It's not true that I cherry-picked a slow PRNG for my 7 GB/s number. In fact I selected the second-fastest PRNG on that page (because it's popular)! The fastest one is 8 GB/s. PCG32 is 3 GB/s.
Your 4000x factor speed up for a linear-congruential generator is just a completely false number.
Yes I did pick ChaCha20 for its speed -- it's designed for speed!
"A few hundred FPU instructions" in your Monte Carlo is not comparable to generating a number with ChaCha20. If you need a few hundred FPU instructions per number, you will be running a lot slower than 2 GB/s. ChaCha only requires a few cycles per byte.
I agree that you can optimize out the side-channel free part for non-crypto-purposes. That's a good thing! I recommend doing that.
Your 4000x factor speed up for a linear-congruential generator is just a completely false number.
Yes I did pick ChaCha20 for its speed -- it's designed for speed!
"A few hundred FPU instructions" in your Monte Carlo is not comparable to generating a number with ChaCha20. If you need a few hundred FPU instructions per number, you will be running a lot slower than 2 GB/s. ChaCha only requires a few cycles per byte.
I agree that you can optimize out the side-channel free part for non-crypto-purposes. That's a good thing! I recommend doing that.