On 02/15/2018 07:29 AM, Moraad Biagooi wrote:
I have some problems with the signs of VectorTools::point_gradient.
Here's an example:
I modified Step-4 of tutorial so that the mesh is a
GridGenerator::hyperball with half of its boundary_id equal to one.
After solving the problem, a function is called that prints
VectorTools::point_gradient function versus a simple 1st order gradient
at some points inside the mesh.
The result is almost the same but there's sign difference at some
points.
Do you know which function is correct? For example, have you taken a
look at the solution at that point and determined visually what the
gradient is, and then compared it with what the two ways of computing
things return? (This may be easier to do in 2d.)
There is of course always the possibility of a bug, but it would
surprise me if there was one in the function that computes the gradient
at a point.
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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