MPI - counting maximum from a matrix column

I have sequential code for looking for maximum value in matrix columns. Because this matrix could be even 5000 x 5000, I am thinking of speeding it in MPI. I don't know how to achieve this now, but I looked up functions MPI_Scatter for distributing items from a columns (maybe block mapping) and MPI_Gather 开发者_Python百科for getting max values from all processes (in my case max 3 processes) and then comparing them... Do you think this could have some benefit in lesser computing time? If so, can someone give me a kick off?

Is all you want to do find out the maximum entry in the matrix (or within a part of the matrix)?

If so, the easiest way for you is probably split the matrix up to different processes, search for the maximum value in the part each process gets assigned and then compare them using MPI_Allreduce, which is able to send the maximum value of a variable which has different values in each processes to all processes.

No matter if you are dealing with a whole matrix or just a column, this technique can of course always be applied. You just have to think about a good way of splitting the area up to different processes

Of course this will speed up your computation only from a certain matrix size upwards. I assume if you are dealing with a 10 x 10 matrix and want to split it into 3 processes, the overhead for MPI is larger than the gain from parallelization. :)