better user experience

- no meaningless warnings regarding floating point precision
- meaningful error message for invalid header

python/damask/_geom.py

@@ -300,13 +300,16 @@ class Geom:
             f = fname
 
         f.seek(0)
-        header_length,keyword = f.readline().split()[:2]
-        header_length = int(header_length)
-        content = f.readlines()
-
+        try:
+            header_length,keyword = f.readline().split()[:2]
+            header_length = int(header_length)
+        except ValueError:
+            header_length,keyword = (-1, 'invalid')
         if not keyword.startswith('head') or header_length < 3:
             raise TypeError('Header length information missing or invalid')
 
+        content = f.readlines()
+
         comments = []
         for i,line in enumerate(content[:header_length]):
             items = line.split('#')[0].lower().strip().split()
@@ -584,7 +587,7 @@ class Geom:
                - ((np.ones(3)-(1./self.grid if np.array(center).dtype in np.sctypes['int'] else 0))*0.5 if periodic else c)  # periodic center is always at CoG
         coords_rot = R.broadcast_to(tuple(self.grid))@coords
 
-        with np.errstate(over='ignore',under='ignore'):
+        with np.errstate(over='ignore',under='ignore',invalid='ignore'):
             mask = np.where(np.sum(np.power(coords_rot/r,2.0**exponent),axis=-1) <= 1.0,False,True)
 
         if periodic:                                                                                # translate back to center