Also this uses 16 threads while the contest restricts to running in 8 cores. Needs to compare the benchmarks in the same environment to make a fair comparison.
The AMD Ryzen 4800U has 8 cores total so the author follows the contest restriction. This CPU supports hyperthreading. (I’d be very interested in seeing hyperoptimized CUDA code using unlimited GPU cores FWIW.)
1brc in the contest had SMT disabled [0]. (hyperthreading is an intel marketing name and trademark for their implementation of smt, but the benchmark was run on an amd cpu)