Use decorrelation in conformer layers also

egs/librispeech/ASR/pruned_transducer_stateless2/scaling.py

@@ -746,7 +746,7 @@ class DecorrelateFunction(torch.autograd.Function):
             inv_sqrt_diag = (cov.diag() + ctx.eps) ** -0.5
             norm_cov = cov * (inv_sqrt_diag * inv_sqrt_diag.unsqueeze(-1))
 
-            loss = ((norm_cov - norm_cov.diag().diag()) ** 2).sum() / num_channels - 1
+            loss = ((norm_cov - norm_cov.diag().diag()) ** 2).sum() / num_channels
             if random.random() < 0.01:
                 logging.info(f"Decorrelate: loss = {loss}")
             loss.backward()
@@ -758,7 +758,9 @@ class DecorrelateFunction(torch.autograd.Function):
             # `loss ** 0.5` times the magnitude of the original grad.
             x_grad_new_scale = (x_grad_new ** 2).sum(dim=1)
             x_grad_old_scale = (x_grad ** 2).sum(dim=1)
-            decorr_loss_scale = ctx.scale
+
+            decorr_loss_scale = ctx.scale * loss.detach().clamp(min=0.0, max=1.0)
+
             scale = decorr_loss_scale * (x_grad_old_scale / (x_grad_new_scale + 1.0e-10)) ** 0.5
             x_grad_new = x_grad_new * scale.unsqueeze(-1)
 
@@ -776,27 +778,56 @@ class Decorrelate(torch.nn.Module):
     This module does nothing in the forward pass, but in the backward pass, modifies
     the derivatives in such a way as to encourage the dimensions of its input to become
     decorrelated.
+
+    Args:
+            num_channels:  The number of channels, e.g. 256.
+          apply_prob_decay:  The probability with which we apply this each time, in
+                           training mode, will decay as apply_prob_decay/(apply_prob_decay + step).
+                   scale: This number determines the scale of the gradient contribution from
+                          this module, relative to whatever the gradient was before;
+                          this is applied per frame or pixel, by scaling gradients.
+                     eps: An epsilon used to prevent division by zero.
+                    beta: A value 0 < beta < 1 that controls decay of covariance stats
+             channel_dim: The dimension of the input corresponding to the channel, e.g.
+                          -1, 0, 1, 2.
+
     """
     def __init__(self,
                  num_channels: int,
                  scale: float = 0.1,
+                 apply_prob_decay: int = 1000,
                  eps: float = 1.0e-05,
                  beta: float = 0.95,
                  channel_dim: int = -1):
         super(Decorrelate, self).__init__()
         self.scale = scale
+        self.apply_prob_decay = apply_prob_decay
         self.eps = eps
         self.beta = beta
         self.channel_dim = channel_dim
 
         self.register_buffer('cov', torch.zeros(num_channels, num_channels))
+        # step_buf is a copy of step, included so it will be loaded/saved with
+        # the model.
+        self.register_buffer('step_buf', torch.tensor(0))
         self.step = 0
 
 
+
+    def load_state_dict(self, *args, **kwargs):
+        super(Decorrelate, self).load_state_dict(*args, **kwargs)
+        self.step = self.step_buf.item()
+
+
     def forward(self, x: Tensor) -> Tensor:
         if not self.training:
             return x
         else:
+            apply_prob = self.apply_prob_decay / (self.step + self.apply_prob_decay)
+            self.step += 1
+            self.step_buf.fill_(self.step)
+            if random.random() > apply_prob:
+                return x
             with torch.cuda.amp.autocast(enabled=False):
                 ans = DecorrelateFunction.apply(x, self.cov.clone(),
                                                 self.scale, self.eps, self.beta,
@@ -807,7 +838,6 @@ class Decorrelate(torch.nn.Module):
                 cov = torch.matmul(x.t(), x)
                 with torch.no_grad():
                     self.cov.mul_(self.beta).add_(cov, alpha=(1-self.beta))
-                self.step += 1
 
                 return ans  # ans == x.
 
@@ -825,9 +855,8 @@ class JoinDropout(torch.nn.Module):
 
     Args:
            num_channels:  The number of channels, e.g. 256.
-             apply_prob:  The probability with which we apply this each time, in
+        apply_prob_decay:  The probability with which we apply this each time, in
-                          training mode.  This is to save time (but of course it
+                          training mode, will decay as apply_prob_decay/(apply_prob_decay + step).
-                          will tend to make the effect weaker).
             dropout_rate: This number determines the average dropout probability
                           (it will actually vary across dimensions).
                      eps: An epsilon used to prevent division by zero.
@@ -925,7 +954,8 @@ class JoinDropout(torch.nn.Module):
 
 
     def forward(self, bypass: Tensor, x: Tensor) -> Tensor:
-        if not self.training or random.random() > self.apply_prob:
+        apply_prob = self.apply_prob
+        if not self.training or random.random() > apply_prob:
             return bypass + x
         else:
             x = x.transpose(self.channel_dim, -1)  # (..., num_channels)
@@ -1049,6 +1079,28 @@ def _test_gauss_proj_drop():
             m1.eval()
             m2.eval()
 
+def _test_decorrelate():
+    D = 384
+    x = torch.randn(30000, D)
+    # give it a non-unit covariance.
+    m = torch.randn(D, D) * (D ** -0.5)
+    _, S, _ = m.svd()
+    print("M eigs = ", S[::10])
+    x = torch.matmul(x, m)
+
+
+    # check that class Decorrelate does not crash when running..
+    decorrelate = Decorrelate(D)
+    x.requires_grad = True
+    y = decorrelate(x)
+    y.sum().backward()
+
+    decorrelate2 = Decorrelate(D)
+    decorrelate2.load_state_dict(decorrelate.state_dict())
+    assert decorrelate2.step == decorrelate.step
+
+
+
 def _test_join_dropout():
     D = 384
     x = torch.randn(30000, D)
@@ -1060,13 +1112,6 @@ def _test_join_dropout():
     x = torch.matmul(x, m)
 
 
-    if True:
-        # check that class Decorrelate does not crash when running..
-        decorrelate = Decorrelate(D)
-        x.requires_grad = True
-        y = decorrelate(x)
-        y.sum().backward()
-
     for dropout_rate in [0.2, 0.1, 0.01, 0.05]:
         m1 = torch.nn.Dropout(dropout_rate)
         m2 = JoinDropout(D, apply_prob=1.0, dropout_rate=dropout_rate)
@@ -1089,6 +1134,7 @@ if __name__ == "__main__":
     logging.getLogger().setLevel(logging.INFO)
     torch.set_num_threads(1)
     torch.set_num_interop_threads(1)
+    _test_decorrelate()
     _test_join_dropout()
     _test_gauss_proj_drop()
     _test_activation_balancer_sign()

egs/librispeech/ASR/pruned_transducer_stateless5/conformer.py

@@ -198,10 +198,8 @@ class ConformerEncoderLayer(nn.Module):
             channel_dim=-1, min_positive=0.45, max_positive=0.55, max_abs=6.0
         )
 
-        self.dropout_ff_macaron = JoinDropout(d_model, apply_prob=0.5, dropout_rate=dropout)
+        self.dropout = nn.Dropout(dropout)
-        self.dropout_conv = JoinDropout(d_model, apply_prob=0.5, dropout_rate=dropout)
+        self.decorrelate = Decorrelate(d_model, scale=0.02)
-        self.dropout_self_attn = JoinDropout(d_model, apply_prob=0.5, dropout_rate=dropout)
-        self.dropout_ff = JoinDropout(d_model, apply_prob=0.5, dropout_rate=dropout)
 
 
     def forward(
@@ -245,7 +243,7 @@ class ConformerEncoderLayer(nn.Module):
             alpha = 1.0
 
         # macaron style feed forward module
-        src = self.dropout_ff_macaron(src, self.feed_forward_macaron(src))
+        src = src + self.dropout(self.feed_forward_macaron(src))
 
         # multi-headed self-attention module
         src_att = self.self_attn(
@@ -256,16 +254,18 @@ class ConformerEncoderLayer(nn.Module):
             attn_mask=src_mask,
             key_padding_mask=src_key_padding_mask,
         )[0]
-        src = self.dropout_self_attn(src, src_att)
+        src = src + self.dropout(src_att)
 
         # convolution module
-        src = self.dropout_conv(src, self.conv_module(src))
+        src = src + self.dropout(self.conv_module(src))
 
         # feed forward module
-        src = self.dropout_ff(src, self.feed_forward(src))
+        src = src + self.dropout(self.feed_forward(src))
 
         src = self.norm_final(self.balancer(src))
 
+        src = self.decorrelate(src)
+
         if alpha != 1.0:
             src = alpha * src + (1 - alpha) * src_orig
 
@@ -1032,7 +1032,6 @@ class Conv2dSubsampling(nn.Module):
         # itself has learned scale, so the extra degree of freedom is not
         # needed.
         self.out_norm = BasicNorm(out_channels, learn_eps=False)
-        self.decorrelate = Decorrelate(out_channels)
         # constrain median of output to be close to zero.
         self.out_balancer = ActivationBalancer(
             channel_dim=-1, min_positive=0.45, max_positive=0.55
@@ -1057,7 +1056,6 @@ class Conv2dSubsampling(nn.Module):
         x = self.out(x.transpose(1, 2).contiguous().view(b, t, c * f))
         # Now x is of shape (N, ((T-1)//2 - 1))//2, odim)
         x = self.out_norm(x)
-        x = self.decorrelate(x)
         x = self.out_balancer(x)
         return x