On Tuesday, 24 May 2016 at 10:44:12 UTC, qznc wrote:
Unfortunately, it is slower. My current measurements [0]:
$ ./benchmark 10000000 10 # large haystack, few iterations
std find took 753837231
manual find took 129561980
$ ./benchmark 10 10000000 # small haystack, many iterations
std find took 721676721
manual find took 216418870
The nested-for-loop implementation is roughly 4 times faster!
Caveat: I'm not completely sure my benchmark is fair yet.
[0] https://github.com/qznc/find-is-too-slow
Plot twist: manual find is not always faster.
My benchmark now generates random haystack and needle. Sometimes
Phobos clearly wins. Example:
$ ./benchmark.ldc -n39 -l10000 -i10000
Found at 10000
std find took 289529102
manual find took 368958679
This is compiled with LDC, needle is 39 chars, haystack 10000
chars, and 10000 iterations. "Found at 10000" means the needle
was not found.
Very often manual find wins though. Takeaway: Manual find is too
naive. However, something slows down std find in general. More
research needed.
PS: Any recommendations for a Linux dissassembler? Objdump is ok,
but some arrows for jumps would be nice.
