robust deviceid handling

contrib/Python/cntk/conftest.py

@@ -3,12 +3,22 @@ import sys
 collect_ignore = ["setup.py"]
 
 # content of conftest.py
+_DEFAULT_DEVICE_ID=-1
 
 def pytest_addoption(parser):
-    parser.addoption("--deviceid", action="append", default=[],
+    parser.addoption("--deviceid", action="append", default=[_DEFAULT_DEVICE_ID],
         help="list of device ids to pass to test functions")
 
 def pytest_generate_tests(metafunc):    
     if 'device_id' in metafunc.fixturenames:        
-        metafunc.parametrize("device_id",
-                             metafunc.config.option.deviceid)
+        if (len(metafunc.config.option.deviceid)) > 1:
+            del metafunc.config.option.deviceid[0]
+            
+        devices = set()
+        for d_id in metafunc.config.option.deviceid:
+            try:
+                devices.add(int(d_id))
+            except ValueError:
+                raise RuntimeError("invalid deviceid value {0}, please use integer values".format(d_id))
+                    
+        metafunc.parametrize("device_id", devices)