Does ginkgo copy the csr matrix data?

[Fabian188]

I have the following code

  auto vv = gko::make_array_view(exec, nnz, vdp);
  auto cv = gko::make_array_view(exec, nnz, (int*) m->GetColPointer());
  auto rv = gko::make_array_view(exec, nrow + 1, (int*) m->GetRowPointer());

  auto csr = gko::share(gko::matrix::Csr<GK_T, int>::create(exec, gko::dim<2>(nrow,ncol), vv, cv, rv));

I understand make_array_view such that it does not copy data, but does Csr::create copy the data?

The question is, if I need to keep the sources of the make_array_view available.

[MarcelKoch]

The make_array_view doesn't copy the data, that is correct. The Csr::create however will copy the data from the vv, cv, and rv arrays.

This is because the create function takes in its arguments by value. Since you are doing nothing special here, the copy constructor of the gko::array will be called. If, however, you want to not copy the data, then you have to pass in the arrays by r-value reference. This essentially means to wrap the views in std::move(vv), etc.

So, to answer your question, you don't need to keep around the sources for the make_array_view after the call to Csr::create.

[Fabian188]

Thanks for you answer. I'm actually interested in avoiding unnecessary copy in case the system is huge and jacobi/cg shall not add that much memory.

I added the std::move, can I be sure my matrix will not be altered?

[upsj]

If you want to make sure your matrix isn't altered, you can instead use make_const_array_view and use Csr::create_const instead with the same parameters.

[Fabian188]

Thanks a lot!