fix issue#101 (#102)

* fix issue#101

* yapf

parl/utils/machine_info.py

@@ -16,6 +16,7 @@ import os
 import platform
 import subprocess
 from parl.utils import logger
+from parl.utils import utils
 
 __all__ = ['get_gpu_count', 'get_ip_address', 'is_gpu_available']
 
@@ -95,4 +96,11 @@ def is_gpu_available():
     Returns:
       True if a gpu device can be found.
     """
-    return get_gpu_count() > 0
+    ret = get_gpu_count() > 0
+    if utils._HAS_FLUID:
+        from paddle import fluid
+        if ret is True and not fluid.is_compiled_with_cuda():
+            logger.warn("Found non-empty CUDA_VISIBLE_DEVICES. \
+                But PARL found that Paddle was not complied with CUDA, which may cause issues."
+                        )
+    return ret