Remove unneeded modules after using nn.Module for BetterTransformer (#1693)

Summary:
Pull Request resolved: #1693

Remove unneeded modules after using nn.Module for BetterTransformer

Differential Revision: D36038830

fbshipit-source-id: 5663217ca4989dc07962f239b3365bc48edad490

Author: Michael Gschwind

torchtext/models/roberta/modules.py

@@ -30,159 +30,6 @@ def _make_positions(self, tensor, pad_index: int):
         return torch.cumsum(masked, dim=1) * masked + pad_index
 
 
-class ResidualMLP(Module):
-    def __init__(
-        self,
-        input_dim: int,
-        hidden_dims: List[int],
-        dropout: float = 0.1,
-        activation=nn.GELU,
-        add_residual=True,
-    ):
-        super().__init__()
-        modules = []
-        for last_dim, dim in zip([input_dim] + hidden_dims, hidden_dims):
-            modules.extend([nn.Linear(last_dim, dim), activation(), nn.Dropout(dropout)])
-
-        last_dim = hidden_dims[-1] if hidden_dims else input_dim
-        modules.extend([nn.Linear(last_dim, input_dim), nn.Dropout(dropout)])
-
-        self.mlp = nn.Sequential(*modules)
-        self.add_residual = add_residual
-        self.hidden_dim = hidden_dims[0] if hidden_dims else input_dim
-
-    def forward(self, input):
-        bias = self.mlp(input)
-        if not hasattr(self, "add_residual"):
-            self.add_residual = True
-        if self.add_residual:
-            return input + bias
-        else:
-            return bias
-
-
-class MultiheadSelfAttention(Module):
-    def __init__(
-        self,
-        embed_dim: int,
-        num_heads: int,
-        scaling: Optional[float] = None,
-        dropout: float = 0.1,
-    ):
-        super().__init__()
-        self.embed_dim = embed_dim
-        self.num_heads = num_heads
-        self.head_dim = embed_dim // num_heads
-
-        expected_scaling = float(1 / math.sqrt(self.head_dim))
-
-        assert embed_dim % num_heads == 0, f"embed_dim={embed_dim} should be a multiple of num_heads={num_heads}"
-
-        if not scaling:
-            logger.warn(
-                f"""
-                Scaling not set. Please manually set scaling for transformers.
-                In this case the suggested value {expected_scaling} will be inferred,
-                or float(1 / math.sqrt(head_dim))
-                where head_dim = embed_dim // num_heads = {self.head_dim}
-                and embed_dim = {embed_dim} and num_heads = {num_heads}.
-                """
-            )
-            scaling = expected_scaling
-
-        self.scaling = scaling
-        self.dropout = nn.Dropout(dropout)
-        self.input_projection = nn.Linear(embed_dim, 3 * embed_dim)
-        self.output_projection = nn.Linear(embed_dim, embed_dim)
-
-    def forward(self, query: torch.Tensor, key_padding_mask: torch.Tensor, attn_mask: Optional[torch.Tensor] = None):
-        target_length, batch_size, embed_dim = query.size()
-        mask_batch_size, source_length = key_padding_mask.size()
-
-        torch._assert(embed_dim == self.embed_dim, "query embed dim doesn't match")
-        torch._assert(
-            batch_size == mask_batch_size,
-            "query and key_padding_mask batch sizes differed",
-        )
-
-        projection = self.input_projection(query)
-        q, k, v = projection.chunk(3, dim=-1)
-        q = self.scaling * q
-
-        batch_heads = batch_size * self.num_heads
-
-        q = q.contiguous().view(-1, batch_heads, self.head_dim).transpose(0, 1)
-        k = k.contiguous().view(-1, batch_heads, self.head_dim).transpose(0, 1)
-        v = v.contiguous().view(-1, batch_heads, self.head_dim).transpose(0, 1)
-
-        torch._assert(k.size(1) == source_length, "key size should be equal to source length")
-
-        attn_weights = torch.bmm(q, k.transpose(1, 2))
-        if attn_mask is not None:
-            torch._assert(attn_mask.dim() == 2, "Expected attn_mask of dim 2 but got {}".format(attn_mask.dim()))
-            torch._assert(
-                attn_mask.size(0) == target_length,
-                "attn_mask shape didn't match for target length {}".format(target_length),
-            )
-            torch._assert(
-                attn_mask.size(1) == source_length,
-                "attn_mask shape didn't match for source length {}".format(source_length),
-            )
-            torch._assert(
-                attn_mask.is_floating_point() or attn_mask.dtype == torch.bool,
-                f"Only float or bool types are supported for attn_mask not {attn_mask.dtype}",
-            )
-            if attn_mask.dtype == torch.bool:
-                new_attn_mask = torch.zeros_like(attn_mask, dtype=query.dtype)
-                new_attn_mask.masked_fill_(attn_mask, -1e8 if query.dtype == torch.float32 else -1e4)
-                attn_mask = new_attn_mask
-            attn_mask = attn_mask.unsqueeze(0)
-            attn_weights += attn_mask
-
-        torch._assert(attn_weights.dim() == 3, "Unexpected attn_weights dim")
-        torch._assert(
-            attn_weights.size(0) == batch_heads,
-            "attn_weights shape didn't match for batch heads",
-        )
-        torch._assert(
-            attn_weights.size(1) == target_length,
-            "attn_weights shape didn't match for target length",
-        )
-        torch._assert(
-            attn_weights.size(2) == source_length,
-            "attn_weights shape didn't match for source length",
-        )
-
-        attn_weights = attn_weights.view(batch_size, self.num_heads, target_length, source_length)
-        attn_weights = attn_weights.masked_fill(key_padding_mask.unsqueeze(1).unsqueeze(2), float("-inf"))
-        attn_weights = attn_weights.view(batch_heads, target_length, source_length)
-
-        attn_weights = F.softmax(attn_weights, dim=-1, dtype=torch.float32).type_as(attn_weights)
-        attn_weights = self.dropout(attn_weights)
-
-        attn = torch.bmm(attn_weights, v)
-
-        torch._assert(
-            attn.dim() == 3,
-            "unexpected attn dim size",
-        )
-        torch._assert(
-            attn.size(0) == batch_heads,
-            "attn shape didn't match for batch heads",
-        )
-        torch._assert(
-            attn.size(1) == target_length,
-            "attn shape didn't match for target length",
-        )
-        torch._assert(
-            attn.size(2) == self.head_dim,
-            "attn shape didn't match for head dim",
-        )
-        attn = attn.transpose(0, 1).contiguous().view(target_length, batch_size, self.head_dim * self.num_heads)
-        attn = self.output_projection(attn)
-
-        return attn
-
 
 class TransformerEncoderLayer(Module):
     def __init__(