Binary XML

Jimmy Zhang hits the nail on the head when he notes that parsing ASCII text is not the primary problem in XML performance, object allocation is. I was surprised by the same finding when I started working on Objective-XML around a decade ago.

Sean McGrath claims that Binary XML solves the wrong problem.

Yes and no: it doesn't help much with existing structures and parsing methods, but with the right methods, it can be extremely helpful!

Also: "...how weird is it that we have not moved on from the DOM and SAX in terms of "standard" APIs for XML processing?"

Code is not an asset

Michael Feathers wonders how to go beyond technical debt. I have been wondering about this for some time, and I think the answer is to account for code as a liability, not an asset.

The functionality that the code has, the value it delivers is an asset, but the code itself is a liability. This easily explains how refactoring and removing code add value, as long as functionality is preserved.

Higher Order Messaging backgrounded

Piers Cawley talks about RSpec's use of HOM:

It is, however, encouraging to see initiatives like Rspec which, through judicious use of higher order messages enables a much more fluent environment for writing tests:

I think that's the first time I've seen HOM used to explain something else, rather than being the object of attention itself. So HOM is starting to be seen as simply a part of the computing landscape, at least by some. Cool. HOM was never conceived of as an interesting thing by itself but rather as a (meta-)building block for building more expressive computational forms. RSpec looks exactly like one of those cool things HOM enables that I would never have come up with myself. I look forward to seeing more.

Not just high performance Objective-C

Addendum to my article on implementing a high performance Postscript interpreter in Objective-C: not just is performance better, so is accuracy. Despite the fact that we are optimizing the heck out of the Objective-C objects we are using, they still give us encapsulation and polymorphism, allowing us to choose arbitrary representations. For example, most Postscript interpreters use a fixed-size value object (polymorphic in a C-union type of way) that constraints floating point precision to 32 bits. With Objective-C, we have no such constraints, so EGOS floats are actually 64 bit doubles, so running the modified benchmark below in PostView doesn't just yield the result 75% faster than Preview, it also produces it with 7 orders of magnitude less error. Not that that is necessarily important in Postscript, but it is a pleasant side effect and shows the power of combining performance with abstraction.

%!
  usertime
  1000 0 1 10000000 { pop 0.0001 sub  } bind for
  exch usertime exch sub dup ==
  20 20 moveto /Times-Roman 24 selectfont
  100 string cvs show ( ms) show ( error:  ) show 
  1000.0 div 100.0 mul abs  100 string cvs show ( %) show
  showpage

Better HOM selects

Wincent Colaiuta discusses a variant of the select HOM that takes an arbitrary number of argument messages. I like it!

My initial implementation actually had arbitrary nesting, but as he discusses with collect, that requires a trigger message to start, as there is no way of knowing at runtime when the expression terminates. It never occurred to me that this limitation did not apply to select, which can look at the return type of the messages sent and stop when it reaches a BOOL (char).

Nice.

p.s.: the arbitrary nesting is still in the implementation, with each of the collection processing HOMs actually running an enumerator and those enumerators stackable, and this is two of the reasons the implementation is so gnarly: (1) there is extra generality that is not needed and (2) making that more general mechanism run fast was really, really tricky.

p.p.s: He actually discussed it almost a year ago, but I just saw it now.

Reading Helps

James Robertson slams the proposal by the EU free market institute to unbundle the OS from PCs sold in the EU.

I've seen a lot of stupid ideas float past, but this one from the EU's Globalization Institute makes it into the top 5 - only the existence of the RIAA and the MPAA prevent a complete victory for these morons:

[..] The think tank recommended to the EU that all computers be sold without an operating system and sees no reason "why computer operating systems could not follow the same model as computer hard drives and processors."

Yes, installing an OS from scratch is exactly what most buyers long to do - it's such a productive use of their time.

Hmmm, what could they mean with the "same model as computer hard drives and processors"?

Well, of course! We all buy processors and hard drives separately, mount the CPU on our separately purchased motherboard, hook up hard-drive and power-supply and stick it all in a chassis. That *must* be what they meant with that phrase.

Or maybe, they meant that you can configure your computer with different CPUs and hard drives, and have the vendor ship you a machine configured to your specifications, whereas you cannot actually get a computer and not pay the Microsoft tax? Nah, that's just *crazy*:

IT professionals are being forced to adopt Microsoft's operating systems — even if they tell their PC supplier they want a system free of Microsoft software, ZDNet UK's research has revealed.

Oh.

'Thousands' or transistor²

The Alan Kay quote in my previous post made me think of Montecito, the new Itanic version with 1.72 billion transistors. Compare that to the ARM6, which had a measly 35K transistors, including its 4K cache.

Dividing the two numbers gets you almost 50K. That's how many ARM6 CPUs you could get on the same chip with the same transistor budget as the Montecito. A processor for every object. Or viewed another way, more ARM6-equivalents than the ARM6 has transistors. Which begs the question: is the Montecito proportionally as much an improvement in computational capacity as an ARM6 is over a single transistor?