on Tuesday, September 29, 1998, 6:30pm
at the Rogers Communication Centre, Ryerson University, 
(corner of Gould & Church streets)
Eaton Lecture Theatre - room V204 (2nd floor, west end of building)

*Note - change of date and room from previous announcements 

The Toronto APL Special Interest Group presents:

   "All Roads Lead to Rome - Some Highlights of APL 98"

Our September meeting features talks and highlights from the recent
APL98 conference in Rome.

Speakers:

Robert Bernecky - APL98 Program Co-Chair, Snake Island Research
Dr. Sven-Bodo Scholz - Dept. of Computer Science, University of Kiel 

Talks:

1. Highlights of APL 98 
     Robert Bernecky

The next two talks look at techniques for compiling and 
optimizing array operations.

2. SAC as a Meta-Level Language for Compiling APL
     Sven-Bodo Scholz

3. Reducing Computational Complexity with Array Predicates
     Robert Bernecky


Abstracts:

1. Highlights of APL 98 - Robert Bernecky

Bob will give us a whirlwind tour of some of his favorite talks
from APL 98, and perhaps comment on Roman summer weather and 
night-life.


2. SAC as a Meta-Level Language for Compiling APL
     Sven-Bodo Scholz

"In this talk Dr. Scholz gives us an introduction to SAC (Single
assignement C). On top of a purely functional subset of C, SAC 
provides an array concept for specifying array operations 
irrespective of the rank of argument arrays. A few examples show 
that the high-level operations that are typically available
in array processing languages such as APL or Fortran90 can be easily
specified in SAC by using a special language construct, the so-called 
with-loop. The most important optimization techniques used in the 
current SAC compiler are outlined. 

"Finally, a performance comparison between a SAC, a Fortran77, and 
a SISAL implementation for a 3D multigrid relaxation is presented. 
It shows that the SAC implementation, despite its higher level of 
abstraction, is competitive with the other two both in terms of 
program runtimes and memory consumption."


3. Reducing Computational Complexity with Array Predicates
     Robert Bernecky

"This talk describes how "array predicates" are used to reduce the 
computational complexity of four APL primitive functions when one 
of their arguments is a permutation vector. The search primitives, 
"indexof" and "set membership", and the sorting primitives, "upgrade" 
and "downgrade", execute in linear time on such arguments. Our 
contribution, a method for static determination of array properties, 
lets us generate code that is optimized for special cases of 
primitives. Our approach eliminates run-time checks which 
would otherwise slow down the execution of all cases of the effected 
primitives. We use the same analysis technique to reduce the type
complexity of certain array primitives."

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Free Admission