linux-kernel - Re: [PATCH v3] replace timeconst bc script with an sh script

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Date:   Sun, 03 Nov 2019 14:00:47 -0800
From:   hpa@...or.com
To:     Ethan Sommer <e5ten.arch@...il.com>
CC:     Jonathan Corbet <corbet@....net>,
        Federico Vaga <federico.vaga@...a.pv.it>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...e.de>,
        Mark Rutland <mark.rutland@....com>,
        John Stultz <john.stultz@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Corey Minyard <cminyard@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-doc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] replace timeconst bc script with an sh script

On November 3, 2019 1:56:50 PM PST, Ethan Sommer <e5ten.arch@...il.com> wrote:
>> Please let me point out, again, that bc *is* part of the basic POSIX
>toolset, and the only tool in that toolset that allows for
>arbitrary-precision arithmetic. That being said, GNU as, which we also
>depends on, also contains bigint arithmetic, so it might be possible to
>coax as into outputting ASCII output without manually implementing
>bigints manually.
>>
>> Another option would be to use a C program linked with gmp. Binutils
>requires gmp, so it doesn't inherently add dependencies, but running it
>though as would probably be easier at least for the LLVM guys.
>>
>> I also have written a small, portable C bigint library, but that is a
>lot of code to add to the tree.
>I don't know what the requirement is for the level of precision this
>would need to support is, so I don't know if this meets them, but I
>made
>a C program that doesn't use gmp, so while it probably doesn't
>theoretically have the same level of precision as bc, it does match it
>for output on anything up to 15000 (it doesn't stop matching
>timeconst.bc above 15000 I just didn't test any higher). The program is
>here: http://ix.io/20Ka
>If this is considered precise enough to be an acceptable replacement
>I will make a new patch to use it in place of timeconst.bc.

The point isn't to make it work *now*, but getting it to *stay* work.
-- 
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