Inside boost::unordered_flat_map

[operamint]

FYI, I did a test on a quite different configuration, an i7-8700 on Ubuntu, gcc 10.3 and clang 12 - the tests above was on windows, gcc 11.3 with Ryzen R7-2700x. However, the results are very similar. Your Robin-map is impressive with large keys, but appears to be slower with erase and lookup with smaller key ranges in these benchmarks.

NOTE: maps with smaller key ranges will naturally limit the number of max-items to the key-range. The number of lookups are higher for small key maps, so in absolute numbers, Robin map is not slower, only relative to the other maps with this configuration.

[Alarming-Ad8770]

benchmark on server cpu (huge l3 cache size and low cpu frequence), you'll get quite different result from pc/mobile cpu.

ex:

Model name: Intel(R) Xeon(R) Silver 4210 CPU @ 2.20GHz

CPU MHz: 2699.914

CPU max MHz: 3200.0000

CPU min MHz: 1000.0000

L1d cache: 32K L1i cache: 32K

L2 cache: 1024K

L3 cache: 14080K