message: Update README.md, add more details in Benchmark Session
diff: @@ -132,7 +132,7 @@ $ doxygen
  ```
  ## Benchmark ##
  -Random data can be generated according to your JSON network config file (`your_config.json`) with `data_generator` for easy benchmark. Usage:
  +Random data set can be generated according to your JSON network config file (`your_config.json`) with `data_generator` for easy benchmark. Usage:
  ```shell
  $ ./data_generator your_config.json data_folder vocabulary_size max_nnz [option:#files] [option:#samples per file]
  $ ./huge_ctr --train your_config.json
  @@ -140,7 +140,9 @@ $ ./huge_ctr --train your_config.json
  Arguments:
  * `data_folder`: You have to specify the folder for the generated data
  * `vocabulary_size`: Vocabulary size of your target data set
  -* `max_nnz`: [1,max_nnz] values will be generated for each feature (slot) in the data set.
  +* `max_nnz`: [1,max_nnz] values will be generated for each feature (slot) in the data set. Note that max_nnz * #slot should be less than the `max_feature_num` in your data layer.
  +* `#files`: number of data file will be generated.
  +* `#samples per file`: number of samples per file.
  ## File Format ##
  