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Date: Wed, 20 Nov 2013 11:00:12 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Andrea Mazzoleni <amadvance@gmail.com>
CC: David Brown <david.brown@hesbynett.no>,
        Linux RAID Mailing List <linux-raid@vger.kernel.org>,
        Btrfs BTRFS <linux-btrfs@vger.kernel.org>,
        David Smith <creamyfish@gmail.com>
Subject: Re: Triple parity and beyond
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On 11/20/2013 10:56 AM, Andrea Mazzoleni wrote:
> Hi,
> 
> Yep. At present to multiply for 2^-1 I'm using in C:
> 
> static inline uint64_t d2_64(uint64_t v)
> {
>         uint64_t mask = v & 0x0101010101010101U;
>         mask = (mask << 8) - mask;

(mask << 7) I assume...