From: bosullvn@serd.cscs.ch (Bryan O'Sullivan)
To: dev%scrg.cs@tcd.ie, blandy
Subject: My research proposal
Date: Tue, 21 Sep 93 19:33:04 +0200
CALL FOR PARTICIPATION:
A PROJECT ON GUILT-DRIVEN COMPILATION
Bryan O'Sullivan
Lazy Research Group
Computer Science Department
J. Random University
ABSTRACT
With recent advances in the state of the art in the fields of Artificial
Intelligence and Functional Programming, opportunities have arisen for innovative
projects in the area of Guilt-Driven Compilation, or as it is also known, Lazy
(but Functional) Compilation. Building on our other successful research work in
the areas of Partial Completion and Incomplete Specification, the Lazy Research
Group has obtained funding for a new research effort exploring Guilt-Driven
Compilation.
BACKGROUND
General guilt-driven computation has a long, but largely unacknowledged, history
in Computer Science. It is largely responsible for such familiar working
practices as:
- the Deadline Frenzy, whereby a large number of undergraduate
programmers attempt to gain the maximum utility from a time-sharing
machine by all writing their assignemnts at the latest possible moment
- Last Minutes, the small sheaf of Xeroxed paper handed around
just before meetings in many organisations which gives a detailed
account of the minute-keeper's recollections (as of fifteen minutes ago)
of the previous quarter's meeting
- Late Return from the Stack, which involves a long-lost colleague
turning up and giving back an invaluable technical book which he had
borrowed several years previously
More recently, companies such as
Sun Microsystems
have explored the guilt-driven
area. Sun's foray in this direction was heralded by the release, in June of 1993,
of a patch for a well-known security hole in SunOS `ex3.7preserve' which had been
documented for *four* *years*. The accompanying press release mentioned that
``well, we hadn't quite gotten round to it up to now''. Sun CEO Scott McNealy was
reported in the press as saying ``we felt pretty bad that we sat on our asses for
four years, so we thought we'd best plug the hole'', Sun's first public admission
that they, too, were doing guilt-related work.
INTENTIONS
The Lazy Research Group intends to bring guilt-driven techniques in Computer
Science into the twenty first century by focussing in particular on the area of
guilt-driven computation.
We have begun the design of a special guilt-driven compiler. This will have
several guilt-related features:
- A special calling convention: "late evaluation".
When a procedure is entered, no parameters are pushed onto the stack;
rather, the parameters are evaluated after the first few were due to be used.
An apologetic message stub (known as a Grovel) is automatically called when a
parameter has not yet been evaluated; it explains that "evaluation took longer
than was expected, and if you'll wait just a little while, we'll push those
values you've been waiting for".
- Static analysis techniques will be used by the compiler to allow
it to determine which statements it can get away with not compiling.
At the moment, the compiler generates object code after parsing 75%
of each procedure; a second compilation produces a new executable
which contains the other 25% that should really have been in the
first executable (this technique has been pioneered by software
engineers at Microsoft).
- The compiler will automatically keep track of the load during the
previous few weeks on the machine on which it runs. If the host has been
busy for a long time, the compiler sits idle, in the hope that the user
will not notice that it isn't doing anything (and thereby saving on computation).
Once either the load goes above a certain critical value or (in a batch system)
the compiler's expert system indicates that it might miss its deadline, the
compiler is spurred into action.
- Human psychology shall be taken into account by the compiler's expert system;
it will adapt over time to the degree of lateness and dysfunction which the user
is willing to tolerate, and while the compiler will not perform steps 1 through 3
any differently, it will adopt a suitably guilty tone in the messages printed by
the Grovel stubs.
CONCLUSIONS
It is hoped that the steps outlined in 1 through 4 above will enable compilers to
accurately simulate the behaviour of software engineers, thereby increasing the
ability of observant and competent engineers to estimate the amount of time that
compilations will take.
The Lazy Research Group is loking for sort of motivated researchers. Please apply
to the address at the beginning of this announcement; the deadline is September
25th, and we definitely won't take applications after October 15th.