Add precision log in apply with profiler_hook

[yhmtsai]

This PR allows profiler hook to log the precision in apply which can help checking the mixed precision setup.

I am thinking whether to have Dense/Vector in that, which might be useful when identify it is local solver or distributed solver in distributed setup

The current format will be like Dense, Vector, or linop
spmv: obj*input_type=output_type
advanced: alpha_type*obj*input_type+beta_type*output_type

[MarcelKoch]

nit: maybe just put the in- and output vector as arguments to the apply, i.e.:

Suggested change

	ss << "apply(" << stringify_object(A);
	if (log_apply_precision_) {
	ss << "*" << check_vector_type(b) << "=" << check_vector_type(x);
	}
	ss << ")";
	ss << "apply(" << stringify_object(A) << ", " << check_vector_type(b) << ", " << check_vector_type(x) << ")";

same at the other instances

[yhmtsai]

I will still put the scalar type for log because the mismatched type will trigger temporary clone

[MarcelKoch]

I think the output still needs some discussion, especially how it interacts with stringify_objects.

[MarcelKoch]

nit: maybe remove this.

[yhmtsai]

could you point where should be removed? github does not show the lines

[MarcelKoch]

This file only has the license date changed. Nothing else.

[MarcelKoch]

Perhaps this should better be merged with stringify_objects. If a user explicitly sets a name for an object, it should override this behavior here.

[MarcelKoch]

By the way, isn't stringify_objects already enough?

[yhmtsai]

Good point!
I try it and it works smoothly.
only some nit: it contains the full name like gko::matrix::...
for complex, it gives additional space like gko::matrix::Dense<std::complex<double> >