updating README

Author: Jacob Schroder

README.md

@@ -14,10 +14,10 @@ Install any dependencies for your testbed (like PyMFEM or FireDrake)
 Call testbed for your example to generate matrices
 
    from pyamg import testbed as tb
-   args = {'gamma' : 0.1, 'meshfile' : 'pathtomesh/inline-quad.mesh', 'order' : 1}
+   meshpath = tb.__path__[0] + '/mfem_adv_diff/inline-quad.mesh'
+   args = {'gamma' : 0.1, 'meshfile' : meshpath, 'order' : 1}
    data = tb.get_mat(tb.examples.mfem_adv_diff, 0, **args)
-   print(data['A'])
-   print(data['b'])
+   print(data.keys())
    print(data['docstring'])
 
 # add new testbed matrix example

pyamg/testbed/matrices.py

@@ -71,7 +71,11 @@ def get_mat(example, refinement, **kwargs):
     ##
     # Based on the example, call the appropriate matrix testbed
     if example == examples.mfem_adv_diff:
-        # inside the call here, check for pymfem, and check kwargs...
+        try:
+            import mfem.ser as mfem
+        except:
+            raise NameError("Install PyMFEM for this example")
+
         data = mfem_adv_diff(0, **kwargs)
         return data