Choose --num_blocks for bigscience/bloom-petals automatically (#119)

src/petals/server/server.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import gc
+import math
 import multiprocessing as mp
 import random
 import threading
@@ -130,7 +131,9 @@ class Server:
         )
         self.module_uids = [f"{self.prefix}.{block_index}" for block_index in range(self.block_config.n_layer)]
 
-        assert (block_indices is None) != (num_blocks is None), "please specify num_blocks or block_indices, not both"
+        assert num_blocks is None or block_indices is None, "Please specify num_blocks or block_indices, not both"
+        if num_blocks is None and block_indices is None:
+            num_blocks = self._choose_num_blocks()
         if block_indices is not None:
             try:
                 first_block_index, last_block_index = block_indices.split(":")
@@ -167,6 +170,26 @@ class Server:
 
         self.stop = threading.Event()
 
+    def _choose_num_blocks(self) -> int:
+        assert (
+            self.converted_model_name_or_path == "bigscience/bloom-petals"
+        ), "If you use a model other than bigscience/bloom-petals, please specify --num blocks manually"
+        assert self.device.type == "cuda", "If you run a non-GPU server, please specify --num_blocks manually"
+
+        gib = 1024**3
+        total_memory_gib = torch.cuda.get_device_properties(self.device).total_memory / gib
+        block_size_gib = 176 / 70 + 0.5
+        if not self.load_in_8bit:
+            block_size_gib *= 2 if self.dtype in (torch.float16, torch.bfloat16) else 4
+        num_blocks = math.floor((total_memory_gib - 2) / block_size_gib)
+        assert num_blocks >= 1, "Your GPU does not have enough memory to serve at least one block"
+
+        logger.info(
+            f"Server will fill all your GPU memory with {num_blocks} transformer blocks. "
+            f"If you want to leave some free GPU memory, please specify a lesser --num_blocks manually"
+        )
+        return num_blocks
+
     def run(self):
         while True:
             block_indices = self._choose_blocks()