This paper discusses a multi-threaded software architecture for Message-Passing Interface (MPI) software specification. The architecture is thread-safe, allows for concurrent communication over several communications media (multi-fabric communication), efficiently utilizes available hardware concurrency over a wide range of target platforms, and allows for concurrent communication and computation within the limits imposed by the hardware. The architecture is developed in the framework of the MPICH software architecture, a well-known MPI implementation used worldwide. The proposed architecture adopts wide portability of the MPICH design and remedies some of its deficiencies such as inefficient multifabric communication and non-thread-safety. The paper also considers the issues concerning development of high-performance portable message-passing systems for general-purpose architectures. The contributions of the paper are: improving architecture and addressing thread safety of modern reli...

Device Interface) that defines a conceptual set of services which should be provided by any lower-level communication mechanism for the MPIR layer), and Device (the implementation of the ADI services for the particular platform) (Gropp et al. 1995). A part of the Device layer in the current MPICH implementation is called the Channel Device Interface; this sub-layer is actually an interface between the ADI and lower-level device code; the services of the lower-level device layer are further conceptualized and reduced to a small set of basic message-passing routines that should be implemented for a target platform (Gropp and Lusk 1995b; Gropp and Lusk 1995a; Gropp and Lusk 1996a; Gropp and Lusk 1996b). All devices which use the Channel Device Interface are called "channel devices." One can choose any layer (MPIR, ADI, or Device) and implement everything below it in order to port MPICH to a target platform. The MPICH design and implementation is still being improved and corrected. User b...