Add Hyperopt example for BERT classifier (#186)

* Add Hyperopt example for BERT classifier

* Address review comments

* Address review comments

* Remove hyperparams from config_downstream

* Add URL for Batch object. Removed unused args

* Add docs for Batch and FieldBatch

* Address review comments

docs/code/data.rst

@@ -130,6 +130,11 @@ Data Loaders
 Data Iterators
 ===============
 
+:hidden:`Batch`
+~~~~~~~~~~~~~~~~~~~~~~~~
+.. autoclass:: texar.torch.data.Batch
+    :members:
+
 :hidden:`DataIterator`
 ~~~~~~~~~~~~~~~~~~~~~~~~
 .. autoclass:: texar.torch.data.DataIterator

examples/bert/README.md

@@ -15,6 +15,8 @@ To summarize, this example showcases:
 * Building and fine-tuning on downstream tasks
 * Use of Texar `RecordData` module for data loading and processing
 * Use of Texar `Executor` module for simplified training loops and TensorBoard visualization
+* Use of [Hyperopt]((https://github.com/hyperopt/hyperopt)) library to tune hyperparameters with 
+`Executor` module
 
 Future work:
 
@@ -178,3 +180,25 @@ tensorboard --logdir runs/
 ```
 
 ![Visualizing loss/accuarcy on Tensorboard](tbx.png)
+
+## Hyperparameter tuning with Executor
+
+To run this example, please install `hyperopt` by issuing the following command
+
+```commandline
+pip install hyperopt
+```
+
+`bert_with_hypertuning_main.py` shows an example of how to tune hyperparameters with Executor using `hyperopt`. 
+To run this example, run the following command
+
+```commandline
+python bert_with_hypertuning_main.py
+```
+
+In this simple example, the hyperparameters to be tuned are provided as a `dict` in
+`bert_hypertuning_config_classifier.py` which are fed into `objective_func()` . We use `TPE`
+(Tree-structured Parzen Estimator) algorithm for tuning the hyperparams (provided in `hyperopt`
+library). The example runs for 3 trials to find the best hyperparam settings. The final model is
+saved in `output_dir` provided by the user. More  information about the libary can be 
+found at [Hyperopt](https://github.com/hyperopt/hyperopt)

examples/bert/bert_classifier_main.py

@@ -56,7 +56,7 @@
 config_downstream = importlib.import_module(args.config_downstream)
 config_downstream = {
     k: v for k, v in config_downstream.__dict__.items()
-    if not k.startswith('__')}
+    if not k.startswith('__') and k != "hyperparams"}
 
 device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
 

examples/bert/bert_classifier_using_executor_main.py

@@ -65,7 +65,7 @@
 config_downstream = importlib.import_module(args.config_downstream)
 config_downstream = {
     k: v for k, v in config_downstream.__dict__.items()
-    if not k.startswith('__')}
+    if not k.startswith('__') and k != "hyperparams"}
 
 device = torch.device("cuda" if torch.cuda.is_available() else "cpu")