Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!uflorida!gatech!hubcap!utter
From: utter@tcgould.tn.cornell.edu (Paula Sue Utter)
Newsgroups: comp.parallel
Subject: Opinions on Debugging Parallel Programs
Message-ID: <4810@hubcap.UUCP>
Date: 16 Mar 89 15:40:43 GMT
Sender: fpst@hubcap.UUCP
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Approved: parallel@hubcap.clemson.edu


One of the hot topics of research today is how to debug parallel
programs, both on shared memory multiprocessors and on distributed
memory machines.  Often it seems these debugger systems are developed
more for ease of implementation rather than for providing maximum
utility and ease of use.  What I'd like to do is get some opinions on
just what sort of features a good debugger system for parallel programs
should provide.
 
 
The kind of information I'm looking for includes:
 
Is it harder to write and debug new parallel programs, or to parallelize
"dusty deck" serial programs?
 
What are the most common bugs you have encountered during parallel
programming development and production runs (e.g., unintentional change
to a shared variable, etc.).
 
What methods have you used in your attempts to debug parallel programs?
Of these, which were most successful?
 
What types of tools do you think would be helpful in developing and
debugging parallel programs?  (For example, would it be helpful to
observe sequential execution within each process executing in parallel?)
 
What important events or features should be displayed when representing
parallel program execution?  (Some suggestions might be synchronization
mechanisms, interprocess communication patterns, updates to shared
variables, etc.)
 
When working with parallel programs, people often employ graphical
representations that reflect their mental model of the problem at hand.
Could you give me a verbal description of the way you envision such
things as:
          Parallel execution
          Interprocess communication
          Synchronization schemes
 
Since many people now include performance evaluation and improvement as
part of the debugging process when dealing with parallel programs, what
type of information would be useful in this area?
 
If you have used any existing parallel debugger systems, either
commercial or experimental, could you name them and give me some
feedback on their usefulness?
 
 
I'd really appreciate any opinions you have on this matter.  Please send
responses to utter@tcgould.tn.cornell.edu.  If I get enough responses,
I'll compile the results and post them here.  Thanks in advance.
 
Sue Utter
Technology Integration Group
Cornell National Supercomputer Facility