Re: Query about monitor (passive) task optimization

[cis.ohio-state.edu!math.ohio-state.edu!darwin.sura.net!seas.gwu.edu!mfeld man@ucbvax.Berkeley.EDU (Michael Feldman)]

In article <244khh$58@schonberg.cs.nyu.edu> dewar@cs.nyu.edu (Robert Dewar) wri
tes:

[stuff deleted]
>
>In short, I think it is probably a bad idea to put too much effort into this
>kind of optimization. Believe me, there are *plenty* of opportunities for
>more straightforward optimization that have by no means been fully exploited.
>As a result I think it would be a bad idea for vendors to put much effort
>in this area.

OK, you convinced me.
>
>One more thing. As we well know, Mike is on the lookout for cheap compilers
>for educational use, which is fair enough, but he cannot at the same time
>expect to influence the commercial vendors in terms of what optimizations
>they might offer. If indeed the constituency that he imagines exists, it
>would presumably have resources to encourage the vendors to move in this
>direction. The fact that vendors have not heard people clamoring for this
>kind of support I think legitimately indicates that this constuency does
>not in fact exist. 

Well, I certainly have two goals, and the constituencies are in fact
different ones. There are three things I'd like to see:

(1) cheap and fast commercial compilers to teach large classes:
    These are in reasonably good supply now that the vendors
    have heard our pleas and recognized the virtues of partnership.
    Who cares how fast the executables are - it's how fast they
    compile "hello world" that counts. This is the WATFIV genre.

(2) compilers that come with source code, to encourage the kind of
    experimentation with new features and optimization that, at
    least in part, made the C craze happen. Researchers and their grad
    students got their mitts on C compiler sources, which led to all
    wonderful dialects and extended languages, and caused these folks
    to have LOTS of FUN. It's no fun hacking a compiler for which no
    source files are available. Ada/Ed is a start; GNAT is what we need
    and will get. My compiler class will study GNAT as an artifact.
    Maybe we'll even hack on it; who knows? QED.

(3) Commercial Ada compilers that can compete with and beat the best of 
    those for the other languages. We are getting there for some kinds of
    algorithms. Robert has not persuaded me that Ada compilers are
    exploiting the language the very best they can. He says there
    seems to be no constituency for such things. That's because he
    seems to be looking only in the Ada community. He keeps looking
    at the choir; I keep trying to make the congregation bigger.

    Does he truly believe that real-live support for the functionality
    of ADAR wouldn't serve as a wedge to get Ada into more MIS shops?

    Does he truly believe that real-live support for a good Fortran
    interface wouldn't serve as a wedge to get Ada into more engineering
    shops?

    I would like to see some vendor come forward and say "we have done
    a real, live, market study of engineering shops and we are convinced
    that those guys just wanna stay with Fortran instead of interfacing
    their old codes to new Ada." If my engineering school is any example,
    the way they are getting out of Fortran is _re-writing_ all those old
    codes - in C. They have NO IDEA there's an alternative.

I have no problem whatsoever in thinking there is room in the world for
all three kinds of compilers. Indeed, the early ramblings on Ada
predicted that these would exist by now, because the standard would
eliminate feature wars and therefore compilers would compete on these
other factors, on a level playing field. It didn't happen. That doesn't
mean it _couldn't_ happen. I can still lobby for it, and will.
>
>The facile belief that compilers can do amazing optimizations is often
>heard. Indeed I think the original Ada design was in some cases badly
>influenced by this belief (why for instance is there no proper control
>over storage management in Ada 83 -- at least part of the answer is that
>some people thought that compilers would be able to do an amazing job
>of implementing garbage collectors and special storage management
>optimizations. Well ten years ago I would have said this was an unrealistic
>expectation. Ten years later my opinion is not changed one iota, since
>there has been essentially no advance in compiler optimization technology
>(of a relevant kind) in this time.
A lot of this kind of stuff happens in the universities, as witness the
people who have built whole careers on tweaking Lisp garbage collectors.
Real funded research on Ada issues has just about dried up - just try to
get an NSF grant to work on Ada. Besides, research on optimizations can
only happen if compiler sources are available. Let's see what happens in
a few years after we've all had our chances to hack on GNAT.

Mike Feldman