Fix excess attention_mask getting causing test fails

transformer_lens/HookedTransformer.py

@@ -297,16 +297,6 @@ def get_residual(
             # Because tokens only need for defining batch size and sequence length, we can simply synthesize them
             tokens = torch.ones((embed.size(0), embed.size(1))).int().to(device)
 
-        if attention_mask is None:
-            # If the padding side is left or we are using caching, we need to compute the attention
-            # mask for the adjustment of absolute positional embeddings and attention masking so
-            # that pad tokens are not attended.
-            if prepend_bos is USE_DEFAULT_VALUE:
-                prepend_bos = self.cfg.default_prepend_bos
-            attention_mask = utils.get_attention_mask(self.tokenizer, tokens, prepend_bos).to(
-                device
-            )
-
         if self.cfg.positional_embedding_type == "standard":
             pos_embed = self.hook_pos_embed(
                 self.pos_embed(tokens, pos_offset, attention_mask)
@@ -2237,9 +2227,13 @@ def generate(
             sampled_tokens_list = []
             for index in tqdm.tqdm(range(max_new_tokens), disable=not verbose):
                 pos_offset = self.get_pos_offset(past_kv_cache, batch_size)
+
+                tokens = torch.zeros((embeds.size(0), embeds.size(1))).to(torch.int)
+                attention_mask = utils.get_attention_mask(self.tokenizer, tokens, prepend_bos).to(device)
                 residual, shortformer_pos_embed = self.get_residual(
-                    embeds, pos_offset, return_shortformer_pos_embed=True, device=device
+                    embeds, pos_offset, return_shortformer_pos_embed=True, device=device, attention_mask=attention_mask
                 )
+
                 # While generating, we keep generating logits, throw away all but the final logits,
                 # and then use those logits to sample from the distribution We keep adding the
                 # sampled tokens to the end of tokens.