At 10:10 AM 2/13/2009, Supalov, Alexander wrote:

Thanks. Could you please clarify to me, if possible, using some practically relevant example, how fault notification for a set of undefined fault types that may vary from MPI implementation to implementation differs from the equally abstract MPI_Checkpoint/MPI_Restart that semantically clearly prepare the MPI implementation at hand for the checkpoint action done by the checkpointing system involved, and then semantically clearly recover the MPI part of the program after the system restore?

Simple. As you've pointed out, the checkpointing API is well defined from the application's point of view. However, its semantics are weak from the checkpointer's point of view. Seen from this angle, it is not clear what the checkpointer can expect from the MPI library and the whole thing devolves into a negotiation between individual checkpointers and individual MPI libraries on a variety of specific system configurations. In contrast, the fault notification API only has an application view, which is in fact well-defined. The weakness of the fault notification API is what you've already described, that it provides no guarantees about the quality of the implementation in a way that is more significant than for other portions of MPI, such as network details for MPI_Send/MPI_Recv. Greg Bronevetsky Post-Doctoral Researcher 1028 Building 451 Lawrence Livermore National Lab (925) 424-5756 [email protected]