XLA optimized Implementation of StaticCache with Tensor Indexing API

src/transformers/cache_utils.py

@@ -9,7 +9,6 @@
 from .configuration_utils import PretrainedConfig
 from .utils import is_hqq_available, is_quanto_available, logging
 
-
 if is_quanto_available():
     from quanto import QBitsTensor, qint2, qint4
 
@@ -935,3 +934,108 @@ def get_max_length(self) -> Optional[int]:
     def reset(self):
         self.key_cache.zero_()
         self.value_cache.zero_()
+
+class StaticCacheXLA(StaticCache):
+    """
+    Static Cache class to be used with `torch.compile(model)`.
+
+    Parameters:
+        config (`PretrainedConfig):
+            The configuration file defining the shape-related attributes required to initialize the static cache.
+        max_batch_size (`int`):
+            The maximum batch size with which the model will be used.
+        max_cache_len (`int`):
+            The maximum sequence length with which the model will be used.
+        device (`torch.device`):
+            The device on which the cache should be initialized. Should be the same as the layer.
+        dtype (*optional*, defaults to `torch.float32`):
+            The default `dtype` to use when initializing the layer.
+    """
+
+    def __init__(self, config: PretrainedConfig, max_batch_size: int, max_cache_len: int, device, dtype=None) -> None:
+        super().__init__(config, max_batch_size, max_cache_len, device, dtype)
+        self.max_batch_size = max_batch_size
+        self.max_cache_len = config.max_position_embeddings if max_cache_len is None else max_cache_len
+        # Some model define a custom `head_dim` != config.hidden_size // config.num_attention_heads
+        self.head_dim = (
+            config.head_dim if hasattr(config, "head_dim") else config.hidden_size // config.num_attention_heads
+        )
+
+        self.dtype = dtype if dtype is not None else torch.float32
+        self.num_key_value_heads = (
+            config.num_attention_heads if config.num_key_value_heads is None else config.num_key_value_heads
+        )
+
+        self.key_cache: List[torch.Tensor] = []
+        self.value_cache: List[torch.Tensor] = []
+        cache_shape = (max_batch_size, self.num_key_value_heads, self.max_cache_len, self.head_dim)
+        for _ in range(config.num_hidden_layers):
+            # Note: `mark_static_address` is used to tag the cache as an fixed data pointer, preventing cuda graph
+            # breaks when updating the cache.
+            new_layer_key_cache = torch.zeros(cache_shape, dtype=self.dtype, device=device)
+            new_layer_value_cache = torch.zeros(cache_shape, dtype=self.dtype, device=device)
+            self.key_cache.append(new_layer_key_cache)
+            self.value_cache.append(new_layer_value_cache)
+
+    def update(
+        self,
+        key_states: torch.Tensor,
+        value_states: torch.Tensor,
+        layer_idx: int,
+        cache_kwargs: Optional[Dict[str, Any]] = None,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        """
+        Updates the cache with the new `key_states` and `value_states` for the layer `layer_idx`.
+        It is VERY important to index using a tensor, otherwise you introduce a copy to the device.
+
+        Parameters:
+            key_states (`torch.Tensor`):
+                The new key states to cache.
+            value_states (`torch.Tensor`):
+                The new value states to cache.
+            layer_idx (`int`):
+                The index of the layer to cache the states for.
+            cache_kwargs (`Dict[str, Any]`, `optional`):
+                Additional arguments for the cache subclass. The `StaticCache` needs the `cache_position` input
+                to know how where to write in the cache.
+
+        Return:
+            A tuple containing the updated key and value states.
+        """
+        cache_position = cache_kwargs.get("cache_position")
+
+        k_out = self.key_cache[layer_idx]
+        v_out = self.value_cache[layer_idx]
+
+        k_out = k_out.index_copy(2, cache_position, key_states)
+        v_out = v_out.index_copy(2, cache_position, value_states)
+
+        self.key_cache[layer_idx] = k_out
+        self.value_cache[layer_idx] = v_out
+
+        return k_out, v_out
+
+    def get_seq_length(self, layer_idx: Optional[int] = 0) -> int:
+        """Returns the sequence length of the cached states that were seen by the model."""
+        # 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`
+        logger.debug("Use cache_position parameter in your model for better performance.")
+        key_cache = self.key_cache[layer_idx]
+        device = key_cache.device
+
+        item = key_cache.index_select(0, torch.tensor(0, device=device))
+        head = item.index_select(1, torch.tensor(0, device=device))
+
+        return head.any(dim=-1).sum()
+
+    def get_max_length(self) -> Optional[int]:
+        """Returns the maximum sequence length of the cached states."""
+        return self.max_cache_len
+
+    def reset(self):
+        """Resets the cache values while preserving the objects"""
+        for layer_idx in range(len(self.key_cache)):
+            # In-place ops prevent breaking the static address
+            self.key_cache[layer_idx].zero_()
+            self.value_cache[layer_idx].zero_()