From: "Jochen Küpper" <jochen@fhi-berlin.mpg.de>
To: gsl-discuss@sourceware.org
Subject: Unwanted compiler optimization (was: Bug report and fix for adaptive step size control in ODE solving)
Date: Thu, 03 Jan 2008 09:01:00 -0000 [thread overview]
Message-ID: <9AFC9075-1EA3-4E26-9BE9-EB9C475FE3D9@fhi-berlin.mpg.de> (raw)
In-Reply-To: <477BDBEE.2000603@googlemail.com>
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Dear Optimization specialists,
On 02.01.2008, at 19:46, Frank Reininghaus wrote:
> Jochen Küpper wrote:
>
>> However, why don't you test what you really describe your comment?
>> This would look like the following (untested):
>>
>> h0 = GSL_MAX_DBL(GSL_DBL_MIN, (t0 != t0+h0) ? h0 :
>> GSL_DBL_EPSILON*t0);
>
> Actually, I had been thinking of something like that first, but then
> I was afraid that an optimising compiler might transform 't0 !=
> t0+h0' into '0 != h0', making the patch useless for the 'h0 <
> GSL_DBL_EPSILON*t0' problem.
Is this an optimization that is considered valid even for floating-
point calculations in compiler building?
Maybe we should ask our friends from the GCC development about it...
Greetings,
Jochen
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next prev parent reply other threads:[~2008-01-03 9:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-26 22:14 Bug report and fix for adaptive step size control in ODE solving Frank Reininghaus
2008-01-02 13:40 ` Kevin H. Hobbs
2008-01-02 14:18 ` Jochen Küpper
2008-01-02 18:51 ` Frank Reininghaus
2008-01-03 9:01 ` Jochen Küpper [this message]
2008-01-04 10:44 ` Unwanted compiler optimization (was: Bug report and fix for adaptive step size control in ODE solving) Brian Gough
2008-01-03 5:15 ` Bug report and fix for adaptive step size control in ODE solving Michael Stauffer
2008-01-03 15:54 ` Brian Gough
2008-01-04 9:46 ` Brian Gough
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