[MATZ] Re: ruby-inline and alias_method

On Thursday, September 19, 2002, at 05:54 PM, Joseph McDonald wrote:

> I have be experimenting with Ruby-Inline, and I have to say it is
> super cool.  I have run into a problem that is either a problem in my
> code (likely), or a problem with inline, or perhaps a problem with
> ruby.  The problem is that when I access an inlined method that has
> been aliased, it slows down 100 fold.  below is an example that just
> sums the elements of an array.  I also run it without using the alias
> and it runs fast (about 9 times as fast as ruby native).  I also
> include at the bottom the code that Ruby-Inline generated.

Matz or other extern/ruby gurus:

I'm reasonably sure that it's not RubyInline that is causing this 
problem. I'm still not sure what is, but it seems to be centered around 
the following line:

	    Array.send(:alias_method, :thesum, meth.intern)

If he runs the benchmark w/o this madness, then the inlined C code is 
9x faster than the ruby code.

> #!/usr/local/bin/ruby
> require 'RubyInline-1.0.5/inline'
>
> class Array
>   include Inline
>
>   def sum(*args)
>     inline args, <<-'END'
>     int len, result = 0;
>     int j;
>     VALUE *arr;
>
>     arr = RARRAY(self)->ptr;
>     len = RARRAY(self)->len;
>     for(j=0; j<len; j++) {
>         result += FIX2INT(arr[j]);
>     }
>     return INT2FIX(result);
>     END
>   end
>
>     def slowsum
>       result = 0
>       each { |x| result += x }
>       result;
>     end
> end
>
> iters = 100000
> methods = ['slowsum','sum']
>
> methods.each do |meth|
>     Array.send(:alias_method, :thesum, meth.intern)
>
>     tstart = Time.now
>     iters.times do
>       [0,1,2,3,4,5,6,7,8,9,10].thesum
>     end
>     tend = Time.now
>     total = tend - tstart
>     avg = total / iters
>
>     printf "Type = #{meth}, Iter = #{iters}, time = %.8f sec, %.8f sec 
> / iter\n", total, avg
> end
>
> # now check this without the aliased version
> tstart = Time.now
> iters.times do
>   [0,1,2,3,4,5,6,7,8,9,10].sum
> end
> tend = Time.now
> total = tend - tstart
> avg = total / iters
>
> printf "Type = normal sum (no alias), Iter = #{iters}, time = %.8f 
> sec, %.8f sec / iter\n", total, avg
>
> exit
>
> #--------------
> The code that was generated by inline is:
>
>
> #include "ruby.h"
>
>   static VALUE t_sum(int argc, VALUE *argv, VALUE self) {
>     int len, result = 0;
>     int j;
>     VALUE *arr;
>
>     arr = RARRAY(self)->ptr;
>     len = RARRAY(self)->len;
>     for(j=0; j<len; j++) {
>         result += FIX2INT(arr[j]);
>     }
>     return INT2FIX(result);
>
>   }
>
>   VALUE cMod_Array_sum;
>
>   void Init_Mod_Array_sum() {
>     cMod_Array_sum = rb_define_module("Mod_Array_sum");
>     rb_define_method(cMod_Array_sum, "_sum", t_sum, -1);
>   }
>
>
> #--------------
> The output of the program was:
>
> Type = slowsum, Iter = 100000, time = 1.36584400 sec, 0.00001366 sec / 
> iter
> Type = sum, Iter = 100000, time = 16.48371500 sec, 0.00016484 sec / 
> iter
> Type = normal sum (no alias), Iter = 100000, time = 0.14434800 sec, 
> 0.00000144 sec / iter
>
> thanks,
> -joe
>