On 5/1/23 16:15, Corbin Foucart wrote:
Is there an developer-intended way to view a Vector<double> object with
dim entries as a Tensor<1, dim> object for ease of multiplication with
other Tensor<1, dim> instances such as normal vectors?
I can do something like:
// dim = 3
Vector<double> vec({4,5,6});
ArrayView<double> view(&a[0], 3);
Tensor<1, 3, double> tensor(view);
but from the documentation this seems to make a copy, and I wondered if
there was a deal.ii way to "view" the Vector<double> as a Tensor object.
This operation is the result of a numerical flux computation and is
called many times during assembly.
Correct, this makes a copy. There really isn't a different way (in
deal.II): Tensor objects own their data, they are not "views", and so
they cannot avoid the copy. Of course, if you don't want to do the copy,
then you can always write out the tensor operation you are interested in
from the original vector elements by hand.
That said: It would greatly surprise me if the copying of elements is
limiting the speed of your program. Have you benchmarked this? Are you
sure that you aren't trying to optimize a part of the program that
doesn't actually need to be optimized?
Best
W.
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Wolfgang Bangerth email: [email protected]
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