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Date:   Wed, 20 Dec 2017 16:41:46 +0100
From:   Crt Mori <>
To:     David Laight <>
Cc:     Jonathan Cameron <>,
        Ingo Molnar <>,
        Andrew Morton <>,
        Kees Cook <>,
        Rusty Russell <>,
        Ian Abbott <>,
        Larry Finger <>,
        Niklas Soderlund <>,
        Thomas Gleixner <>,
        Krzysztof Kozlowski <>,
        Masahiro Yamada <>,
        "" <>,
        "" <>,
        Peter Zijlstra <>,
        Joe Perches <>
Subject: Re: [PATCH v10 1/3] lib: Add strongly typed 64bit int_sqrt

On 20 December 2017 at 15:39, David Laight <> wrote:
> From: Crt Mori
>> Sent: 20 December 2017 14:20
>> There is no option to perform 64bit integer sqrt on 32bit platform.
>> Added stronger typed int_sqrt64 enables the 64bit calculations to
>> be performed on 32bit platforms. Although int_sqrt() is a rough
>> approximation, the same algorithm is used in int_sqrt64() as good
>> enough on 32bit platform.
> The algorithm used gives an exact (rounded down) square root,
> not an approximation.

OK, noted. This is from new changed function indeed - will change in v11.

> With minor changes it ought to be possible to remove most of the
> 64bit arithmetic and shifts.
> If you care about performance then using 32 bit maths will be much faster.

I need precision not the performance. That is why I would like to
leave int_sqrt as one for good performance while my will be used when
you require a precision.

>         David

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