From: Joseph McDonald <joe@...>
Date: 2002-09-20T09:54:56+09:00
Subject: ruby-inline and alias_method


Hi,

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.

#!/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