On 3/13/19 8:21 PM, Phạm Ngọc Kiên wrote:
> I am testing my codes for output the solution at a point in my numerical
> model.
> I saw in the library 2 ways to do this task. The first one is to use
> VectorTools::point_value() function and the second one is
> fe_values.get_function_values().
These functions are really used in very different contexts. The first of these
is when you want to evaluate a solution vector at some arbitrary point in the
domain. As a consequence, you have to specify this point when you call the
function.
The second function is used when you want to evaluate the function at very
specific points, namely the quadrature points of the current cell. You can of
course only use this if the point at which you want to evaluate the solution
happens to be a quadrature point of the current cell, and not just any point
anywhere. In return the second function is then vastly more efficient than the
first.
Does this help?
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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