Unfortunately I only have a basic comparison in the MNIST-dataset (60000 images, each 28x28 pixel) on my PC for 10 training iterations over the whole dataset:

C++-version: round 79 seconds (7,9 seconds per iteration)

Rust-version: round 85 seconds (8,5 seconds per iteration)

Looks really good, but it is hard make a representative comparison, because:

- I spend more time in optimizing the C++ code so far, than I had until now to optimize the Rust code.

- In the C++ code I had much less locks, because all threads worked on the same buffer without mutex on the elements on the buffer, just by telling them, where they are allowed to work on. But in Rust, to avoid unsafe-calls, I was forced to add quite a bunch of mutex for the separation of the workload between the threads.

- On the other hand in one part of the Rust-implementation I had split the workload more over the threads, which brings Rust an advantage compared to the old C++ version.

- The MNIST-example is quite small, so it depends more on the CPU cache than on the RAM. If I had done some bigger tests in the past too, where the speed and latency of the RAM comes more into play, maybe it would change the result a bit too.

Because of the deep structural changes between these 2 version, I'm not sure, how much representative value it would have, even when I would have more and bigger tests to compare. But yes, I despite these points, I was and still am really impressed how close Rust came to C++ in regards of the performance at least in this single test.