c++ v java
Posted: Thu May 10, 2007 6:04 am
Ok yall, if you want to continue the debate, keep it in here. 
Get outa oodmb's raytracer topic cause its just rude
Get outa oodmb's raytracer topic cause its just rude
)But the last benchmark posted by Deus...
First run on my Core2Duo gives a time of 17.0s.
Timing the loop within the program itself knocks off half a second (removing the startup-time for the JVM which is irrelevant for programs that run for any measurable amount of time).
Adding the "-server" option to the command-line invocation of the JVM brings it down to 10.8s (come on, everyone knows the server JVM is much quicker than the client version).
Then changing the code to the following...
Code: Select all
import java.io.*;
import java.util.*;
public class matrix {
static int SIZE = 30;
public static void main(String args[]) {
long t0 = System.currentTimeMillis();
int n = Integer.parseInt(args[0]);
int m1[] = mkmatrix(SIZE, SIZE);
int m2[] = mkmatrix(SIZE, SIZE);
int mm[] = new int[SIZE * SIZE];
for (int i=0; i<n; i++) {
mmult(SIZE, SIZE, m1, m2, mm);
}
System.out.print(mm[0]);
System.out.print(" ");
System.out.print(mm[2 + 3 * SIZE]);
System.out.print(" ");
System.out.print(mm[3 + 2 * SIZE]);
System.out.print(" ");
System.out.println(mm[4 + 4 * SIZE]);
System.out.println("" + (System.currentTimeMillis() - t0) + " ms");
}
public static int[] mkmatrix(int rows, int cols) {
int count = 1;
int m[] = new int[rows * cols];
int ind = 0;
for (int i=0; i<rows; i++) {
for (int j=0; j<cols; j++) {
m[ind++] = count++;
}
}
return(m);
}
public static void mmult(int rows, int cols,
int[] m1, int[] m2, int[] m3) {
int ind = 0;
int ind0, ind1, ind2, val;
for (int i=0; i<rows; i++) {
ind1 = 0;
for (int j=0; j<cols; j++) {
ind0 = i;
val = 0;
ind2 = ind1;
for (int k=0; k<cols; k++) {
val += m1[ind0] * m2[ind2++];
ind0 += cols;
}
m3[ind++] = val;
ind1 += cols;
}
}
}
}Anything using Java arrays is always going to be slow (because of the run-time range checking), that's why I personally avoid them in performance-critical code ...
Benchmarks really need do need to be run by someone with at least a modicum of knowledge about how to code and run Java efficiently
Ian.