Use the -U option to execute with the specified user ID or user name. For example,
% mprun -U traveler a.out
executes a.out as the user traveler.
Use the -G option to execute with the specified group ID or group name.
% mprun -G qa-team a.out
executes a.out as the group qa-team.
You must have the appropriate level of permissions to use these options. For example, you must belong to the group you specify, or be the superuser.