From: Bastian Bloessl <bastianbloessl@googlemail.com>
To: Nicolas Kaiser <nikai@nikai.net>
Cc: Michal Nazarewicz <mina86@mina86.com>,
linux-c-programming@vger.kernel.org
Subject: Re: duplicated modulo
Date: Fri, 01 Apr 2011 12:28:09 +0200 [thread overview]
Message-ID: <4D95A8B9.3070308@googlemail.com> (raw)
In-Reply-To: <20110401121916.34a567da@absol.kitzblitz>
Am 01.04.2011 12:19, schrieb Nicolas Kaiser:
> * "Michal Nazarewicz"<mina86@mina86.com>:
>> On Fri, 01 Apr 2011 11:41:13 +0200, Nicolas Kaiser 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];
>>
>> It's not just a module. It's also an assignment.
>
> Sure. But I fail to see where between
>
> a %= b;
> a %= b;
>
> and
>
> a = (a % b) % b;
>
> and
>
> a %= b;
>
> would be a difference?
Perhaps an issue with signed / unsigned, or long vs. int?
next prev parent reply other threads:[~2011-04-01 10:28 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 [this message]
2011-04-01 11:20 ` Michal Nazarewicz
2011-04-04 8:26 ` Hendrik Visage
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