[linux] Testovací dátový súbor

[Ľubomír Varga]

Nie som expert na javu a performace, ale hadam ako radovy prehlad bude moj 
prispevok hodnotnejsi ako spam :-)

Kod:
		long cas = System.currentTimeMillis();
		for(int i = 0; i < 1000000; i++) {
			System.out.print("x");
		}
		System.out.println();
		System.err.println("cas=" + (System.currentTimeMillis() - cas) + " ms");

Vystupy:

luvar at blackhorse:~/eclipseworkspace/Test$ java -version
java version "1.6.0_13"
Java(TM) SE Runtime Environment (build 1.6.0_13-b03)
Java HotSpot(TM) Client VM (build 11.3-b02, mixed mode, sharing)

----------------------------
luvar at blackhorse:~/eclipseworkspace/Test$ time java -server -jar Test_fat.jar 
> /dev/null
cas=1576 ms

real    0m1.698s
user    0m1.380s
sys     0m0.252s

----------------------------
luvar at blackhorse:~/eclipseworkspace/Test$ time java -jar Test_fat.jar 
> /dev/null
cas=1302 ms

real    0m1.395s
user    0m1.048s
sys     0m0.280s



Ked som v jave zmenil styl, ako bolo naznacene v predoslych prispevkoch, 
zlepsilo sa to. Kod:

		long cas = System.currentTimeMillis();
		String a = "";
		for(int j = 0; j < 100; j++) {
			a += "xxxxxxxxxx";
		}
		for(int i = 0; i < 1000; i++) {
			System.out.print(a);
		}
		System.out.println();
		System.err.println("cas=" + (System.currentTimeMillis() - cas) + " ms");

Vystup:

luvar at blackhorse:~/eclipseworkspace/Test$ time java -server -jar Test_fat.jar 
> /dev/null
cas=85 ms

real    0m0.260s
user    0m0.180s
sys     0m0.020s



Daco na porovnanie vykonu mojeho stroja (1.6GHz pentium M a beziaci boinc na 
pozadi):

luvar at blackhorse:~/eclipseworkspace/Test$ time dd if=/dev/zero bs=500 
count=2000 2>/dev/null | tr '\0' x > /dev/null

real    0m0.020s
user    0m0.008s
sys     0m0.008s

-- 
Odborník na všetko je zlý odborník. Ja sa snažím byť výnimkou potvrdzujúcou 
pravidlo.