updates

train.py

@@ -168,11 +168,12 @@ def train(
                             collate_fn=dataset.collate_fn)
 
     # Mixed precision training https://github.com/NVIDIA/apex
-    # install help: https://github.com/NVIDIA/apex/issues/259
-    mixed_precision = False
-    if mixed_precision:
+    try:
         from apex import amp
         model, optimizer = amp.initialize(model, optimizer, opt_level='O1')
+        mixed_precision = True
+    except:  # not installed: install help: https://github.com/NVIDIA/apex/issues/259
+        mixed_precision = False
 
     # Start training
     model.hyp = hyp  # attach hyperparameters to model