Cadence - Add RNNT joiner from torchaudio (pytorch#3920)

Summary:
Pull Request resolved: pytorch#3920

As titled.

Reviewed By: tarun292

Differential Revision: D58271588

fbshipit-source-id: e1e1d33a5a28ec2c0147b79b6e48cf59bdd01b7e

examples/cadence/models/rnnt_joiner.py

@@ -0,0 +1,65 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+# Example script for exporting simple models to flatbuffer
+
+import logging
+
+import torch
+
+from executorch.backends.cadence.aot.ops_registrations import *  # noqa
+
+from typing import Tuple
+
+from executorch.backends.cadence.aot.export_example import export_model
+
+
+FORMAT = "[%(levelname)s %(asctime)s %(filename)s:%(lineno)s] %(message)s"
+logging.basicConfig(level=logging.INFO, format=FORMAT)
+
+
+if __name__ == "__main__":
+
+    class Joiner(torch.nn.Module):
+        def __init__(
+            self, input_dim: int, output_dim: int, activation: str = "relu"
+        ) -> None:
+            super().__init__()
+            self.linear = torch.nn.Linear(input_dim, output_dim, bias=True)
+            if activation == "relu":
+                # pyre-fixme[4]: Attribute must be annotated.
+                self.activation = torch.nn.ReLU()
+            elif activation == "tanh":
+                self.activation = torch.nn.Tanh()
+            else:
+                raise ValueError(f"Unsupported activation {activation}")
+
+        def forward(
+            self,
+            source_encodings: torch.Tensor,
+            target_encodings: torch.Tensor,
+        ) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
+            joint_encodings = (
+                source_encodings.unsqueeze(2).contiguous()
+                + target_encodings.unsqueeze(1).contiguous()
+            )
+            activation_out = self.activation(joint_encodings)
+            output = self.linear(activation_out)
+            return output
+
+    # Joiner
+    model = Joiner(256, 128)
+
+    # Get dummy joiner inputs
+    source_encodings = torch.randn(1, 25, 256)
+    target_encodings = torch.randn(1, 10, 256)
+
+    example_inputs = (
+        source_encodings,
+        target_encodings,
+    )
+
+    export_model(model, example_inputs)