[rllib] PyTorch A2C is not GPU accelerated

[nautilus22]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Ubuntu 16.04.6 LTS (GCP)
• Ray installed from (source or binary): source
• Ray version: 0.6.4
• Python version: 3.6.8

Describe the problem

I tested atari-a2c with tuned parameter(/tuned_examples/atari-a2c.yaml)
It showed great result for atari breakout.
However if "use_pytorch": true was added, the result is quite different. (I used "atari-a2c-pytorch.yaml" in the 'Source code / logs' section)
It was very slow and it seems that there was no improvement.
I guess there's some performance issue on pytorch a2c, but are there any necessary options for pytorch a2c?

Source code / logs

atari-a2c.yaml

atari-a2c:
    env:
        grid_search:
            - BreakoutNoFrameskip-v4
            - BeamRiderNoFrameskip-v4
            - QbertNoFrameskip-v4
            - SpaceInvadersNoFrameskip-v4
    run: A2C
    config:
        sample_batch_size: 20
        clip_rewards: True
        num_workers: 5
        num_envs_per_worker: 5
        num_gpus: 1
        lr_schedule: [
            [0, 0.0007],
            [20000000, 0.000000000001],
        ]

atari-a2c-pytorch.yaml

atari-a2c:
    env:
        grid_search:
            - BreakoutNoFrameskip-v4
            - BeamRiderNoFrameskip-v4
            - QbertNoFrameskip-v4
            - SpaceInvadersNoFrameskip-v4
    run: A2C
    config:
        sample_batch_size: 20
        clip_rewards: True
        num_workers: 5
        num_envs_per_worker: 5
        num_gpus: 1
        lr_schedule: [
            [0, 0.0007],
            [20000000, 0.000000000001],
        ]
        use_pytorch: True

[ericl]

We haven't spent time tuning the torch vision models, so this is probably expected. Also, PyTorch needs explicit tensor.cuda() calls to support GPU acceleration, which is not implemented as well (help here would be welcome)!

pong-a3c-pytorch.yaml might still work ok though, cc @richardliaw

[nautilus22]

Thank you for your answer.
Me and my team are seriously considering working on pytorch A2C acceleration.