rychlost NIO

[Martin Kuba]

[EMAIL PROTECTED] wrote:

 V tomto konkretnim pripade navic jeste je dobre pouzit NIO kvuli vykonu
(je to obrovsky rozdil), ale hlavni je funkcnost.

Zkusil jsem si ted porovnat klasicke IO a NIO a vychazi mi, ze NIO
je pomalejsi:

import java.io.*;
import java.nio.channels.*;

public class Copy {
    static final int BUFSIZE = 1024*64;
    public static void main(String args[]) throws IOException {
        if(args.length!=2) {
            System.err.println("Usage: java Copy <src_file> <dst_file>");
            System.exit(1);
        }
        long t1 = System.currentTimeMillis();
        classicIO(args[0],args[1]+".old");
        long t2 = System.currentTimeMillis();
        newIO(args[0],args[1]+".new");
        long t3 = System.currentTimeMillis();

    }

    static void classicIO(String src,String dst) throws IOException {

        byte[] buffer = new byte[BUFSIZE];
        int nacteno;
        while((nacteno=in.read(buffer,0,BUFSIZE))>0) {
            out.write(buffer,0,nacteno);
        }
        in.close();
        out.close();
    }
    static void newIO(String src,String dst) throws IOException {
        FileChannel in = new FileInputStream(src).getChannel();
        FileChannel out = new FileOutputStream(dst).getChannel();
        out.transferFrom(in,0,in.size());
        in.close();
        out.close();
    }
}

Kdyz spustim:

size: 4589 CLASSIC: 1ms   NIO: 12ms
size: 37400824 CLASSIC: 135ms   NIO: 121ms

tj. pro dlouhe soubory se to srovnava, ale pro male je klasicke IO
rychlejsi. Jak to ?

Makub
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Supercomputing Center Brno             Martin Kuba
Institute of Computer Science    email: [EMAIL PROTECTED]
Masaryk University             http://www.ics.muni.cz/~makub/
Botanicka 68a, 60200 Brno, CZ     mobil: +420-603-533775
--------------------------------------------------------------

System.out.println("size: "+(new File(args[0]).length())+" CLASSIC: "+(t2-t1)+"ms NIO: "+(t3-t2)+"ms"); BufferedInputStream in = new BufferedInputStream(new FileInputStream(src),BUFSIZE); BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(dst),BUFSIZE);

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