message: #threads should be the same as #chunk
diff: @@ -87,7 +87,7 @@ class DataReader {
  private:
  std::shared_ptr<FileList> file_list_; /**< file list of data set */
  const int NumChunks{31}; /**< NumChunks will be used in HeapEx*/
  - const int NumThreads{20}; /**< number of threads for data reading */
  + const int NumThreads{31}; /**< number of threads for data reading */
  std::shared_ptr<HeapEx<CSRChunk<TypeKey>>> csr_heap_; /**< heap to cache the data set */
  std::vector<std::shared_ptr<DataReaderWorker<TypeKey>>>
  @@ -182,7 +182,7 @@ class DataReader {
  DataReader(const std::string& file_list_name, int batchsize, int label_dim, int dense_dim,
  Check_t check_type, std::vector<DataReaderSparseParam>& params,
  const std::shared_ptr<GPUResourceGroup>& gpu_resource_group,
  - int num_chunks = 31, int num_threads = 20);
  + int num_chunks = 31, int num_threads = 31);
  /**
  * process of evaluation will call this to create a new object of DataReader
  