Feature Request: load_state_dict should take filenames

[soumith]

In high memory pressure situations, the following is a common occurrence:

1. create model
2. read state_dict from checkpoint file (loads on GPU)
3. model.load_state_dict(s)

Because of memory pressure, a common workaround is to first do:

s = torch.load('my_file.pt', map_location=lambda storage, loc: storage)

And then load s into model.

This is a very common scenario that we should be able to avoid, and this scenario might have some pitfalls: what happens on part-GPU part-CPU models, what happens on multi-GPU models...

if load_state_dict took a filename directly, it can delete it's existing parameter storages and set them to the new one on the fly, thereby requiring no extra memory.

[soumith]

the same applies to optimizer state_dicts. for some optimizers like Adagrad, the checkpoints are large, and we can have the same memory pressure situation. optimizers dont even have a .cuda(), so we manually first have to load state_dict onto CPU, and then manually copy over parts to the GPU.

I ran into this while helping @aszlam today.

[alykhantejani]

If load_state_dict takes a filename we should also allow for the map_location param too. A common situation for me is to save a checkpoint on cluster machine and then load it on my macbook (so need to load params onto CPU)

[vadimkantorov]

Me and @szagoruyko are fans of HDF5 format for serialized models, maybe if it could get along nicely with this proposal