Not widely publicized, but the benchmarking code is in the source. At one point I was running it on my specific target machines to get performance estimates in

Not widely publicized, but the benchmarking code is in the source. At one point I was running it on my specific target machines to get performance estimates in support of porting some large-ish CPU stuff from Matlab into C++. The max performance was in Eigen-calling Intel MKL, but it was a big plus to not need MKL licenses on every development machine.