), 1);
+      ctx->SetLoDLevel(out_var_name, x_lod_level);
     } else {
       ctx->SetLoDLevel(out_var_name, 1);
     }
@@ -84,6 +91,7 @@ class LoDResetOpMaker : public framework::OpProtoAndCheckerMaker {
     AddAttr<std::vector<int>>("target_lod",
                               "The target level 0 LoD from Attr().")
         .SetDefault(std::vector<int>{});
+    AddAttr<bool>("append", "Append data to lod vector.").SetDefault(false);
     AddComment(R"DOC(LoDReset operator
 
 Set LoD of `X` to a new one specified by `Y` or attribute `target_lod`. When `Y`

paddle/fluid/operators/lod_reset_op.h

@@ -29,6 +29,7 @@ class LoDResetKernel : public framework::OpKernel<T> {
     auto* out = ctx.Output<framework::LoDTensor>("Out");
     auto* in = ctx.Input<framework::LoDTensor>("X");
     auto* lod_t = ctx.Input<framework::LoDTensor>("Y");
+    bool append = ctx.Attr<bool>("append");
 
     out->ShareDataWith(*in);
 
@@ -71,10 +72,15 @@ class LoDResetKernel : public framework::OpKernel<T> {
     std::vector<size_t> ulevel0(level0.size(), 0);
     std::transform(level0.begin(), level0.end(), ulevel0.begin(),
                    [](int a) { return static_cast<size_t>(a); });
+    if (append) {
+      auto* out_lod = out->mutable_lod();
+      out_lod->push_back(ulevel0);
+    } else {
       framework::LoD target_lod;
       target_lod.push_back(ulevel0);
       out->set_lod(target_lod);
     }
+  }
 };
 
 template <typename DeviceContext, typename T>

python/paddle/fluid/layers/nn.py

@@ -107,6 +107,7 @@ __all__ = [
     'squeeze',
     'unsqueeze',
     'lod_reset',
+    'lod_append',
     'lrn',
     'pad',
     'pad_constant_like',
@@ -6980,7 +6981,7 @@ def lod_reset(x, y=None, target_lod=None):
     considered as target LoD first, otherwise :attr:`y.data` would be
     considered as target LoD. If :attr:`y` is not provided, target LoD should
     be specified by :attr:`target_lod`. If target LoD is specified by
-    :attr:`Y.data` or :attr:`target_lod`, only one level LoD is supported.
+    :attr:`y.data` or :attr:`target_lod`, only one level LoD is supported.
 
     .. code-block:: text
 
@@ -7032,7 +7033,7 @@ def lod_reset(x, y=None, target_lod=None):
                 out.dims = [6, 1]
 
     Args:
-        x (Variable): Input variable which could be a Tensor or LodTensor.
+        x (Variable): Input variable which could be a Tensor or LoDTensor.
         y (Variable|None): If provided, output's LoD would be derived
                            from :attr:`y`.
         target_lod (list|tuple|None): One level LoD which should be considered
@@ -7065,8 +7066,60 @@ def lod_reset(x, y=None, target_lod=None):
             attrs={'target_lod': target_lod},
             outputs={'Out': out})
     else:
-        raise ValueError("y and target_lod should not be both None.")
+        raise ValueError("y and target_lod should not be both none.")
+    return out
+
+
+def lod_append(x, level):
+    """
+    Append level to LoD of :attr:`x`.
+
+    .. code-block:: text
+
+        * Example 1:
+
+            given a 1-level LoDTensor x:
+                x.lod =  [[ 2,           3,                   1 ]]
+                x.data = [[1.0], [2.0], [3.0], [4.0], [5.0], [6.0]]
+                x.dims = [6, 1]
+
+            level: [1, 1, 1, 1, 1, 1, 1]
+
+            then we get a 2-level LoDTensor:
+                x.lod =  [[ 2, 3, 1 ], [1, 1, 1, 1, 1, 1]]
+                x.data = [[1.0], [2.0], [3.0], [4.0], [5.0], [6.0]]
+                x.dims = [6, 1]
 
+    Args:
+        x (Variable): Input variable which could be a tensor or LoDTensor.
+        level (list|tuple): The LoD level to be appended into LoD of x.
+
+    Returns:
+        Variable: Output variable with new LoD level.
+
+    Raises:
+        ValueError: If :attr:`y` is None or and :attr:`level` is not Iterator.
+
+    Examples:
+        .. code-block:: python
+
+            import paddle.fluid as fluid
+            x = fluid.layers.data(name='x', shape=[6, 10], lod_level=1)
+            out = fluid.layers.lod_append(x, [1,1,1,1,1,1])
+    """
+    from collections import Iterable
+    if x is None:
+        raise ValueError("Input(x) can't be None.")
+    if not isinstance(level, Iterable):
+        raise ValueError("Input(level) must be list or tuple.")
+    helper = LayerHelper("lod_append", **locals())
+    out = helper.create_variable_for_type_inference(dtype=x.dtype)
+    helper.append_op(
+        type="lod_reset",
+        inputs={'X': x},
+        attrs={'target_lod': level,
+               'append': True},
+        outputs={'Out': out})
     return out
 
 

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

@@ -1793,6 +1793,14 @@ class TestBook(LayerTest):
             self.assertTrue(z.lod_level == 1)
             return z
 
+    def test_lod_append(self):
+        with self.static_graph():
+            x = layers.data(
+                name='x', shape=[6, 10], dtype='float32', lod_level=1)
+            y = layers.lod_append(x, [1, 1, 1, 1, 1, 1])
+            self.assertTrue(y.lod_level == 1)
+            return y
+
     def test_affine_grid(self):
         with self.static_graph():
             data = layers.data(name='data', shape=[2, 3, 3], dtype="float32")

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

@@ -101,5 +101,26 @@ class TestLodResetOpYIsLoDTensor(OpTest):
         self.check_grad(["X"], "Out", no_grad_set=set("Y"))
 
 
+class TestLodAppendOpByAttr(OpTest):
+    def setUp(self):
+        self.op_type = "lod_reset"
+        x = np.random.random((10, 20)).astype("float32")
+        lod = [[3, 2, 5]]
+        # target_offset_lod and target_lod are the same lod info represented
+        # in offset-based format and length-based format, respectively.
+        target_offset_lod = [i for i in range(11)]
+        self.inputs = {'X': (x, lod)}
+        out_lod = [[3, 2, 5], [1] * 10]
+        # The `target_lod` attribute is still based on offset
+        self.attrs = {'target_lod': target_offset_lod, 'append': True}
+        self.outputs = {'Out': (x, out_lod)}
+
+    def test_check_output(self):
+        self.check_output()
+
+    def test_check_grad(self):
+        self.check_grad(["X"], "Out")
+
+
 if __name__ == '__main__':
     unittest.main()