Issue #16897 has been updated by Eregon (Benoit Daloze).
FWIW this works :
```ruby
H =3D Hash.new { |h,k| h[k] =3D k ** 2 }
def sq(...); H.[](...); end
sq(44) # =3D> 1936
sq(42) # =3D> 1764
H # =3D> {44=3D>1936, 42=3D>1764}
```
Can such an approach be used for your case?
----------------------------------------
Feature #16897: Can a Ruby 3.0 compatible general purpose memoizer be writt=
en in such a way that it matches Ruby 2 performance?
https://bugs.ruby-lang.org/issues/16897#change-85967
* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
----------------------------------------
```ruby
require 'benchmark/ips'
module Memoizer
def memoize_26(method_name)
cache =3D {}
uncached =3D "#{method_name}_without_cache"
alias_method uncached, method_name
define_method(method_name) do |*arguments|
found =3D true
data =3D cache.fetch(arguments) { found =3D false }
unless found
cache[arguments] =3D data =3D public_send(uncached, *arguments)
end
data
end
end
def memoize_27(method_name)
cache =3D {}
uncached =3D "#{method_name}_without_cache"
alias_method uncached, method_name
define_method(method_name) do |*args, **kwargs|
found =3D true
all_args =3D [args, kwargs]
data =3D cache.fetch(all_args) { found =3D false }
unless found
cache[all_args] =3D data =3D public_send(uncached, *args, **kwargs)
end
data
end
end
def memoize_27_v2(method_name)
uncached =3D "#{method_name}_without_cache"
alias_method uncached, method_name
cache =3D "MEMOIZE_#{method_name}"
params =3D instance_method(method_name).parameters
has_kwargs =3D params.any? {|t, name| "#{t}".start_with? "key"}
has_args =3D params.any? {|t, name| !"#{t}".start_with? "key"}
args =3D []
args << "args" if has_args
args << "kwargs" if has_kwargs
args_text =3D args.map do |n|
n =3D=3D "args" ? "*args" : "**kwargs"
end.join(",")
class_eval <<~RUBY
#{cache} =3D {}
def #{method_name}(#{args_text})
found =3D true
all_args =3D #{args.length =3D=3D=3D 2 ? "[args, kwargs]" : args[0]}
data =3D #{cache}.fetch(all_args) { found =3D false }
unless found
#{cache}[all_args] =3D data =3D public_send(:#{uncached} #{args.e=
mpty? ? "" : ", #{args_text}"})
end
data
end
RUBY
end
end
module Methods
def args_only(a, b)
sleep 0.1
"#{a} #{b}"
end
def kwargs_only(a:, b: nil)
sleep 0.1
"#{a} #{b}"
end
def args_and_kwargs(a, b:)
sleep 0.1
"#{a} #{b}"
end
end
class OldMethod
extend Memoizer
include Methods
memoize_26 :args_and_kwargs
memoize_26 :args_only
memoize_26 :kwargs_only
end
class NewMethod
extend Memoizer
include Methods
memoize_27 :args_and_kwargs
memoize_27 :args_only
memoize_27 :kwargs_only
end
class OptimizedMethod
extend Memoizer
include Methods
memoize_27_v2 :args_and_kwargs
memoize_27_v2 :args_only
memoize_27_v2 :kwargs_only
end
OptimizedMethod.new.args_only(1,2)
methods =3D [
OldMethod.new,
NewMethod.new,
OptimizedMethod.new
]
Benchmark.ips do |x|
x.warmup =3D 1
x.time =3D 2
methods.each do |m|
x.report("#{m.class} args only") do |times|
while times > 0
m.args_only(10, b: 10)
times -=3D 1
end
end
x.report("#{m.class} kwargs only") do |times|
while times > 0
m.kwargs_only(a: 10, b: 10)
times -=3D 1
end
end
x.report("#{m.class} args and kwargs") do |times|
while times > 0
m.args_and_kwargs(10, b: 10)
times -=3D 1
end
end
end
x.compare!
end
# # Ruby 2.6.5
# #
# OptimizedMethod args only: 974266.9 i/s
# OldMethod args only: 949344.9 i/s - 1.03x slower
# OldMethod args and kwargs: 945951.5 i/s - 1.03x slower
# OptimizedMethod kwargs only: 939160.2 i/s - 1.04x slower
# OldMethod kwargs only: 868229.3 i/s - 1.12x slower
# OptimizedMethod args and kwargs: 751797.0 i/s - 1.30x slower
# NewMethod args only: 730594.4 i/s - 1.33x slower
# NewMethod args and kwargs: 727300.5 i/s - 1.34x slower
# NewMethod kwargs only: 665003.8 i/s - 1.47x slower
#
# #
# # Ruby 2.7.1
#
# OptimizedMethod kwargs only: 1021707.6 i/s
# OptimizedMethod args only: 955694.6 i/s - 1.07x (=B1 0.00) slower
# OldMethod args and kwargs: 940911.3 i/s - 1.09x (=B1 0.00) slower
# OldMethod args only: 930446.1 i/s - 1.10x (=B1 0.00) slower
# OldMethod kwargs only: 858238.5 i/s - 1.19x (=B1 0.00) slower
# OptimizedMethod args and kwargs: 773773.5 i/s - 1.32x (=B1 0.00) slower
# NewMethod args and kwargs: 772653.3 i/s - 1.32x (=B1 0.00) slower
# NewMethod args only: 771253.2 i/s - 1.32x (=B1 0.00) slower
# NewMethod kwargs only: 700604.1 i/s - 1.46x (=B1 0.00) slower
```
The bottom line is that a generic delegator often needs to make use of all =
the arguments provided to a method.
```ruby
def count(*args, **kwargs)
counter[[args, kwargs]] +=3D 1
orig_count(*args, **kwargs)
end
```
The old pattern meant we could get away with one less array allocation per:
```ruby
def count(*args)
counter[args] +=3D 1
orig_count(*args, **kwargs)
end
```
I would like to propose some changes to Ruby 3 to allow to recover this per=
formance. =
Perhaps:
```ruby
def count(...)
args =3D ...
counter[args] +=3D 1
orig_count(...)
end
```
Or:
```ruby
def count(***args)
counter[args] +=3D 1
orig_count(***args)
end
```
Thoughts? =
-- =
https://bugs.ruby-lang.org/
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