linux-kernel - Re: [PATCH v1 1/1] drm/i915/selftests: Replace too verbose for-loop with simpler while

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Date:   Wed, 16 Feb 2022 10:02:10 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH v1 1/1] drm/i915/selftests: Replace too verbose for-loop
 with simpler while

On Wed, Feb 16, 2022 at 9:55 AM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
> On Tue, 15 Feb 2022, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> > On Tue, Feb 15, 2022 at 07:14:49PM +0200, Jani Nikula wrote:
> >> On Tue, 15 Feb 2022, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> >> > It's hard to parse for-loop which has some magic calculations inside.
> >> > Much cleaner to use while-loop directly.
> >>
> >> I assume you're trying to prove a point following our recent
> >> for-vs-while loop discussion. I really can't think of any other reason
> >> you'd end up looking at this file or this loop.
> >>
> >> With the change, the loop indeed becomes simpler, but it also runs one
> >> iteration further than the original. Whoops.
> >
> > Yeah, sorry for that, the initial condition should be d = depth - 1,
> > of course.
>
> Well, no, the condition should be while (--i) instead to also match the
> values the original loop takes. ;D

"There are two hard things in computer science: cache invalidation,
 naming things, and off-by-one errors."

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds