Improved performance and arguably simpler code for dictionaries by changing the keys layout

Current layout

Currently the _dictkeysobject struct is laid out like this:

ptr ---->  +--------------+
           |     header   |
           +--------------+
           |    indices   |
           +--------------+
           |     keys     |
           +--------------+

which requires some relatively expensive calculation to find the start of the keys, as the indices are not only variable in number, but variable in size also.

Proposed layout

If instead it is laid out as follows:

           +--------------+
           |    indices   |
ptr ---->  +--------------+
           |     header   |
           +--------------+
           |     keys     |
           +--------------+

and the indices laid from highest to lowest with 0 just before ptr, finding the start of the keys is as simple as ptr->keys . Accessing an index is no slower, and the code barely any more complex.

Linked PRs

• gh-145097
• gh-150640

作業がそちらに移っているため、まず提案されている _dictkeysobject のレイアウトと、リンクされている PR gh-145097 および gh-150640 を確認してください。現在の index、header、keys の配置と提案された配置を比較してください。完了するには、新しいレイアウトをサポートする実装と、その性能または正しさの検証が必要です。