Re: vs Ada - Don't forget the prime directive!

[erwin@trwacs.UUCP (Harry Erwin)]

Ada is clearly more maintainable. It is also much easier
to prove Ada code correct (because it avoids programming
constructs that result in non-commutative parallel code).
Barry Boehm has noted, however, that there are major types
of software that Ada is very poor at implementing (simulations,
parallel processing in open environments, test generation
code, anything involving pointers to functions, anything
that approaches the full generality of a Turing Machine--
although you can still implement a Turing Machine in Ada--
most AI applications). Al Perlis took much the same position,
although he was markedly less enamored with Ada.

As a performance engineer, I find Ada unattractive. If the
conversion ratio for C is 5 MLI per source statement, then
Fortran generally comes in at 6-7 MLI and Ada at 10-12.
And these source statements are no more powerful than
C statements; there's just a lot more bounds checking,
and other overhead, going on. As long as applications
press the capabilities of the host hardware, alternatives
to Ada will be needed (and not just for the applications
listed above where Ada is clumsy at best). Another factor
is that it's very easy to write inefficient code in Ada.
The machine architecture is deliberately hidden from the
coder, and the natural implementations are usually the
most expensive. These factors come together in code that
will never be as efficient as the corresponding C code
and that requires 10-20 times as many CPU cycles until
tuned during integration and test. It's hard to overcome
those handicaps.

Harry Erwin   erwin@trwacs.fp.trw.com
--The usual disclaimers. 

-- 
Harry Erwin
Internet: erwin@trwacs.fp.trw.com