M3. Each xSDK-compatible package that utilizes MPI must restrict its MPI operations to MPI communicators that are provided to it and not use directly MPI_COMM_WORLD. The package should use configure tests or version tests to detect MPI 2 or MPI 3 features that may not be available; it should not be assumed that a full MPI 2 or MPI 3 implementation is available. The package can change the MPI error-handling mode by default but should have an option to prevent it from changing the MPI error handling (which may have been set by another package or the application). The package should also behave appropriately regardless of the MPI error handling being used. There is no requirement that the package provide a sequential (non-MPI) version, although this functionality is welcome, too. If the package provides a sequential version, there is no requirement that it be compatible or usable with other xSDK-compatible packages running without MPI.