[zero] add warning for ignored parameters (#2446)

colossalai/gemini/chunk/utils.py

@@ -10,13 +10,18 @@ from colossalai.gemini.chunk.search_utils import search_chunk_configuration
 from colossalai.utils import is_ddp_ignored
 
 
+def safe_div(a, b):
+    if a == 0:
+        return 0
+    return a / b
+
+
 def init_chunk_manager(model: nn.Module,
                        init_device: Optional[torch.device] = None,
                        hidden_dim: Optional[int] = None,
                        search_range_mb: Optional[float] = None,
                        min_chunk_size_mb: Optional[float] = None,
                        filter_exlarge_params: Optional[bool] = None) -> ChunkManager:
-
     kwargs_dict = dict()
 
     if hidden_dim:
@@ -50,7 +55,7 @@ def init_chunk_manager(model: nn.Module,
     if dist.get_rank() == 0:
         print("searching chunk configuration is completed in {:.2f} s.\n".format(span_s),
               "used number: {:.2f} MB, wasted number: {:.2f} MB\n".format(total_size, wasted_size),
-              "total wasted percentage is {:.2f}%".format(100 * wasted_size / (total_size + wasted_size)),
+              "total wasted percentage is {:.2f}%".format(100 * safe_div(wasted_size, total_size + wasted_size)),
               sep='',
               flush=True)
     dist.barrier()

colossalai/nn/optimizer/zero_optimizer.py

 import math
+import warnings
 from enum import Enum
 from typing import Any, Dict, Set, Tuple
 
@@ -78,8 +79,16 @@ class ZeroOptimizer(ColossalaiOptimizer):
         if self.clipping_flag:
             assert norm_type == 2.0, "ZeroOptimizer only supports L2 norm now"
 
-        params_list = [p for p in module.parameters() if not is_ddp_ignored(p)]
-        for p, fp32_p in zip(params_list, module.fp32_params):
+        ddp_param_list = []
+        for name, param in module.named_parameters():
+            if is_ddp_ignored(param):
+                if param.requires_grad:
+                    warnings.warn(f"Parameter `{name}` is ignored by DDP but requires gradient! "
+                                  "You should handle its optimizer update by yourself!")
+            else:
+                ddp_param_list.append(param)
+
+        for p, fp32_p in zip(ddp_param_list, module.fp32_params):
             chunk_16 = self.chunk_manager.get_chunk(p)
             if chunk_16 not in self.chunk16_set:
                 chunk_16.l2_norm_flag = self.clipping_flag
@@ -290,6 +299,8 @@ class ZeroOptimizer(ColossalaiOptimizer):
             fake_params_list = list()
 
             for param in group['params']:
+                if is_ddp_ignored(param):
+                    continue
                 chunk16 = self.chunk_manager.get_chunk(param)
                 range_pair = get_range_pair(chunk16, param)
                 if range_pair[0] >= range_pair[1]: