[Cactuseinstein] IDAnalyticBH -- making Kerr.c a bit more robust

[Erik Schnetter]

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On Thursday 16 December 2004 22:03, Bernard Kelly wrote:
> Hi.
>
> This may be something that only affects me, but would it be possible
> to alter the analytic BH data thorns to protect against pathological
> values on the coordinate origin and axes?

That is a very good idea.

> In particular, I have "Kerr.c" in mind. I've been using it with
> "avoid_origin = 'no'", and it doesn't like on-axis points. This could
> be fixed by adding a minimum (small) to a particular variable --
> "rho_2" -- which would then propagate through the remaining values.
> Later calculations of analytic derivatives (of the conformal factor)
> would have to be slightly rewritten to avoid pathologies.
>
> To be specific, the few changes below allow me to work on-axis and do
> pointwise convergence tests. Could something like this be implemented
> in CactusEinstein? It should have no adverse effects on existing
> off-axis calculations.

Your suggested changes seem incomplete -- for example, the variable 
tmp_BEAN is neither declared nor set.

If you have a piece of changed, working code, then you can give the 
command

 cvs diff -u Kerr.c

which will produce a list of the differences.  This list is 
automatically correct, and can also be automatically applied with the 
"patch" command.

As a side remark, try not to litter the code with NEW CODE and OLD CODE 
statements; this information is already in CVS and will confuse people 
who want to understand the code without caring about its history.

I could easily add the fudge factor to rho_2.  I would use the parameter 
"eps" for that which is already defined in the param.ccl for that 
purpose.  I don't understand some of your later changes where you 
change a minus to a division.  Could you send me the output of the diff 
command mentioned above?  I'll apply the changes.

Thanks for your effort,
- -erik

- -- 
Erik Schnetter <schnetter at aei.mpg.de>   http://www.aei.mpg.de/~eschnett/

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