Issue #9614 has been updated by Koichi Sasada.


>  ko1: adding flag for ordering might complicate the st code even more.
>  I think st should only be for implementing Hash.

I agree that st.c is already complicated.
But I think Hash class should use original one.

Adding similar data structure can also increase complexity.
At least, I like same interfaces for such similar data structures.

>  My primary goals for ihash are to reduce pointer chasing and malloc use.
>  ihash uses container_of, like ccan/list:

It makes sense.

I think open addressing is better for such internal, small tables such as method table.
It doesn't need chain buckets.

So I wanted to extend st to introduce open addressing mode.

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Feature #9614: ordering of non-Hash items which use st_ internally
https://bugs.ruby-lang.org/issues/9614#change-46723

* Author: Eric Wong
* Status: Open
* Priority: Normal
* Assignee: Yukihiro Matsumoto
* Category: core
* Target version: current: 2.2.0
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Hi matz, I would like your permission to remove the order preservation from
any or all of the following currently implemented using `st_table`:

* method tables
* global symbols (`Symbol.all_symbols`)
* constant tables
* instance variable tables
* `global_variables` method
* `Thread#keys`
* anything besides the `Hash` class

I am currently working on a patch series to reduce internal memory usage,
so far I have only converted three pieces:

1. method tables (~200K reduction)
2. symbol table (`global_symbols.`{`id_str`,`sym_id`}) (~200K)
3. `frozen_strings` (~100K)

n.b. `frozen_strings` ordering is never exposed to users, so I expect
it to be OK.

Memory reduction is just based on "`ruby -e exit`" (which loads RubyGems);
bigger programs with more methods/symbols will save more memory.

Work-in-progress patches attached (0002 describes implementation details)


---Files--------------------------------
0001-adjust-tests-to-account-for-unsorted-methods.patch (1.87 KB)
0002-ihash-initial-implementation-method-table-conversion.patch (32.8 KB)
0004-ihash-implement-rb_ihash_update-to-support-rb_fstrin.patch (7.84 KB)
0003-parse.y-switch-to-ihash-saves-200K-out-of-the-box.patch (9.51 KB)


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