Huh?

Ok , consider this..

Code:

#include <iostream>
#include <time.h>	// for clock()
#include <stddef.h>	// for size_t
#include <string.h>	// for memcpy()
using namespace std;

void copy_with_pointers(const char *src, char *dst, size_t n)
{
	for (size_t k =0; k!=n; ++k)
		*dst++ = *src++;
}


void copy_with_indices(const char *src, char *dst, size_t n)
{
	for (size_t k =0; k!=n; ++k)
		dst[k] = src[k];
}

int main()
{
	const int n_bytes = 100000;
	const int n_calls = 100;
	const char *src = new char[n_bytes];
	char *dst = new char[n_bytes];
	
	
	// reduce paging effect by accessing all bytes:
	memcpy(dst, src, n_bytes);
	clock_t start, end, reftime;
	
	
	
	// test 1 (reference time)
	start = clock();
	for (int k = 0; k!=n_calls; ++k)
		memcpy(dst, src, n_bytes);
	end = clock();
	reftime = end - start;
	

	
	// test 2 (pointers)
	start = clock();
	for (int k = 0; k!=n_calls; ++k)
		copy_with_pointers(src, dst, n_bytes);
	end = clock();
	
	cout << "with pointers:" << static_cast<double>(end-start)/reftime << " times slowers then memcpy. \n";
	
	// test 3 (indices)
	start = clock();
	for (int k = 0; k!=n_calls; ++k)
		copy_with_indices(src, dst, n_bytes);
	end = clock();
	
	cout << "with indices:" << static_cast<double>(end-start)/reftime << " times slowers then memcpy. \n";
	

	
	delete[] src;
	delete[] dst;
	
	return 0;
	
}

I've runned that code few times.. and i kept having different answers.
sometimes pointers were slowers sometimes indices were.

Shouldn't i get always the same timing?

Luigi
I use code warrior 7.0 on mac os X (10.2)
thx

Not at all. Sometimes you are running 18 different programs at once, other times you are running only 1. Even while running 1 you may get different times based on other issues such as how hot the cpu is.

Originally posted by master5001
Not at all. Sometimes you are running 18 different programs at once, other times you are running only 1. Even while running 1 you may get different times based on other issues such as how hot the cpu is.

how is that poseble the cpu doesn't have a thermo senser so unless it heats up the hardware its not posseble.

Well that isn't what I mean. I am refering to the fact that when a cpu gets too hot your software (even your OS!) starts to become unstable. Surely you've had your computer lockup because of overheating before?

Originally posted by master5001
Well that isn't what I mean. I am refering to the fact that when a cpu gets too hot your software (even your OS!) starts to become unstable. Surely you've had your computer lockup because of overheating before?

nope

Yep, over overclocking does that

Apparently the Intel processors do have built-in thermal sensors. I was surprised to find this out too, but I've had a couple of CPU fans go bad, and the computer got really slow. I"ve read this somewhere too... When the processor overheats, it slows down to protect itself. This ONLY happens when there is something wrong with the CPU cooling.

I don't know about other processors, althought the little Z180's that we use in our imbedded systems don't have this feature.

Originally posted by DougDbug
Apparently the Intel processors do have built-in thermal sensors. I was surprised to find this out too, but I've had a couple of CPU fans go bad, and the computer got really slow. I"ve read this somewhere too... When the processor overheats, it slows down to protect itself. This ONLY happens when there is something wrong with the CPU cooling.

I don't know about other processors, althought the little Z180's that we use in our imbedded systems don't have this feature.

mine is a custom
33 gigs
400 ghz ( overload by 50 ghz)
ati 7500 video card
ali mother board

Originally posted by master2000
mine is a custom
33 gigs
400 ghz ( overload by 50 ghz)
ati 7500 video card
ali mother board

ghz=mhz

The pentium 3 line first introduced some protection against
overheating,by locking up itself and thereby preventing damaged
caused by heat,the pentium 4 took it a step further and build
in a system that could slow down the cpu, the AMD line
(wich i have in my pc) unfortunatly does not have this,if your
cooler fails your cpu is gone

Originally posted by master2000
mine is a custom
400 ghz ( overload by 50 ghz)

oh that's custom all right.

my computer (both)
are perfect they work over night and mine is 400 mhz when its supose to be at 350

This getting VERY offtopic people

Originally posted by moi
oh that's custom all right.

what the h%$& is up with your code

Originally posted by Travis Dane
ghz=mhz

The pentium 3 line first introduced some protection against
overheating,by locking up itself and thereby preventing damaged
caused by heat,the pentium 4 took it a step further and build
in a system that could slow down the cpu, the AMD line
(wich i have in my pc) unfortunatly does not have this,if your
cooler fails your cpu is gone

alternatives with AMD:

some abit motherboards will shut down the system when cpu fan fails (i have one, abit kt7).
MBM can be configured to shut down system in event of too much heat.

Originally posted by master2000
what the h%$& is up with your code

h%$& <- that english?