Add Falcon support (new) (#592)

README.md

@@ -44,6 +44,7 @@ vLLM seamlessly supports many Huggingface models, including the following archit
 
 - Baichuan-7B (`baichuan-inc/Baichuan-7B`)
 - BLOOM (`bigscience/bloom`, `bigscience/bloomz`, etc.)
+- Falcon (`tiiuae/falcon-7b`, `tiiuae/falcon-40b`, `tiiuae/falcon-rw-7b`, etc.)
 - GPT-2 (`gpt2`, `gpt2-xl`, etc.)
 - GPT BigCode (`bigcode/starcoder`, `bigcode/gpt_bigcode-santacoder`, etc.)
 - GPT-J (`EleutherAI/gpt-j-6b`, `nomic-ai/gpt4all-j`, etc.)

csrc/pos_encoding_kernels.cu

@@ -10,7 +10,8 @@ __global__ void rotary_embedding_neox_kernel(
   scalar_t* __restrict__ key,                   // [num_tokens, num_kv_heads, head_size]
   const scalar_t* __restrict__ cos_sin_cache,   // [max_position, 2, rot_dim // 2]
   const int rot_dim,
-  const int stride,
+  const int query_stride,
+  const int key_stride,
   const int num_heads,
   const int num_kv_heads,
   const int head_size) {
@@ -23,14 +24,14 @@ __global__ void rotary_embedding_neox_kernel(
   const int nq = num_heads * embed_dim;
   for (int i = threadIdx.x; i < nq; i += blockDim.x) {
     const int head_idx = i / embed_dim;
-    const int token_head = token_idx * stride + head_idx * head_size;
+    const int token_head = token_idx * query_stride + head_idx * head_size;
 
     const int rot_offset = i % embed_dim;
     const int x_index = rot_offset;
     const int y_index = embed_dim + rot_offset;
 
-    const int out_x = token_idx * stride + head_idx * head_size + x_index;
-    const int out_y = token_idx * stride + head_idx * head_size + y_index;
+    const int out_x = token_idx * query_stride + head_idx * head_size + x_index;
+    const int out_y = token_idx * query_stride + head_idx * head_size + y_index;
 
     const scalar_t cos = __ldg(cache_ptr + x_index);
     const scalar_t sin = __ldg(cache_ptr + y_index);
@@ -39,13 +40,27 @@ __global__ void rotary_embedding_neox_kernel(
     const scalar_t q_y = query[token_head + y_index];
     query[out_x] = q_x * cos - q_y * sin;
     query[out_y] = q_y * cos + q_x * sin;
+  }
+
+  const int nk = num_kv_heads * embed_dim;
+  for (int i = threadIdx.x; i < nk; i += blockDim.x) {
+    const int head_idx = i / embed_dim;
+    const int token_head = token_idx * key_stride + head_idx * head_size;
+
+    const int rot_offset = i % embed_dim;
+    const int x_index = rot_offset;
+    const int y_index = embed_dim + rot_offset;
+
+    const int out_x = token_idx * key_stride + head_idx * head_size + x_index;
+    const int out_y = token_idx * key_stride + head_idx * head_size + y_index;
+
+    const scalar_t cos = __ldg(cache_ptr + x_index);
+    const scalar_t sin = __ldg(cache_ptr + y_index);
 
-    if (head_idx < num_kv_heads) {
-      const scalar_t k_x = key[token_head + x_index];
-      const scalar_t k_y = key[token_head + y_index];
-      key[out_x] = k_x * cos - k_y * sin;
-      key[out_y] = k_y * cos + k_x * sin;
-    }
+    const scalar_t k_x = key[token_head + x_index];
+    const scalar_t k_y = key[token_head + y_index];
+    key[out_x] = k_x * cos - k_y * sin;
+    key[out_y] = k_y * cos + k_x * sin;
   }
 }
 
@@ -62,8 +77,8 @@ void rotary_embedding_neox(
   int rot_dim = cos_sin_cache.size(1);
   int num_heads = query.size(1) / head_size;
   int num_kv_heads = key.size(1) / head_size;
-  int stride = query.stride(0);
-  TORCH_CHECK(stride == key.stride(0));
+  int query_stride = query.stride(0);
+  int key_stride = key.stride(0);
 
   dim3 grid(num_tokens);
   dim3 block(std::min(num_heads * rot_dim / 2, 512));
@@ -80,7 +95,8 @@ void rotary_embedding_neox(
         key.data_ptr<scalar_t>(),
         cos_sin_cache.data_ptr<scalar_t>(),
         rot_dim,
-        stride,
+        query_stride,
+        key_stride,
         num_heads,
         num_kv_heads,
         head_size);

docs/source/models/supported_models.rst

@@ -20,6 +20,9 @@ Alongside each architecture, we include some popular models that use it.
   * - :code:`BloomForCausalLM`
     - BLOOM, BLOOMZ, BLOOMChat
     - :code:`bigscience/bloom`, :code:`bigscience/bloomz`, etc.
+  * - :code:`FalconForCausalLM`
+    - Falcon
+    - :code:`tiiuae/falcon-7b``, :code:`tiiuae/falcon-40b`, :code:`tiiuae/falcon-rw-7b`, etc.
   * - :code:`GPT2LMHeadModel`
     - GPT-2
     - :code:`gpt2`, :code:`gpt2-xl`, etc.

examples/llm_engine_example.py

@@ -10,7 +10,8 @@ def main(args: argparse.Namespace):
 
     # Test the following prompts.
     test_prompts = [
-        ("A robot may not injure a human being", SamplingParams()),
+        ("A robot may not injure a human being",
+         SamplingParams(temperature=0.0)),
         ("To be or not to be,",
          SamplingParams(temperature=0.8, top_k=5, presence_penalty=0.2)),
         ("What is the meaning of life?",

vllm/config.py

@@ -94,8 +94,13 @@ class ModelConfig:
         return self.hf_config.hidden_size // self.hf_config.num_attention_heads
 
     def get_num_heads(self, parallel_config: "ParallelConfig") -> int:
-        # For GPTBigCode:
-        if getattr(self.hf_config, "multi_query", False):
+        # For GPTBigCode & Falcon:
+        # Note: for falcon, when new_decoder_architecture is True, the
+        # multi_query flag is ignored and we use n_head_kv for the number of
+        # KV heads.
+        if (getattr(self.hf_config, "multi_query", False) and
+            (self.hf_config.model_type == "falcon" and
+             not getattr(self.hf_config, "new_decoder_architecture", False))):
             # Multi-query attention, only one KV head.
             return 1
         # For Falcon:

vllm/model_executor/layers/attention.py

@@ -314,14 +314,13 @@ class PagedAttentionWithRoPE(PagedAttention):
 class PagedAttentionWithALiBi(PagedAttention):
     """PagedAttention with ALiBi attention bias."""
 
-    def __init__(
-        self,
-        num_heads: int,
-        head_size: int,
-        scale: float,
-        slopes: List[float],
-    ) -> None:
-        super().__init__(num_heads, head_size, scale)
+    def __init__(self,
+                 num_heads: int,
+                 head_size: int,
+                 scale: float,
+                 slopes: List[float],
+                 num_kv_heads: Optional[int] = None) -> None:
+        super().__init__(num_heads, head_size, scale, num_kv_heads)
         assert len(slopes) == num_heads
 
         slopes = torch.tensor(slopes, dtype=torch.float32)
@@ -334,6 +333,11 @@ class PagedAttentionWithALiBi(PagedAttention):
         # Generates ALiBi mask for each prompt.
         for prompt_len in input_metadata.prompt_lens:
             bias = torch.arange(prompt_len)
+            # Note(zhuohan): HF uses
+            #     `bias = bias[None, :].repeat(prompt_len, 1)`
+            # here. We find that both biases give the same results, but
+            # the bias below more accurately follows the original ALiBi
+            # paper.
             bias = bias[None, :] - bias[:, None]
             bias = bias.to(self.alibi_slopes.device)
 
@@ -363,10 +367,17 @@ class PagedAttentionWithALiBi(PagedAttention):
         Args:
             output: shape = [num_prompt_tokens, num_heads, head_size]
             query: shape = [num_prompt_tokens, num_heads, head_size]
-            key: shape = [num_prompt_tokens, num_heads, head_size]
-            value: shape = [num_prompt_tokens, num_heads, head_size]
+            key: shape = [num_prompt_tokens, num_kv_heads, head_size]
+            value: shape = [num_prompt_tokens, num_kv_heads, head_size]
             input_metadata: metadata for paged attention.
         """
+        if self.num_kv_heads != self.num_heads:
+            # Project the key and value tensors to the desired number of heads.
+            key = torch.repeat_interleave(key, self.num_queries_per_kv, dim=1)
+            value = torch.repeat_interleave(value,
+                                            self.num_queries_per_kv,
+                                            dim=1)
+
         # FIXME(woosuk): Because xformers does not support dynamic sequence
         # lengths with custom attention bias, we process each prompt one by
         # one. This is inefficient, especially when we have many short prompts.
@@ -400,9 +411,10 @@ class PagedAttentionWithALiBi(PagedAttention):
         Args:
             output: shape = [num_generation_tokens, num_heads, head_size]
             query: shape = [num_generation_tokens, num_heads, head_size]
-            key_cache: shape = [num_blocks, num_heads, head_size/x,
+            key_cache: shape = [num_blocks, num_kv_heads, head_size/x,
                 block_size, x]
-            value_cache: shape = [num_blocks, num_heads, head_size, block_size]
+            value_cache: shape = [num_blocks, num_kv_heads, head_size,
+                block_size]
             input_metadata: metadata for paged attention.
         """
         block_size = value_cache.shape[3]

vllm/model_executor/model_loader.py

@@ -14,6 +14,7 @@ _MODEL_REGISTRY = {
     "BaiChuanForCausalLM": BaiChuanForCausalLM,  # baichuan-7b
     "BaichuanForCausalLM": BaichuanForCausalLM,  # baichuan-13b
     "BloomForCausalLM": BloomForCausalLM,
+    "FalconForCausalLM": FalconForCausalLM,
     "GPT2LMHeadModel": GPT2LMHeadModel,
     "GPTBigCodeForCausalLM": GPTBigCodeForCausalLM,
     "GPTJForCausalLM": GPTJForCausalLM,
@@ -22,6 +23,7 @@ _MODEL_REGISTRY = {
     "LLaMAForCausalLM": LlamaForCausalLM,  # For decapoda-research/llama-*
     "MPTForCausalLM": MPTForCausalLM,
     "OPTForCausalLM": OPTForCausalLM,
+    "RWForCausalLM": FalconForCausalLM,
 }
 
 

vllm/model_executor/models/__init__.py

 from vllm.model_executor.models.baichuan import BaiChuanForCausalLM, BaichuanForCausalLM
 from vllm.model_executor.models.bloom import BloomForCausalLM
+from vllm.model_executor.models.falcon import FalconForCausalLM
 from vllm.model_executor.models.gpt2 import GPT2LMHeadModel
 from vllm.model_executor.models.gpt_bigcode import GPTBigCodeForCausalLM
 from vllm.model_executor.models.gpt_j import GPTJForCausalLM
@@ -12,6 +13,7 @@ __all__ = [
     "BaiChuanForCausalLM",
     "BaichuanForCausalLM",
     "BloomForCausalLM",
+    "FalconForCausalLM",
     "GPT2LMHeadModel",
     "GPTBigCodeForCausalLM",
     "GPTJForCausalLM",

vllm/model_executor/parallel_utils/parallel_state.py

@@ -44,7 +44,6 @@ _PIPELINE_GLOBAL_RANKS = None
 # rank when broadcasting weights from src to all other data parallel ranks
 _DATA_PARALLEL_GLOBAL_RANKS = None
 
-_ALL_REDUCE_LAUNCHER: Optional['GraphAllReduce'] = None
 
 def initialize_model_parallel(
     tensor_model_parallel_size: int = 1,
@@ -196,20 +195,6 @@ def initialize_model_parallel(
         if rank in ranks:
             _POSITION_EMBEDDING_GLOBAL_RANKS = position_embedding_ranks
 
-def initialize_all_reduce_launcher(
-    max_num_tokens: int,
-    hidden_size: int,
-    dtype: torch.dtype,
-    disable_graph: bool = False,
-) -> None:
-    global _ALL_REDUCE_LAUNCHER
-    _ALL_REDUCE_LAUNCHER = GraphAllReduce(
-        max_num_tokens=max_num_tokens,
-        hidden_size=hidden_size,
-        dtype=dtype,
-        disable_graph=disable_graph,
-    )
-
 def model_parallel_is_initialized():
     """Check if model and data parallel groups are initialized."""
     if _TENSOR_MODEL_PARALLEL_GROUP is None or \
@@ -458,6 +443,7 @@ def get_pipeline_model_parallel_last_rank():
     last_rank_local = get_pipeline_model_parallel_world_size() - 1
     return _PIPELINE_GLOBAL_RANKS[last_rank_local]
 
+
 def get_pipeline_model_parallel_next_rank():
     """Return the global rank that follows the caller in the pipeline"""
     assert _PIPELINE_GLOBAL_RANKS is not None, \
@@ -485,10 +471,6 @@ def get_data_parallel_rank():
     """Return my rank for the data parallel group."""
     return torch.distributed.get_rank(group=get_data_parallel_group())
 
-def get_all_reduce_launcher() -> 'GraphAllReduce':
-    assert _ALL_REDUCE_LAUNCHER is not None, 'all reduce launcher is not initialized'
-    return _ALL_REDUCE_LAUNCHER
-
 def destroy_model_parallel():
     """Set the groups to none."""
     global _MODEL_PARALLEL_GROUP
@@ -515,56 +497,3 @@ def destroy_model_parallel():
     _MPU_TENSOR_MODEL_PARALLEL_RANK = None
     global _MPU_PIPELINE_MODEL_PARALLEL_RANK
     _MPU_PIPELINE_MODEL_PARALLEL_RANK = None
-
-
-class GraphAllReduce:
-
-    def __init__(
-        self,
-        max_num_tokens: int,
-        hidden_size: int,
-        dtype: torch.dtype,
-        disable_graph: bool = False,
-    ) -> None:
-        self.max_num_tokens = max_num_tokens
-        self.hidden_size = hidden_size
-        self.disable_graph = disable_graph
-
-        tp_world_size = get_tensor_model_parallel_world_size()
-        if tp_world_size == 1:
-            return
-
-        self.group = get_tensor_model_parallel_group()
-        self.buffer = torch.empty(
-            size=(max_num_tokens, hidden_size),
-            dtype=dtype,
-            device='cuda',
-        )
-
-        # Build graphs for different number of tokens.
-        if not self.disable_graph:
-            self.graphs = {}
-            for num_tokens in range(8, max_num_tokens + 1, 8):
-                self.graphs[num_tokens] = self._build_graph(num_tokens)
-
-    def _build_graph(self, num_tokens: int) -> torch.cuda.CUDAGraph:
-        # Warm up.
-        torch.distributed.all_reduce(self.buffer[:num_tokens], group=self.group)
-        torch.cuda.synchronize()
-
-        # Build graph.
-        graph = torch.cuda.CUDAGraph()
-        with torch.cuda.graph(graph):
-            torch.distributed.all_reduce(
-                self.buffer[:num_tokens], group=self.group)
-        torch.cuda.synchronize()
-        return graph
-
-    def launch(self, x: torch.Tensor) -> torch.Tensor:
-        # NOTE: x must be a slice of self.buffer.
-        num_tokens = x.shape[0]
-        if self.disable_graph:
-            torch.distributed.all_reduce(x, group=self.group)
-        else:
-            self.graphs[num_tokens].replay()
-        return x

vllm/model_executor/parallel_utils/tensor_parallel/__init__.py

@@ -12,6 +12,7 @@ from .mappings import (
     copy_to_tensor_model_parallel_region,
     gather_from_tensor_model_parallel_region,
     gather_from_sequence_parallel_region,
+    reduce_from_tensor_model_parallel_region,
     scatter_to_tensor_model_parallel_region,
     scatter_to_sequence_parallel_region,
 )
@@ -38,7 +39,7 @@ __all__ = [
     "copy_to_tensor_model_parallel_region",
     "gather_from_tensor_model_parallel_region",
     "gather_from_sequence_parallel_region",
-#    "reduce_from_tensor_model_parallel_region",
+    "reduce_from_tensor_model_parallel_region",
     "scatter_to_tensor_model_parallel_region",
     "scatter_to_sequence_parallel_region",
     # random.py

vllm/model_executor/parallel_utils/tensor_parallel/layers.py

@@ -14,7 +14,6 @@ from torch.nn.parameter import Parameter
 from vllm.model_executor.parallel_utils.parallel_state import (
     get_tensor_model_parallel_rank,
     get_tensor_model_parallel_world_size,
-    get_all_reduce_launcher,
 )
 from .mappings import (
     copy_to_tensor_model_parallel_region,
@@ -248,8 +247,8 @@ class ColumnParallelLinear(torch.nn.Module):
         self.output_size = output_size
         self.gather_output = gather_output
         # Divide the weight matrix along the last dimension.
-        world_size = get_tensor_model_parallel_world_size()
-        self.output_size_per_partition = divide(output_size, world_size)
+        self.world_size = get_tensor_model_parallel_world_size()
+        self.output_size_per_partition = divide(output_size, self.world_size)
         self.skip_bias_add = skip_bias_add
 
         if params_dtype is None:
@@ -350,6 +349,7 @@ class RowParallelLinear(torch.nn.Module):
         params_dtype:
         use_cpu_initialization:
         perform_initialization:
+        reduce_results:
     """
 
     def __init__(self, input_size, output_size, *,
@@ -360,6 +360,7 @@ class RowParallelLinear(torch.nn.Module):
                  params_dtype=None,
                  use_cpu_initialization=False,
                  perform_initialization=True,
+                 reduce_results=True,
                  ):
         super(RowParallelLinear, self).__init__()
 
@@ -367,14 +368,19 @@ class RowParallelLinear(torch.nn.Module):
         self.input_size = input_size
         self.output_size = output_size
         self.input_is_parallel = input_is_parallel
+        self.reduce_results = reduce_results
         if params_dtype is None:
             params_dtype = torch.get_default_dtype()
 
         # Divide the weight matrix along the last dimension.
-        world_size = get_tensor_model_parallel_world_size()
-        self.input_size_per_partition = divide(input_size, world_size)
+        self.world_size = get_tensor_model_parallel_world_size()
+        self.input_size_per_partition = divide(input_size, self.world_size)
         self.skip_bias_add = skip_bias_add
 
+        if not reduce_results and (bias and not skip_bias_add):
+            raise ValueError("When not reduce the results, adding bias to the "
+                             "results can lead to incorrect results")
+
         # Parameters.
         # Note: torch.nn.functional.linear performs XA^T + b and as a result
         # we allocate the transpose.
@@ -427,17 +433,12 @@ class RowParallelLinear(torch.nn.Module):
             input_parallel = input_
         else:
             input_parallel = scatter_to_tensor_model_parallel_region(input_)
-        if get_tensor_model_parallel_world_size() == 1:
-            # Matrix multiply.
-            output_ = F.linear(input_parallel, self.weight)
+        # Matrix multiply.
+        output_parallel = F.linear(input_parallel, self.weight)
+        if self.reduce_results and self.world_size > 1:
+            output_ = reduce_from_tensor_model_parallel_region(output_parallel)
         else:
-            # Matrix multiply.
-            all_reduce_launcher = get_all_reduce_launcher()
-            num_tokens = input_parallel.shape[0]
-            output_buffer = all_reduce_launcher.buffer[:num_tokens]
-            torch.matmul(input_parallel, self.weight_t, out=output_buffer)
-            # All-reduce across all the partitions.
-            output_ = all_reduce_launcher.launch(output_buffer)
+            output_ = output_parallel
 
         if not self.skip_bias_add:
             output = output_ + self.bias if self.bias is not None else output_

vllm/transformers_utils/config.py

@@ -5,6 +5,8 @@ from vllm.transformers_utils.configs import *  # pylint: disable=wildcard-import
 _CONFIG_REGISTRY = {
     "mpt": MPTConfig,
     "baichuan": BaiChuanConfig,
+    "RefinedWeb": RWConfig,  # For tiiuae/falcon-40b(-instruct)
+    "RefinedWebModel": RWConfig,  # For tiiuae/falcon-7b(-instruct)
 }
 
 

vllm/transformers_utils/configs/__init__.py

 from vllm.transformers_utils.configs.mpt import MPTConfig
 from vllm.transformers_utils.configs.baichuan import BaiChuanConfig
+# RWConfig is for the original tiiuae/falcon-40b(-instruct) and
+# tiiuae/falcon-7b(-instruct) models. Newer Falcon models will use the
+# `FalconConfig` class from the official HuggingFace transformers library.
+from vllm.transformers_utils.configs.falcon import RWConfig
 
 __all__ = [
     "MPTConfig",
     "BaiChuanConfig",
+    "RWConfig",
 ]

vllm/transformers_utils/configs/falcon.py

+# Adapted from
+# https://huggingface.co/tiiuae/falcon-7b/blob/main/configuration_RW.py
+# Copyright 2023 The vLLM team.
+# Copyright 2022 the Big Science Workshop and HuggingFace Inc. team.
+# All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Falcon configuration"""
+from transformers.configuration_utils import PretrainedConfig
+
+
+class RWConfig(PretrainedConfig):
+    model_type = "falcon"
+    keys_to_ignore_at_inference = ["past_key_values"]
+    attribute_map = {
+        "num_hidden_layers": "n_layer",
+        "num_attention_heads": "n_head",
+        "num_kv_heads": "n_head_kv",
+    }
+
+    def __init__(
+        self,
+        vocab_size=250880,
+        hidden_size=64,
+        n_layer=2,
+        n_head=8,
+        layer_norm_epsilon=1e-5,
+        initializer_range=0.02,
+        use_cache=True,
+        bos_token_id=1,
+        eos_token_id=2,
+        hidden_dropout=0.0,
+        attention_dropout=0.0,
+        multi_query=True,
+        n_head_kv=None,
+        alibi=False,
+        bias=False,
+        parallel_attn=False,
+        new_decoder_architecture=False,
+        **kwargs,
+    ) -> None:
+        self.vocab_size = vocab_size
+        # Backward compatibility with n_embed kwarg
+        n_embed = kwargs.pop("n_embed", None)
+        self.hidden_size = hidden_size if n_embed is None else n_embed
+        self.n_layer = n_layer
+        self.n_head = n_head
+        self.layer_norm_epsilon = layer_norm_epsilon
+        self.initializer_range = initializer_range
+        self.use_cache = use_cache
+        self.hidden_dropout = hidden_dropout
+        self.attention_dropout = attention_dropout
+
+        self.bos_token_id = bos_token_id
+        self.eos_token_id = eos_token_id
+        self.multi_query = multi_query
+        self.n_head_kv = 1 if n_head_kv is None else n_head_kv
+        self.alibi = alibi
+        self.bias = bias
+        self.parallel_attn = parallel_attn
+        self.new_decoder_architecture = new_decoder_architecture
+
+        if self.hidden_size == 8192:
+            # Hack for falcon-40b
+            self.new_decoder_architecture = True
+
+        super().__init__(bos_token_id=bos_token_id,
+                         eos_token_id=eos_token_id,
+                         **kwargs)
+
+    @property
+    def head_dim(self):
+        return self.hidden_size // self.n_head
+
+    @property
+    def rotary(self):
+        return not self.alibi

vllm/worker/worker.py

@@ -9,7 +9,7 @@ from vllm.config import (CacheConfig, ModelConfig, ParallelConfig,
                          SchedulerConfig)
 from vllm.model_executor import get_model, InputMetadata, set_random_seed
 from vllm.model_executor.parallel_utils.parallel_state import (
-    initialize_model_parallel, initialize_all_reduce_launcher)
+    initialize_model_parallel)
 from vllm.sampling_params import SamplingParams
 from vllm.sequence import SequenceData, SequenceGroupMetadata, SequenceOutputs
 from vllm.worker.cache_engine import CacheEngine
@@ -65,11 +65,6 @@ class Worker:
         # Initialize the model.
         set_random_seed(self.model_config.seed)
         self.model = get_model(self.model_config)
-        initialize_all_reduce_launcher(
-            self.scheduler_config.max_num_batched_tokens,
-            self.model_config.get_hidden_size(),
-            self.model_config.dtype,
-        )
 
     @torch.inference_mode()
     def profile_num_available_blocks(