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Re: pmiostat qa failures

To: Mark Goodwin <mgoodwin@xxxxxxxxxx>
Subject: Re: pmiostat qa failures
From: fche@xxxxxxxxxx (Frank Ch. Eigler)
Date: Mon, 08 Sep 2014 08:30:14 -0400
Cc: Ken McDonell <kenj@xxxxxxxxxxxxxxxx>, pcp@xxxxxxxxxxx
Delivered-to: pcp@xxxxxxxxxxx
In-reply-to: <540D6219.8010308@xxxxxxxxxx> (Mark Goodwin's message of "Mon, 08 Sep 2014 18:00:25 +1000")
References: <540D316D.7060400@xxxxxxxxxxxxxxxx> <540D3413.50309@xxxxxxxxx> <540D3871.80201@xxxxxxxxxxxxxxxx> <540D3DE3.9010502@xxxxxxxxx> <540D6219.8010308@xxxxxxxxxx>
User-agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux)
Mark Goodwin <mgoodwin@xxxxxxxxxx> writes:

> [...]
> I checked the raw values:
> the correct value is 0.05 = (7504 - 7503) / 20.00 [...]
> Here's pmval on RHEL65/i386 (32bit) :
> Breakpoint 2, printreal (v=0.049999999799474608, minwidth=21) at pmval.c:456
> Breakpoint 1, printreal (v=0.050000000000000003, minwidth=21) at pmval.c:456
>
> Both are wrong! - as checked above, the correct value is 0.05. [...]

Not sure about that - binary floating point calculations naturally
vary between compiler versions / cpu families / optimization levels,
and those two numbers are identical to apprx. ~28 bits of mantissa.
The test should have a larger epsilon range for acceptance.


- FChE

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