# OpenMP Parallel Efficiency

The OpenMP Parallel Efficiency measures the cost of inefficiencies within OpenMP parallel regions, averaged over the processes. Inefficiency is any time spent outside useful computation within an OpenMP parallel region and can include time in MPI.

It can be split into OpenMP Parallel Efficiency for each OpenMP region to identify which regions contribute most to the inefficiency.

It can also be split into contributions per source of inefficiency, e.g. OpenMP Load Balance Efficiency and other OpenMP Parallel Efficiency sub-metrics, such as time in MPI, time in critical regions, etc.

$OpenMP Parallel Efficiency = 1 - \frac{Avg_{t}(OpenMP - OpenMP\_Useful)}{Runtime}$

In order to fully understand the formulas, you may also visit the glossary of the metrics terms.