On 23.11.2015 19:05, Yann Ylavic wrote:
> while (ucharmap[*ps1] == ucharmap[*ps2++]) {
> if (*ps1++ == '\0') {
> return (0);
> }
> }
> return (ucharmap[*ps1] - ucharmap[*--ps2]);
Is there really a gain in inc- and decrementing this way? Would not it
be easier to read with the explicit increments -- and, incidentally, no
decrements at all?
while (ucharmap[*ps1] == ucharmap[*ps2]) {
if (*ps1 == '\0') {
return (0);
}
++ps1;
++ps2;
}
return (ucharmap[*ps1] - ucharmap[*ps2]);
> We don't care about the whole process time and other counters.
That's certainly true. But, then, why bother with building time-counter
into the test at all -- instead of simply relying on time(1)?
But something is still not right -- the result (for either of the
methods) can depend on the number of iterations (!!):
./strncasecmp 1 27 aCaa Ac 2
Optimized (nb=27, len=2)
time = 0.000001 : res = 32
./strncasecmp 1 26 aCaa Ac 2
Optimized (nb=26, len=2)
time = 0.000001 : res = 0
./strncasecmp 0 27 aCaa Ac 2
<string.h> (nb=27, len=2)
time = 0.000003 : res = 32
./strncasecmp 0 26 aCaa Ac 2
<string.h> (nb=26, len=2)
time = 0.000003 : res = 0
Using clang on FreeBSD/amd64 here. Yours,
-mi
