Run on only 1 GPU, how to run on all the 4 available GPUs

[pramodkp]

Model training and molecule generation run only on single GPU even if 4 GPUs are available.
How to run on all the GPUs available.

[topazape]

As you said, the Model only uses one GPU.
To be able to use multiple GPUs, it seems to use tf.distribute.MirroredStrategy().
But I don't have a GPU, so I can't test it.
If you can run it on multiple GPUs, please PR it!