fix https://github.com/facebookresearch/maskrcnn-benchmark/issues/802 (#516)

apex/amp/lists/torch_overrides.py

@@ -74,9 +74,12 @@ if version_num < 1.1:
 _bmms = ['addbmm',
          'baddbmm',
          'bmm']
-if utils.get_cuda_version() >= (9, 1, 0):
+
+if utils.is_cuda_enabled():
+  # workaround https://github.com/facebookresearch/maskrcnn-benchmark/issues/802
+  if utils.get_cuda_version() >= (9, 1, 0):
       FP16_FUNCS.extend(_bmms)
-else:
+  else:
       FP32_FUNCS.extend(_bmms)
 
 # Multi-tensor fns that may need type promotion

apex/amp/utils.py

@@ -5,6 +5,9 @@ import itertools
 
 import torch
 
+def is_cuda_enabled():
+    return torch.version.cuda is not None
+
 def get_cuda_version():
     return tuple(int(x) for x in torch.version.cuda.split('.'))