[Developers] How about changing avoid_origin* restricted ?

Erik Schnetter schnetter at cct.lsu.edu
Sat Apr 14 09:09:52 CDT 2007

On Apr 14, 2007, at 07:15:01, jtao at cct.lsu.edu wrote:

> It is sometime necessary to check if the grid contains origin.
> If avoid_origin parameters can be accessed directly,
> one doesn't have to do explicit checking. Is it ok to change
> those avoid_origin parameters restricted ?

I'm afraid that this would not work in the general case.  Even  
CartGrid3D ignores the avoid_origin parameter under certain  
circumstances.  CoordBase does not take them into account.  With mesh  
refinement, avoid_origin describes only the coarsest grid, and finer  
grids can have different behaviour.  avoid_origin is meant for a  
human being to give instructions to CartGrid3D.  It is not a good  
idea to use it to draw conclusions about how the grid is laid out in  
the end.

Instead, you can calculate the quantity


and test whether it is integer or not:

if (fabs (nx0 - floor(nx0)) < 0.01) /* grid point at origin */

else if (fabs (nx0 - floor(nx0) + 0.5) < 0.01) /* staggered about  
origin */

else /* no definite relation */


Erik Schnetter <schnetter at cct.lsu.edu>

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