MPI imbalance documentation question

[kddevin]

On https://github.com/kokkos/kokkos-tools/wiki/Space-Time-Stack the documentation says "The second column is the imbalance across MPI ranks, defined as the maximum time consumed by the kernel in any MPI rank divided by the average time consumed by the kernel over all MPI ranks."

That means the number reported should always be one or greater. But the values shown in the example are percentages all less than 100%.

How should one interpret the MPI imbalance field? For example, does 100% mean perfectly balanced, or that some process takes twice as long as the average?

[crtrott]

I think there is "minus one" missing. I.e. 0 is no imbalance, 1 means, some rank is using 2 times longer than the average.