Re: [PATCH 1/2] bitreversal program

From: Soumyadip Das Mahapatra
Date: Wed May 21 2008 - 04:54:44 EST




On Tue, 20 May 2008, Benoit Boissinot wrote:

A quick benchmarking (that you should have done at least one your
computer gives for 100000000 iterations):
old:
real 0m1.631s
user 0m1.628s
sys 0m0.004s

new:
real 0m5.553s
user 0m5.540s
sys 0m0.004s

So I guess there's no need to discuss this further.

Sorry to disturb you again. But i tested my code against Akinobu's one
and the test result shows my code takes less cpu time than that of
Akinobu's.
Here is the code i used to determine performance
--
#include<stdio.h>
#include<time.h>

int main()
{
int i = 100000000;
printf("%ld\n", (long)clock());
for(; i>0; i--) {
bitrev32(0x00face32);
}
printf("%ld", (long)clock());
}
--
OUTPUT:
[using Akinobu's bitrev32()]
0
6010000

[using my bitrev32()]
0
3990000

And using bitrev8() instead of bitrev32() the result gives the output
like this:
[using Akinobu's bitrev8()]
0
770000

[using my bitrev8()]
0
2360000

My processor is 1.4 GHz one.
I am not forcing you to review my code( or i've no expectation of
inclusion of it ) but its just a curiousity: what is truth behind
the output.

Regards,
Soumya

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