Some questions and comments

Doug Way dway at riskmetrics.com
Thu Mar 14 00:59:48 UTC 2002


Bill Schwab wrote:
> 
> The following are some questions and comments based on a little
> "real" work in Squeak.  This has occured on a confusing mix of
> versions and platforms.  When in doubt, assume 3.2 gamma,
> Win98 on a P2-400, though I've done some of it on NT4 and some
> on a P-200 running Win95.  The goal was to get Squeak to read
> incoming MIDI data and to display it in a variety of morphs.  It
> works (for a while anyway, see below) but, isn't anything to brag
> about yet.
> 
> First, an aside on 3D graphics: the only time that I've crashed
> Squeak was by enabling (well, trying to anyway<g>) hardware
> acceleration on the Explore 3D morph.  I'm actually glad it
> happened, because it showed me that Squeak has a crash dump;
> does the dump feature also exist on Linux?

I believe all platforms will output a crash dump, but I'm not positive.

> I have managed to get Squeak to lock up though.  Some of it is
> probably my fault, but, in 3.0 again playing with the Explore 3D
> morph, I find that by "running into the cube", I can get Squeak to
> freeze to the point that I have to kill it from the task list.
> 
> In 3.2 gamma at least, I've had some less extreme freezes, some
> of which happened while experimenting with Morphic, and I think
> they were definitely my fault.  It was generally possible to control-
> c/break into a debugger, at least on a P2-400.
> 
> During some MIDI experiments on a P-200, I've had some freezes
> that control-break won't interrupt.  Squeak's message loop appears
> to be running though, because it will shut down via the [x] on the
> title bar.  It's possible that the work load is too much to ask of the
> machine, though the IDE runs fairly well on it.  The choice of
> machine was mostly due to having a hand-me-down box that
> wasn't doing anything and happens to be MIDI-aware.  A faster
> machine will become available in the near future.
> 
> Any suggestions for figuring out why Squeak locks up in any given
> case?

There is a FAQ item on the swiki about "What to do if Squeak crashes/freezes" that you may want to look at:  http://minnow.cc.gatech.edu/squeak/2168

> Again, a lot of my trouble could be inadequate hardware for
> the MIDI application.  However, I also get a non-breakable lockup
> when loading Bob's UI into 3.2 gamma.  Any suggestions for how
> one would debug that?

The FAQ page covers this a little bit...  I think that a freeze is usually either caused by the VM hanging (which is unusual), or by a higher-level Squeak process running in an infinite loop.  The Process Browser/CPUWatcher might be able to help with this second case.

(It's useful to know that loading BobsUI in 3.2gamma is a repeatable way to get a freeze, if that's true.  I've been (casually) maintaining BobsUI lately anyway, so I should probably look at it. :-) )

> It seems fairly common for window resizing to leave Morphic in a
> confused state; restore display fixes it, but, I find myself falling
> back on that too often.  Disabling "Defer display udpate" appears to
> fix it, but, (I think) at some performance penalty???
> 
> Squeak's appearance has improved a lot recently.  The feel is still
> a little off, and my past comment that it would be hard to sell a
> Squeak app to clerical users stands; please don't underestimate
> the value of the kind of data they enter into machines, nor the
> volume of their complaints when asked to reach for a mouse.

With some work, it would be possible to create an end-user application which didn't require use of the mouse.  It would have to be pretty restrictive, though.

- Doug Way
  dway at riskmetrics.com



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