[Gemini] GeminiDPP convert to PyTorch Module. (#2151)

colossalai/nn/parallel/utils.py

@@ -2,6 +2,7 @@ import torch
 import torch.distributed as dist
 
 from colossalai.gemini.chunk import Chunk
+from colossalai.tensor import ColoTensor
 from colossalai.utils import get_current_device
 
 
@@ -19,3 +20,30 @@ def get_temp_total_chunk_on_cuda(chunk: Chunk):
     dist.all_gather(tensor_list=gather_list, tensor=shard_temp, group=chunk.torch_pg)
 
     return total_temp
+
+
+def _add_param(model, name, param):
+    name_list = name.split('.')
+    module = model._modules[name_list[0]]
+    for i in range(1, len(name_list) - 1):
+        module = module._modules[name_list[i]]
+    module._parameters[name_list[-1]] = param
+
+
+def convert_to_torch_module(gemini_ddp_model) -> torch.nn.Module:
+    """convert_to_torch_module
+
+    Args:
+        gemini_ddp_model (GeminiDDP): a gemini ddp model
+
+    Returns:
+        torch.nn.Module: a torch model contains the params of gemini_ddp_model
+    """
+    module = gemini_ddp_model.module
+
+    for n, p in module.named_parameters():
+        if isinstance(p, ColoTensor):
+            p.to_replicate_()
+            _add_param(module, n, p.data)
+
+    return module

colossalai/tensor/colo_tensor.py

@@ -103,7 +103,6 @@ class ColoTensor(torch.Tensor):
                 self.process_group = spec.pg
 
         self._type = TensorType.NONMODEL
-        self._graph_node = None
 
     def has_compute_spec(self) -> bool:
         return self.compute_spec is not None

tests/test_gemini/update/test_convert_torch_module.py

+from functools import partial
+
+import pytest
+import torch.multiprocessing as mp
+
+import colossalai
+from colossalai.nn.parallel.utils import convert_to_torch_module
+from colossalai.tensor import ColoTensor
+from colossalai.testing import parameterize, rerun_if_address_is_in_use
+from colossalai.utils import free_port
+from colossalai.utils.cuda import get_current_device
+from colossalai.utils.model.colo_init_context import ColoInitContext
+from tests.components_to_test.registry import non_distributed_component_funcs
+
+
+@parameterize('model_name', ['resnet18', 'bert'])
+def run_convert_torch_module(model_name: str):
+    get_components_func = non_distributed_component_funcs.get_callable(model_name)
+    model_builder, _, _, _, _ = get_components_func()
+
+    with ColoInitContext(device='cpu'):
+        model = model_builder(checkpoint=False)
+
+    from colossalai.nn.parallel import GeminiDDP
+    model = GeminiDDP(model, device=get_current_device(), placement_policy='auto', pin_memory=True)
+
+    pytorch_model = convert_to_torch_module(model)
+
+    for n, p in pytorch_model.named_parameters():
+        assert not isinstance(p, ColoTensor)
+
+
+def run_dist(rank, world_size, port):
+    config = {}
+    colossalai.launch(config=config, rank=rank, world_size=world_size, host='localhost', port=port, backend='nccl')
+    run_convert_torch_module()
+
+
+@pytest.mark.dist
+@pytest.mark.parametrize('world_size', [1, 4])
+@rerun_if_address_is_in_use()
+def test_convert_torch_module(world_size):
+    run_func = partial(run_dist, world_size=world_size, port=free_port())
+    mp.spawn(run_func, nprocs=world_size)
+
+
+if __name__ == '__main__':
+    test_convert_torch_module(2)