common_graph_table.cc

// Copyright (c) 2021 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/distributed/table/common_graph_table.h"
#include <time.h>
#include <algorithm>
#include <chrono>
#include <set>
#include <sstream>
#include "paddle/fluid/distributed/common/utils.h"
#include "paddle/fluid/distributed/table/graph/graph_node.h"
#include "paddle/fluid/framework/generator.h"
#include "paddle/fluid/string/printf.h"
#include "paddle/fluid/string/string_helper.h"

namespace paddle {
namespace distributed {

std::vector<Node *> GraphShard::get_batch(int start, int end, int step) {
  if (start < 0) start = 0;
  std::vector<Node *> res;
  for (int pos = start; pos < std::min(end, (int)bucket.size()); pos += step) {
    res.push_back(bucket[pos]);
  }
  return res;
}

size_t GraphShard::get_size() { return bucket.size(); }

int32_t GraphTable::add_graph_node(std::vector<uint64_t> &id_list,
                                   std::vector<bool> &is_weight_list) {
  size_t node_size = id_list.size();
  std::vector<std::vector<std::pair<uint64_t, bool>>> batch(task_pool_size_);
  for (size_t i = 0; i < node_size; i++) {
    size_t shard_id = id_list[i] % shard_num;
    if (shard_id >= shard_end || shard_id < shard_start) {
      continue;
    }
    batch[get_thread_pool_index(id_list[i])].push_back(
        {id_list[i], i < is_weight_list.size() ? is_weight_list[i] : false});
  }
  std::vector<std::future<int>> tasks;
  for (size_t i = 0; i < batch.size(); ++i) {
    if (!batch[i].size()) continue;
    tasks.push_back(_shards_task_pool[i]->enqueue([&batch, i, this]() -> int {
      for (auto &p : batch[i]) {
        size_t index = p.first % this->shard_num - this->shard_start;
        this->shards[index].add_graph_node(p.first)->build_edges(p.second);
      }
      return 0;
    }));
  }
  for (size_t i = 0; i < tasks.size(); i++) tasks[i].get();
  return 0;
}

int32_t GraphTable::remove_graph_node(std::vector<uint64_t> &id_list) {
  size_t node_size = id_list.size();
  std::vector<std::vector<uint64_t>> batch(task_pool_size_);
  for (size_t i = 0; i < node_size; i++) {
    size_t shard_id = id_list[i] % shard_num;
    if (shard_id >= shard_end || shard_id < shard_start) continue;
    batch[get_thread_pool_index(id_list[i])].push_back(id_list[i]);
  }
  std::vector<std::future<int>> tasks;
  for (size_t i = 0; i < batch.size(); ++i) {
    if (!batch[i].size()) continue;
    tasks.push_back(_shards_task_pool[i]->enqueue([&batch, i, this]() -> int {
      for (auto &p : batch[i]) {
        size_t index = p % this->shard_num - this->shard_start;
        this->shards[index].delete_node(p);
      }
      return 0;
    }));
  }
  for (size_t i = 0; i < tasks.size(); i++) tasks[i].get();
  return 0;
}

void GraphShard::clear() {
  for (size_t i = 0; i < bucket.size(); i++) {
    delete bucket[i];
  }
  bucket.clear();
  node_location.clear();
}

GraphShard::~GraphShard() { clear(); }
void GraphShard::delete_node(uint64_t id) {
  auto iter = node_location.find(id);
  if (iter == node_location.end()) return;
  int pos = iter->second;
  delete bucket[pos];
  if (pos != (int)bucket.size() - 1) {
    bucket[pos] = bucket.back();
    node_location[bucket.back()->get_id()] = pos;
  }
  node_location.erase(id);
  bucket.pop_back();
}
GraphNode *GraphShard::add_graph_node(uint64_t id) {
  if (node_location.find(id) == node_location.end()) {
    node_location[id] = bucket.size();
    bucket.push_back(new GraphNode(id));
  }
  return (GraphNode *)bucket[node_location[id]];
}

FeatureNode *GraphShard::add_feature_node(uint64_t id) {
  if (node_location.find(id) == node_location.end()) {
    node_location[id] = bucket.size();
    bucket.push_back(new FeatureNode(id));
  }
  return (FeatureNode *)bucket[node_location[id]];
}

void GraphShard::add_neighboor(uint64_t id, uint64_t dst_id, float weight) {
  find_node(id)->add_edge(dst_id, weight);
}

Node *GraphShard::find_node(uint64_t id) {
  auto iter = node_location.find(id);
  return iter == node_location.end() ? nullptr : bucket[iter->second];
}

int32_t GraphTable::load(const std::string &path, const std::string &param) {
  bool load_edge = (param[0] == 'e');
  bool load_node = (param[0] == 'n');
  if (load_edge) {
    bool reverse_edge = (param[1] == '<');
    return this->load_edges(path, reverse_edge);
  }
  if (load_node) {
    std::string node_type = param.substr(1);
    return this->load_nodes(path, node_type);
  }
  return 0;
}

int32_t GraphTable::get_nodes_ids_by_ranges(
    std::vector<std::pair<int, int>> ranges, std::vector<uint64_t> &res) {
  int start = 0, end, index = 0, total_size = 0;
  res.clear();
  std::vector<std::future<std::vector<uint64_t>>> tasks;
  for (size_t i = 0; i < shards.size() && index < (int)ranges.size(); i++) {
    end = total_size + shards[i].get_size();
    start = total_size;
    while (start < end && index < ranges.size()) {
      if (ranges[index].second <= start)
        index++;
      else if (ranges[index].first >= end) {
        break;
      } else {
        int first = std::max(ranges[index].first, start);
        int second = std::min(ranges[index].second, end);
        start = second;
        first -= total_size;
        second -= total_size;
        tasks.push_back(_shards_task_pool[i % task_pool_size_]->enqueue(
            [this, first, second, i]() -> std::vector<uint64_t> {
              return shards[i].get_ids_by_range(first, second);
            }));
      }
    }
    total_size += shards[i].get_size();
  }
  for (size_t i = 0; i < tasks.size(); i++) {
    auto vec = tasks[i].get();
    for (auto &id : vec) {
      res.push_back(id);
      std::swap(res[rand() % res.size()], res[(int)res.size() - 1]);
    }
  }
  return 0;
}

int32_t GraphTable::load_nodes(const std::string &path, std::string node_type) {
  auto paths = paddle::string::split_string<std::string>(path, ";");
  int64_t count = 0;
  int64_t valid_count = 0;
  for (auto path : paths) {
    std::ifstream file(path);
    std::string line;
    while (std::getline(file, line)) {
      count++;
      auto values = paddle::string::split_string<std::string>(line, "\t");
      if (values.size() < 2) continue;
      auto id = std::stoull(values[1]);

      size_t shard_id = id % shard_num;
      if (shard_id >= shard_end || shard_id < shard_start) {
        VLOG(4) << "will not load " << id << " from " << path
                << ", please check id distribution";
        continue;
      }

      if (count % 1000000 == 0) {
        VLOG(0) << count << " nodes are loaded from filepath";
      }

      std::string nt = values[0];
      if (nt != node_type) {
        continue;
      }

      size_t index = shard_id - shard_start;

      auto node = shards[index].add_feature_node(id);

      node->set_feature_size(feat_name.size());

      for (size_t slice = 2; slice < values.size(); slice++) {
        auto feat = this->parse_feature(values[slice]);
        if (feat.first >= 0) {
          node->set_feature(feat.first, feat.second);
        } else {
          VLOG(4) << "Node feature:  " << values[slice]
                  << " not in feature_map.";
        }
      }
      valid_count++;
    }
  }

  VLOG(0) << valid_count << "/" << count << " nodes in type " << node_type
          << " are loaded successfully in " << path;
  return 0;
}

int32_t GraphTable::load_edges(const std::string &path, bool reverse_edge) {
  auto paths = paddle::string::split_string<std::string>(path, ";");
  int64_t count = 0;
  std::string sample_type = "random";
  bool is_weighted = false;
  int valid_count = 0;

  for (auto path : paths) {
    std::ifstream file(path);
    std::string line;
    while (std::getline(file, line)) {
      auto values = paddle::string::split_string<std::string>(line, "\t");
      count++;
      if (values.size() < 2) continue;
      auto src_id = std::stoull(values[0]);
      auto dst_id = std::stoull(values[1]);
      if (reverse_edge) {
        std::swap(src_id, dst_id);
      }
      float weight = 1;
      if (values.size() == 3) {
        weight = std::stof(values[2]);
        sample_type = "weighted";
        is_weighted = true;
      }

      size_t src_shard_id = src_id % shard_num;

      if (src_shard_id >= shard_end || src_shard_id < shard_start) {
        VLOG(4) << "will not load " << src_id << " from " << path
                << ", please check id distribution";
        continue;
      }
      if (count % 1000000 == 0) {
        VLOG(0) << count << " edges are loaded from filepath";
      }

      size_t index = src_shard_id - shard_start;
      shards[index].add_graph_node(src_id)->build_edges(is_weighted);
      shards[index].add_neighboor(src_id, dst_id, weight);
      valid_count++;
    }
  }
  VLOG(0) << valid_count << "/" << count << " edges are loaded successfully in "
          << path;

  // Build Sampler j

  for (auto &shard : shards) {
    auto bucket = shard.get_bucket();
    for (size_t i = 0; i < bucket.size(); i++) {
      bucket[i]->build_sampler(sample_type);
    }
  }
  return 0;
}

Node *GraphTable::find_node(uint64_t id) {
  size_t shard_id = id % shard_num;
  if (shard_id >= shard_end || shard_id < shard_start) {
    return nullptr;
  }
  size_t index = shard_id - shard_start;
  Node *node = shards[index].find_node(id);
  return node;
}
uint32_t GraphTable::get_thread_pool_index(uint64_t node_id) {
  return node_id % shard_num % shard_num_per_server % task_pool_size_;
}

uint32_t GraphTable::get_thread_pool_index_by_shard_index(
    uint64_t shard_index) {
  return shard_index % shard_num_per_server % task_pool_size_;
}

int32_t GraphTable::clear_nodes() {
  std::vector<std::future<int>> tasks;
  for (size_t i = 0; i < shards.size(); i++) {
    tasks.push_back(
        _shards_task_pool[get_thread_pool_index_by_shard_index(i)]->enqueue(
            [this, i]() -> int {
              this->shards[i].clear();
              return 0;
            }));
  }
  for (size_t i = 0; i < tasks.size(); i++) tasks[i].get();
  return 0;
}

int32_t GraphTable::random_sample_nodes(int sample_size,
                                        std::unique_ptr<char[]> &buffer,
                                        int &actual_size) {
  int total_size = 0;
  for (int i = 0; i < shards.size(); i++) {
    total_size += shards[i].get_size();
  }
  if (sample_size > total_size) sample_size = total_size;
  int range_num = random_sample_nodes_ranges;
  if (range_num > sample_size) range_num = sample_size;
  if (sample_size == 0 || range_num == 0) return 0;
  std::vector<int> ranges_len, ranges_pos;
  int remain = sample_size, last_pos = -1, num;
  std::set<int> separator_set;
  for (int i = 0; i < range_num - 1; i++) {
    while (separator_set.find(num = rand() % (sample_size - 1)) !=
           separator_set.end())
      ;
    separator_set.insert(num);
  }
  for (auto p : separator_set) {
    ranges_len.push_back(p - last_pos);
    last_pos = p;
  }
  ranges_len.push_back(sample_size - 1 - last_pos);
  remain = total_size - sample_size + range_num;
  separator_set.clear();
  for (int i = 0; i < range_num; i++) {
    while (separator_set.find(num = rand() % remain) != separator_set.end())
      ;
    separator_set.insert(num);
  }
  int used = 0, index = 0;
  last_pos = -1;
  for (auto p : separator_set) {
    used += p - last_pos - 1;
    last_pos = p;
    ranges_pos.push_back(used);
    used += ranges_len[index++];
  }
  std::vector<std::pair<int, int>> first_half, second_half;
  int start_index = rand() % total_size;
  for (size_t i = 0; i < ranges_len.size() && i < ranges_pos.size(); i++) {
    if (ranges_pos[i] + ranges_len[i] - 1 + start_index < total_size)
      first_half.push_back({ranges_pos[i] + start_index,
                            ranges_pos[i] + ranges_len[i] + start_index});
    else if (ranges_pos[i] + start_index >= total_size) {
      second_half.push_back(
          {ranges_pos[i] + start_index - total_size,
           ranges_pos[i] + ranges_len[i] + start_index - total_size});
    } else {
      first_half.push_back({ranges_pos[i] + start_index, total_size});
      second_half.push_back(
          {0, ranges_pos[i] + ranges_len[i] + start_index - total_size});
    }
  }
  for (auto &pair : first_half) second_half.push_back(pair);
  std::vector<uint64_t> res;
  get_nodes_ids_by_ranges(second_half, res);
  actual_size = res.size() * sizeof(uint64_t);
  buffer.reset(new char[actual_size]);
  char *pointer = buffer.get();
  memcpy(pointer, res.data(), actual_size);
  return 0;
}
int32_t GraphTable::random_sample_neighboors(
    uint64_t *node_ids, int sample_size,
    std::vector<std::shared_ptr<char>> &buffers,
    std::vector<int> &actual_sizes) {
  size_t node_num = buffers.size();
  std::function<void(char *)> char_del = [](char *c) { delete[] c; };
  std::vector<std::future<int>> tasks;
  if (use_cache) {
    std::vector<std::vector<uint32_t>> seq_id(shard_end - shard_start);
    std::vector<std::vector<SampleKey>> id_list(shard_end - shard_start);
    size_t index;
    for (size_t idx = 0; idx < node_num; ++idx) {
      index = get_thread_pool_index(node_ids[idx]);
      seq_id[index].emplace_back(idx);
      id_list[index].emplace_back(node_ids[idx], sample_size);
    }
    for (int i = 0; i < seq_id.size(); i++) {
      if (seq_id[i].size() == 0) continue;
      tasks.push_back(_shards_task_pool[i]->enqueue([&, i, this]() -> int {
        uint64_t node_id;
        std::vector<std::pair<SampleKey, SampleResult>> r;
        auto response =
            scaled_lru->query(i, id_list[i].data(), id_list[i].size(), r);
        int index = 0;
        uint32_t idx;
        std::vector<SampleResult> sample_res;
        std::vector<SampleKey> sample_keys;
        auto &rng = _shards_task_rng_pool[i];
        for (size_t k = 0; k < id_list[i].size(); k++) {
          if (index < r.size() &&
              r[index].first.node_key == id_list[i][k].node_key) {
            idx = seq_id[i][k];
            actual_sizes[idx] = r[index].second.actual_size;
            buffers[idx] = r[index].second.buffer;
            index++;
          } else {
            node_id = id_list[i][k].node_key;
            Node *node = find_node(node_id);
            idx = seq_id[i][k];
            int &actual_size = actual_sizes[idx];
            if (node == nullptr) {
              actual_size = 0;
              continue;
            }
            std::shared_ptr<char> &buffer = buffers[idx];
            std::vector<int> res = node->sample_k(sample_size, rng);
            actual_size = res.size() * (Node::id_size + Node::weight_size);
            int offset = 0;
            uint64_t id;
            float weight;
            char *buffer_addr = new char[actual_size];
            if (response == LRUResponse::ok) {
              sample_keys.emplace_back(node_id, sample_size);
              sample_res.emplace_back(actual_size, buffer_addr);
              buffer = sample_res.back().buffer;
            } else {
              buffer.reset(buffer_addr, char_del);
            }
            for (int &x : res) {
              id = node->get_neighbor_id(x);
              weight = node->get_neighbor_weight(x);
              memcpy(buffer_addr + offset, &id, Node::id_size);
              offset += Node::id_size;
              memcpy(buffer_addr + offset, &weight, Node::weight_size);
              offset += Node::weight_size;
            }
          }
        }
        if (sample_res.size()) {
          scaled_lru->insert(i, sample_keys.data(), sample_res.data(),
                             sample_keys.size());
        }
        return 0;
      }));
    }
    for (auto &t : tasks) {
      t.get();
    }
    return 0;
  }
  for (size_t idx = 0; idx < node_num; ++idx) {
    uint64_t &node_id = node_ids[idx];
    std::shared_ptr<char> &buffer = buffers[idx];
    int &actual_size = actual_sizes[idx];

    int thread_pool_index = get_thread_pool_index(node_id);
    auto rng = _shards_task_rng_pool[thread_pool_index];

    tasks.push_back(_shards_task_pool[thread_pool_index]->enqueue([&]() -> int {
      Node *node = find_node(node_id);

      if (node == nullptr) {
        actual_size = 0;
        return 0;
      }
      std::vector<int> res = node->sample_k(sample_size, rng);
      actual_size = res.size() * (Node::id_size + Node::weight_size);
      int offset = 0;
      uint64_t id;
      float weight;
      char *buffer_addr = new char[actual_size];
      buffer.reset(buffer_addr, char_del);
      for (int &x : res) {
        id = node->get_neighbor_id(x);
        weight = node->get_neighbor_weight(x);
        memcpy(buffer_addr + offset, &id, Node::id_size);
        offset += Node::id_size;
        memcpy(buffer_addr + offset, &weight, Node::weight_size);
        offset += Node::weight_size;
      }
      return 0;
    }));
  }
  for (size_t idx = 0; idx < node_num; ++idx) {
    tasks[idx].get();
  }
  return 0;
}

int32_t GraphTable::get_node_feat(const std::vector<uint64_t> &node_ids,
                                  const std::vector<std::string> &feature_names,
                                  std::vector<std::vector<std::string>> &res) {
  size_t node_num = node_ids.size();
  std::vector<std::future<int>> tasks;
  for (size_t idx = 0; idx < node_num; ++idx) {
    uint64_t node_id = node_ids[idx];
    tasks.push_back(_shards_task_pool[get_thread_pool_index(node_id)]->enqueue(
        [&, idx, node_id]() -> int {
          Node *node = find_node(node_id);

          if (node == nullptr) {
            return 0;
          }
          for (int feat_idx = 0; feat_idx < feature_names.size(); ++feat_idx) {
            const std::string &feature_name = feature_names[feat_idx];
            if (feat_id_map.find(feature_name) != feat_id_map.end()) {
              // res[feat_idx][idx] =
              // node->get_feature(feat_id_map[feature_name]);
              auto feat = node->get_feature(feat_id_map[feature_name]);
              res[feat_idx][idx] = feat;
            }
          }
          return 0;
        }));
  }
  for (size_t idx = 0; idx < node_num; ++idx) {
    tasks[idx].get();
  }
  return 0;
}

int32_t GraphTable::set_node_feat(
    const std::vector<uint64_t> &node_ids,
    const std::vector<std::string> &feature_names,
    const std::vector<std::vector<std::string>> &res) {
  size_t node_num = node_ids.size();
  std::vector<std::future<int>> tasks;
  for (size_t idx = 0; idx < node_num; ++idx) {
    uint64_t node_id = node_ids[idx];
    tasks.push_back(_shards_task_pool[get_thread_pool_index(node_id)]->enqueue(
        [&, idx, node_id]() -> int {
          size_t index = node_id % this->shard_num - this->shard_start;
          auto node = shards[index].add_feature_node(node_id);
          node->set_feature_size(this->feat_name.size());
          for (int feat_idx = 0; feat_idx < feature_names.size(); ++feat_idx) {
            const std::string &feature_name = feature_names[feat_idx];
            if (feat_id_map.find(feature_name) != feat_id_map.end()) {
              node->set_feature(feat_id_map[feature_name], res[feat_idx][idx]);
            }
          }
          return 0;
        }));
  }
  for (size_t idx = 0; idx < node_num; ++idx) {
    tasks[idx].get();
  }
  return 0;
}

std::pair<int32_t, std::string> GraphTable::parse_feature(
    std::string feat_str) {
  // Return (feat_id, btyes) if name are in this->feat_name, else return (-1,
  // "")
  auto fields = paddle::string::split_string<std::string>(feat_str, " ");
  if (this->feat_id_map.count(fields[0])) {
    int32_t id = this->feat_id_map[fields[0]];
    std::string dtype = this->feat_dtype[id];
    std::vector<std::string> values(fields.begin() + 1, fields.end());
    if (dtype == "feasign") {
      return std::make_pair<int32_t, std::string>(
          int32_t(id), paddle::string::join_strings(values, ' '));
    } else if (dtype == "string") {
      return std::make_pair<int32_t, std::string>(
          int32_t(id), paddle::string::join_strings(values, ' '));
    } else if (dtype == "float32") {
      return std::make_pair<int32_t, std::string>(
          int32_t(id), FeatureNode::parse_value_to_bytes<float>(values));
    } else if (dtype == "float64") {
      return std::make_pair<int32_t, std::string>(
          int32_t(id), FeatureNode::parse_value_to_bytes<double>(values));
    } else if (dtype == "int32") {
      return std::make_pair<int32_t, std::string>(
          int32_t(id), FeatureNode::parse_value_to_bytes<int32_t>(values));
    } else if (dtype == "int64") {
      return std::make_pair<int32_t, std::string>(
          int32_t(id), FeatureNode::parse_value_to_bytes<int64_t>(values));
    }
  }
  return std::make_pair<int32_t, std::string>(-1, "");
}

int32_t GraphTable::pull_graph_list(int start, int total_size,
                                    std::unique_ptr<char[]> &buffer,
                                    int &actual_size, bool need_feature,
                                    int step) {
  if (start < 0) start = 0;
  int size = 0, cur_size;
  std::vector<std::future<std::vector<Node *>>> tasks;
  for (size_t i = 0; i < shards.size() && total_size > 0; i++) {
    cur_size = shards[i].get_size();
    if (size + cur_size <= start) {
      size += cur_size;
      continue;
    }
    int count = std::min(1 + (size + cur_size - start - 1) / step, total_size);
    int end = start + (count - 1) * step + 1;
    tasks.push_back(_shards_task_pool[i % task_pool_size_]->enqueue(
        [this, i, start, end, step, size]() -> std::vector<Node *> {
          return this->shards[i].get_batch(start - size, end - size, step);
        }));
    start += count * step;
    total_size -= count;
    size += cur_size;
  }
  for (size_t i = 0; i < tasks.size(); ++i) {
    tasks[i].wait();
  }
  size = 0;
  std::vector<std::vector<Node *>> res;
  for (size_t i = 0; i < tasks.size(); i++) {
    res.push_back(tasks[i].get());
    for (size_t j = 0; j < res.back().size(); j++) {
      size += res.back()[j]->get_size(need_feature);
    }
  }
  char *buffer_addr = new char[size];
  buffer.reset(buffer_addr);
  int index = 0;
  for (size_t i = 0; i < res.size(); i++) {
    for (size_t j = 0; j < res[i].size(); j++) {
      res[i][j]->to_buffer(buffer_addr + index, need_feature);
      index += res[i][j]->get_size(need_feature);
    }
  }
  actual_size = size;
  return 0;
}

int32_t GraphTable::get_server_index_by_id(uint64_t id) {
  return id % shard_num / shard_num_per_server;
}

int32_t GraphTable::initialize() {
  _shards_task_pool.resize(task_pool_size_);
  for (size_t i = 0; i < _shards_task_pool.size(); ++i) {
    _shards_task_pool[i].reset(new ::ThreadPool(1));
    _shards_task_rng_pool.push_back(paddle::framework::GetCPURandomEngine(0));
  }
  server_num = _shard_num;
  // VLOG(0) << "in init graph table server num = " << server_num;
  /*
  _shard_num is actually server number here
  when a server initialize its tables, it sets tables' _shard_num to server_num,
  and _shard_idx to server
  rank
  */
  auto common = _config.common();

  this->table_name = common.table_name();
  this->table_type = common.name();
  VLOG(0) << " init graph table type " << this->table_type << " table name "
          << this->table_name;
  int feat_conf_size = static_cast<int>(common.attributes().size());
  for (int i = 0; i < feat_conf_size; i++) {
    auto &f_name = common.attributes()[i];
    auto &f_shape = common.dims()[i];
    auto &f_dtype = common.params()[i];
    this->feat_name.push_back(f_name);
    this->feat_shape.push_back(f_shape);
    this->feat_dtype.push_back(f_dtype);
    this->feat_id_map[f_name] = i;
    VLOG(0) << "init graph table feat conf name:" << f_name
            << " shape:" << f_shape << " dtype:" << f_dtype;
  }

  shard_num = _config.shard_num();
  VLOG(0) << "in init graph table shard num = " << shard_num << " shard_idx"
          << _shard_idx;
  shard_num_per_server = sparse_local_shard_num(shard_num, server_num);
  shard_start = _shard_idx * shard_num_per_server;
  shard_end = shard_start + shard_num_per_server;
  VLOG(0) << "in init graph table shard idx = " << _shard_idx << " shard_start "
          << shard_start << " shard_end " << shard_end;
  shards = std::vector<GraphShard>(shard_num_per_server, GraphShard(shard_num));
  return 0;
}
}  // namespace distributed
};  // namespace paddle