cuda check and better comment

docker/check_cuda_torch.py

@@ -1,3 +1,4 @@
+#!/usr/bin/env python
 '''
 little script to check if cuda is available in pytorch and working
 organised as a check that raises an exception if cuda is not available, and data cannot be moved to the gpu

src/PrimaryGeneratorAction.cc

@@ -121,7 +121,7 @@ void PrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
     G4Exception("PrimaryGeneratorAction::GeneratePrimaries()",
       "MyCode0002", JustWarning, msg);
   }
-  //draw particle position from a unit distribution in x-y with +-5 cm around the center
+  //draw particle position from a unit distribution in x-y with +-7.5 cm around the center
   G4double x = -1000;
   G4double y = -1000;
   G4double x_width = 15;