WIP: extract clonable feature from LinOp

[yhmtsai]

This PR is still under process but I will collect some potential issues to users or developers when we move this direction.

Idea: we usually only need to clone the matrix to generate new preconditioner or solver, but we do not need that for solver or preconditioner. It will remove the clone/copy_from out of LinOp.

We plan to have several prs to reach that, but need to have this to check whether we will have trouble having that.

Clonable: only Matrix now, but maybe also need stop criterion?
Note. Partition is also clonable.
I also include one test to show when user defines a custom class inherit from ginkgo class, which is already inherited from ClonableObject.
ExecutorHolder is unnecessary. will move back in the end.

clear is relying on the operator=.
I feel create_default and clear not need other than clone. we might be able to make LinOp without any mixin.

Issue:

• We use clone to keep executor consistent in LinOp generation.
  • gko::clone throw exception when they can not do it. (current in this branch)
  • turn .on(exec) strictly on user behalf. -> need to make it optional such that awareness of the cost and behavior.
  • How do we have two same set of factory to generate solver? (we use clone to test reference and backend on the same solver settings). It will require to manually set two same set factory and corresponding LinOp
• clone/copy_from usage is a bit harder now because LinOp is not holding clone/copy_from.
  • free function gko::clone() takes care of that.
  • member function will leads as<LinOp>(as<ClonableObject>(linop)->clone()). copy_from is worse because we might also need to use as<> in the input. Note. if they are concrete type, we can directly call the function.

TODO:

• check the clone when the base class also have clone

[ginkgo-bot]

Error: The following files need to be formatted:

accessor/hip_helper.hpp
benchmark/utils/preconditioners.hpp
common/cuda_hip/base/bf16_alias.hpp
common/cuda_hip/base/math.hpp
common/unified/components/fill_array_kernels.cpp
common/unified/components/precision_conversion_kernels.cpp
core/config/preconditioner_config.cpp
core/config/preconditioner_ic_config.cpp
core/config/preconditioner_ilu_config.cpp
core/preconditioner/ic.cpp
core/preconditioner/ilu.cpp
core/test/config/preconditioner.cpp
core/test/config/solver.cpp
core/test/matrix/sellp.cpp
core/test/preconditioner/ic.cpp
core/test/preconditioner/ilu.cpp
core/test/solver/direct.cpp
cuda/base/types.hpp
examples/ilu-preconditioned-solver/ilu-preconditioned-solver.cpp
examples/ir-ilu-preconditioned-solver/ir-ilu-preconditioned-solver.cpp
examples/multigrid-preconditioned-solver-customized/multigrid-preconditioned-solver-customized.cpp
examples/preconditioner-export/preconditioner-export.cpp
examples/reordered-preconditioned-solver/reordered-preconditioned-solver.cpp
hip/base/exception.hip.cpp
hip/base/hipblas_bindings.hip.hpp
hip/base/hipblas_handle.hpp
hip/base/hiprand_bindings.hip.hpp
hip/base/hipsparse_bindings.hip.hpp
hip/base/hipsparse_block_bindings.hip.hpp
hip/base/hipsparse_handle.hpp
hip/base/memory.hip.cpp
hip/base/pointer_mode_guard.hip.hpp
hip/base/roctx.hip.cpp
hip/base/types.hip.hpp
hip/components/memory.hip.hpp
hip/test/base/exception_helpers.hip.cpp
hip/test/matrix/fft_kernels.hip.cpp
test/mpi/distributed/row_gatherer.cpp
test/mpi/solver/solver.cpp
test/solver/direct.cpp

You can find a formatting patch under Artifacts here or run format! if you have write access to Ginkgo