Re: And speaking of fast compilers...

A while back I wrote about how the Brand X compiler took 6 minutes to
compile a 7,000-line program made up of one-page functions. And how Brand
Y took 40 minutes; over 1.5 hours with optimization turned on.


Well, according to my conversational friend, the latest Brand Y is down to
10 minutes and 25 minutes with optimization on. He's also had a chance to
test it on the latest and greatest from some other vendors and he found
(among other things):


    Brand I: 10 minutes with optimization off, fails with optimiation on.
    Brand J: Crashed the brand J hardware.
    Brand K: Based on the brand I front-end, fails during code generation.


All are validated Ada compilers.


I also heard from Vinod Grover <grover@Eng.Sun.COM> that he knows of an
Ada compiler front end that took 14 hours on a VAX 11/780 to parse and
semanticise a 3-line Ada program. The problem was that the overload
resolution phase of the front end was a two-pass backtracking algorithm
and the 3-line program had 6 levels of overloading of every symbol.




To summarize: language design is tricky and correctness doubly so.


"A program that produces wrong answers twice as fast is infinitely
slower." -- John Ousterhout


;-D on ( Slowing the way to success ) Pardo
[Back when I was writing an F77 compiler, I also found that I could pass
a lot of validation tests with amazingly broken versions of the compiler.
-John]
--

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