On: Reasons to Prefer Blake3 over Sha256

[wmf]

If Blake3 is 2.5x faster then it's going to be roughly 2.5x less energy.

[silotis → wmf]

That's not how it works on modern CPUs. Power draw at "100%" utilization can vary widely depending on what part of the core is being utilized. The SIMD units are typically the most power hungry part of the CPU by a large margin so just because a job finishes in less time doesn't mean total energy is necessarily lower.

[wmf → silotis]

I'm assuming that both SHA256 and Blake3 are using integer SIMD.

[api → wmf]

In some CPUs that may be true, but in many there are dedicated SHA instructions that amount to a SHA ASIC in the CPU.

AES units are even more common. Most non-tiny CPUs have them these days.

[wmf → api]

The AES and SHA instructions are part of the vector units so their energy will be similar to other integer SIMD instructions. The overhead of issuing the instruction is higher than the work that it does so the details don't matter.