From: Hendrik Visage <hvjunk@gmail.com>
To: Nicolas Kaiser <nikai@nikai.net>
Cc: linux-c-programming@vger.kernel.org
Subject: Re: duplicated modulo
Date: Mon, 4 Apr 2011 10:26:05 +0200 [thread overview]
Message-ID: <BANLkTikDWQcXY+5quaRk-Qz9PBxnDdXt0A@mail.gmail.com> (raw)
In-Reply-To: <20110401114113.6e2e91af@absol.kitzblitz>
On Fri, Apr 1, 2011 at 11:41 AM, Nicolas Kaiser <nikai@nikai.net> wrote:
> I'm curious: a duplicated modulo operation can't possibly make
> any difference, can it?
>
> diff -u -p ./arch/powerpc/platforms/powermac/nvram.c /tmp/nothing/arch/powerpc/platforms/powermac/nvram.c
> --- ./arch/powerpc/platforms/powermac/nvram.c 2011-03-31 09:52:41.674292401 +0200
> +++ /tmp/nothing/arch/powerpc/platforms/powermac/nvram.c
> @@ -246,7 +246,6 @@ static u32 core99_calc_adler(u8 *buffer)
> high = 0;
> for (cnt=0; cnt<(NVRAM_SIZE-CORE99_ADLER_START); cnt++) {
> if ((cnt % 5000) == 0) {
> - high %= 65521UL;
> high %= 65521UL;
> }
> low += buffer[cnt];
The emphasis should be on "shouldn't" not "possibly" ;)
As other mentioned, you could have issues with going to different types etc.
However, the major reason *I* would remove it, is that the division
operation is an expensive operation, and then you still need to get
the remainder too and also since it's mostly superfluous thus adding
bloat.
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prev parent reply other threads:[~2011-04-04 8:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-01 9:41 duplicated modulo Nicolas Kaiser
2011-04-01 9:50 ` Michal Nazarewicz
2011-04-01 10:19 ` Nicolas Kaiser
2011-04-01 9:30 ` Bogdan Cristea
2011-04-01 10:28 ` Bastian Bloessl
2011-04-01 11:20 ` Michal Nazarewicz
2011-04-04 8:26 ` Hendrik Visage [this message]
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