PyText Notes

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Pytext

• git : https://github.com/facebookresearch/pytext
• paper : PyText-A-seamless-path-from-NLP-research-to-production-using-PyTorch3.pdf
• blog: https://code.fb.com/ai-research/pytext-open-source-nlp-framework/

Notes

what

PyText is a modeling framework that helps researchers and engineers build end-to-end pipelines for training or inference.

goal

PyText, built on PyTorch 1.0 6, is designed to achieve the following:

1. Make experimentation with new modeling ideas as easy and as fast as possible.
2. Make it easy to use pre-built models on new data with minimal extra work.
3. Define a clear workflow for both researchers and en- gineers to build, evaluate, and ship their models to production with minimal overhead.
4. Ensure high performance (low latency and high throughput) on deployed models at inference.

design

• Everything in PyText is a component.
• Task: combines various componentsrequired for a training or inference task into a pipeline.
  there is a sample config for a document classification task. It can be configured as a JSON file that defines the parameters of all the children components

{
    "config":{
        "task":{
            "DocClassificationTask":{
                "data_handler":{
                    "columns_to_read":[
                        "doc_label",
                        "text"
                    ],
                    "shuffle":true
                },
                "model":{
                    "representation":{
                        "BiLSTMPooling":{
                            "pooling":{
                                "SelfAttention":{
                                    "attn_dimension":128,
                                    "dropout":0.4
                                }
                            },
                            "bidirectional":true,
                            "dropout":0.4,
                            "lstm":{
                                "lstm_dim":200,
                                "num_layers":2
                            }
                        }
                    },
                    "output_config":{
                        "loss":{
                            "CrossEntropyLoss":{

                            }
                        }
                    },
                    "decoder":{
                        "hidden_dims":[
                            128
                        ]
                    }
                },
                "features":{
                    "word_feat":{
                        "embed_dim":200,
                        "pretrained_embeddings_path":"/tmp/embeds",
                        "vocab_size":250000,
                        "vocab_from_train_data":true
                    }
                },
                "trainer":{
                    "random_seed":0,
                    "epochs":15,
                    "early_stop_after":0,
                    "log_interval":1,
                    "eval_interval":1,
                    "max_clip_norm":5
                },
                "optimizer":{
                    "type":"adam",
                    "lr":0.001,
                    "weight_decay":0.00001
                },
                "metric_reporter":{
                    "output_path":"/tmp/test_out.txt"
                },
                "exporter":{

                }
            }
        }
    }
}

features

• It provides ways to customize handling of raw data, reporting of metrics, training methodologyand exporting of trained models.
• PyText users are free to implement one or more of these components and can expect the entire pipeline to work out of the box.
• A number of default pipelines are implemented for popular tasks which can be used as-is.

workflow

1. Implement the model in PyText, and make sure offline metrics on the test set look good.
2. Publish the model to the bundled PyTorch-based infer- ence service, and do a real-time small scale evaluation on a live traffic sample.
3. Export it automatically to a Caffe2 net. In some cases, e.g. when using complex control flow logic and custom data-structures, this might not yet be supported via PyTorch 1.0.
4. If the procedure in 3 isn’t supported, use the Py- Torch C++ API9 to rewrite the model (only the torch.nn.Module10 subclass) and wrap it in a Caffe2 operator.
5. Publish the model to the production-grade Caffe2 pre- diction service and start serving live traffic

Challenges

• Data pre-processing

  This library, a featurization library, preprocesses the raw input by performing tasks like

  • Text tokenization and normalization
  • Mapping characters to IDs for character-based models
  • Perform token alignments for gazetteer features

  • Training: raw data -> Data Handler( invoke a feature lib) -> Trainer -> Exporter
  • Inference: raw data -> Data Processor(invoke the same feature lib) -> Predictor(holding a model exported by a exporter) -> Predictions

• Vocabulary management

Future Work

• Modeling Capabilities
• Performance Benchmarks and Improvements
  • Training speed
  • Inference speed
• Model Interpretability
• Model Robustness
• Mobile Deployment Support

Other Intro Doc

• https://www.jiqizhixin.com/articles/2018-12-15-3?from=synced&keyword=pytext
• https://blog.youkuaiyun.com/sinat_33455447/article/details/85064284