[aidenn0]

> You can just divide the speed-up by the number of cores, and that gives you the parallelization efficiency.

The linked benchmark document does this. 82% for 4 cores on Spice with a small workload, and 69% for 16 cores on Spice with a large workload. Compared to about 25% for Rayon on 4 cores with a small workload and 88% for Rayon on 16 cores with a large workload.

> Sure, there is probably some extra latency to get everything running, but for a sufficiently long program run, that is all irrelevant.

The entire point of the linked benchmark README.md is to deal with insufficiently long program runs. Spice is an attempt to allow parallelization of very small amounts of work by decreasing fixed overhead. Perhaps such a thing is not useful but that doesn't prevent it from being interesting.