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Re: [Bug-gsl] msadams.c:973 aborts with GSL_ESANITY

From: Michael Kaufman
Subject: Re: [Bug-gsl] msadams.c:973 aborts with GSL_ESANITY
Date: Mon, 2 Oct 2017 09:52:40 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:52.0) Gecko/20100101 Thunderbird/52.3.0

On 9/30/17 3:29 AM, Tuomo Keskitalo wrote:

Ok, interesting. So likely it's not GSL optimization issue. What happens with a different ODE-solver on OSX?

No trip.

Also, maybe check that the solver is not making a huge number of small steps (stiff problem?).

Not sure how I do that.

Not being able to reproduce(?) on Linux suggests something OSX specific, some linked math library maybe?

I'm not being clear. I've got a case (call it case #1) that will reproduce on OSX. This particular case #1 will not abort on Linux. However, there are other cases which have indeed aborted on Linux, I've just not yet captured the exact random seed which will enabled me to reproduce those cases at will on Linux, though I imagine it wouldn't take more than a couple of days of running to locate one.

The reason that I think it's not reproducing on Linux is simply numerical roundoff error. With case #1, if I change dt=t1-t in gsl_odeiv2_driver_apply() by 0.002%, the abort will not trip. For case #1, the trip happens after the 1082th call to gsl_odeiv2_driver_apply(), so the initial conditions of the 1083rd step are _just_ different enough to cause the trip.


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