[Users] Problem with CarpetRegrid2/AMR

[Erik Schnetter]

On Wed, Sep 14, 2011 at 9:41 PM, Erik Schnetter <schnetter at cct.lsu.edu> wrote:
> Hal
>
> I believe I found the cause; I am attaching a patch. Could you try the
> patch and see whether it works? Unfortunately I have other, unrelated
> changes in my source tree as well.
>
> The problem is the mapping from component number to process number.
> This mapping may change during regridding. Carpet always used the
> mapping of the current grid structure, and never used the mapping from
> the previous grid structure, and this can lead to failure during
> regridding.

This is related not only to the mapping from components to processes,
but also the mapping from global component indices to process-local
component indices. While both were (probably) wrong, it is the latter
that caused problems for you: The number of components decreased
during regridding, and component #8 was looked up in the new mapping
instead of the old.

> It boggles my mind that such a problem would not manifest itself
> itself in other simulations as well, either leading to catastrophic
> errors in simulations or in outright crashes. I assume that the reason
> is that all other simulations have many fewer components than you, and
> the mapping is thus trivial and never changes, so that this error is
> not triggered.
>
> -erik
>
> --
> Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/
>



-- 
Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/