Thread Efficiency

Thread Efficiency considers two sources of inefficiency:

Serial computation on the master outside OpenMP, i.e. reflects Amdahl's law
Inefficiencies within threads, e.g. serialisation across threads

These two can be measured with Amdahl's Efficeincy and OpenMP region Efficiency respectively. Thread Efficeincy can be computed directly or as a product of these two sub-metrics:

$\begin{eqnarray*}Thread\; Efficiency=\frac{avg( computation\; time) }{avg( time\; in\; OpenMP ) + avg( serial\; computation )} \end{eqnarray*}$

= Amdahl's Efficiency ⋅ OpenMP Region Efficiency

Where average time in OpenMP and average serial computation are computed as weighted arithmetic mean. If number of threads is equal across processes average time in OpenMP and average serial computation can be computed as ordinary arithmetic mean.