how to transfer an allocated array on GPU to solver-appl

[ztdepztdep]

The d_b and d_x is two double arraies which have been allocated on GPU. I want to know how to transfer it to the solver-apply.
I tried to use the following code:
solver->apply(gko::lend(d_b), gko::lend(d_x));
but it doesn't wok.

[yhmtsai]

Are the type of d_b and d_x double*?
If they are, the solver needs to use the gko::matrix::Dense<double>* type.
You can create the Dense matrix by reading a mtx file.
ex. gko::read<gko::matrix::Dense<>>(std::ifstream("filepath"), exec);
or create the Dense first then fill in the data

auto x = gko::matrix::Dense<>::create(exec, gko::dim<2>(n, 1));
// copy the data to x->get_values()

or create the Dense on the preallocated array
auto x = gko::matrix::Dense<>::create(exec, gko::dim<2>(n, 1), gko::array<double>::view(exec, n, d_x));
note. array view to indicate the size and location for the plain pointer.

[yhmtsai]

there is another discussion transfer from issue, which is the same discussion as this.
I will lock this conversation, please go to another one #1132