Re: Why is Java so slow????

On Nov 20, 9:41 am, bugbear <bugbear@trim_papermule.co.uk_trim> wrote:


hi BugBear,

what I'm tyring to do is convince management that there isn't anything
we cannot do as fast in Java as in "C" and this initial exercise was
a simple example. It is more about managing the risk of being "up
against a wall" with regard to the ability to speed up any arbitrary
portion of the system.

I understand I have the JNI and native methods at my disposal as
well and this will probably be the life-saver.

FYI, I've rid my example of all references to String and it is
faster again by two. My latest version is below. Still far from
the "C" version in speed but it I think it is good enough.

Thx

Larry (a.k.a. the Java Hound)

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.util.Date;

class t1
{
    static byte[] prompt = "This is line ".getBytes();
    static byte[] prompt2 = "\n".getBytes();

    static public void main(String[] argv)
    {
        int lim = new Integer(argv[0]);
        int nbench = new Integer(argv[1]);
        int b;
        for (b=0; b < nbench; b++) {
            System.err.println("Bench " + b);
            Date start = new Date();

            try {
                mytest(lim);
            }
            catch ( Exception e) {
                System.err.println("Exception occurred");
                System.err.println(e.toString());
            }

            Date now = new Date();
            System.err.println("Took " + ((now.getTime() -
start.getTime())/1000) + " seconds");
        }
    }

    static public void mytest(int lim) throws Exception
    {
        int i;
        BufferedOutputStream bos = new
BufferedOutputStream(System.out, 1000000);
        DataOutputStream dos = new DataOutputStream(bos);
        for (i=0; i < lim; i++) {

            // byte[] ibytes = new Integer(i).toString().getBytes();

            writebytes(prompt, dos);
            writebytes(iconv(i), dos);
            writebytes(prompt2, dos);
        }
        dos.flush();
    }

    static public void writebytes(byte[] arr, DataOutputStream dos)
throws Exception
    {
        int n = arr.length;
        int i;
        for ( i=0; i < n; i++ ) {
            dos.writeByte(arr[i]);
        }
    }

    static byte[] iconv(int i)
    {
        byte[] digs = new byte[20];
        int ndig = 0;
        while ( i >= 10 ) {
            digs[ndig] = (byte) (48 + i % 10);
            ndig++;
            i = i / 10;
        }
        digs[ndig] = (byte) (48 + i);
        ndig++;

        byte[] result = new byte[ndig];
        int dig;
        int j = 0;
        for (dig=ndig-1; dig>= 0; dig--) {
            result[j] = digs[dig];
            j++;
        }
        return result;
    }
}