Hi,
I'm writing a program that runs Poly/ML as a child process, redirecting
standard input and output. I'm working on the Windows XP platform.
Poly/ML behaves suboptimally in this setting. I'm experiencing two problems.
One problem is fatal, the other is very annoying.
The fatal problem is that Poly/ML simply hangs at some point during the
interaction. I suppose it's some kind of deadlock. The problem is
reproducible in that it happens at the exact same point, every time I run
the program with the same input. But the entire environment in which the
program runs is so big (it's Isabelle) that I'm not going to try to describe
it. I'm just hoping that someone out there already knows about this. I don't
have a debugger now, but when I get hold of one, I will try to hunt down the
bug myself.
The annoying problem is that Poly/ML goes to sleep for 0.5 seconds after
every command. My program feeds hundreds of commands at a time to Poly/ML,
so this means a *huge* slowdown. Putting all commands on a single line is
not an option, since I need to stop feeding commands as soon as a command
prints an error message.
I think I found the cause of this sleeping problem: it's the
MsgWaitForMultipleObjects call in processes.c. In the comments in the source
code, David Matthews explains that it's just too hard to avoid this. I'm
sure that's true in the general case, when you're running many lightweight
processes, all of which are reading, writing, doing GUI stuff, etc., but in
my case, Poly/ML is really just a simple sequential single-threaded
read-eval-print loop. So, what I'm saying is, would it be possible to do
some special-casing for the one-lightweight-process case on the Windows
platform, so that you could just do blocking I/O calls? (This would probably
also solve the fatal problem described above.) And I also don't really need
the DDE functionality, so that we could do away with the message pump.
These problems would have caused me to defect to another ML implementation,
if it wasn't that Poly/ML is simply by far the best implementation out
there. Many thanks to David Matthews for this great piece of software! But
again, I hope there is some way to fix these problems.
Bart
