add logging message for using GPU (#450)

Summary:
Pull Request resolved: #450

added a logger message when GPU is successfully used with the model and generator included.

Reviewed By: crasanders

Differential Revision: D65907247

fbshipit-source-id: af51f3051cf709a57b7e4bac213c4f2a80bd4fca

Author: JasonKChow

aepsych/strategy.py

@@ -170,6 +170,7 @@ def __init__(
                     self.model_device = torch.device("cpu")
                 else:
                     self.model_device = torch.device("cuda")
+                    logger.info(f"Using GPU for modeling with {type(model).__name__}")
             else:
                 self.model_device = torch.device("cpu")
 
@@ -195,6 +196,9 @@ def __init__(
                     self.generator_device = torch.device("cpu")
                 else:
                     self.generator_device = torch.device("cuda")
+                    logger.info(
+                        f"Using GPU for generating with {type(generator).__name__}"
+                    )
         else:
             self.generator_device = torch.device("cpu")