for the a given face before the compute step.
The position of the face in faces to be checked.
The description of the faces.
Returns 0 if no information has to be received from remote ranks before a compute step can be done. In case that information has to be received it will return a non-zero positive value. Furhtermore, it determines whether information for the left face value (left adjacent element) or the right face value (right adjacent element) has to be received. In the first case it will return tem_left and in the second case it will return tem_right. If something went wrong, e.g. an unknown combination occurs, it will return -1.