[FLASH-USERS] WARNING after gc filling

[Klaus Weide]

On Mon, 7 Sep 2009, Latif wrote:

> Hi
> Dear All,
> I am using FLASH 3.2. I am getting following warnings which i saw in FLASH
> 3.1. After discussion about them, it was suggested that they are not harmful.
> Same warnings are appearing in FLASH 3.2, which are coming from
> gr_sanitizeDataAfterInterp.F90. If i look at values in Visit they seem normal.
> what is your take on this.
> WARNING after gc filling: min. unk(EINT_VAR)=79113608.35385749 PE=0 block=433 type=1

My take:

- If the min values are 0.0 exactly, then this may be an indication that 
something went wrong within Paramesh (or with FLASH's use if it).  
However, if the warnings only occur for non-leaf blocks, i.e. for type=2 
or type=3, then this *may* still be ok.  Also, some warnings with min 
values .ne. 0.0 *may* be ignorable if the block type is non-leaf.

- If the min values are positive but slightly below the minimum given by 
smlrho (for density) or smalle (for energy variables ener, eint), as 
perhaps in the example quoted above, then this is probably an indication 
of interpolation undershooting.  The interpolation here is the one that 
happens automatically for filling finer-resolution guard cells at 
fine/coarse boundaries.  One can expect this to happen for some sorts
of setups with steep gradients.  Whether this is a serious problem should 
be analyzed for the specific setup. It could indicate, for example, that
the resolution is not good enough, or even that the model of the 
physics that is being implement is not appropriate.

Klaus