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       LAM  SSI  checkpoint  /  restart  -  overview of LAM's MPI checkpoint /
       restart SSI modules


       The "kind" for checkpoint / restart SSI modules is "cr".  Specifically,
       the  string "cr" (without the quotes) is the prefix that should be used
       with the mpirun command line with the -ssi switch.  For example:

       mpirun -ssi cr blcr C my_mpi_program

       LAM/MPI can involuntarily checkpoint and  restart  parallel  MPI  jobs.
       Doing  so  requires  that  LAM/MPI was compiled with thread support and
       that back-end checkpointing systems are  available  at  run-time.   MPI
       jobs  will have to run with at least MPI_THREAD_SERIALIZED support.  If
       a job elects to run with checkpoint/restart support and an available cr
       module  is found, the job's thread level will automatically be promoted
       to MPI_THREAD_SERIALIZED.  See the User's Guide for more details.

   Checkpoint Phases
       LAM defines three phases for checkpoint / restart support in  each  MPI

           When  the  checkpoint request arrives, before the actual checkpoint

           After a checkpoint has successfully completed, in the same  process
           as the checkpoint was invoked in.

           After a checkpoint has successfully completed, in a new / restarted

       The Continue and Restart phases are identical except for the process in
       which  they  are  invoked  -- the Continue phase is invoked in the same
       process as the Checkpoint phase was invoked.  The Restart phase is only
       invoked in newly restarted processes.


       LAM  currently  has two cr modules: blcr and self.  In order for an MPI
       job to be able to be checkpointed and restarted, all  of  its  MPI  SSI
       modules  must  support checkpoint/restart.  Currently, this means using
       the crtcp RPI module or the gm RPI module when compiled  with  gm_get()
       support (see the User's Guide for more details).

   blcr CR Module
       The  Berkeley Lab Checkpoint/Restart (BLCR) single-node checkpointer is
       a software system from Lawrence Berkeley Labs.   See  the  project  web
       page for more details:

       The blcr module has one SSI parameter:

           blcr's default priority is 50.

   self CR Module
       The  self  CR module effectively allows application-level checkpointing
       by invoking user-specified functions at the Checkpoint,  Continue,  and
       Restart phases of LAM/MPI C/R support.

       Multiple SSI parameters are available:

           Specify  a  string prefix for the name of the checkpoint, continue,
           and restart functions that should be  invoked  by  LAM.   That  is,
           specifying "-ssi cr_self_user_prefix_foo" means that LAM expects to
           find three functions at run-time: foo_checpkoint(), foo_continue(),
           and  foo_restart().   This  is  a convenience parameter that can be
           used instead of the three parameters listed below.

           Name of the user function to invoke during the Checkpoint phase.

           Name of the user function to invoke during the Continue phase.

           Name of the user function to invoke during the Restart phase.

       If none of these parameters  are  specified  and  the  self  module  is
       selected,  it will abort.  Finally, the usual priority SSI parameter is
       also available:

           self's default priority is 25.


       lamssi(7), mpirun(1), LAM User's Guide