The lowest level way to create logfiles is with the CLOG interface, which logs the various event types and manages the activities described in Section How It Works . The change from ALOG to CLOG logfile formats was accomplished by re-implementing the MPE logging library in terms of CLOG calls, without changing the MPE interface. In addition, the transition from ALOG format to CLOG format has been eased for MPICH users by providing a CLOG-to-ALOG translator, so that the older tools, upshot and nupshot, can still be used with the newer CLOG file format. This was important for the period between the adoption of the CLOG format and the implementation of Jumpshot.