Error condition: error loading the pre training model

RuntimeError: Error(s) in loading state_dict for :

Missing key(s) in state_dict: “features.0.weight” …

Unexpected key(s) in state_dict: “module.features.0.weight” …

Error reason:

The keywords of model parameters wrapped with nn.DataParallel will have an extra “module.” in front of them than the keywords of model parameters not wrapped with nn.DataParallel

Solution:

1. Loading nn.DataParallel(net) trained models using net.

Delete module.

# original saved file with DataParallel
state_dict = torch.load('model_path')
# create new OrderedDict that does not contain `module.`
from collections import OrderedDict
new_state_dict = OrderedDict()
for k, v in state_dict.items():
    name = k[7:] # remove `module.`
    new_state_dict[name] = v
# load params
net.load_state_dict(new_state_dict)

Code source

checkpoint = torch.load('model_path')
for key in list(checkpoint.keys()):
    if 'model.' in key:
        checkpoint[key.replace('model.', '')] = checkpoint[key]
        del checkpoint[key]

net.load_state_dict(checkpoint)

Use nn.DataParallel when loading the model

checkpoint = torch.load('model_path')
net = torch.nn.DataParallel(net)
net.load_state_dict(checkpoint)

2. Load the net trained model using nn.DataParallel(net).

Before saving the weight, add module

If you use torch.save() when saving weights, use model.module.state_dict() to get model weight

torch.save(net.module.state_dict(), 'model_path')

Read the model before using nn.DataParallel and then use nn.

net.load_state_dict(torch.load('model_path'))
net = nn.DataParallel(net, device_ids=[0, 1]) 

Add module manually

net = nn.DataParallel(net) 
from collections import OrderedDict
new_state_dict = OrderedDict()
state_dict =savepath #Pre-trained model path
for k, v in state_dict.items():
	# add “module.” manually
    if 'module' not in k:
        k = 'module.'+k
    else:
    # Swap the location of modules and features
        k = k.replace('features.module.', 'module.features.')
    new_state_dict[k]=v

net.load_state_dict(new_state_dict)