Hybrid conformer export (#6983) (#6995)

* Implemented generic kv-pair setting of export_config from args



* Hybrid conformer export



* Hybrid decoder export



* Cleanup



* Changed from **kwargs



* Docstring



* Docs added



* Stringify args



* Added docs for ASR export configs



* lowercase ctc



---------

Signed-off-by: Boris Fomitchev <bfomitchev@nvidia.com>
Co-authored-by: Boris Fomitchev <borisfom@users.noreply.github.com>

docs/source/asr/models.rst

@@ -215,6 +215,11 @@ It is recommended to train a model in streaming model with limited context for t
 
 You may find FastConformer variants of cache-aware streaming models under ``<NeMo_git_root>/examples/asr/conf/fastconformer/``.
 
+Note cache-aware streaming models are being exported without caching support by default.
+To include caching support, `model.set_export_config({'cache_support' : 'True'})` should be called before export.
+Or, if ``<NeMo_git_root>/scripts/export.py`` is being used:
+`python export.py cache_aware_conformer.nemo cache_aware_conformer.onnx --config cache_support=True`
+
 .. _LSTM-Transducer_model:
 
 LSTM-Transducer
@@ -291,6 +296,11 @@ Similar example configs for FastConformer variants of Hybrid models can be found
 ``<NeMo_git_root>/examples/asr/conf/fastconformer/hybrid_transducer_ctc/``
 ``<NeMo_git_root>/examples/asr/conf/fastconformer/hybrid_cache_aware_streaming/``
 
+Note Hybrid models are being exported as RNNT (encoder and decoder+joint parts) by default.
+To export as CTC (single encoder+decoder graph), `model.set_export_config({'decoder_type' : 'ctc'})` should be called before export.
+Or, if ``<NeMo_git_root>/scripts/export.py`` is being used:
+`python export.py hybrid_transducer.nemo hybrid_transducer.onnx --config decoder_type=ctc`
+
 .. _Conformer-HAT_model:
 
 Conformer-HAT (Hybrid Autoregressive Transducer)

docs/source/core/export.rst

@@ -177,6 +177,37 @@ Another common requirement for models that are being exported is to run certain
     # call base method for common set of modifications
 	Exportable._prepare_for_export(self, **kwargs)
 
+Some models that require control flow, need to be exported in multiple parts. Typical examples are RNNT nets.
+To facilitate that, the hooks below are provided. To export, for example, 'encoder' and 'decoder' subnets of the model, overload list_export_subnets to return ['encoder', 'decoder'].
+
+.. code-block:: Python
+
+    def get_export_subnet(self, subnet=None):
+        """
+        Returns Exportable subnet model/module to export 
+        """
+
+
+    def list_export_subnets(self):
+        """
+        Returns default set of subnet names exported for this model
+        First goes the one receiving input (input_example)
+        """
+
+Some nertworks may be exported differently according to user-settable options (like ragged batch support for TTS or cache support for ASR). To facilitate that - `set_export_config()` method is provided by Exportable to set key/value pairs to predefined model.export_config dictionary, to be used during the export:
+
+.. code-block:: Python	
+    def set_export_config(self, args):
+        """
+        Sets/updates export_config dictionary
+        """
+Also, if an action hook on setting config is desired, this method may be overloaded by `Exportable` descendants to include one.
+An example can be found in ``<NeMo_git_root>/nemo/collections/asr/models/rnnt_models.py``.
+
+Here is example on now `set_export_config()` call is being tied to command line arguments in ``<NeMo_git_root>/scripts/export.py`` :
+
+.. code-block:: Python
+    python scripts/export.py  hybrid_conformer.nemo hybrid_conformer.onnx --config decoder_type=ctc
 
 Exportable Model Code
 ~~~~~~~~~~~~~~~~~~~~~

nemo/collections/asr/models/asr_model.py

@@ -215,3 +215,11 @@ def disabled_deployment_input_names(self):
     @property
     def disabled_deployment_output_names(self):
         return self.encoder.disabled_deployment_output_names
+
+    def set_export_config(self, args):
+        if 'cache_support' in args:
+            enable = bool(args['cache_support'])
+            self.encoder.export_cache_support = enable
+            logging.info(f"Caching support enabled: {enable}")
+            self.encoder.setup_streaming_params()
+        super().set_export_config(args)

nemo/collections/asr/models/hybrid_rnnt_ctc_models.py

@@ -645,6 +645,20 @@ def multi_test_epoch_end(self, outputs, dataloader_idx: int = 0):
         self.finalize_interctc_metrics(metrics, outputs, prefix="test_")
         return metrics
 
+    # EncDecRNNTModel is exported in 2 parts
+    def list_export_subnets(self):
+        if self.cur_decoder == 'rnnt':
+            return ['encoder', 'decoder_joint']
+        else:
+            return ['self']
+
+    @property
+    def output_module(self):
+        if self.cur_decoder == 'rnnt':
+            return self.decoder
+        else:
+            return self.ctc_decoder
+
     @classmethod
     def list_available_models(cls) -> Optional[PretrainedModelInfo]:
         """

nemo/collections/asr/models/rnnt_models.py

@@ -28,7 +28,7 @@
 from nemo.collections.asr.data.audio_to_text_dali import AudioToCharDALIDataset, DALIOutputs
 from nemo.collections.asr.losses.rnnt import RNNTLoss, resolve_rnnt_default_loss_name
 from nemo.collections.asr.metrics.rnnt_wer import RNNTWER, RNNTDecoding, RNNTDecodingConfig
-from nemo.collections.asr.models.asr_model import ASRModel
+from nemo.collections.asr.models.asr_model import ASRModel, ExportableEncDecModel
 from nemo.collections.asr.modules.rnnt import RNNTDecoderJoint
 from nemo.collections.asr.parts.mixins import ASRModuleMixin
 from nemo.collections.asr.parts.utils.audio_utils import ChannelSelectorType
@@ -39,7 +39,7 @@
 from nemo.utils import logging
 
 
-class EncDecRNNTModel(ASRModel, ASRModuleMixin, Exportable):
+class EncDecRNNTModel(ASRModel, ASRModuleMixin, ExportableEncDecModel):
     """Base class for encoder decoder RNNT-based models."""
 
     def __init__(self, cfg: DictConfig, trainer: Trainer = None):
@@ -960,6 +960,14 @@ def list_export_subnets(self):
     def decoder_joint(self):
         return RNNTDecoderJoint(self.decoder, self.joint)
 
+    def set_export_config(self, args):
+        if 'decoder_type' in args:
+            if hasattr(self, 'change_decoding_strategy'):
+                self.change_decoding_strategy(decoder_type=args['decoder_type'])
+            else:
+                raise Exception("Model does not have decoder type option")
+        super().set_export_config(args)
+
     @classmethod
     def list_available_models(cls) -> List[PretrainedModelInfo]:
         """

nemo/core/classes/exportable.py

@@ -302,3 +302,17 @@ def list_export_subnets(self):
         First goes the one receiving input (input_example)
         """
         return ['self']
+
+    def get_export_config(self):
+        """
+        Returns export_config dictionary
+        """
+        return getattr(self, 'export_config', {})
+
+    def set_export_config(self, args):
+        """
+        Sets/updates export_config dictionary
+        """
+        ex_config = self.get_export_config()
+        ex_config.update(args)
+        self.export_config = ex_config

scripts/export.py

@@ -62,6 +62,15 @@ def get_args(argv):
     )
     parser.add_argument("--device", default="cuda", help="Device to export for")
     parser.add_argument("--check-tolerance", type=float, default=0.01, help="tolerance for verification")
+    parser.add_argument(
+        "--config",
+        metavar="KEY=VALUE",
+        nargs='+',
+        help="Set a number of key-value pairs to model.export_config dictionary "
+        "(do not put spaces before or after the = sign). "
+        "Note that values are always treated as strings.",
+    )
+
     args = parser.parse_args(argv)
     return args
 
@@ -130,10 +139,12 @@ def nemo_export(argv):
         in_args["max_dim"] = args.max_dim
         max_dim = args.max_dim
 
-    if args.cache_support and hasattr(model, "encoder") and hasattr(model.encoder, "export_cache_support"):
-        model.encoder.export_cache_support = True
-        logging.info("Caching support is enabled.")
-        model.encoder.setup_streaming_params()
+    if args.cache_support:
+        model.set_export_config({"cache_support": "True"})
+
+    if args.config:
+        kv = dict(map(lambda s: s.split('='), args.config))
+        model.set_export_config(kv)
 
     autocast = nullcontext
     if args.autocast: