Originally, the VPRI claims to be able to do a system that's 10,000
smaller than our current bloatware. That's going from roughly 200
million lines to 20,000. (Or, as Alan Kay puts it, from a whole library
to a single book.) That's 4 orders of magnitude.
From the report, I made a rough break down of the causes for code
reduction. It seems that
- 1 order of magnitude is gained by removing feature creep. I agree
feature creep can be important. But I also believe most feature
belong to a long tail, where each is needed by a minority of users.
It does matter, but if the rest of the system is small enough,
adding the few features you need isn't so difficult any more.
- 1 order of magnitude is gained by mere good engineering principles.
In Frank for instance, there is _one_ drawing system, that is used
for everywhere. Systematic code reuse can go a long way.
Another example is the code I work with. I routinely find
portions whose volume I can divide by 2 merely by rewriting a couple
of functions. I fully expect to be able to do much better if I
could refactor the whole program. Not because I'm a rock star (I'm
definitely not). Very far from that. Just because the code I
maintain is sufficiently abysmal.
- 2 orders of magnitude are gained through the use of Problem Oriented
Languages (instead of C or C++). As examples, I can readily recall:
+ Gezira vs Cairo (÷95)
+ Ometa vs Lex+Yacc (÷75)
+ TCP-IP (÷93)
So I think this is not exaggerated.
Looked at it this way, it doesn't seems so impossible any more. I
don't expect you to suddenly agree the "4 orders of magnitude" claim
(It still defies my intuition), but you probably disagree specifically
with one of my three points above. Possible objections I can think of
are:
- Features matter more than I think they do.
- One may not expect the user to write his own features, even though
it would be relatively simple.
- Current systems may be not as badly written as I think they are.
- Code reuse could be harder than I think.
- The two orders of magnitude that seem to come from problem oriented
languages may not come from _only_ those. It could come from the
removal of features, as well as better engineering principles,
meaning I'm counting some causes twice.
Loup.
BGB wrote:
On 2/27/2012 10:08 PM, Julian Leviston wrote:
Structural optimisation is not compression. Lurk more.
probably will drop this, as arguing about all this is likely pointless
and counter-productive.
but, is there any particular reason for why similar rules and
restrictions wouldn't apply?
(I personally suspect that similar applies to nearly all forms of
communication, including written and spoken natural language, and a
claim that some X can be expressed in Y units does seem a fair amount
like a compression-style claim).
but, anyways, here is a link to another article:
http://en.wikipedia.org/wiki/Shannon%27s_source_coding_theorem
Julian
On 28/02/2012, at 3:38 PM, BGB wrote:
granted, I remain a little skeptical.
I think there is a bit of a difference though between, say, a log
table, and a typical piece of software.
a log table is, essentially, almost pure redundancy, hence why it can
be regenerated on demand.
a typical application is, instead, a big pile of logic code for a
wide range of behaviors and for dealing with a wide range of special
cases.
"executable math" could very well be functionally equivalent to a
"highly compressed" program, but note in this case that one needs to
count both the size of the "compressed" program, and also the size of
the program needed to "decompress" it (so, the size of the system
would also need to account for the compiler and runtime).
although there is a fair amount of redundancy in typical program code
(logic that is often repeated, duplicated effort between programs,
...), eliminating this redundancy would still have a bounded
reduction in total size.
increasing abstraction is likely to, again, be ultimately bounded
(and, often, abstraction differs primarily in form, rather than in
essence, from that of moving more of the system functionality into
library code).
much like with data compression, the concept commonly known as the
"Shannon limit" may well still apply (itself setting an upper limit
to how much is expressible within a given volume of code).
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