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From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	James Bottomley <JBottomley@Odin.com>,
	Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] lib/string_helpers.c: don't lose precision in string_get_size()
Date: Mon, 26 Oct 2015 22:48:55 +0100	[thread overview]
Message-ID: <8737wx712w.fsf@rasmusvillemoes.dk> (raw)
In-Reply-To: <1445867720-25473-3-git-send-email-vkuznets@redhat.com> (Vitaly Kuznetsov's message of "Mon, 26 Oct 2015 14:55:19 +0100")

So I also played with this over the weekend, and also threw together a
stupid script to check the output. I see you have more or less the same
idea I used, namely to combine size and blk_size earlier.

I put some code on github, https://github.com/Villemoes/get_size. All
versions still fail a very simply case, size=1594323, blk_size=1, for
which the correct answer is "1.52 MiB", but we get "1.51 MiB". But both
your version and my two attempts seem to have the property that they are
always at most one ULP (unit in the last place) too low, and never too
high. ATM, my version 2 fails 70 of the 13598 test cases, while yours
fail 86 (the former being a strict subset of the latter), so they're
very similar.

Regardless of which algorithm we go with, I have some cleanups I'd like
to do, but they're mostly independent and can wait.

Rasmus


  parent reply	other threads:[~2015-10-26 21:48 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-26 13:55 [PATCH 0/3] lib/string_helpers: fix precision issues and introduce tests Vitaly Kuznetsov
2015-10-26 13:55 ` [PATCH 1/3] lib/string_helpers: change blk_size to u32 for string_get_size() interface Vitaly Kuznetsov
2015-10-26 13:55 ` [PATCH 2/3] lib/string_helpers.c: don't lose precision in string_get_size() Vitaly Kuznetsov
2015-10-26 16:08   ` Andy Shevchenko
2015-10-27  8:36     ` Vitaly Kuznetsov
2015-10-27  9:34       ` Andy Shevchenko
2015-10-26 21:48   ` Rasmus Villemoes [this message]
2015-10-27  8:45     ` Vitaly Kuznetsov
2015-10-26 13:55 ` [PATCH 3/3] lib/test-string_helpers.c: add string_get_size() tests Vitaly Kuznetsov
2015-10-26 15:13   ` Andy Shevchenko
2015-10-26 15:18     ` Vitaly Kuznetsov
2015-10-26 15:21       ` Andy Shevchenko
2015-10-26 15:50         ` Vitaly Kuznetsov
2015-10-26 21:54   ` Rasmus Villemoes
2015-10-27  8:56     ` Vitaly Kuznetsov

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