add smooth-regularized CTC

egs/librispeech/ASR/zipformer/model.py

@@ -16,11 +16,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Optional, Tuple
+from typing import List, Optional, Tuple
 
 import k2
 import torch
 import torch.nn as nn
+import torch.nn.functional as F
 from encoder_interface import EncoderInterface
 from scaling import ScaledLinear
 
@@ -111,9 +112,8 @@ def __init__(
         if use_ctc:
             # Modules for CTC head
             self.ctc_output = nn.Sequential(
-                nn.Dropout(p=0.1),
+                nn.Dropout(p=0.1),  # TODO: test removing this
                 nn.Linear(encoder_dim, vocab_size),
-                nn.LogSoftmax(dim=-1),
             )
 
         self.use_attention_decoder = use_attention_decoder
@@ -159,71 +159,82 @@ def forward_ctc(
         encoder_out_lens: torch.Tensor,
         targets: torch.Tensor,
         target_lengths: torch.Tensor,
-    ) -> torch.Tensor:
-        """Compute CTC loss.
-        Args:
-          encoder_out:
-            Encoder output, of shape (N, T, C).
-          encoder_out_lens:
-            Encoder output lengths, of shape (N,).
-          targets:
-            Target Tensor of shape (sum(target_lengths)). The targets are assumed
-            to be un-padded and concatenated within 1 dimension.
-        """
-        # Compute CTC log-prob
-        ctc_output = self.ctc_output(encoder_out)  # (N, T, C)
-
-        ctc_loss = torch.nn.functional.ctc_loss(
-            log_probs=ctc_output.permute(1, 0, 2),  # (T, N, C)
-            targets=targets.cpu(),
-            input_lengths=encoder_out_lens.cpu(),
-            target_lengths=target_lengths.cpu(),
-            reduction="sum",
-        )
-        return ctc_loss
-
-    def forward_cr_ctc(
-        self,
-        encoder_out: torch.Tensor,
-        encoder_out_lens: torch.Tensor,
-        targets: torch.Tensor,
-        target_lengths: torch.Tensor,
+        use_consistency_reg: bool = False,
+        use_smooth_reg: bool = False,
+        smooth_kernel: List[float] = [0.25, 0.5, 0.25],
+        eps: float = 1e-6,
     ) -> Tuple[torch.Tensor, torch.Tensor]:
         """Compute CTC loss with consistency regularization loss.
         Args:
           encoder_out:
-            Encoder output, of shape (2 * N, T, C).
+            Encoder output, of shape (N or 2 * N, T, C).
           encoder_out_lens:
-            Encoder output lengths, of shape (2 * N,).
+            Encoder output lengths, of shape (N or 2 * N,).
           targets:
             Target Tensor of shape (2 * sum(target_lengths)). The targets are assumed
             to be un-padded and concatenated within 1 dimension.
+          use_consistency_reg:
+            Whether use consistency regularization.
+          use_smooth_reg:
+            Whether use smooth regularization.
         """
+        ctc_output = self.ctc_output(encoder_out)  # (N or 2 * N, T, C)
+        length_mask = make_pad_mask(encoder_out_lens).unsqueeze(-1)
+
+        if not use_smooth_reg:
+            ctc_log_probs = F.log_softmax(ctc_output, dim=-1)
+        else:
+            ctc_probs = ctc_output.softmax(dim=-1)   # Used in sr_loss
+            ctc_log_probs = (ctc_probs + eps).log()
+
         # Compute CTC loss
-        ctc_output = self.ctc_output(encoder_out)  # (2 * N, T, C)
         ctc_loss = torch.nn.functional.ctc_loss(
-            log_probs=ctc_output.permute(1, 0, 2),  # (T, 2 * N, C)
+            log_probs=ctc_log_probs.permute(1, 0, 2),  # (T, N or 2 * N, C)
             targets=targets.cpu(),
             input_lengths=encoder_out_lens.cpu(),
             target_lengths=target_lengths.cpu(),
             reduction="sum",
         )
 
-        # Compute consistency regularization loss
-        exchanged_targets = ctc_output.detach().chunk(2, dim=0)
-        exchanged_targets = torch.cat(
-            [exchanged_targets[1], exchanged_targets[0]], dim=0
-        )  # exchange: [x1, x2] -> [x2, x1]
-        cr_loss = nn.functional.kl_div(
-            input=ctc_output,
-            target=exchanged_targets,
-            reduction="none",
-            log_target=True,
-        )  # (2 * N, T, C)
-        length_mask = make_pad_mask(encoder_out_lens).unsqueeze(-1)
-        cr_loss = cr_loss.masked_fill(length_mask, 0.0).sum()
+        if use_consistency_reg:
+            assert ctc_log_probs.shape[0] % 2 == 0
+            # Compute cr_loss
+            exchanged_targets = ctc_log_probs.detach().chunk(2, dim=0)
+            exchanged_targets = torch.cat(
+                [exchanged_targets[1], exchanged_targets[0]], dim=0
+            )  # exchange: [x1, x2] -> [x2, x1]
+            cr_loss = nn.functional.kl_div(
+                input=ctc_log_probs,
+                target=exchanged_targets,
+                reduction="none",
+                log_target=True,
+            )  # (2 * N, T, C)
+            cr_loss = cr_loss.masked_fill(length_mask, 0.0).sum()
+        else:
+            cr_loss = torch.empty(0)
 
-        return ctc_loss, cr_loss
+        if use_smooth_reg:
+            # Hard code the kernel here, could try other values
+            assert len(smooth_kernel) == 3 and sum(smooth_kernel) == 1.0, smooth_kernel
+            smooth_kernel = torch.tensor(smooth_kernel, dtype=ctc_probs.dtype,
+                                         device=ctc_probs.device, requires_grad=False)
+            smooth_kernel = smooth_kernel.unsqueeze(0).unsqueeze(1).expand(ctc_probs.shape[-1], 1, 3)
+            # Now kernel: (C, 1, 3)
+            smoothed_ctc_probs = F.conv1d(
+                ctc_probs.detach().permute(0, 2, 1),  # (N or 2 * N, C, T)
+                weight=smooth_kernel, stride=1, padding=0, groups=ctc_probs.shape[-1]
+            ).permute(0, 2, 1)  # (N or 2 * N, T - 2, C)
+            sr_loss = nn.functional.kl_div(
+                input=ctc_log_probs[:, 1:-1],
+                target=(smoothed_ctc_probs + eps).log(),
+                reduction="none",
+                log_target=True,
+            )  # (N, T - 1 , C)
+            sr_loss = sr_loss.masked_fill(length_mask[:, 1:-1], 0.0).sum()
+        else:
+            sr_loss = torch.empty(0)
+
+        return ctc_loss, cr_loss, sr_loss
 
     def forward_transducer(
         self,
@@ -341,6 +352,7 @@ def forward(
         am_scale: float = 0.0,
         lm_scale: float = 0.0,
         use_cr_ctc: bool = False,
+        use_sr_ctc: bool = False,
         use_spec_aug: bool = False,
         spec_augment: Optional[SpecAugment] = None,
         supervision_segments: Optional[torch.Tensor] = None,
@@ -367,6 +379,8 @@ def forward(
             part
           use_cr_ctc:
             Whether use consistency-regularized CTC.
+          use_sr_ctc:
+            Whether use smooth-regularized CTC.
           use_spec_aug:
             Whether apply spec-augment manually, used only if use_cr_ctc is True.
           spec_augment:
@@ -445,26 +459,23 @@ def forward(
         if self.use_ctc:
             # Compute CTC loss
             targets = y.values
-            if not use_cr_ctc:
-                ctc_loss = self.forward_ctc(
-                    encoder_out=encoder_out,
-                    encoder_out_lens=encoder_out_lens,
-                    targets=targets,
-                    target_lengths=y_lens,
-                )
-                cr_loss = torch.empty(0)
-            else:
-                ctc_loss, cr_loss = self.forward_cr_ctc(
-                    encoder_out=encoder_out,
-                    encoder_out_lens=encoder_out_lens,
-                    targets=targets,
-                    target_lengths=y_lens,
-                )
+            ctc_loss, cr_loss, sr_loss = self.forward_ctc(
+                encoder_out=encoder_out,
+                encoder_out_lens=encoder_out_lens,
+                targets=targets,
+                target_lengths=y_lens,
+                use_consistency_reg=use_cr_ctc,
+                use_smooth_reg=use_sr_ctc,
+            )
+            if use_cr_ctc:
+                # We duplicate the batch when use_cr_ctc is True
                 ctc_loss = ctc_loss * 0.5
                 cr_loss = cr_loss * 0.5
+                sr_loss = sr_loss * 0.5
         else:
             ctc_loss = torch.empty(0)
             cr_loss = torch.empty(0)
+            sr_loss = torch.empty(0)
 
         if self.use_attention_decoder:
             attention_decoder_loss = self.attention_decoder.calc_att_loss(
@@ -478,4 +489,4 @@ def forward(
         else:
             attention_decoder_loss = torch.empty(0)
 
-        return simple_loss, pruned_loss, ctc_loss, attention_decoder_loss, cr_loss
+        return simple_loss, pruned_loss, ctc_loss, attention_decoder_loss, cr_loss, sr_loss

egs/librispeech/ASR/zipformer/train.py

@@ -312,6 +312,13 @@ def add_model_arguments(parser: argparse.ArgumentParser):
         help="If True, use consistency-regularized CTC.",
     )
 
+    parser.add_argument(
+        "--use-sr-ctc",
+        type=str2bool,
+        default=False,
+        help="If True, use smooth-regularized CTC.",
+    )
+
 
 def get_parser():
     parser = argparse.ArgumentParser(
@@ -464,6 +471,13 @@ def get_parser():
         help="Scale for consistency-regularization loss.",
     )
 
+    parser.add_argument(
+        "--sr-loss-scale",
+        type=float,
+        default=0.2,
+        help="Scale for smooth-regularization loss.",
+    )
+
     parser.add_argument(
         "--time-mask-ratio",
         type=float,
@@ -916,6 +930,7 @@ def compute_loss(
     y = k2.RaggedTensor(y)
 
     use_cr_ctc = params.use_cr_ctc
+    use_sr_ctc = params.use_sr_ctc
     use_spec_aug = use_cr_ctc and is_training
     if use_spec_aug:
         supervision_intervals = batch["supervisions"]
@@ -931,14 +946,15 @@ def compute_loss(
         supervision_segments = None
 
     with torch.set_grad_enabled(is_training):
-        simple_loss, pruned_loss, ctc_loss, attention_decoder_loss, cr_loss = model(
+        simple_loss, pruned_loss, ctc_loss, attention_decoder_loss, cr_loss, sr_loss = model(
             x=feature,
             x_lens=feature_lens,
             y=y,
             prune_range=params.prune_range,
             am_scale=params.am_scale,
             lm_scale=params.lm_scale,
             use_cr_ctc=use_cr_ctc,
+            use_sr_ctc=use_sr_ctc,
             use_spec_aug=use_spec_aug,
             spec_augment=spec_augment,
             supervision_segments=supervision_segments,
@@ -967,6 +983,8 @@ def compute_loss(
             loss += params.ctc_loss_scale * ctc_loss
             if use_cr_ctc:
                 loss += params.cr_loss_scale * cr_loss
+            if use_sr_ctc:
+                loss += params.sr_loss_scale * sr_loss
 
         if params.use_attention_decoder:
             loss += params.attention_decoder_loss_scale * attention_decoder_loss
@@ -985,8 +1003,10 @@ def compute_loss(
         info["pruned_loss"] = pruned_loss.detach().cpu().item()
     if params.use_ctc:
         info["ctc_loss"] = ctc_loss.detach().cpu().item()
-        if params.use_cr_ctc:
+        if use_cr_ctc:
             info["cr_loss"] = cr_loss.detach().cpu().item()
+        if use_sr_ctc:
+            info["sr_loss"] = sr_loss.detach().cpu().item()
     if params.use_attention_decoder:
         info["attn_decoder_loss"] = attention_decoder_loss.detach().cpu().item()