Issue #14794 has been reported by ahorek (Pavel Rosick).

----------------------------------------
Feature #14794: Primitive arrays (Ruby 3x3)
https://bugs.ruby-lang.org/issues/14794

* Author: ahorek (Pavel Rosick)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
dynamic arrays in ruby can contain various object types:
```ruby
[1, 1.0, 'text', Object.new]
```

however if I create a primitive array, let say only with integers (very common case). It should be more efficient.
```ruby
[1, 2, 3]
```

let me show you an example. I have an array and I want to find a maximum. I can use a native method(:max) or a naive pure ruby implementation.
I expect that the native function will always be much faster because it”Ēs written in C right?

```ruby
require 'benchmark/ips'
arr_int = Array.new(50000) { rand 10000 }

def max_ruby(arr)
  max = arr[0]
  size = arr.size
  i = 1
  while i < size
    if arr[i] > max
      max = arr[i]
    end
    i += 1
  end
  max
end

benchmark.ips do |x|
  x.report('native') { arr_int.max }
  x.report('pure')   { max_ruby(arr_int) }
  x.compare!
end
```

here's a comparsion chart of different ruby & python's runtimes (lower is better)
![](https://raw.githubusercontent.com/ahorek/ruby/7976ede8c27291d50abadcd99835c0f3dae98a44/obrazek.png)


as expected on ruby 2.6, the native function was faster.

Let”Ēs compare it if we use a JIT
native  no difference
pure ruby  sometimes even faster than native

It's because JIT can't do anything with native functions (inlining, type checks etc.). Native fuctions should be as fast as possible.

MRI implementation of rb_ary_max
https://github.com/ruby/ruby/blob/trunk/array.c#L4335
```c
for (i = 0; i < RARRAY_LEN(ary); i++) {
	   v = RARRAY_AREF(ary, i);
	   if (result == Qundef || OPTIMIZED_CMP(v, result, cmp_opt) > 0) {
	       result = v;
	   }
}
```

this is great for mixed arrays, but for primitive arrays it's quite ineffective. C compiler can't optimize it.
1/ unbox it if possible, don't dereference objects and load it in chunks
2/ if <=> is not redefined, we can use a simplier algorithm
3/ it”Ēs a trivial example that can be written in SIMD #14328, there's even a special instruction for it https://software.intel.com/en-us/node/524201
C compiler can do it for us, but this metod it too complex for auto-vectorization and the data type isn't known during compile time.

Array max is just an example, but the same strategy could be applied for many other methods.

I found a great article about it, check it out.
## http://tratt.net/laurie/research/pubs/html/bolz_diekmann_tratt__storage_strategies_for_collections_in_dynamically_typed_languages/

I think this feature could speed-up real ruby applications significantly and it shouldn”Ēt be very hard to implement. We also don't have to change ruby syntax, define types etc. No compatibility issues.



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