NUM2DBL slow BigDecimal convertion

benchmark.rb

# Passos para rodar:
# 1. ruby extconf.rb
# 2. make
# 3. ruby benchmark.rb

require 'benchmark'
require 'bigdecimal'
require './test'

n = 50
decimals = (1..10_000).map { |value| BigDecimal.new [value, (rand * 10000000000).to_i].join(".") }
floats   = (1..10_000).map(&:to_f)

Benchmark.bm do |b|
  b.report do
    n.times { decimals.each(&:convert) }
  end

  b.report do
    n.times { floats.each(&:convert) }
  end
end

# Resultados Mac 2.4ghz
#      user     system      total        real
#  2.790000   0.010000   2.800000 (  2.824529)
#  0.030000   0.000000   0.030000 (  0.038669)

extconf.rb

require "mkmf"
create_makefile("test")

test.c

#include <ruby.h>

static VALUE convert(VALUE self) {
  NUM2DBL(self);
  return self;
}

void Init_test() {
  rb_define_method(rb_cNumeric, "convert", convert, 0);
}