outlier variable residual norms

[Andrew....@csiro.au]

Hey,

after some time steps i now get

Outlier Variable Residual Norms
variable1: number1
variable2: number2

etc. I must say this is pretty cool, but i'm not sure what the numbers actually mean. Eg, my Nonlinear |R| is 1E-4, but the Outliers are 1E-1. I would have expected the latter to be a lot smaller than the former. So what are these norms?

a

[Permann, Cody J]

The outliers are those variables whose square of their individual L2-norm  is "too far" from the square of the average norm.  Right now "two far" is some fixed value (currently 2.0) determined empirically by a computer scientist ;)  If you want to see the actually calculation of that value, it's in NonlinearSystem.C.

We print them because they might be too big to reliably pass a tolerance check.  It's sort of like a yellow flag if you see a bunch of those coming out.  You might try tighter tolerances or different solver options, etc.

Cody

a

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[Slaughter, Andrew E]

Correction, the code you should examine is Console::writeVariableNorms() in framework/src/outputs/Console.C. I am in the process of removing the code in NonlinearSystem, although they are nearly identical. 

[Andrew....@csiro.au]

Thanks Cody and Andrew.  I suggest the Outliers be scaled in the same way as the Nonlinear |R|.  It seems strange to me that |R|=1E-4, while the outliers are 1E-1.

 

a

 

 

Ph: +61 7 3327 4497.  Fax: +61 7 3327 4666
Queensland Centre for Advanced Technologies
PO Box 883, Kenmore, Qld, 4069 
 

[Permann, Cody J]

Andy,

We don't scale anything here.  We simply do a comparison.  Your output doesn't make sense to us, can you paste the actual output of one of your solves with the norm and outliers?

Thanks,
Cody 

[Andrew....@csiro.au]

Sure:

 

Time Step  2, time = 18400219.8

                dt = 119.800000

0 Nonlinear |R| = 9.484776e-01

1 Nonlinear |R| = 6.886460e-03

2 Nonlinear |R| = 6.095817e-05

Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2

Solve Converged!

 

Outlier Variable Residual Norms:

  pwater: 9.484776e-01

  pgas: 7.285548e-05

  conc: 9.178726e-05

 

a

 

 

Ph: +61 7 3327 4497.  Fax: +61 7 3327 4666
Queensland Centre for Advanced Technologies
PO Box 883, Kenmore, Qld, 4069