Dear Wolfgang,
Here is a simple test code (I also attached the source code):
int main()
{
using namespace dealii;
const unsigned int *matrix_dimension* = 4;
Tensor<2, matrix_dimension> myTensor;
FullMatrix<double> myMatrix(matrix_dimension,
matrix_dimension);
for (unsigned int i = 0; i < matrix_dimension; i++)
for (unsigned int j = 0; j < matrix_dimension; j++)
{
myMatrix(i,j) = i + j;
}
myMatrix.copy_to(myTensor);
std::cout << myTensor.dimension << std::endl;
return 0;
}
When *matrix_dimension =*2 or 3, the code works fine. When
*matrix_dimension *= 4, it has a linking error as below:
*error: undefined reference to 'void
dealii::FullMatrix<double>::copy_to<4>(dealii::Tensor<2, 4, double>&,
unsigned long, unsigned long, unsigned long, unsigned long, unsigned int,
unsigned int) const'collect2: error: ld returned 1 exit statusmake[3]: ***
[CMakeFiles/main.dir/build.make:116: main] Error 1*
The version of deal.ii is 9.4.0.
I looked into the source code. Indeed, in "full_matrix.h", there is a
declaration of "copy_to". However, the actual implementation is not in
"/dealii-9.4.0/src/source/lac/full_matrix.cc", but in
"/dealii-9.4.0/src/source/lac/full_matrix.inst.in"
*for (S : REAL_SCALARS) { template void
FullMatrix<S>::copy_to<1>(Tensor<2, 1> &,
const size_type, const
size_type, const size_type,
const size_type,
const unsigned int,
const unsigned int) const; template void
FullMatrix<S>::copy_to<2>(Tensor<2, 2> &,
const size_type, const
size_type, const size_type,
const size_type,
const unsigned int,
const unsigned int) const; template void
FullMatrix<S>::copy_to<3>(Tensor<2, 3> &,
const size_type, const
size_type, const size_type,
const size_type,
const unsigned int,
const unsigned int) const; }*
I assume this is related with explicit instantiation?
Best,
Tao
On Wednesday, June 7, 2023 at 10:38:35 AM UTC-4 Wolfgang Bangerth wrote:
> On 6/6/23 15:46, Tao Jin wrote:
> >
> > However, the above copy_to() function only works when the tensor
> dimension is
> > less or equal to 3, that is,
> > Tensor<2, dim>, dim <=3.
> > When dim is larger than 3, I have to use for loops to copy each matrix
> entry
> > into the rank-2 tensor.
>
> What happens for dim>3? You only say "it only works when", but you don't
> describe what goes wrong if dim>3?
>
>
> > I know that it is typical to set dim as 2 or 3. However, does it make
> sense to
> > make FullMatrix::copy_to() work for a general rank-2 tensor?
>
> I see no reason why this should not work. The function is implemented in
> the
> full_matrix.h file, so I believe it should just work if you call the
> function
> on tensors that are larger than 3x3.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> www: http://www.math.colostate.edu/~bangerth/
>
>
>
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/* ---------------------------------------------------------------------
*
* Copyright (C) 2006 - 2020 by the deal.II authors
*
* This file is part of the deal.II library.
*
* The deal.II library is free software; you can use it, redistribute
* it, and/or modify it under the terms of the GNU Lesser General
* Public License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* The full text of the license can be found in the file LICENSE.md at
* the top level directory of deal.II.
*
* ---------------------------------------------------------------------
*
* Author: Tao Jin
* University of Ottawa, Ottawa, Ontario, Canada
* June 2023
*/
// In this example, we test the copy_to member function of
// FullMatrix
#include <deal.II/lac/full_matrix.h>
#include <deal.II/base/tensor.h>
int main()
{
using namespace dealii;
const unsigned int matrix_dimension = 4;
Tensor<2, matrix_dimension> myTensor;
FullMatrix<double> myMatrix(matrix_dimension,
matrix_dimension);
for (unsigned int i = 0; i < matrix_dimension; i++)
for (unsigned int j = 0; j < matrix_dimension; j++)
{
myMatrix(i,j) = i + j;
}
myMatrix.copy_to(myTensor);
std::cout << myTensor.dimension << std::endl;
return 0;
}
