Proceedings of: First International Workshop on Sustainable Ultrascale Computing Systems (NESUS 2014). Porto (Portugal), August 27-28, 2014.Exascale systems are likely to have orders of magnitude less memory per core than current systems (though still large amounts of memory). As the amount of memory per core is dropping, going to thread-based models might be an unavoidable step towards the exascale milestone. AzequiaMPI is a thread-based open source full conformant implementation of MPI-1.3 for shared memory. We expose the techniques introduced in AzequiaMPI that, first, simplify the implementation and second, make the thread-based model to significantly improve the bandwidth of process-based implementations. Current version is also compliant with the MPI_THREAD_MULTIPLE thread-safety level, a feature of MPI-2.0 standard. The well known Thakur and Gropp MPI_THREAD_MULTIPLE tests show that both latency and bandwidth figures of AzequiaMPI significantly improve that of MPC-MPI, MPICH and Open MPI in an eight cores Intel Xeon E5620 Nehalem machine.The work presented in this paper has been partially supported
by EU under the COST programme Action IC1305, ’Network for
Sustainable Ultrascale Computing (NESUS)’
