Hi Jay,
On Sunday, 26 June 2016 at 16:40:08 UTC, Jay Norwood wrote:
After watching Andre's sentinel thing, I'm playing with strlen
on char strings with 4 terminating 0s instead of a single one.
Seems to work and is 4x faster compared to the runtime version.
Please keep general discussions like this off the announce list,
which would e.g. be suitable for announcing a fleshed out
collection of high-performance string handling routines.
nothrow pure size_t strlen2(const(char)* c) {
if (c is null)
return 0;
size_t l=0;
while (*c){ c+=4; l+=4;}
while (*c==0){ c--; l--;}
return l+1;
}
A couple of quick hints:
- This is not a correct implementation of strlen, as it already
assumes that the array is terminated by four zero bytes. That
iterating memory with a stride of 4 instead of 1 will be faster
is a self-evident truth.
- You should be benchmarking against a "proper" SIMD-optimised
strlen implementation.
— David
