Joern Wolfgang Rennecke <g...@amylaar.uk> writes: > This has come up several time over the years: > https://gcc.gnu.org/legacy-ml/gcc/2006-07/msg00158.html > https://gcc.gnu.org/legacy-ml/gcc/2006-07/msg00155.html > https://gcc.gnu.org/pipermail/gcc/2010-March/190234.html > > , but maybe now (or maybe a while ago) is the right time to do this, > considering the changes in relative costs of basic operations? > Multiply and barrel shift are cheap on many modern microarchitectures.
There are much more powerfull primitives for hashes on modern CPUs, like CRC or AES rounds. I don't know if anybody has tried to do a perfect hash on top of those though, but perhaps it wouldn't need to be. > Control flow and non-linear memory access is expensive. Before going to hashes I would rather exploit SIMD first, e.g. to do multiple comparisons in a single instruction. Modern hash table implementations like Swiss tables are already doing that for good results. -Andi
