From: Eric Wong <normalperson@...>
Date: 2017-04-15T07:49:20+00:00
Subject: [ruby-dev:50080] Re: [Ruby trunk Bug#13341] Improve performance of implicit type conversion

+cc ruby-core since this post was English

watson1978@gmail.com wrote:
> Issue #13341 has been reported by watson1978 (Shizuo Fujita).
> 
> ----------------------------------------
> Bug #13341: Improve performance of implicit type conversion
> https://bugs.ruby-lang.org/issues/13341

Interesting...

> ----------------------------------------
> At least, Array#flatten will be faster around 20%.
> Seems that strncmp() & strcmp() in convert_type() are slightly heavy to look up the method's id for type conversion.
> (https://github.com/ruby/ruby/blob/4f2db15b42d7b8eb5b304a92ba2296632dba3edf/object.c#L2634-L2643)
> 
> This patch will use known method's id directly.
> 
> ### Before
> ~~~
>                                              user     system      total        real
> Array#flatten (rb_check_convert_type2)   1.000000   0.000000   1.000000 (  1.001917)
> Array#+ (rb_convert_type2)               1.010000   0.000000   1.010000 (  1.006383)
> ~~~
> 
> ### After
> ~~~
>                                              user     system      total        real
> Array#flatten (rb_check_convert_type2)   0.830000   0.000000   0.830000 (  0.833411)
> Array#+ (rb_convert_type2)               0.950000   0.000000   0.950000 (  0.953832)
> ~~~

<snip>

> The patch is in https://github.com/ruby/ruby/pull/1537

I use "fetch = +refs/pull/*:refs/remotes/pull/*" in my
.git/config to check pull/1537/head in ruby.git without using
only standard git (no proprietary JavaScript) and
looked at following commits:

e189f53a26 use rb_convert_type2() for #to_r
5e836acef6 Improve performance of implicit type conversion

So yes, I hate strcmp/strncmp, too.

If we change the API, I prefer we drastically shorten
the function args for common case types.

I'm not sure if including new APIs in ruby/intern.h is a good
idea right away, since that is technically public API.

Perhaps keep it in internal.h for now.

So, maybe:

	    rb_convert_type2(a1, idTo_a);
	    rb_convert_type2(a1, idTo_ary);

will lookup a small static table based on ID which fills in
T_*** (and tname string for error reporting).

Corner cases like StringIO may use old API, maybe that is
less critical.