[Paraview] Difference between "Compute Derivatives" and "Gradient (Unstructured)"...

[Stefan Melber]

Hi,

i have a question regarding the filters "Compute Derivatives" and 
"Gradient (Unstructured)". I have to calculate a equation on an 
unstructured data set with some derivatives of the velocity.

Using the "Gradient (Unstructured)" it works, but it is really slow. 
Using the "Compute Derivatives" and the convert the result back from 
cell centers to points i can get nearly the same results - but much 
faster (the most time takes the conversion from cell center to points!).

So i made a comparison of both results with an isosurface of the 
magnitude of the difference between both gradients an i can only find 
minor changes. So my question to the developers: Where is the difference 
between both filters? Why is the "Gradient (Unstructured)" so much slower?

Best regards and thank you in advance,

     Stefan


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                                        Stefan Melber-Wilkending
                          _/
                        _/_/            Fields of activities:
                      _/  _/            -) High-Lift Research
              _/_/_/_/_/_/_/_/_/_/      -) Complex Configurations
            _/    _/    _/    _/        -) Numerical Wind-Tunnel
          _/    _/    _/    _/          -) Supercomputing
        _/_/_/_/_/_/_/_/_/_/            -) Glider-Aerodynamics
              _/  _/  _      _
              _/_/   | \ |  |_|         German Aerospace Center, DLR
              _/     |_/ |_ | \         in the Helmholtz-Association

       Phone ..: +49 531/295-2836       Institute of Aerodynamics
       Fax. ...: +49 531/295-2320       and Flow Technology
       Email ..: Stefan.Melber at dlr.de   Lilienthalplatz 7
       Web ....: http://www.dlr.de/AS   D-38106 Braunschweig/Germany
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