On 21 Nov 2012, at 16:03, Scott Hawley scott.hawley@belmont.edu wrote:

My thorn BruiserSetBG saves a background spacetime which is then used by the solver thorn BruiserConstraints.

The background is set via an analytic expression, even in the regions designated as ghost zones. The ones I'm concerned about in this e-mail are not inter-processor ghost zones, rather they are regions which (for all OTHER gridfunctions) are typically filled in via prolongation from a coarser grid.

But for the background, I don't want this prolongation to occur, and it's happening automatically without my specifying to do so.

BrusierSetBG is created in local mode, thus I'm not explicitly calling any sync operation, but the ghost info is getting overwritten before the data makes it to BrusierConstraints. Presumably this sync is being called inside the flesh/scheduler. BruiserConstraints is a global thorn.

Question: Is there any way to specify that, for a particular set of grid functions (i.e. the background spacetime), no prolongation is to occur? I haven't seen a parameter that does this.

You can set the tag prolongation="none" in the interface.ccl entry for that group.

e.g.

arrangements/Carpet/Carpet/interface.ccl:

CCTK_INT point_classification TYPE=gf TAGS='checkpoint="no" prolongation="none"'

I am open to re-writing BrusierSetBG as a 'global' thorn if that will make a difference. Otherwise perhaps I'll create a thorn called "BrusierBoth" or something, that feeds the background straight into the solver.

Thanks very much, Scott

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