On 6/26/2016 11:47 AM, Jay Norwood via Digitalmars-d-announce wrote:
On Sunday, 26 June 2016 at 16:59:54 UTC, David Nadlinger wrote:
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.
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
- You should be benchmarking against a "proper" SIMD-optimised strlen
This is more of just an observation that the choice of the single zero
sentinel for C string termination comes at a cost of 4x strlen speed vs
using four terminating zeros.
I don't see a SIMD strlen implementation in the D libraries.
The strlen2 function I posted works on any string that is terminated by
four zeros, and returns the same len as strlen in that case, but much
How to get strings initialized with four terminating zeros at compile
time is a separate issue. I don't know the solution, else I might
consider doing more with this.
Yup.. there's a reason that many many hours have been spent optimizing
strlen and other memory related length and comparison routines. They
are used a lot and the number of ways of making them fast varies almost
as much as the number of cpu's that exist. This effort is embedded in
the code gen of compilers (other than dmd) and libc runtimes. Trying to
re-invent it is noble, and very educational, but largely redundant.