[Users] CCTK_InterpGridArrays yields NaNs/Infs

[Jens Mahlmann]

Dear all,

following up on last week's questions regarding a tracer particle 
implementation into an evolution code I am having problems with the 
function *CCTK_**InterpGridArrays*. In general, my implementation 
follows the GRHydro_particle approach (in C++), and is working in some 
cases. However, at some interpolation points, the interpolation routine 
returns nans/infs. This error occurs mainly for the interpolation points 
in refined regions and changes when I change buffer zones, grid 
refinement or scheduling options.

Currently, I am not finding the explicit problem, and, I observe that my 
tracer particles are evolved fine in the less refined regions (e.g., 
further away from the origin). For example, I may set up 500 particles 
and in the first evolution step the interpolation produces 112 
nans/infs. Throughout the further evolution, the remaining 388 particles 
(the ones the most far away from the origin) are evolved fine. 
Therefore, I assume I am missing something in my understanding of the 
interpolation routines. Has somebody encountered similar problems or an 
idea where I could direct my debugging to overcome the interpolations to 
NaNs/Infs?

Thank you very much and my best from Valencia

Jens

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