  The efficiency and scalability of MPI collective operations, in particular
the broadcast operation, plays an integral part in high performance computing
applications. MPICH, as one of the contemporary widely-used MPI software
stacks, implements the broadcast operation based on point-to-point operation.
Depending on the parameters, such as message size and process count, the
library chooses to use different algorithms, as for instance binomial
dissemination, recursive-doubling exchange or ring all-to-all broadcast
(allgather). However, the existing broadcast design in latest release of MPICH
does not provide good performance for large messages (\textit{lmsg}) or medium
messages with non-power-of-two process counts (\textit{mmsg-npof2}) due to the
inner suboptimal ring allgather algorithm. In this paper, based on the native
broadcast design in MPICH, we propose a tuned broadcast approach with
bandwidth-saving in mind catering to the case of \textit{lmsg} and
\textit{mmsg-npof2}. Several comparisons of the native and tuned broadcast
designs are made for different data sizes and program sizes on Cray XC40
cluster. The results show that the performance of the tuned broadcast design
can get improved by a range from 2\% to 54\% for \textit{lmsg} and
\textit{mmsg-npof2} in terms of user-level testing.
