I am working on the development of a parallel CFD solver and I am using MPI_Allreduce for the global summation of the local errors calculated on all processes of a group and the summation is to be used by all the processes. My concern is that MPI_Allreduce is taking almost 27-30% of the total time used, which is a significant amount. So, I want to ask if anyone can suggest me better alternative/s to replace MPI_Allreduce which can reduce the time consumption.

Thank you.