I can't reproduce these results. Running his program, GCC's own strlen() soundly beats all the other strlens in all three test cases. Compiled without optimizat

I can't reproduce these results. Running his program, GCC's own strlen() soundly beats all the other strlens in all three test cases. Compiled without optimization (gcc -g -Wall -o mystrlen mystrlen.c mystrlen.s) with gcc 4.1.2 on an AMD Opteron 265, I get strlen() taking about 0.04 each time, compared with 0.18 for my_strlen() and 0.06 or 0.06 for ap_strlen_utf8_s (the elite assembly version). Although honestly, you should not expect GCC unoptimized to beat your hand-coded assembly anyway! These tests need to be done with optimization. Compiled with optimization, (gcc -g -Wall -std=c99 -O2 -march=i686 -pedantic -o mystrlen mystrlen.c mystrlen.s), I get strlen() taking 0.02, versus my_strlen() at 0.04 and ap_strlen_utf8_s (the awesome assembly one) at 0.06 -- 200% slower. So I'm not sure his results are right, even in the direction. The general theme, though (that strlen is not a very expensive operation) is true. Here are the complete results: % gcc -g -Wall -o mystrlen mystrlen.c mystrlen.s mystrlen.c: In function 'timethings': mystrlen.c:57: warning: implicit declaration of function 'my_strlen_utf8_s' mystrlen.c:59: warning: implicit declaration of function 'ap_strlen_utf8_s' % ./mystrlen "": 0 0 0 0 0 0 "hello, world": 12 12 12 12 12 12 "naïve": 6 6 6 5 5 5 "ããã«ã¡ã¯": 15 15 15 5 5 5 1: all 'a': 1: my_strlen(string) = 33554431: 0.176222 1: strlen(string) = 33554431: 0.041959 1: my_strlen_s(string) = 33554431: 0.157842 1: my_strlen_utf8_s(string) = 33554431: 0.158211 1: my_strlen_utf8_c(string) = 33554431: 0.307177 1: ap_strlen_utf8_s(string) = 33554431: 0.063365 2: all '\xe3': 2: my_strlen(string) = 33554431: 0.180825 2: strlen(string) = 33554431: 0.043419 2: my_strlen_s(string) = 33554431: 0.166384 2: my_strlen_utf8_s(string) = 33554431: 0.161270 2: my_strlen_utf8_c(string) = 33554431: 0.309674 2: ap_strlen_utf8_s(string) = 33554431: 0.064023 3: all '\x81': 3: my_strlen(string) = 33554431: 0.176232 3: strlen(string) = 33554431: 0.042303 3: my_strlen_s(string) = 33554431: 0.157776 3: my_strlen_utf8_s(string) = 0: 0.083548 3: my_strlen_utf8_c(string) = 0: 0.311597 3: ap_strlen_utf8_s(string) = 0: 0.083935 % gcc -g -Wall -std=c99 -O2 -march=i686 -pedantic -o mystrlen mystrlen.c mystrlen.s mystrlen.c: In function 'timethings': mystrlen.c:57: warning: implicit declaration of function 'my_strlen_utf8_s' mystrlen.c:59: warning: implicit declaration of function 'ap_strlen_utf8_s' % ./mystrlen "": 0 0 0 0 0 0 "hello, world": 12 12 12 12 12 12 "naïve": 6 6 6 5 5 5 "ããã«ã¡ã¯": 15 15 15 5 5 5 1: all 'a': 1: my_strlen(string) = 33554431: 0.039751 1: strlen(string) = 33554431: 0.020602 1: my_strlen_s(string) = 33554431: 0.158968 1: my_strlen_utf8_s(string) = 33554431: 0.159315 1: my_strlen_utf8_c(string) = 33554431: 0.075991 1: ap_strlen_utf8_s(string) = 33554431: 0.063607 2: all '\xe3': 2: my_strlen(string) = 33554431: 0.039673 2: strlen(string) = 33554431: 0.021445 2: my_strlen_s(string) = 33554431: 0.159388 2: my_strlen_utf8_s(string) = 33554431: 0.158209 2: my_strlen_utf8_c(string) = 33554431: 0.127230 2: ap_strlen_utf8_s(string) = 33554431: 0.063322 3: all '\x81': 3: my_strlen(string) = 33554431: 0.039742 3: strlen(string) = 33554431: 0.020674 3: my_strlen_s(string) = 33554431: 0.158717 3: my_strlen_utf8_s(string) = 0: 0.082357 3: my_strlen_utf8_c(string) = 0: 0.076103 3: ap_strlen_utf8_s(string) = 0: 0.064756