On 08/03/2017 03:16 AM, 'Maxi Miller' via deal.II User Group wrote:
I am following example 52 for writing code which should solve a system of
three equations. In it I can rewrite my equations such that my source term is
zero, but my matrices on the left side are depending on time, which means that
I have to reassemble the system matrix and the inverse system matrix at every
time step. Is that a good idea, or rather performance-degrading?
Like all performance questions, it is not worth thinking about them *unless
you have concrete evidence* that your performance is too slow for what you
want to do. For example, if your solver takes 90% of the time, then it doesn't
make sense to look at the run time of the assembly.
Furthermore I then have to call
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assemble_system(time)
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in the function
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evaluate_diffusion(constdoubletime,constVector<double>&y)
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but compilation fails with
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error:passing ‘constStep52::Diffusion<3>’as‘this’argument discards qualifiers
[-fpermissive]
assemble_system(time);
|
but why? And how can I fix that?
Your evaluate_diffusion() function is declared as `const`. But you can only
call `const` functions from `const` functions, so you are not allowed to call
the non-`const` function assemble_system().
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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