[context]use meta tensor to init model lazily. (#1187)

* [CLI] add CLI launcher

* Revert "[CLI] add CLI launcher"

This reverts commit df7e6506d4.

* [context]use meta tensor to init model lazily.

* polish

* make module with device kwargs bypass the normal init.

* change unit test to adapt updated context.

tests/test_utils/test_lazy_init_ctx.py

@@ -1,23 +1,22 @@
 import torch
-import torch.nn as nn
 from colossalai.utils.model.lazy_init_context import LazyInitContext
+from torchvision.models import resnet34
 
-def test_lazy_init_ctx():
 
-    with LazyInitContext() as ctx:
-        model = nn.Linear(10, 10)
-        model.weight.zero_()
-    
-    # make sure the weight is a meta tensor
-    assert model.weight.is_meta
-    
-    # initialize weights
+def test_lazy_init():
+    ctx = LazyInitContext()
+    with ctx:
+        model = resnet34(num_classes=10)
+    for param in model.parameters():
+        assert param.is_meta
+    for buffer in model.buffers():
+        assert buffer.is_meta
     ctx.lazy_init_parameters(model)
-    
-    # make sure the weight is not a meta tensor 
-    # and initialized correctly
-    assert not model.weight.is_meta and torch.all(model.weight == 0)
+    for param in model.parameters():
+        assert not param.is_meta
+    for buffer in model.buffers():
+        assert not buffer.is_meta
 
 
 if __name__ == '__main__':
-    test_lazy_init_ctx()
+    test_lazy_init()