[Tutorial Request] Elementwise Operation about viennacl-dev

[WenyinWei]

Hello, Karl, @karlrupp I have some trouble while using element_op functions.

When I use the following command to get the element_geq, _greater, _less and etc, I got the result matrix_expression but I don't know how to handle it. I can't impose copy functions to fetch the result back to CPU or do other things. And I have no idea about what it would return, if 1 for geq, 0 for less or -1 for less?

[karlrupp]

Assign it to a matrix object, e.g. A = element_geq(B, C);

[WenyinWei]

Yeah, I have tried, but still stuck by a bug.

I tried to select the binary elementwise functions which can work.
element_prod, _div, _pow works,
_eq, _neq, _greater, etc. don't work.

[karlrupp]

Uh, then I guess that these other operators have not been implemented for matrices yet.

[WenyinWei]

Uh, Karl, I found that arctan function works well. Maybe that could serve as a temporary workaround, but just temp.

[WenyinWei]

Hello Karl, would you mind requesting the original maintainers to have a minor update? Though atan function serves as a kind of workaround, it sacrifices too much performance.

[WenyinWei]

Here is my test error of viennacl::linalg::element_abs on matrix.

[WenyinWei]

Hello @karlrupp , may I ask about whether viennacl is not maintained anymore and shall I turn to PETSc?

[karlrupp]

As I said, element_abs is not implemented for matrices yet. Thus, this is not a question about maintenance, but a feature request ;-)

Do you need abs for the full matrix, or just for a submatrix? For a full matrix you could reuse the existing vector kernels (I can show you how to do it).

[WenyinWei]

Yeah, Karl, I would appreciate it if you could show me how to do that when you are free. It would be better if the trick is generic for geq and max.