Pensieri di un lunatico minore

Ruby versus Smalltalk, a useless comparison

Ruby is heavily inspired by Smalltalk. I’d say it’s about 50% Smalltalk-insired, and 50% Perl-inspired. Obviously, one can detect what my preference is in those inspirations. Since I’m talking about performance, a little anyway, I’d like to compare a bit.

Here’s the situation. I have a file, with 22,291 “micro-content” XML bits. Each root “document” has 29 elements that are interesting. All I am interested in is the textual content of these elements. The code for Smalltalk is:

firewallStream := 'ns_fw.xml' asFilename readStream.
[firewallStream atEnd] whileFalse: 
    [xml := parser parse: (firewallStream upTo: Character cr) readStream.
    root := xml root.
    newEvent := NormalizedEvent new.
    newEvent xmlConversionMap keysAndValuesDo: 
        [:elementName :selector | 
        newEvent perform: selector
            with: (root elementNamed: elementName) characterData]].

The code for Ruby:

File.open('ns_fw.xml', 'r') do |file|
  file.each_line {|line|
    tmp = NormalizedEvent.new.from_xml(line)
  }
end

This uses this code, inside the class:

def from_xml(xml_string)
    xml = REXML::Document.new(xml_string)
    root = xml.root
    XML_EVENT_MAP.each {|xml_form, event_form|
        tmp = root.elements[xml_form].text
        self.send(event_form, tmp)
    }   
end

The big difference is that the Ruby code I used a method inside the object to populate the instance attributes, as I honestly had no idea how to do this dynamically in a clean way. I’m new to Ruby, so this is likely not the optimal way to do it. Honestly, they both do the same basic thing, just moved the code inside the class for Ruby, which should make it faster.

Time? 0.89ms/iteration for Smalltalk, 24.7ms for Ruby. Both are using “native” XML parsers, not wrappers for some other library. For Ruby, this is REXML. Definitely a difference in maturity for the VMs in both places. This is not to say Ruby is bad, it’s probably roughly on par with Python and Perl, but it’s not quite in the league of Smalltalk (or Lisp, likely), which have extremely mature VMs with on-the-fly compilation and optimization.

Remember, Java’s JVM (HotSpot) came from Strongtalk, an explicitly-typed version of Smalltalk.

And for those who have read my red herring of performance comments, and wondered if I’m a hypocrite, the answer is yes, but not in this case. I happen to know from profiling that this component is used tens of millions of times, representing a large percentage of the time consumed, and worse, in a real-time fashion, so performance matters in this case.

Sadly, this is not something I can fix by saying “go away, damn XML atrocity,” because it’s something dictated by entities outside my influence.