[Users] problems with AHFinderDirect

[Ian Hinder]

On 14 Jun 2012, at 13:53, Eloisa Bentivegna wrote:

> On Jun 14, 2012, at 12:01 PM, Vassilios Mewes wrote:
> 
>> Hello all,
>> 
>> when using the AHFinderDirect thorn in a simulation of a relativistic wind past a TOV neutron star, i get the following error message:
>> 
>> INFO (AHFinderDirect): proc 0: searching for horizon 1/1
>> WARNING level 0 in thorn AHFinderDirect processor 0 host permeability.daa.uv.es
>>  (line 78 of /Users/vass/programs/Cactus/arrangements/EinsteinAnalysis/AHFinderDirect/src/jtutil/error_exit.cc): 
>>  -> ***** row_sparse_Jacobian__UMFPACK::solve_linear_system():
>>        error return status=1 from umfpack_numeric() routine
>> 
>> is that an indication that umfpack is not installed correctly (i was never prompted to install it manually and the compilation of the Einstein toolkit [Maxwell release] went on smoothly without any errors), or rather that something is wrong trying to find the horizon? (there should be an horizon, because the lapse goes to 0 fairly quickly, after which the simulation eventually crashes)
> 
> Hi Vassili,
> 
> this error usually comes up when the arguments to umfpack_numeric() are not numbers (as would happen, for instance, if the metric had become singular). Could you check that your 3+1 variables are finite? Thorn NaNChecker could help you do that.

If this turns out to be the problem, we should probably check for this in AHFinderDirect and give an error message.  Something like "The metric has become singular at [x,y,z]; unable to compute horizon and aborting the run".

-- 
Ian Hinder
http://numrel.aei.mpg.de/people/hinder