Hi all, I would like to propose an addition of a function call to dynamically modify the thread level required by the application, instead of at MPI_Init_thread() time. I'm sending this over email for comments (attached with this email); I'll upload it on the wiki this evening. -- Pavan -- Pavan Balaji http://www.mcs.anl.gov/~balaji Dynamic Thread Levels Author: Pavan Balaji, Argonne National Laboratory Background: MPI 2.1 standard allows users to set thread level only at MPI_Init_thread time. This means that for applications that dynamically create threads (e.g., hybrid MPI + OpenMP applications), even non-threaded portions of the application have to rely on the maximum thread level used in the application (e.g., MULTIPLE). Proposal: Add an additional function call to dynamically set thread-level during the application. int MPI_Set_thread_level(int required, int * provided); Rational: The requirement to specify the thread-level at MPI_Init_thread time is too restrictive for applications that perform a small amount of communication requiring a high-level of thread support. For correctness, the standard requires all of the code to follow the same thread-level, and provides the applications with no way to give the MPI library more information about their behavior. Impact on MPI implementations: Most MPI implementations already provide runtime support for thread-level, i.e., locks are compiled in, but whether they are invoked or not is decided at runtime. For implementations that choose not to respect this option, MPI_Set_thread_level() can just set the provided level to the current level, by ignoring the required level specified by the user. Impact on MPI applications: Existing MPI applications do not need to be modified at all. But newer applications can benefit from this additional functionality.