The performance difference is probably based simply on the fact that the
Java example has to do run-time garbage collection and the C++ version
doesn't have to do any memory management in your example. Try allocating a
large number of heap items from C++ before deleting them. Right now you are
being overly nice to the heap allocation with C++ because you never allocate
more than one heap object at a time. There is no chance that you will get
close to filling up the heap or cause any sort of slowdown with your C++
example.
With Java you are constantly filling the run-time heap and then relying on
garbage collection to clean up after you. Your C++ code is in no way
equivalent to the Java code. In fact, in comparison to the real world, your
C++ code is pretty useless. No one uses a heap that way in the real world.
-----Original Message-----
From: skeptical [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, August 30, 2000 6:31 AM
To: [EMAIL PROTECTED]
Subject: slow memory allocation problem
guys:
i am doing a benchmark on java memory management. i wrote an app to allocate
and free memory from 1 to 300k bytes. it runs forever. i notice it takes
longer to allocate additional memory as time goes on. the same app only
takes 9 seconds on C++. here's the code listing. can anyone pls help out?
tks,
peter
=======JAVA CODE LISTING =======
public class Class1
{
private static final int NUM_MAX_BYTES = 300000;
public static void main (String[] args)
{
int i;
long t1;
t1 = System.currentTimeMillis();
System.err.print("memory alloc/free 1 - "+NUM_MAX_BYTES+" bytes. ");
for (i = 0; i < NUM_MAX_BYTES; i++)
{
byte[] p;
p = new byte[i];
if (i % 1000 == 0)
{
// Runtime rt = Runtime.getRuntime();
// rt.gc();
System.err.println("current: "+i);
}
}
System.err.println("time taken: %d "+ (System.currentTimeMillis()-t1) +
"ms");
}
}
======= C++ CODE LISTING =========
#include "stdafx.h"
#include <stdio.h>
#include <windows.h>
#define NUM_MAX_BYTES 300000
int main(int argc, char* argv[])
{
int i;
DWORD t1;
t1 = GetTickCount();
BYTE * p;
printf("memory alloc/free 1 - %d bytes. ", NUM_MAX_BYTES);
for (i = 0; i < NUM_MAX_BYTES; i++)
{
p = new BYTE[i];
delete p;
}
printf("time taken: %d ms\n",GetTickCount()-t1);
return 0;
}
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