hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Som1Lse

The confusion with std::is_constant_evaluated, hopefully cleared up

Disclaimer: I am not on the committee, and while I have done my due diligence, I could easily have missed something. This is also not an attack on anyone. As stated the confusion is quite understandable, and the talk mentioned generally does a good job of introducing some small features of C++20, even if it does contain a minor mistake.

Introduction

This is inspired by Timur Doumler's C++20: The small things given at CppCon 2019 where, at 48:00, somebody points out a mistake on