Merge pull request #13122 from JiayiFeng/cherrypick_seq_pad

Cherrypick seq pad

paddle/fluid/API.spec

@@ -114,6 +114,7 @@ paddle.fluid.layers.beam_search_decode ArgSpec(args=['ids', 'scores', 'beam_size
 paddle.fluid.layers.conv2d_transpose ArgSpec(args=['input', 'num_filters', 'output_size', 'filter_size', 'padding', 'stride', 'dilation', 'groups', 'param_attr', 'bias_attr', 'use_cudnn', 'act', 'name'], varargs=None, keywords=None, defaults=(None, None, 0, 1, 1, None, None, None, True, None, None))
 paddle.fluid.layers.conv3d_transpose ArgSpec(args=['input', 'num_filters', 'output_size', 'filter_size', 'padding', 'stride', 'dilation', 'groups', 'param_attr', 'bias_attr', 'use_cudnn', 'act', 'name'], varargs=None, keywords=None, defaults=(None, None, 0, 1, 1, None, None, None, True, None, None))
 paddle.fluid.layers.sequence_expand ArgSpec(args=['x', 'y', 'ref_level', 'name'], varargs=None, keywords=None, defaults=(-1, None))
+paddle.fluid.layers.sequence_pad ArgSpec(args=['x', 'pad_value', 'maxlen'], varargs=None, keywords=None, defaults=(None,))
 paddle.fluid.layers.lstm_unit ArgSpec(args=['x_t', 'hidden_t_prev', 'cell_t_prev', 'forget_bias', 'param_attr', 'bias_attr', 'name'], varargs=None, keywords=None, defaults=(0.0, None, None, None))
 paddle.fluid.layers.reduce_sum ArgSpec(args=['input', 'dim', 'keep_dim', 'name'], varargs=None, keywords=None, defaults=(None, False, None))
 paddle.fluid.layers.reduce_mean ArgSpec(args=['input', 'dim', 'keep_dim', 'name'], varargs=None, keywords=None, defaults=(None, False, None))

paddle/fluid/operators/CMakeLists.txt

@@ -282,6 +282,7 @@ op_library(unsqueeze_op DEPS reshape_op)
 op_library(squeeze_op DEPS reshape_op)
 op_library(extract_rows_op DEPS memory)
 op_library(flatten_op DEPS reshape_op)
+op_library(sequence_pad_op DEPS sequence_padding)
 
 if (WITH_GPU)
     op_library(conv_op DEPS vol2col depthwise_conv im2col)

paddle/fluid/operators/math/sequence_padding.cc

@@ -18,65 +18,86 @@ namespace paddle {
 namespace operators {
 namespace math {
 
+template <typename T>
+void CopyValidData(framework::Tensor* dst_tensor,
+                   const framework::Tensor* src_tensor,
+                   const framework::Vector<size_t>& seq_offsets,
+                   int pad_seq_len, int step_width, bool norm_by_len,
+                   CopyType type, PadLayout layout) {
+  int seq_num = seq_offsets.size() - 1;
+  const T* src_data = src_tensor->data<T>();
+  T* dst_data = dst_tensor->data<T>();
+
+  int seq_cpy_gap = step_width;
+  int pad_cpy_gap =
+      layout == kBatchLengthWidth ? step_width : seq_num * step_width;
+  for (int seq_idx = 0; seq_idx < seq_num; ++seq_idx) {
+    int valid_seq_len = seq_offsets[seq_idx + 1] - seq_offsets[seq_idx];
+    PADDLE_ENFORCE_GE(
+        pad_seq_len, valid_seq_len,
+        "The padded sequence length can not be less than its original length.");
+    int seq_data_offset = seq_offsets[seq_idx] * step_width;
+    int pad_data_offset = layout == kBatchLengthWidth
+                              ? seq_idx * pad_seq_len * step_width
+                              : seq_idx * step_width;
+    float scale = 1.0f / static_cast<float>(valid_seq_len);
+
+    for (int step_idx = 0; step_idx < valid_seq_len; ++step_idx) {
+      const T* src =
+          src_data + (type == kSeqToPad ? seq_data_offset : pad_data_offset);
+      T* dst =
+          dst_data + (type == kSeqToPad ? pad_data_offset : seq_data_offset);
+      memcpy(dst, src, step_width * sizeof(T));
+      if (norm_by_len) {
+        for (int i = 0; i < step_width; ++i) {
+          *(dst + i) *= scale;
+        }
+      }
+      seq_data_offset += seq_cpy_gap;
+      pad_data_offset += pad_cpy_gap;
+    }
+  }
+}
+
 template <typename T>
 class PaddingLoDTensorFunctor<platform::CPUDeviceContext, T> {
  public:
   void operator()(const platform::CPUDeviceContext& context,
-                  const framework::LoDTensor& seq, framework::Tensor* padding,
-                  bool norm_by_times) {
-    auto lod = seq.lod();
-    PADDLE_ENFORCE_GT(lod.size(), 0UL,
-                      "The LoD of LoDTensor seq should not be null.");
-
-    const size_t level = 0;
-    framework::LoD abs_offset_lod = framework::ToAbsOffset(lod);
-
-    auto seq_dims = seq.dims();
-    PADDLE_ENFORCE_EQ(seq_dims[0],
-                      static_cast<int64_t>(abs_offset_lod[level].back()),
-                      "The first dimension of LoDTensor seq should be "
-                      "equal to the sum of all sequences's length.");
-
-    auto padding_dims = padding->dims();
-    PADDLE_ENFORCE_EQ(padding_dims.size(), 3UL,
-                      "The input padding should be a 3-D Tensor of shape "
-                      "[max_sequence_length, num_sequences, sequence_width].");
-
-    const int64_t max_sequence_length = MaximumSequenceLength(lod, level);
-    PADDLE_ENFORCE_EQ(padding_dims[0], max_sequence_length,
-                      "The first dimension of Tensor padding should be the "
-                      "maximum length of all sequences in LoDTensor seq.");
-
-    const int64_t num_sequences = abs_offset_lod[level].size() - 1;
-    PADDLE_ENFORCE_EQ(padding_dims[1], num_sequences,
-                      "The second dimension of Tensor padding should be the "
-                      "number of sequences in LoDTensor seq.");
-
-    const int64_t sequence_width = seq.numel() / seq_dims[0];
-    PADDLE_ENFORCE_EQ(padding_dims[2], sequence_width,
-                      "The third dimension of Tensor padding should be the "
-                      "width of sequence in LoDTensor seq.");
-
-    const T* seq_data = seq.data<T>();
-    T* padding_data = padding->data<T>();
-    for (int64_t i = 0; i < max_sequence_length; ++i) {
-      for (int64_t j = 0; j < num_sequences; ++j) {
-        int64_t start_pos = abs_offset_lod[level][j];
-        int64_t sequence_length = abs_offset_lod[level][j + 1] - start_pos;
-        if (i < sequence_length) {
-          // i > 0 => sequence_length > 0
-          T scale =
-              norm_by_times ? (1.0f / static_cast<T>(sequence_length)) : 1.0f;
-          for (int64_t k = 0; k < sequence_width; ++k) {
-            padding_data[(i * num_sequences + j) * sequence_width + k] =
-                seq_data[(start_pos + i) * sequence_width + k] * scale;
-          }
-        } else {
-          memset(padding_data + (i * num_sequences + j) * sequence_width, 0,
-                 sequence_width * sizeof(T));
-        }
+                  const framework::LoDTensor& seq_tensor,
+                  framework::LoDTensor* pad_tensor,
+                  const framework::LoDTensor& pad_value, int pad_seq_len = -1,
+                  int lod_level = 0, bool norm_by_times = false,
+                  const PadLayout layout = kBatchLengthWidth) {
+    auto seq_lod = seq_tensor.lod();
+    const auto seq_offsets = framework::ToAbsOffset(seq_lod)[lod_level];
+    const auto& seq_tensor_dims = seq_tensor.dims();
+    const auto& pad_tensor_dims = pad_tensor->dims();
+    if (pad_seq_len == -1) {
+      pad_seq_len = MaximumSequenceLength(seq_offsets);
+    }
+    int step_width = seq_tensor.numel() / seq_tensor_dims[0];
+
+    CheckDims(seq_tensor_dims, pad_tensor_dims, seq_offsets, pad_seq_len,
+              step_width, layout);
+    PADDLE_ENFORCE(pad_value.numel() == 1 || pad_value.numel() == step_width,
+                   "The numel of 'pad_value' can only be 1 or be equal to the "
+                   "'step_width'.");
+
+    // fill padding value
+    T* pad_data = pad_tensor->data<T>();
+    const T* pad_value_data = pad_value.data<T>();
+    if (pad_value.numel() == 1) {
+      for (int i = 0; i < pad_tensor->numel(); ++i) {
+        pad_data[i] = *pad_value_data;
+      }
+    } else {
+      for (int i = 0; i < pad_tensor->numel(); i += step_width) {
+        memcpy(pad_data + i, pad_value_data, step_width * sizeof(T));
       }
     }
+
+    CopyValidData<T>(pad_tensor, &seq_tensor, seq_offsets, pad_seq_len,
+                     step_width, norm_by_times, kSeqToPad, layout);
   }
 };
 
@@ -84,62 +105,35 @@ template <typename T>
 class UnpaddingLoDTensorFunctor<platform::CPUDeviceContext, T> {
  public:
   void operator()(const platform::CPUDeviceContext& context,
-                  framework::LoDTensor* seq, const framework::Tensor& padding,
-                  bool norm_by_times) {
-    auto lod = seq->lod();
-    PADDLE_ENFORCE_GT(lod.size(), 0UL,
-                      "The LoD of LoDTensor seq should not be null.");
-
-    const size_t level = 0;
-    framework::LoD abs_offset_lod = framework::ToAbsOffset(lod);
-
-    auto seq_dims = seq->dims();
-    PADDLE_ENFORCE_EQ(seq_dims[0],
-                      static_cast<int64_t>(abs_offset_lod[level].back()),
-                      "The first dimension of LoDTensor seq should be "
-                      "equal to the sum of all sequences's length.");
-
-    auto padding_dims = padding.dims();
-    PADDLE_ENFORCE_EQ(padding_dims.size(), 3UL,
-                      "The input padding should be a 3-D Tensor of shape "
-                      "[max_sequnece_length, num_sequences, sequence_width].");
-
-    const int64_t max_sequence_length = MaximumSequenceLength(lod, level);
-    PADDLE_ENFORCE_EQ(padding_dims[0], max_sequence_length,
-                      "The first dimension of Tensor padding should be "
-                      "the maximum length of all sequences in LoDTensor seq.");
-
-    const int64_t num_sequences = abs_offset_lod[level].size() - 1;
-    PADDLE_ENFORCE_EQ(padding_dims[1], num_sequences,
-                      "The second dimension of Tensor padding should be "
-                      "the number of sequences in LoDTensor seq.");
-
-    const int64_t sequence_width = seq->numel() / seq_dims[0];
-    PADDLE_ENFORCE_EQ(padding_dims[2], sequence_width,
-                      "The third dimension of Tensor padding should be the "
-                      "width of sequence in LoDTensor seq.");
-
-    const T* padding_data = padding.data<T>();
-    T* seq_data = seq->data<T>();
-    for (int64_t i = 0; i < num_sequences; ++i) {
-      int64_t start_pos = abs_offset_lod[level][i];
-      int64_t sequence_length = abs_offset_lod[level][i + 1] - start_pos;
-      for (int64_t j = 0; j < sequence_length; ++j) {
-        // sequence_width > j > 0
-        T scale =
-            norm_by_times ? (1.0f / static_cast<T>(sequence_length)) : 1.0f;
-        for (int64_t k = 0; k < sequence_width; ++k) {
-          seq_data[(start_pos + j) * sequence_width + k] =
-              padding_data[(j * num_sequences + i) * sequence_width + k] *
-              scale;
-        }
-      }
+                  const framework::LoDTensor& pad_tensor,
+                  framework::LoDTensor* seq_tensor, int pad_seq_len = -1,
+                  int lod_level = 0, bool norm_by_times = false,
+                  const PadLayout layout = kBatchLengthWidth) {
+    auto seq_offsets = framework::ToAbsOffset(seq_tensor->lod())[lod_level];
+    const auto& seq_tensor_dims = seq_tensor->dims();
+    const auto& pad_tensor_dims = pad_tensor.dims();
+    if (pad_seq_len == -1) {
+      pad_seq_len = MaximumSequenceLength(seq_offsets);
     }
+    int step_width = seq_tensor->numel() / seq_tensor_dims[0];
+
+    CheckDims(seq_tensor_dims, pad_tensor_dims, seq_offsets, pad_seq_len,
+              step_width, layout);
+
+    CopyValidData<T>(seq_tensor, &pad_tensor, seq_offsets, pad_seq_len,
+                     step_width, norm_by_times, kPadToSeq, layout);
   }
 };
 
+template class PaddingLoDTensorFunctor<platform::CPUDeviceContext, int>;
+template class PaddingLoDTensorFunctor<platform::CPUDeviceContext, int64_t>;
 template class PaddingLoDTensorFunctor<platform::CPUDeviceContext, float>;
+template class PaddingLoDTensorFunctor<platform::CPUDeviceContext, double>;
+
+template class UnpaddingLoDTensorFunctor<platform::CPUDeviceContext, int>;
+template class UnpaddingLoDTensorFunctor<platform::CPUDeviceContext, int64_t>;
 template class UnpaddingLoDTensorFunctor<platform::CPUDeviceContext, float>;
+template class UnpaddingLoDTensorFunctor<platform::CPUDeviceContext, double>;
 
 }  // namespace math
 }  // namespace operators

paddle/fluid/operators/math/sequence_padding.cu

@@ -19,41 +19,32 @@ namespace paddle {
 namespace operators {
 namespace math {
 
-template <typename T, bool NormByTimes, bool Padding>
-__global__ void SequencePaddingKernel(T* padding, T* sequence,
-                                      const size_t* sequence_start_positions,
-                                      const size_t sequence_width,
-                                      const size_t max_sequence_length,
-                                      const size_t num_sequences) {
-  size_t padding_idx = blockIdx.y;
-  size_t start_pos = sequence_start_positions[padding_idx];
-  size_t sequence_length =
-      sequence_start_positions[padding_idx + 1] - start_pos;
-
-  size_t sequence_idx = blockIdx.x * blockDim.y + threadIdx.y;
-  size_t padding_base_idx =
-      (sequence_idx * num_sequences + padding_idx) * sequence_width;
-  size_t sequence_base_idx = (start_pos + sequence_idx) * sequence_width;
-
-  if (sequence_idx < sequence_length) {
-    T scale = NormByTimes ? (1.0f / static_cast<T>(sequence_length)) : 1.0f;
-    if (Padding) {
-      /* sequence -> padding */
-      for (size_t i = threadIdx.x; i < sequence_width; i += blockDim.x) {
-        padding[padding_base_idx + i] = scale * sequence[sequence_base_idx + i];
-      }
-    } else {
-      /* padding -> sequence */
-      for (size_t i = threadIdx.x; i < sequence_width; i += blockDim.x) {
-        sequence[sequence_base_idx + i] = scale * padding[padding_base_idx + i];
-      }
+template <typename T, CopyType Type>
+__global__ void SequencePaddingKernel(
+    T* dst, const T* src, const T* pad_value, bool is_constant_pad,
+    const size_t* seq_offsets, const size_t seq_num, const size_t pad_seq_len,
+    const size_t step_width, bool norm_by_len, const PadLayout layout) {
+  size_t seq_idx = blockIdx.y;
+  size_t seq_len = seq_offsets[seq_idx + 1] - seq_offsets[seq_idx];
+
+  size_t step_idx = blockIdx.x * blockDim.y + threadIdx.y;
+  size_t seq_data_offset = (seq_offsets[seq_idx] + step_idx) * step_width;
+  size_t pad_data_offset = layout == kBatchLengthWidth
+                               ? (seq_idx * pad_seq_len + step_idx) * step_width
+                               : (step_idx * seq_num + seq_idx) * step_width;
+
+  T* dst_data = dst + (Type == kSeqToPad ? pad_data_offset : seq_data_offset);
+  const T* src_data =
+      src + (Type == kSeqToPad ? seq_data_offset : pad_data_offset);
+
+  if (step_idx < seq_len) {
+    float scale = norm_by_len ? (1.0f / static_cast<float>(seq_len)) : 1.0f;
+    for (size_t i = threadIdx.x; i < step_width; i += blockDim.x) {
+      dst_data[i] = scale * src_data[i];
     }
-  } else if (sequence_idx < max_sequence_length) {
-    if (Padding) {
-      /* sequence -> padding */
-      for (size_t i = threadIdx.x; i < sequence_width; i += blockDim.x) {
-        padding[padding_base_idx + i] = 0;
-      }
+  } else if (step_idx < pad_seq_len && Type == kSeqToPad) {
+    for (size_t i = threadIdx.x; i < step_width; i += blockDim.x) {
+      dst_data[i] = is_constant_pad ? pad_value[0] : pad_value[i];
     }
   }
 }
@@ -62,74 +53,59 @@ template <typename T>
 class PaddingLoDTensorFunctor<platform::CUDADeviceContext, T> {
  public:
   void operator()(const platform::CUDADeviceContext& context,
-                  const framework::LoDTensor& seq, framework::Tensor* padding,
-                  bool norm_by_times) {
-    auto lod = seq.lod();
-    PADDLE_ENFORCE_GT(lod.size(), 0UL,
-                      "The lod of LoDTensor seq should not be null.");
-
-    const size_t level = 0;
-    framework::LoD abs_offset_lod = framework::ToAbsOffset(lod);
-
-    auto seq_dims = seq.dims();
-    PADDLE_ENFORCE_EQ(seq_dims[0],
-                      static_cast<int64_t>(abs_offset_lod[level].back()),
-                      "The first dimension of LoDTensor seq should be "
-                      "equal to the sum of all sequences's length.");
-
-    auto padding_dims = padding->dims();
-    PADDLE_ENFORCE_EQ(padding_dims.size(), 3UL,
-                      "The input padding should be a 3-D Tensor of shape "
-                      "[max_sequence_length, num_sequences, sequence_width].");
-
-    int64_t max_sequence_length = MaximumSequenceLength(lod, level);
-    PADDLE_ENFORCE_EQ(padding_dims[0], max_sequence_length,
-                      "The first dimension of Tensor padding should be the "
-                      "maximum length of all sequences in LoDTensor seq.");
-
-    const int64_t num_sequences = abs_offset_lod[level].size() - 1;
-    PADDLE_ENFORCE_EQ(padding_dims[1], num_sequences,
-                      "The second dimension of Tensor padding should be the "
-                      "number of sequences in LoDTensor seq.");
-
-    const int64_t sequence_width = seq.numel() / seq_dims[0];
-    PADDLE_ENFORCE_EQ(padding_dims[2], sequence_width,
-                      "The third dimension of Tensor padding should be the "
-                      "width of sequence in LoDTensor seq.");
-
-    if (!norm_by_times && num_sequences == 1UL) {
-      TensorCopy(seq, context.GetPlace(), context, padding);
-      padding->Resize(padding_dims);
+                  const framework::LoDTensor& seq_tensor,
+                  framework::LoDTensor* pad_tensor,
+                  const framework::LoDTensor& pad_value, int pad_seq_len = -1,
+                  int lod_level = 0, bool norm_by_times = false,
+                  const PadLayout layout = kBatchLengthWidth) {
+    auto seq_lod = seq_tensor.lod();
+    const auto seq_offsets = framework::ToAbsOffset(seq_lod)[lod_level];
+    const auto& seq_tensor_dims = seq_tensor.dims();
+    const auto& pad_tensor_dims = pad_tensor->dims();
+    int max_seq_len = MaximumSequenceLength(seq_offsets);
+    if (pad_seq_len == -1) {
+      pad_seq_len = max_seq_len;
+    }
+    PADDLE_ENFORCE_GE(pad_seq_len, max_seq_len,
+                      "The pad_seq_len must be equal to or greater than the "
+                      "original max sequence length.");
+    int step_width = seq_tensor.numel() / seq_tensor_dims[0];
+    int seq_num = seq_offsets.size() - 1;
+
+    CheckDims(seq_tensor_dims, pad_tensor_dims, seq_offsets, pad_seq_len,
+              step_width, layout);
+    PADDLE_ENFORCE(pad_value.numel() == 1 || pad_value.numel() == step_width,
+                   "The numel of 'pad_value' can only be 1 or be equal to the "
+                   "'step_width'.");
+
+    if (!norm_by_times && seq_num == 1UL && pad_seq_len == max_seq_len) {
+      TensorCopy(seq_tensor, context.GetPlace(), context, pad_tensor);
+      pad_tensor->Resize(pad_tensor_dims);
       return;
     }
 
-    const int64_t kBlockSize = 512;
+    const int kBlockSize = 512;
 
     /* At least use 32 threads to copy sequence_width elements,
      * and at least 8 elements for each thread.
      */
     size_t block_dim_x =
-        std::min(((((sequence_width + 7) >> 3) + 31) >> 5) << 5, kBlockSize);
+        std::min(((((step_width + 7) >> 3) + 31) >> 5) << 5, kBlockSize);
     size_t block_dim_y = kBlockSize / block_dim_x;
     dim3 threads(block_dim_x, block_dim_y);
 
-    size_t grid_dim_x = (max_sequence_length + block_dim_y - 1) / block_dim_y;
-    size_t grid_dim_y = num_sequences;
+    size_t grid_dim_x = (pad_seq_len + block_dim_y - 1) / block_dim_y;
+    size_t grid_dim_y = seq_num;
     dim3 grid(grid_dim_x, grid_dim_y);
 
-    const T* seq_data = seq.data<T>();
-    T* padding_data = padding->data<T>();
-    if (norm_by_times) {
-      SequencePaddingKernel<T, 1, 1><<<grid, threads, 0, context.stream()>>>(
-          padding_data, const_cast<T*>(seq_data),
-          abs_offset_lod[level].CUDAData(context.GetPlace()), sequence_width,
-          max_sequence_length, num_sequences);
-    } else {
-      SequencePaddingKernel<T, 0, 1><<<grid, threads, 0, context.stream()>>>(
-          padding_data, const_cast<T*>(seq_data),
-          abs_offset_lod[level].CUDAData(context.GetPlace()), sequence_width,
-          max_sequence_length, num_sequences);
-    }
+    const T* seq_data = seq_tensor.data<T>();
+    T* pad_data = pad_tensor->data<T>();
+    const T* pad_value_data = pad_value.data<T>();
+
+    SequencePaddingKernel<T, kSeqToPad><<<grid, threads, 0, context.stream()>>>(
+        pad_data, seq_data, pad_value_data, pad_value.numel() == 1,
+        seq_offsets.CUDAData(context.GetPlace()), seq_num, pad_seq_len,
+        step_width, norm_by_times, layout);
   }
 };
 
@@ -137,79 +113,62 @@ template <typename T>
 class UnpaddingLoDTensorFunctor<platform::CUDADeviceContext, T> {
  public:
   void operator()(const platform::CUDADeviceContext& context,
-                  framework::LoDTensor* seq, const framework::Tensor& padding,
-                  bool norm_by_times) {
-    auto lod = seq->lod();
-    PADDLE_ENFORCE_GT(lod.size(), 0UL,
-                      "The lod of LoDTensor seq should not be null.");
-
-    const size_t level = 0;
-    framework::LoD abs_offset_lod = framework::ToAbsOffset(lod);
-
-    auto seq_dims = seq->dims();
-    PADDLE_ENFORCE_EQ(seq_dims[0],
-                      static_cast<int64_t>(abs_offset_lod[level].back()),
-                      "The first dimension of LoDTensor seq should be "
-                      "equal to the sum of all sequences's length.");
-
-    auto padding_dims = padding.dims();
-    PADDLE_ENFORCE_EQ(padding_dims.size(), 3UL,
-                      "The input padding should be a 3-D Tensor of shape "
-                      "[max_sequnece_length, num_sequences, sequence_width].");
-
-    int64_t max_sequence_length = MaximumSequenceLength(lod, level);
-    PADDLE_ENFORCE_EQ(padding_dims[0], max_sequence_length,
-                      "The first dimension of Tensor padding should be "
-                      "the maximum length of all sequences in LoDTensor seq.");
-
-    const int64_t num_sequences = abs_offset_lod[level].size() - 1;
-    PADDLE_ENFORCE_EQ(padding_dims[1], num_sequences,
-                      "The second dimension of Tensor padding should be "
-                      "the number of sequences in LoDTensor seq.");
-
-    const int64_t sequence_width = seq->numel() / seq_dims[0];
-    PADDLE_ENFORCE_EQ(padding_dims[2], sequence_width,
-                      "The third dimension of Tensor padding should be the "
-                      "width of sequence in LoDTensor seq.");
-
-    if (!norm_by_times && num_sequences == 1UL) {
-      TensorCopy(padding, context.GetPlace(), context, seq);
-      seq->Resize(seq_dims);
+                  const framework::LoDTensor& pad_tensor,
+                  framework::LoDTensor* seq_tensor, int pad_seq_len = -1,
+                  int lod_level = 0, bool norm_by_times = false,
+                  const PadLayout layout = kBatchLengthWidth) {
+    auto seq_offsets = framework::ToAbsOffset(seq_tensor->lod())[lod_level];
+    const auto& seq_tensor_dims = seq_tensor->dims();
+    const auto& pad_tensor_dims = pad_tensor.dims();
+    int max_seq_len = MaximumSequenceLength(seq_offsets);
+    if (pad_seq_len == -1) {
+      pad_seq_len = max_seq_len;
+    }
+    int step_width = seq_tensor->numel() / seq_tensor_dims[0];
+    int seq_num = seq_offsets.size() - 1;
+
+    CheckDims(seq_tensor_dims, pad_tensor_dims, seq_offsets, pad_seq_len,
+              step_width, layout);
+
+    if (!norm_by_times && seq_num == 1UL && pad_seq_len == max_seq_len) {
+      TensorCopy(pad_tensor, context.GetPlace(), context, seq_tensor);
+      seq_tensor->Resize(seq_tensor_dims);
       return;
     }
 
-    const int64_t kBlockSize = 512;
+    const int kBlockSize = 512;
 
     /* At least use 32 threads to copy sequence_width elements,
      * and at least 8 elements for each thread.
      */
     size_t block_dim_x =
-        std::min(((((sequence_width + 7) >> 3) + 31) >> 5) << 5, kBlockSize);
+        std::min(((((step_width + 7) >> 3) + 31) >> 5) << 5, kBlockSize);
     size_t block_dim_y = kBlockSize / block_dim_x;
     dim3 threads(block_dim_x, block_dim_y);
 
-    size_t grid_dim_x = (max_sequence_length + block_dim_y - 1) / block_dim_y;
-    size_t grid_dim_y = num_sequences;
+    size_t grid_dim_x = (pad_seq_len + block_dim_y - 1) / block_dim_y;
+    size_t grid_dim_y = seq_num;
     dim3 grid(grid_dim_x, grid_dim_y);
 
-    const T* padding_data = padding.data<T>();
-    T* seq_data = seq->data<T>();
-    if (norm_by_times) {
-      SequencePaddingKernel<T, 1, 0><<<grid, threads, 0, context.stream()>>>(
-          const_cast<T*>(padding_data), seq_data,
-          abs_offset_lod[level].CUDAData(context.GetPlace()), sequence_width,
-          max_sequence_length, num_sequences);
-    } else {
-      SequencePaddingKernel<T, 0, 0><<<grid, threads, 0, context.stream()>>>(
-          const_cast<T*>(padding_data), seq_data,
-          abs_offset_lod[level].CUDAData(context.GetPlace()), sequence_width,
-          max_sequence_length, num_sequences);
-    }
+    const T* pad_data = pad_tensor.data<T>();
+    T* seq_data = seq_tensor->data<T>();
+
+    SequencePaddingKernel<T, kPadToSeq><<<grid, threads, 0, context.stream()>>>(
+        seq_data, pad_data, nullptr, false,
+        seq_offsets.CUDAData(context.GetPlace()), seq_num, pad_seq_len,
+        step_width, norm_by_times, layout);
   }
 };
 
+template class PaddingLoDTensorFunctor<platform::CUDADeviceContext, int>;
+template class PaddingLoDTensorFunctor<platform::CUDADeviceContext, int64_t>;
 template class PaddingLoDTensorFunctor<platform::CUDADeviceContext, float>;
+template class PaddingLoDTensorFunctor<platform::CUDADeviceContext, double>;
+
+template class UnpaddingLoDTensorFunctor<platform::CUDADeviceContext, int>;
+template class UnpaddingLoDTensorFunctor<platform::CUDADeviceContext, int64_t>;
 template class UnpaddingLoDTensorFunctor<platform::CUDADeviceContext, float>;
+template class UnpaddingLoDTensorFunctor<platform::CUDADeviceContext, double>;
 
 }  // namespace math
 }  // namespace operators

paddle/fluid/operators/math/sequence_padding.h

@@ -15,6 +15,7 @@ limitations under the License. */
 #pragma once
 
 #include <algorithm>
+#include <vector>
 #include "paddle/fluid/framework/lod_tensor.h"
 #include "paddle/fluid/platform/device_context.h"
 
@@ -22,17 +23,33 @@ namespace paddle {
 namespace operators {
 namespace math {
 
-inline static size_t MaximumSequenceLength(const framework::LoD& lod,
-                                           const size_t level) {
-  const size_t num_sequences = lod[level].size() - 1;
-  size_t max_sequence_length = 0;
-  framework::LoD abs_offset_lod = framework::ToAbsOffset(lod);
-  for (size_t i = 0; i < num_sequences; ++i) {
-    max_sequence_length =
-        std::max(max_sequence_length,
-                 abs_offset_lod[level][i + 1] - abs_offset_lod[level][i]);
+enum PadLayout { kBatchLengthWidth = 0, kLengthBatchWidth };
+
+enum CopyType { kSeqToPad, kPadToSeq };
+
+inline static size_t MaximumSequenceLength(
+    const framework::Vector<size_t>& seq_offset) {
+  size_t seq_num = seq_offset.size() - 1;
+  size_t max_seq_len = 0;
+  for (size_t i = 0; i < seq_num; ++i) {
+    max_seq_len = std::max(max_seq_len, seq_offset[i + 1] - seq_offset[i]);
   }
-  return max_sequence_length;
+  return max_seq_len;
+}
+
+inline static void CheckDims(const framework::DDim& seq_tensor_dims,
+                             const framework::DDim& pad_tensor_dims,
+                             const framework::Vector<size_t>& seq_offset,
+                             int64_t padded_seq_len, int64_t step_width,
+                             const PadLayout& layout) {
+  PADDLE_ENFORCE_EQ(static_cast<size_t>(seq_tensor_dims[0]), seq_offset.back(),
+                    "Value of 1st dimension of the sequence tensor should be "
+                    "equal to sum of lengths of all sequences.");
+
+  PADDLE_ENFORCE(seq_tensor_dims.size() + 1 == pad_tensor_dims.size() ||
+                     seq_tensor_dims.size() == pad_tensor_dims.size(),
+                 "pad_tensor's rank should be 1 greater than seq_tensor's "
+                 "rank, or be equal with it.");
 }
 
 /*
@@ -64,15 +81,22 @@ inline static size_t MaximumSequenceLength(const framework::LoD& lod,
 template <typename DeviceContext, typename T>
 class PaddingLoDTensorFunctor {
  public:
-  void operator()(const DeviceContext& context, const framework::LoDTensor& seq,
-                  framework::Tensor* padding, bool norm_by_times);
+  void operator()(const DeviceContext& context,
+                  const framework::LoDTensor& seq_tensor,
+                  framework::LoDTensor* pad_tensor,
+                  const framework::LoDTensor& pad_value, int pad_seq_len = -1,
+                  int lod_level = 0, bool norm_by_times = false,
+                  const PadLayout layout = kBatchLengthWidth);
 };
 
 template <typename DeviceContext, typename T>
 class UnpaddingLoDTensorFunctor {
  public:
-  void operator()(const DeviceContext& context, framework::LoDTensor* seq,
-                  const framework::Tensor& padding, bool norm_by_times);
+  void operator()(const DeviceContext& context,
+                  const framework::LoDTensor& pad_tensor,
+                  framework::LoDTensor* seq_tensor, int pad_seq_len = -1,
+                  int lod_level = 0, bool norm_by_times = false,
+                  const PadLayout layout = kBatchLengthWidth);
 };
 
 }  // namespace math

paddle/fluid/operators/math/sequence_padding_test.cc

@@ -23,7 +23,9 @@ void TestSequencePadding(const paddle::framework::LoD& lod,
   paddle::framework::LoDTensor cpu_seq_back;
   paddle::framework::LoDTensor seq;
   paddle::framework::LoDTensor seq_back;
-  paddle::framework::Tensor padding;
+  paddle::framework::LoDTensor padding;
+  paddle::framework::LoDTensor cpu_pad_value;
+  paddle::framework::LoDTensor pad_value;
 
   const size_t level = lod.size() - 1;
   auto seq_dims =
@@ -46,20 +48,33 @@ void TestSequencePadding(const paddle::framework::LoD& lod,
   }
 
   const size_t max_sequence_length =
-      paddle::operators::math::MaximumSequenceLength(lod, level);
+      paddle::operators::math::MaximumSequenceLength(lod[level]);
   const size_t num_sequences = lod[level].size() - 1;
   auto padding_dims =
       paddle::framework::make_ddim({static_cast<int64_t>(max_sequence_length),
                                     static_cast<int64_t>(num_sequences),
                                     static_cast<int64_t>(sequence_width)});
+
   padding.mutable_data<T>(padding_dims, *place);
+
+  T* pad_value_data =
+      cpu_pad_value.mutable_data<T>({1}, paddle::platform::CPUPlace());
+  *pad_value_data = static_cast<T>(0);
+  if (paddle::platform::is_cpu_place(*place)) {
+    pad_value = cpu_pad_value;
+  } else {
+    TensorCopySync(cpu_pad_value, *place, &pad_value);
+  }
+
   paddle::operators::math::PaddingLoDTensorFunctor<DeviceContext, T>()(
-      *context, seq, &padding, false);
+      *context, seq, &padding, pad_value, -1, 0, false,
+      paddle::operators::math::kLengthBatchWidth);
 
   seq_back.set_lod(lod);
   seq_back.mutable_data<T>(seq_dims, *place);
   paddle::operators::math::UnpaddingLoDTensorFunctor<DeviceContext, T>()(
-      *context, &seq_back, padding, false);
+      *context, padding, &seq_back, -1, 0, false,
+      paddle::operators::math::kLengthBatchWidth);
 
   if (paddle::platform::is_cpu_place(*place)) {
     cpu_seq_back = seq_back;

paddle/fluid/operators/sequence_pad_op.cc

+/* Copyright (c) 2018 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. */
+
+#include "paddle/fluid/operators/sequence_pad_op.h"
+
+namespace paddle {
+namespace operators {
+
+class SequencePadOp : public framework::OperatorWithKernel {
+ public:
+  using framework::OperatorWithKernel::OperatorWithKernel;
+
+ protected:
+  void InferShape(framework::InferShapeContext* ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"),
+                   "Input(X) of SequencePadOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasInput("PadValue"),
+                   "Input(PadValue) of SequencePadOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasOutput("Out"),
+                   "Output(Out) of SequencePadOp should not be null.");
+
+    auto x_dims = ctx->GetInputDim("X");
+    PADDLE_ENFORCE_GE(x_dims.size(), 2,
+                      "The rank of Input(x) can't be less than 2.");
+    auto time_step_dims = framework::slice_ddim(x_dims, 1, x_dims.size());
+    auto pad_value_dims = ctx->GetInputDim("PadValue");
+    PADDLE_ENFORCE(pad_value_dims == framework::make_ddim({1}) ||
+                       pad_value_dims == time_step_dims,
+                   "The Input(PadValue) must be a scalar or a tensor whose "
+                   "shape equals to time steps in sequences");
+
+    int out_dim_0 = -1;
+    int out_dim_1 = -1;
+
+    if (ctx->IsRuntime()) {
+      // run time
+      framework::Variable* x_var =
+          boost::get<framework::Variable*>(ctx->GetInputVarPtrs("X")[0]);
+      const auto& x_lod = x_var->Get<LoDTensor>().lod();
+      PADDLE_ENFORCE(!x_lod.empty(), "The Input(X) must hold lod info.");
+      const auto& x_lod_0 = x_lod[0];
+      PADDLE_ENFORCE_GE(x_lod_0.size(), 2,
+                        "The Input(X)'s lod info is corrupted.");
+      PADDLE_ENFORCE_EQ(
+          x_dims[0], static_cast<int64_t>(x_lod_0.back()),
+          "The Input(X)'s lod info mismatches the actual tensor shape.");
+
+      int seq_num = x_lod_0.size() - 1;
+      int max_seq_len = math::MaximumSequenceLength(x_lod_0);
+      int padded_length = ctx->Attrs().Get<int>("padded_length");
+      if (padded_length == -1) {
+        padded_length = max_seq_len;
+      }
+      PADDLE_ENFORCE_GE(padded_length, max_seq_len,
+                        "The Attr(padded_length) must be -1 or an int greater "
+                        "than the length of the longest original sequence.");
+      out_dim_0 = seq_num;
+      out_dim_1 = padded_length;
+    } else {
+      // compile time
+      framework::VarDesc* x_desc =
+          boost::get<framework::VarDesc*>(ctx->GetInputVarPtrs("X")[0]);
+      PADDLE_ENFORCE_GE(x_desc->GetLoDLevel(), 1);
+    }
+
+    std::vector<int> out_dims_vec{out_dim_0, out_dim_1};
+    auto time_step_dims_vec = framework::vectorize2int(time_step_dims);
+    out_dims_vec.insert(out_dims_vec.end(), time_step_dims_vec.begin(),
+                        time_step_dims_vec.end());
+    ctx->SetOutputDim("Out", framework::make_ddim(out_dims_vec));
+  }
+};
+
+class SequencePadOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  void Make() override {
+    AddInput("X",
+             "(LoDTensor, default LoDTensor<float>) Input variable which "
+             "should contain lod information.");
+    AddInput("PadValue",
+             "(LoDTensor), this Tensor holds values that will be fill into "
+             "padded steps. It can be a scalar or a tensor whose shape equals "
+             "to time steps in sequences. If it's a scalar, it will be "
+             "automatically broadcasted to the shape of time step.");
+    AddOutput(
+        "Out",
+        "(LoDTensor) The output vairable, which contains padded sequences.");
+    AddAttr<int>(
+        "padded_length",
+        "The length of padded sequences. It can be setted to -1 or "
+        "any positive int. When it is -1, all sequences will be padded up to "
+        "the length of the longest one among them; when it a certain positive "
+        "value, it must be greater than the length of the longest original "
+        "sequence.")
+        .SetDefault(-1);
+    AddComment(R"DOC(
+      Sequence Pad Operator
+
+      This operator pads sequences in a same batch to a consistent length. 
+      The length is specified by attribute 'padded_length'. New elements, 
+      whose values are specified by input 'PadValue', will be appended to 
+      the end of each sequence, to make their final lengths consistent.
+
+      Following are cases to better explain how this works:
+
+      Case 1:
+
+      Given a 1-level LoDTensor input(X):
+          X.lod = [[0, 2,       5]]
+          X.data = [a, b, c, d, e]
+      and Input(PadValue):
+          PadValue.data = [0]
+      and attribite 'padded_length' = 4,
+      then we get LoDTensor:
+          Out.data = [[a, b, 0, 0], 
+                      [c, d, e, 0]]
+      
+      Case 2:
+
+      Given a 1-level LoDTensor input(X):
+          X.lod = [[0,               2,                           5]]
+          X.data = [[a1, a2], [b1, b2], [c1, c2], [d1, d2], [e1, e2]]
+      and Input(PadValue):
+          PadValue.data = [0]
+      and attribite 'padded_length' = -1, which mean using the length 
+      of longest input sequence(3 in this case),
+      then we get LoDTensor:
+          Out.data = [[[a1, a2], [b1, b2], [0, 0]], 
+                      [[c1, c2], [d1, d2], [e1, e2]]]
+
+      Case 3:
+
+      Given a 1-level LoDTensor input(X):
+          X.lod = [[0,               2,                           5]]
+          X.data = [[a1, a2], [b1, b2], [c1, c2], [d1, d2], [e1, e2]]
+      and Input(PadValue):
+          PadValue.data = [p1, p2]
+      and attribite 'padded_length' = -1, which mean using the length 
+      of longest input sequence(3 in this case),
+      then we get LoDTensor:
+          Out.data = [[[a1, a2], [b1, b2], [p1, p2]], 
+                      [[c1, c2], [d1, d2], [e1, e2]]]
+
+    )DOC");
+  }
+};
+
+class SequencePadGradOp : public framework::OperatorWithKernel {
+ public:
+  using framework::OperatorWithKernel::OperatorWithKernel;
+
+  void InferShape(framework::InferShapeContext* ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"),
+                   "Input(X) of SequencePadGradOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasInput(framework::GradVarName("Out")),
+                   "Input(Out@GRAD) of SequencePadGradOp should not be null.");
+
+    if (ctx->HasOutput(framework::GradVarName("X"))) {
+      ctx->SetOutputDim(framework::GradVarName("X"), ctx->GetInputDim("X"));
+      ctx->ShareLoD("X", /*->*/ framework::GradVarName("X"));
+    }
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+REGISTER_OPERATOR(sequence_pad, ops::SequencePadOp, ops::SequencePadOpMaker,
+                  paddle::framework::DefaultGradOpDescMaker<true>);
+REGISTER_OPERATOR(sequence_pad_grad, ops::SequencePadGradOp);
+REGISTER_OP_CPU_KERNEL(
+    sequence_pad,
+    ops::SequencePadOpKernel<paddle::platform::CPUDeviceContext, float>,
+    ops::SequencePadOpKernel<paddle::platform::CPUDeviceContext, double>,
+    ops::SequencePadOpKernel<paddle::platform::CPUDeviceContext, int>,
+    ops::SequencePadOpKernel<paddle::platform::CPUDeviceContext, int64_t>);
+REGISTER_OP_CPU_KERNEL(
+    sequence_pad_grad,
+    ops::SequencePadGradOpKernel<paddle::platform::CPUDeviceContext, float>,
+    ops::SequencePadGradOpKernel<paddle::platform::CPUDeviceContext, double>,
+    ops::SequencePadGradOpKernel<paddle::platform::CPUDeviceContext, int>,
+    ops::SequencePadGradOpKernel<paddle::platform::CPUDeviceContext, int64_t>);

paddle/fluid/operators/sequence_pad_op.cu

+/* Copyright (c) 2018 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. */
+
+#include "paddle/fluid/operators/sequence_pad_op.h"
+
+namespace ops = paddle::operators;
+REGISTER_OP_CUDA_KERNEL(
+    sequence_pad,
+    ops::SequencePadOpKernel<paddle::platform::CUDADeviceContext, float>,
+    ops::SequencePadOpKernel<paddle::platform::CUDADeviceContext, double>,
+    ops::SequencePadOpKernel<paddle::platform::CUDADeviceContext, int>,
+    ops::SequencePadOpKernel<paddle::platform::CUDADeviceContext, int64_t>);
+REGISTER_OP_CUDA_KERNEL(
+    sequence_pad_grad,
+    ops::SequencePadGradOpKernel<paddle::platform::CUDADeviceContext, float>,
+    ops::SequencePadGradOpKernel<paddle::platform::CUDADeviceContext, double>,
+    ops::SequencePadGradOpKernel<paddle::platform::CUDADeviceContext, int>,
+    ops::SequencePadGradOpKernel<paddle::platform::CUDADeviceContext, int64_t>);

paddle/fluid/operators/sequence_pad_op.h

+/* Copyright (c) 2018 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. */
+
+#pragma once
+
+#include <vector>
+#include "paddle/fluid/framework/op_registry.h"
+#include "paddle/fluid/memory/memcpy.h"
+#include "paddle/fluid/operators/math/math_function.h"
+#include "paddle/fluid/operators/math/sequence_padding.h"
+
+namespace paddle {
+namespace operators {
+
+using LoDTensor = framework::LoDTensor;
+using LoD = framework::LoD;
+
+template <typename DeviceContext, typename T>
+class SequencePadOpKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext& ctx) const override {
+    const auto* x = ctx.Input<LoDTensor>("X");
+    auto* out = ctx.Output<LoDTensor>("Out");
+    out->mutable_data<T>(ctx.GetPlace());
+
+    const auto* pad_value = ctx.Input<LoDTensor>("PadValue");
+
+    int padded_length = ctx.Attr<int>("padded_length");
+
+    math::PaddingLoDTensorFunctor<DeviceContext, T>()(
+        ctx.template device_context<DeviceContext>(), *x, out, *pad_value,
+        padded_length, 0, false, math::kBatchLengthWidth);
+  }
+};
+
+template <typename DeviceContext, typename T>
+class SequencePadGradOpKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext& ctx) const override {
+    auto* d_x = ctx.Output<LoDTensor>(framework::GradVarName("X"));
+    if (d_x) {
+      const auto* d_out = ctx.Input<LoDTensor>(framework::GradVarName("Out"));
+      d_x->mutable_data<T>(ctx.GetPlace());
+
+      int padded_length = ctx.Attr<int>("padded_length");
+
+      math::UnpaddingLoDTensorFunctor<DeviceContext, T>()(
+          ctx.template device_context<DeviceContext>(), *d_out, d_x,
+          padded_length, 0, false, math::kBatchLengthWidth);
+    }
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle

paddle/fluid/operators/warpctc_op.h

@@ -153,17 +153,29 @@ class WarpCTCKernel : public framework::OpKernel<T> {
         framework::make_ddim({static_cast<int64_t>(num_sequences), 1});
 
     // warpctc needs sequences data stored in transposed padding format
-    Tensor warpctc_logits;
+    LoDTensor warpctc_logits;
     const size_t max_sequence_length =
-        math::MaximumSequenceLength(logits_lod, level);
+        math::MaximumSequenceLength(logits_lod[level]);
     auto warpctc_logits_dims =
         framework::make_ddim({static_cast<int64_t>(max_sequence_length),
                               static_cast<int64_t>(num_sequences),
                               static_cast<int64_t>(sequence_width)});
     warpctc_logits.mutable_data<T>(warpctc_logits_dims, ctx.GetPlace());
+
+    LoDTensor cpu_pad_value;
+    T* pad_value_data =
+        cpu_pad_value.mutable_data<T>({1}, platform::CPUPlace());
+    *pad_value_data = static_cast<T>(0);
+    LoDTensor pad_value;
+    if (platform::is_cpu_place(ctx.GetPlace())) {
+      pad_value = cpu_pad_value;
+    } else {
+      TensorCopySync(cpu_pad_value, ctx.GetPlace(), &pad_value);
+    }
+
     math::PaddingLoDTensorFunctor<DeviceContext, T>()(
         ctx.template device_context<DeviceContext>(), *logits, &warpctc_logits,
-        false);
+        pad_value, -1, 0, false /* norm_by_times */, math::kLengthBatchWidth);
     const T* warpctc_logits_data = warpctc_logits.data<T>();
 
     std::vector<int> warpctc_label_lengths(num_sequences);
@@ -209,15 +221,15 @@ template <typename DeviceContext, typename T>
 class WarpCTCGradKernel : public framework::OpKernel<T> {
  public:
   void Compute(const framework::ExecutionContext& ctx) const override {
-    auto* warpctc_grad = ctx.Input<Tensor>("WarpCTCGrad");
+    auto* warpctc_grad = ctx.Input<LoDTensor>("WarpCTCGrad");
     auto* logits_grad = ctx.Output<LoDTensor>(framework::GradVarName("Logits"));
     const Tensor* loss_grad = ctx.Input<Tensor>(framework::GradVarName("Loss"));
 
     logits_grad->mutable_data<T>(ctx.GetPlace());
     bool norm_by_times = ctx.Attr<bool>("norm_by_times");
     math::UnpaddingLoDTensorFunctor<DeviceContext, T>()(
-        ctx.template device_context<DeviceContext>(), logits_grad,
-        *warpctc_grad, norm_by_times);
+        ctx.template device_context<DeviceContext>(), *warpctc_grad,
+        logits_grad, -1, 0, norm_by_times, math::kLengthBatchWidth);
 
     const T* loss_grad_data = loss_grad->data<T>();
     math::ScaleLoDTensorFunctor<DeviceContext, T>()(

python/paddle/fluid/layers/nn.py

@@ -55,6 +55,7 @@ __all__ = [
     'conv2d_transpose',
     'conv3d_transpose',
     'sequence_expand',
+    'sequence_pad',
     'lstm_unit',
     'reduce_sum',
     'reduce_mean',
@@ -2657,6 +2658,51 @@ def sequence_expand(x, y, ref_level=-1, name=None):
     return tmp
 
 
+@templatedoc()
+def sequence_pad(x, pad_value, maxlen=None):
+    """
+    ${comment}
+
+    Args:
+        x(Variable): Input variable which should contain lod information.
+        pad_value(Variable): The Variable that holds values that will be fill 
+            into padded steps. It can be a scalar or a tensor whose shape 
+            equals to time steps in sequences. If it's a scalar, it will be 
+            automatically broadcasted to the shape of time step.
+        maxlen(int, default None): The length of padded sequences. It can be 
+            None or any positive int. When it is None, all sequences will be 
+            padded up to the length of the longest one among them; when it a 
+            certain positive value, it must be greater than the length of the 
+            longest original sequence."
+    
+    Returns:
+        Variable: The padded sequence batch. All sequences has the same length.
+    
+    Examples:
+        .. code-block:: python
+
+            import numpy
+
+            x = fluid.layers.data(name='y', shape=[10, 5],
+                             dtype='float32', lod_level=1)
+            pad_value = fluid.layers.assign(input=numpy.array([0]))
+            out = fluid.layers.sequence_pad(x=x, pad_value=pad_value)
+    """
+
+    helper = LayerHelper('sequence_pad', input=x, **locals())
+    dtype = helper.input_dtype()
+    out = helper.create_tmp_variable(dtype)
+    if maxlen is None:
+        maxlen = -1
+    helper.append_op(
+        type='sequence_pad',
+        inputs={'X': x,
+                'PadValue': pad_value},
+        outputs={'Out': out},
+        attrs={'padded_length': maxlen})
+    return out
+
+
 def beam_search(pre_ids,
                 pre_scores,
                 ids,

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

+# Copyright (c) 2018 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.
+
+import unittest
+import numpy as np
+from op_test import OpTest
+
+
+class TestSequencePadOp(OpTest):
+    def set_attr(self):
+        self.x_shape = [12, 4]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [1.0]
+        self.padded_length = -1
+        self.dtype = 'float32'
+
+    def set_data(self):
+        x_data = np.random.uniform(0.1, 0.5, self.x_shape).astype(self.dtype)
+        pad_value_data = np.array(self.pad_value).astype(self.dtype)
+        self.inputs = {
+            'X': (x_data, self.x_len_lod),
+            'PadValue': pad_value_data
+        }
+        self.attrs = {'padded_length': self.padded_length}
+
+    def compute(self):
+        # get padded length
+        padded_length = self.padded_length
+        x_len_lod_0 = self.x_len_lod[0]
+        if padded_length == -1:
+            max_seq_len = 0
+            for l in x_len_lod_0:
+                max_seq_len = max(max_seq_len, l)
+            padded_length = max_seq_len
+
+        # do padding
+        x_data = self.inputs['X'][0]
+        pad_value_data = self.inputs['PadValue']
+        if pad_value_data.shape == (1, ):
+            pad_value_data = np.broadcast_to(
+                pad_value_data, shape=x_data.shape[1:])
+        padded_sequences = []
+        start_idx = 0
+        for l in x_len_lod_0:
+            end_idx = start_idx + l
+            seq = x_data[start_idx:end_idx]
+            to_pad_len = padded_length - l
+            for _ in range(to_pad_len):
+                seq = np.append(seq, pad_value_data[np.newaxis, :], axis=0)
+            padded_sequences.append(seq)
+            start_idx = end_idx
+
+        out_data = np.array(padded_sequences)
+        self.outputs = {'Out': out_data}
+
+    def setUp(self):
+        self.op_type = 'sequence_pad'
+        self.set_attr()
+        self.set_data()
+        self.compute()
+
+    def test_check_output(self):
+        self.check_output()
+
+    def test_check_grad(self):
+        self.check_grad(["X"], "Out")
+
+
+class TestSequencePadOp2(TestSequencePadOp):
+    def set_attr(self):
+        self.x_shape = [12, 4]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [1.0, 2.0, 3.0, 4.0]
+        self.padded_length = -1
+        self.dtype = 'float32'
+
+
+class TestSequencePadOp3(TestSequencePadOp):
+    def set_attr(self):
+        self.x_shape = [12, 4]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [1.0]
+        self.padded_length = 7
+        self.dtype = 'float32'
+
+
+class TestSequencePadOp4(TestSequencePadOp):
+    def set_attr(self):
+        self.x_shape = [12, 4]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [1.0, 2.0, 3.0, 4.0]
+        self.padded_length = 7
+        self.dtype = 'float32'
+
+
+class TestSequencePadOp5(TestSequencePadOp):
+    def set_attr(self):
+        self.x_shape = [12, 2, 2]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [1.0]
+        self.padded_length = -1
+        self.dtype = 'float32'
+
+
+class TestSequencePadOp6(TestSequencePadOp):
+    def set_attr(self):
+        self.x_shape = [12, 2, 2]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [[1.0, 2.0], [3.0, 4.0]]
+        self.padded_length = -1
+        self.dtype = 'float32'
+
+
+class TestSequencePadOp7(TestSequencePadOp):
+    def set_attr(self):
+        self.x_shape = [12, 2, 2]
+        self.x_len_lod = [[2, 3, 4, 3]]
+        self.pad_value = [1.0]
+        self.padded_length = 7
+        self.dtype = 'float32'