Изпечатай

[edmon]

попаднах на тази страница  http://www.network-theory.co.uk/docs/gccintro/gccintro_43.html
и реших да пробвам примера.
На моя Debian Testing това са резултатите.
carredas:/home/edmon# gcc -Wall -O1 test.c -lm
carredas:/home/edmon# time ./a.out
sum = 4e+38

real    0m5.644s
user    0m5.641s
sys     0m0.002s
carredas:/home/edmon# gcc -Wall -O2 test.c -lm
carredas:/home/edmon# time ./a.out
sum = 4e+38

real    0m5.726s
user    0m5.722s
sys     0m0.002s

Т.е. вижда се че с -О2 е по-лош резултата.
Пробвах това и на друг дебиан с друг процесор но  пак тестинг с подобни резултати.
На дебиан woody нещатат са нормално както и с един redhat 9.
Интересно ми ако някои има дебиан тестинг да пробва това и да публикува резултата ....

[astronom]

Примерен код

[unknown@ws-unknown test]$ uname -a Linux ws-unknown 2.6.8-1.521 #1 Mon Aug 16 09:01:18 EDT 2004 i686 athlon i386 GNU/Linux [unknown@ws-unknown test]$ cat /etc/fedora-release Fedora Core release 2 (Tettnang) [unknown@ws-unknown test]$ cat /proc/cpuinfo processor       : 0 vendor_id       : AuthenticAMD cpu family      : 6 model           : 8 model name      : AMD Athlon(TM) XP 1800+ stepping        : 1 cpu MHz         : 1916.546 cache size      : 256 KB fdiv_bug        : no hlt_bug         : no f00f_bug        : no coma_bug        : no fpu             : yes fpu_exception   : yes cpuid level     : 1 wp              : yes flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow bogomips        : 3776.51 [unknown@ws-unknown test]$ gcc --version gcc (GCC) 3.3.3 20040412 (Red Hat Linux 3.3.3-7) Copyright (C) 2003 Free Software Foundation, Inc. This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. [unknown@ws-unknown test]$ cat test.c #include <stdio.h> double powern (double d, unsigned long n) {   double x = 1.0;   unsigned long j;   for (j = 1; j <= n; j++)     x *= d;   return x; } int main (void) {   double sum = 0.0;   unsigned long i;   for (i = 1; i <= 100000000; i++) {     sum += powern (i, i % 5);   }   printf ("res = %g\n", sum);   return 0; } [unknown@ws-unknown test]$ gcc -Wall -O0 -o test-O0 test.c [unknown@ws-unknown test]$ gcc -Wall -O1 -o test-O1 test.c [unknown@ws-unknown test]$ gcc -Wall -O2 -o test-O2 test.c [unknown@ws-unknown test]$ gcc -Wall -O3 -o test-O3 test.c [unknown@ws-unknown test]$ gcc -Wall -O3 -funroll-loops -o test-O3-unroll test.c [unknown@ws-unknown test]$ ls -l total 44 -rw-r--r--  1 unknown Users  334 Jan 24 14:22 test.c -rwxr-xr-x  1 unknown Users 4953 Jan 24 14:22 test-O0 -rwxr-xr-x  1 unknown Users 4857 Jan 24 14:22 test-O1 -rwxr-xr-x  1 unknown Users 4849 Jan 24 14:22 test-O2 -rwxr-xr-x  1 unknown Users 4849 Jan 24 14:22 test-O3 -rwxr-xr-x  1 unknown Users 5109 Jan 24 14:22 test-O3-unroll [unknown@ws-unknown test]$ time ./test-O0 res = 4e+38 real    0m7.941s user    0m7.848s sys     0m0.001s [unknown@ws-unknown test]$ time ./test-O1 res = 4e+38 real    0m4.714s user    0m4.670s sys     0m0.002s [unknown@ws-unknown test]$ time ./test-O2 res = 4e+38 real    0m4.785s user    0m4.611s sys     0m0.001s [unknown@ws-unknown test]$ time ./test-O3 res = 4e+38 real    0m2.830s user    0m2.714s sys     0m0.002s [unknown@ws-unknown test]$ time ./test-O3-unroll res = 4e+38 real    0m3.917s user    0m3.829s sys     0m0.001s

Това е при мен.

[edmon]

мдам както писах проблема  е с дебиан тестинг .

[Joro]

Ето...
Някой ми беше казал, че gcc -O3 е по-добре от gcc -O2 щото L2 кеша ми бил доста голям. В случая - 1МБ.
Не ги разбирам много тея работи с програмирането но тогава търсех начин да го тествам но не открих.
Е, сега го тествах и май наистина е по добре '>))

joro@najoro:~/cpp$ uname -a
Linux najoro 2.6.8-2-k7 #1 Sat Jan 8 15:48:58 EST 2005 i686 GNU/Linux
joro@najoro:~/cpp$ cat /etc/debian_version
3.1
joro@najoro:~/cpp$ cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 4
model name      : AMD Athlon™ 64 Processor 3000+
stepping        : 8
cpu MHz         : 1795.513
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext lm 3dnowext 3dnow
bogomips        : 3555.32
joro@najoro:~$ gcc --version
gcc (GCC) 3.3.5 (Debian 1:3.3.5-5)
Copyright © 2003 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

joro@najoro:~/cpp$ gcc -Wall -O0 -o test-O0 test.c
joro@najoro:~/cpp$ gcc -Wall -O1 -o test-O1 test.c
joro@najoro:~/cpp$ gcc -Wall -O2 -o test-O2 test.c
joro@najoro:~/cpp$ gcc -Wall -O3 -o test-O3 test.c
joro@najoro:~/cpp$ gcc -Wall -O3 -funroll-loops -o test-O3-unroll test.c

joro@najoro:~/cpp$ time ./test-O0
res = 4e+38

real    0m4.332s
user    0m4.224s
sys     0m0.002s

joro@najoro:~/cpp$ time ./test-O1
res = 4e+38

real    0m2.929s
user    0m2.807s
sys     0m0.002s

joro@najoro:~/cpp$ time ./test-O2
res = 4e+38

real    0m2.871s
user    0m2.727s
sys     0m0.000s

joro@najoro:~/cpp$ time ./test-O3
res = 4e+38

real    0m1.903s
user    0m1.848s
sys     0m0.000s

joro@najoro:~/cpp$ time ./test-O3-unroll
res = 4e+38

real    0m1.855s
user    0m1.825s
sys     0m0.000s

[Йордан]

Примерен код

gv@gigavolt:~/bin> uname -a Linux gigavolt 2.6.8-24.11-default #1 Fri Jan 14 13:01:26 UTC 2005 i686 athlon i386 GNU/Linux gv@gigavolt:~/bin> cat /proc/cpuinfo processor       : 0 vendor_id       : AuthenticAMD cpu family      : 6 model           : 3 model name      : AMD Duron(tm) Processor stepping        : 1 cpu MHz         : 751.502 cache size      : 64 KB fdiv_bug        : no hlt_bug         : no f00f_bug        : no coma_bug        : no fpu             : yes fpu_exception   : yes cpuid level     : 1 wp              : yes flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr pni syscall mmxext 3dnowext 3dnow bogomips        : 1486.84 gv@gigavolt:~/bin> gcc --version gcc (GCC) 3.3.4 (pre 3.3.5 20040809) Copyright (C) 2003 Free Software Foundation, Inc. This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. gv@gigavolt:~/bin> cat test.c #include <stdio.h> double powern (double d, unsigned long n) {  double x = 1.0;  unsigned long j;  for (j = 1; j <= n; j++)    x *= d;  return x; } int main (void) {  double sum = 0.0;  unsigned long i;  for (i = 1; i <= 100000000; i++) {    sum += powern (i, i % 5);  }  printf ("res = %g\n", sum);  return 0; } gv@gigavolt:~/bin> gcc -Wall -O0 -o test-O0 test.c gv@gigavolt:~/bin> gcc -Wall -O1 -o test-O1 test.c gv@gigavolt:~/bin> gcc -Wall -O2 -o test-O2 test.c gv@gigavolt:~/bin> gcc -Wall -O3 -o test-O3 test.c gv@gigavolt:~/bin> gcc -Wall -O3 -funroll-loops -o test-O3-unroll test.c gv@gigavolt:~/bin> ls -l total 76 -rwxrwxrwx  1 gv users  199 2004-12-04 04:05 niki -rw-r--r--  1 gv users  319 2005-01-28 21:39 test.c -rw-r--r--  1 gv users  318 2005-01-28 21:34 test.c~ -rwxr-xr-x  1 gv users 9213 2005-01-28 21:39 test-O0 -rwxr-xr-x  1 gv users 9101 2005-01-28 21:39 test-O1 -rwxr-xr-x  1 gv users 9101 2005-01-28 21:39 test-O2 -rwxr-xr-x  1 gv users 9101 2005-01-28 21:39 test-O3 -rwxr-xr-x  1 gv users 9293 2005-01-28 21:39 test-O3-unroll drwxr-xr-x  3 gv users 4096 2005-01-21 13:14 Vitosha 27_11_2004 gv@gigavolt:~/bin> time ./test-O0 res = 4e+38 real    0m20.971s user    0m19.879s sys     0m0.014s gv@gigavolt:~/bin> time ./test-O1 res = 4e+38 real    0m12.337s user    0m11.826s sys     0m0.007s gv@gigavolt:~/bin> time ./test-O2 res = 4e+38 real    0m11.684s user    0m11.174s sys     0m0.008s gv@gigavolt:~/bin> time ./test-O3 res = 4e+38 real    0m7.166s user    0m6.869s sys     0m0.007s gv@gigavolt:~/bin> time ./test-O3-unroll res = 4e+38 real    0m8.454s user    0m8.198s sys     0m0.005s

[Skydive]

$ uname -a
Linux slackbox 2.4.29-1 #1 Tue Jan 25 13:56:52 EET 2005 i686 unknown unknown GNU/Linux

$ cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 6
model           : 3
model name      : AMD Duron™ Processor
stepping        : 1
cpu MHz         : 755.065
cache size      : 64 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr syscall mmxext 3dnowext 3dnow
bogomips        : 1507.32

$ gcc --version
gcc (GCC) 3.3.4

* * *

$ gcc -Wall -O0 test.c -lm
$ time ./a.out
sum = 4e+38
 
real    0m20.662s
user    0m20.630s
sys     0m0.010s


$ gcc -Wall -O1 test.c -lm
$ time ./a.out
sum = 4e+38

real    0m12.142s
user    0m12.140s
sys     0m0.000s


$ gcc -Wall -O2 test.c -lm
$ time ./a.out
sum = 4e+38

real    0m11.734s
user    0m11.730s
sys     0m0.000s


$ gcc -Wall -O3 test.c -lm
$ time ./a.out
sum = 4e+38

real    0m7.004s
user    0m7.000s
sys     0m0.000s


$ gcc -Wall -O3 -funroll-loops test.c -lm
$ time ./a.out
sum = 4e+38

real    0m9.910s
user    0m9.890s
sys     0m0.000s

[rat]

Примерен код

uname -a Linux joro 2.6.8-24-default #1 Wed Oct 6 09:16:23 UTC 2004 i686 athlon i386 GNU/Linux ---------------------------------------------------- rat@joro:~/test> cat /proc/cpuinfo processor       : 0 vendor_id       : AuthenticAMD cpu family      : 6 model           : 8 model name      : AMD Athlon(tm) XP 2000+ stepping        : 1 cpu MHz         : 1662.323 cache size      : 256 KB fdiv_bug        : no hlt_bug         : no f00f_bug        : no coma_bug        : no fpu             : yes fpu_exception   : yes cpuid level     : 1 wp              : yes flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr sse pni syscall mmxext 3dnowext 3dnow bogomips        : 3293.18 ---------------------------------------------------- time ./test0 sum = 4e+38 real    0m23.492s user    0m9.504s sys     0m0.013s rat@joro:~/test> time ./test1 sum = 4e+38 real    0m14.428s user    0m5.640s sys     0m0.009s rat@joro:~/test> time ./test2 sum = 4e+38 real    0m12.726s user    0m5.330s sys     0m0.008s rat@joro:~/test> time ./test3 sum = 4e+38 real    0m7.810s user    0m3.272s sys     0m0.003s rat@joro:~/test> time ./test31-unroll sum = 4e+38 real    0m9.400s user    0m3.933s sys     0m0.003s

Мен ме изненадва последния резултат. Според мен той трябва да по-добър от предпоследния.