Well... last night I thought I'd install EclipseFP, a package for Eclipse to support Haskell development. When you fire it up, it goes looking for packages it wants, and apparently uses cabal to install them. It did; I watched it do so for some time.
It turned out to be a waste of time; when I fired up Eclipse (which I'm rather new to) and clicked on the little lambda over to the left, a window opened up that looked half-drawn and very broken. I suspect that was issues with Eclipse--perhaps I should wipe the latest version that I grabbed and installed, and settle for the ancient version that, for some reason, is what Ubuntu has in its repositories.
OK, so I'll pass on an IDE for Haskell for now, or start up with leksah.
This morning, I had one of those sudden realizations that you get that make you laugh at yourself. Why do those memory usage graphs look like pyramids? Because the default sample interval is 0.1 seconds, and I have the run time down around 0.2 seconds, sort of like taking a sample every couple of minutes and expecting to get an accurate playback of a song.
A peek at Real World Haskell and I see the option to change the interval, so I recompile and run... and it claims that I should link with an option to turn on the RTS capabilities.
What?!
Another compile or two to make sure I did indeed specify the right options... and then some Googling, because the same thing still happened.
From the Google results, I suspect that all those cabal installs pulled in versions of libraries that don't support profiling, and that ghc is pulling them in. Following people's advice, I rm -rf ~/.ghc. No luck, still can't profile.
I have learned one thing: I am not going to let cabal touch my computer ever again. I would have sworn that I specified that packages should just be installed for me, so the rm should have done the trick. I guess I can look for Haskell libraries dated yesterday and delete every single one of them.
UPDATE: BZZT! Turns out the issue comes from trying to use that -i option to override the heap measurement interval. That's what's giving me the problem. I was wrong... and maybe I'll consider using cabal... sometime when I know Haskell much better than I do now.
UPDATE: Found it... since ghc 6.x, you have to compile with -rtsopts=all to be able to use some (OK, most) RTS options, lest the logging they permit be used to breach security. I will have to try to figure out how -i would give you the opportunity to do so over and above the output that -h*, which doesn't require -rtsopts=all, allows. (OK, maybe it would be possible to allocate a lot of RAM or not every [interval], a lot of RAM means a 1, not much means 0.)
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