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Move "Advanced Core Type Selection" RFC from "proposed" to "experimental" #2005

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Move "Advanced Core Type Selection" RFC from "proposed" to "experimental" #2005

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11 changes: 10 additions & 1 deletion rfcs/proposed/core_types/README.md → rfcs/experimental/core_types/README.md
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Expand Up @@ -81,6 +81,8 @@ Similarly, we can create/initialize an arena for core type(s) selected by a user
#### Synopsis

```cpp
#define TBB_HAS_TASK_ARENA_CORE_TYPE_SELECTOR 202xxx

namespace oneapi {
namespace tbb {
class task_arena {
Expand Down Expand Up @@ -138,7 +140,14 @@ This allows querying the effective concurrency without creating a task arena.
The key implementation problem is how to pass the additional information about multiple core types
to the TBB library functions for arena creation while meeting compatibility requirements.

This proposal encapsulates the implementation and can potentially utilize various ways to solve the problem, such as:
This proposal encapsulates the implementation and can potentially utilize various ways to solve the problem.
The experimental implementation encodes the extra information into the existing types, using the bit-packing
scheme described in [Alternative 2](#alternative-2-extend-constraints-api-in-place) internally within the
selector API. To enable applications compiled with the new functionality to handle execution against older
oneTBB binaries, the header-side code checks `TBB_runtime_interface_version()` at runtime to fall back
gracefully when an older library is loaded.

The approaches that were considered include:
- encoding the extra information into the existing types;
- [ab]using other existing entry points / data structures with reserved parameters or space to pass information through;
- for example, using `task_arena_base::my_arena` (which is currently `nullptr` until the arena is initialized),
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