Cache: don't throw warnings on gemma2 when instantiating a new cache

src/transformers/cache_utils.py

@@ -1660,7 +1660,15 @@ def get_max_length(self) -> Optional[int]:
         return self.max_cache_len
 
     def get_seq_length(self, layer_idx: Optional[int] = 0):
-        return None
+        # Occupied cache == any slot in the 3rd dim (sequence length) holds a non-zero value. To save on compute, let's
+        # limit the check to the first batch member and head dimension.
+        # TODO: deprecate this function in favor of `cache_position`
+        if layer_idx != 0:
+            raise ValueError(
+                "`get_seq_length` on `HybridCache` may get inconsistent results depending on the layer index. "
+                "Using the `layer_idx` argument is not supported."
+            )
+        return (self.key_cache[layer_idx][0, 0].any(dim=-1)).sum()
 
     def reset(self):
         """Resets the cache values while preserving the objects"""

src/transformers/models/gemma2/modeling_gemma2.py

@@ -710,20 +710,13 @@ def _check_and_enable_sdpa(cls, config, hard_check_only: bool = False):
             config.n_positions - 1]`.
 
             [What are position IDs?](../glossary#position-ids)
-        past_key_values (`Cache` or `tuple(tuple(torch.FloatTensor))`, *optional*):
+        past_key_values (`HybridCache`, *optional*):
             Pre-computed hidden-states (key and values in the self-attention blocks and in the cross-attention
             blocks) that can be used to speed up sequential decoding. This typically consists in the `past_key_values`
             returned by the model at a previous stage of decoding, when `use_cache=True` or `config.use_cache=True`.
 
-            Two formats are allowed:
-            - a [`~cache_utils.Cache`] instance, see our
-            [kv cache guide](https://huggingface.co/docs/transformers/en/kv_cache);
-            - Tuple of `tuple(torch.FloatTensor)` of length `config.n_layers`, with each tuple having 2 tensors of
-            shape `(batch_size, num_heads, sequence_length, embed_size_per_head)`). This is also known as the legacy
-            cache format.
-
-            The model will output the same cache format that is fed as input. If no `past_key_values` are passed, the
-            legacy cache format will be returned.
+            Gemma 2 uses a unique cache class, [`HybridCache`], and does not guarantee full compatibility with other
+            cache classes.
 
             If `past_key_values` are used, the user can optionally input only the last `input_ids` (those that don't
             have their past key value states given to this model) of shape `(batch_size, 1)` instead of all `input_ids`
@@ -789,7 +782,7 @@ def forward(
         input_ids: torch.LongTensor = None,
         attention_mask: Optional[torch.Tensor] = None,
         position_ids: Optional[torch.LongTensor] = None,
-        past_key_values: Optional[Union[Cache, List[torch.FloatTensor]]] = None,
+        past_key_values: Optional[HybridCache] = None,
         inputs_embeds: Optional[torch.FloatTensor] = None,
         use_cache: Optional[bool] = None,
         output_attentions: Optional[bool] = None,
@@ -818,19 +811,8 @@ def forward(
         if inputs_embeds is None:
             inputs_embeds = self.embed_tokens(input_ids)
 
-        if cache_position is None:
-            if past_key_values is None:
-                cache_position = torch.arange(0, inputs_embeds.shape[1], device=inputs_embeds.device)
-            else:
-                raise ValueError("When `past_key_values` is passed, `cache_position` must be too")
-
-        # Probably a forward call with caching, so we set up cache for one call only
-        if use_cache and past_key_values is None and not self.training:
-            logger.warning_once(
-                "You are calling the model with `use_cache=True` but didn't pass `past_key_values` while not training. ",
-                "If you want to compute with cache, make sure to pass an instance of `HybridCache`. An empty `HybridCache` instance "
-                "will be created for this call. See for more: (https://huggingface.co/docs/transformers/main/en/internal/generation_utils#transformers.HybridCache)",
-            )
+        # Instantiate an empty cache if needed.
+        if use_cache and past_key_values is None:
             batch_size, seq_len, _ = inputs_embeds.shape
             past_key_values = HybridCache(
                 self.config,
@@ -840,6 +822,11 @@ def forward(
                 dtype=inputs_embeds.dtype,
             )
 
+        if cache_position is None:
+            past_seen_tokens = past_key_values.get_seq_length() if past_key_values is not None else 0
+            cache_position = torch.arange(
+                past_seen_tokens, past_seen_tokens + inputs_embeds.shape[1], device=inputs_embeds.device
+            )
         if position_ids is None:
             position_ids = cache_position.unsqueeze(0)
 
@@ -912,7 +899,7 @@ def _update_causal_mask(
         attention_mask: torch.Tensor,
         input_tensor: torch.Tensor,
         cache_position: torch.Tensor,
-        past_key_values: Cache,
+        past_key_values: HybridCache,
         output_attentions: bool,
     ):
         # Flash Attention currently doesn't support static cache but Gemma2 work only with static cache.
@@ -981,7 +968,7 @@ def forward(
         input_ids: torch.LongTensor = None,
         attention_mask: Optional[torch.Tensor] = None,
         position_ids: Optional[torch.LongTensor] = None,
-        past_key_values: Optional[Union[Cache, List[torch.FloatTensor]]] = None,
+        past_key_values: Optional[HybridCache] = None,
         inputs_embeds: Optional[torch.FloatTensor] = None,
         labels: Optional[torch.LongTensor] = None,
         use_cache: Optional[bool] = None,
@@ -1202,7 +1189,7 @@ def forward(
         input_ids: torch.LongTensor = None,
         attention_mask: Optional[torch.Tensor] = None,
         position_ids: Optional[torch.LongTensor] = None,
-        past_key_values: Optional[Union[Cache, List[torch.FloatTensor]]] = None,
+        past_key_values: Optional[HybridCache] = None,
         inputs_embeds: Optional[torch.FloatTensor] = None,
         labels: Optional[torch.LongTensor] = None,
         use_cache: Optional[bool] = None,

src/transformers/models/mimi/modeling_mimi.py

@@ -1000,8 +1000,16 @@ def forward(
             )
             use_cache = False
 
-        if use_cache and past_key_values is None and not self.training:
-            past_key_values = DynamicCache.from_legacy_cache(past_key_values)
+        if use_cache and not isinstance(past_key_values, Cache):
+            if past_key_values is None:
+                past_key_values = DynamicCache()
+            else:
+                past_key_values = DynamicCache.from_legacy_cache(past_key_values)
+                logger.warning_once(
+                    "We detected that you are passing `past_key_values` as a tuple of tuples. This is deprecated and "
+                    "will be removed in v4.47. Please convert your cache or use an appropriate `Cache` class "
+                    "(https://huggingface.co/docs/transformers/kv_cache#legacy-cache-format)"
+                )
 
         if cache_position is None:
             past_seen_tokens = past_key_values.get_seq_length() if past_key_values is not None else 0

tests/models/gemma2/test_modeling_gemma2.py

@@ -86,10 +86,15 @@ def setUp(self):
     def test_model_outputs_equivalence(self, **kwargs):
         pass
 
+    @parameterized.expand([("float16",), ("bfloat16",), ("float32",)])
     @unittest.skip("Gemma2's eager attn/sdpa attn outputs are expected to be different")
     def test_eager_matches_sdpa_inference(self):
         pass
 
+    @unittest.skip("Gemma2's eager attn/sdpa attn outputs are expected to be different")
+    def test_eager_matches_sdpa_generate(self):
+        pass
+
     @parameterized.expand([("random",), ("same",)])
     @unittest.skip("Gemma2 has HybridCache which is not compatible with assisted decoding")
     def test_assisted_decoding_matches_greedy_search(self, assistant_type):