2009-07-05

The best lack all conviction, while the worst are full of passionate intensity

Man, I'm growing truly distressed by the farrago -- the melange -- the, dare I say it, I do dare! gallimaufry -- the widening gyre for sure -- into which my Linux desktop has descended over 2009's first half. The pulseaudio debacle just got worse and worse, until I finally purged all traces of it a month ago; ALSA is once more directly brokering applications and my Intel HDA and/or Fubar II USB DAC (through M-AUDIO Studiophile AV 40's) with panache and elan, with the added benefit of IceWeasel+crappy flash no longer wrecking mplayer/mpd (my original reason for throwing PulseAudio into the mix). Now xfce 4.6 emerges, xfce of course being the "lightweight response to gnome/kde" and having served me well for several years now, and what the holy hell is this:
/usr/lib/xfce4-notifyd/xfce4-notifyd
xfce4-settings-helper --display :0.0 --sm-client-id 29afe6488-185e-4359-a60d-9529c7c05642
/usr/lib/xfconfd
xfsettingsd
xfwm4 --sm-client-id 203c6cff5-bbfe-4d1d-9d1c-3228cb4e24f0 --display :0.0
/usr/bin/xfce4-session
/usr/bin/xfdesktop --sm-client-id 11d81ba305000121438424100000173320018 --display :0.0
xfce4-panel --sm-client-id 28775a015-d9f0-4ded-bdee-1cac6a52936e
/usr/lib/xfce4-screenshooter/xfce4/panel-plugins/xfce4-screenshooter-plugin socket_id 14680099 name screenshooter id 11925955890 display_name Screenshot size 42 screen_position 9
/usr/lib/xfce4-netload-plugin/xfce4/panel-plugins/xfce4-netload-plugin socket_id 14680100 name netload id 11812997820 display_name Network Monitor size 42 screen_position 9
/usr/lib/xfce4-netload-plugin/xfce4/panel-plugins/xfce4-netload-plugin socket_id 14680101 name netload id 12062092340 display_name Network Monitor size 42 screen_position 9
/usr/lib/xfce4-xfapplet-plugin/xfce4/panel-plugins/xfce4-xfapplet-plugin socket_id 14680102 name xfapplet id 12232614662 display_name XfApplet size 42 screen_position 9
/usr/lib/xfce4-timer-plugin/xfce4/panel-plugins/xfce4-timer socket_id 14680108 name xfce4-timer id 12297861572 display_name Xfce4 Timer size 42 screen_position 9
Does this seem fundamentally ridiculous to anyone else (in particular, those are some abominable command lines)? So, xfce obviously does the whole process-per-panel-element thing because:
  1. Sloppy coders imply undefined behavior, and you'd have the whole panel needing to restart every time xfce4-netvisor dropped core due to a device rename
  2. As a corollary, sloppy coders imply bloated loading times (often due to poor use of libraries -- be sure to read Ulrich Drepper's whitepaper, as linked to from that entry), so restarts of the panel in toto couldn't be transparent
  3. Sloppy coders imply blocking and excessive use of global resources (blocking, after all, being misuse of thread-level time resources), and sucking all of this crap into one process would lead to Cartesian products of interactions -- only through reducing interactions to structured implications can debugging hell be avoided. I doubt Dijkstra finds much readership among GUI coders
But that's fine, because hey, if these were system programmers they'd be doing systems programming rather than mucking about in xorg wastelands.

Now, I must break here to commend the efforts of Keith Packard, Carl Worth, and everyone else out there hacking on DRM, GEM, and i915 -- I love y'all, and everything there is awesome (well, KMS broke my workstation with Debian's last xserver-xorg-intel release, but ya gotta spend money to make money). But these are not the people hacking on xfce4, to which we return...

How many processes do you need to implement a config file? I'd have thought 0, but xfce is running no less than 3: xfconfd, xfsettingsd, xfce4-settings-helper. What, between xfconfd and xfsettingsd, do they need help with? Why is the configuration system so bloated and obtuse that this is all necessary? I run hour-long compiles without the benefit of gcc-settingsd, gmakeconfd, ld.so-environment-manager and two baseball players to be named later. If things can't be processed on each process startup, throw a processed data structure into freakin' POSIX.1-2001 shared memory and throw a process-shared semaphore atop that sunnabitch. There's a reason why these capabilities exist, for chrissakes!

This is made all the worse by xfce applications being, aside from a semi-substantial core (xfce4-terminal, I salute you!), underfeatured and generally shitty, and thus GNOME applications being thrown into the mix anyway. I today realized my xfce4 laptop needed gnome-system-monitor -- nothing fancy, a few panels showing CPU/mem/swap etc, nothing WindowMaker hasn't had a dockette (or whatever the hell WindowMaker calls the ass-esque abominations it renders for people working on SPARCStations in university printing labs around the nation) for since 1986 or so. This required installation of ONE-HUNDRED AND THIRTY MEGABYTES (it sounds like a fucking Soviet nuclear yield) of GNOME asstrash including evolution-data-server (more useless processes, hurrah!) and something called "policykit-gnome" which promises to integrate my capability-delegating experience with ponies and sugar cookies. The upshot is the addition of:
/usr/lib/gnome-applets/multiload-applet-2 --oaf-activate-iid=OAFIID:GNOME_MultiLoadApplet_Factory --oaf-ior-fd=18
/usr/lib/gamin/gam_server
/usr/lib/gvfs/gvfsd
/usr/lib/libgconf2-4/gconfd-2
/usr/lib/bonobo-activation/bonobo-activation-server --ac-activate --ior-output-fd=18
That would be the addition of 5 processes for 1 additional applet, which furthermore is shown to be polling-intensive by the magic of powertop(8). Oh wait -- xfce added a lovely xfapplet process to handle the no doubt complex and intensive management of this applet, so 6.

If someone brought this to me at work, I'd have them officially fired and, on my own time, flayed.

Regarding this blog, the lack of threaded comments has really got me down, as bad tools will tend to do. I might migrate the effort to LiveJournal. On the plus side, I've been editing my wiki a lot; go check out http://dank.qemfd.net for some good old-fashioned computational fun.

2009-05-04

and I'll teach you, teach you, teach you, I'll teach you the numeric slide

Sliding numeric scales should pretty much never show up outside of color pickers, volume controllers, and other things so (a) closely linked to sensory input that people get emotional and (b) providing such instantaneous feedback that binary search is possible without taking notes. Not that I write code with UI's, but this applies just as well to bullshit command line arguments like gzip's compression-vs-time level, oggenc's quality-vs-space level, mpd/pulseaudio's sampling-vs-cpu level, and gcc's optimization-vs-everything turkey shoot of -O and -f options.

If gcc had broken tradition with past compilers (Cray and SGI compilers I've known supported a gamut of -O levels beyond -O3, and surely a surfeit of others as well), and called...actually, I guess I give compilers a pass here: you don't want to throw crap like --optimize-space into a compilation line, due to iterated consumption of terminal real estate during a build. Exactly as -Os (optimize for space on gcc) indicates, you'd end up with a series of difficult-to-remember flags, ala the -Q options on Intel's icc c++ compiler (then again, how often need you remember optimization flags outside makefile creation?) I think, however, that the generated-code-speed vs. compilation-time tradeoff will slide (has already slid?) in importance, and the competing axes of compilation decisions -- power-vs-performance, codespace-vs-codecycles, parallelism-vs-fastserial, all that -- will render a single vector meaningless. At this point, you'll need even more rely on descriptions of processing environments and architectures, and almost certainly parameterize on them at runtime.

Let's remove the optimization level decision, aside from as a debugging aid, from the realm of the code's creators and to the code's executers. It'd be a win all around.

Oh, to complete an earlier thought: if -O0..-O9 had never been introduced, I wouldn't have to listen to someone say "I think it ran faster with -O4 than -O2", and tell them "uhhh, gcc on x86 has never meaningfully supported an optimization level higher than -O3." This happens every few years, and it typically results in a bad scene. I'd like to bring out rms ala Annie Hall: "I heard, I heard what you were saying. You, you know nothing of my work. How you ever were hired to write any kind of code is totally amazing." Tyro assholes!

2009-05-03

mother of god

Holy crap, blogger sucks like three bitches in a bitch boat! No threaded comments? What is this, the time of Charlemange? I tried to respond to Leon twice (the missing context, btw, was LU decomposition for solving matrix problems), and both posts were dispatched into the ether. So, we might soon take flight to a more reasonable format.

2009-05-02

totalwonkerr gone??!

[oh yeah, i've just decided that in addition to computers, this blog will talk about nuclear weapons, because they're just as interesting, and I hope to do national lab work at some point]

So I'm in g-reader and notice new TotalWonKerr posts -- hurrah! time to catch up on the world of strategic weapons after finals! oh, hurrah, a phatty new OTA report on SLV's -- and follow through to http://totalwonkerr.com...

This weblog has been taken offline by request. 4/24/2009.

wtf? from the g-cache:
Paul Kerr used to work for the Arms Control Association. Josh Pollack is a consultant specializing in arms control, proliferation, and deterrence issues.
By far my second-favorite nucarms blog, after the inimitable ArmsControlWonk. Lots of good references to original sources, placed handily on his page (as opposed to government links, which so regularly get pulled offline). Where are you, Paul?

In any case, I've downloaded and archived -- so far, at least, as I know -- all the files he's linked. I'll put them up, once I verify he didn't get into trouble or something.

computer scientist trading card 2/32

Today we have an early hero of mine, Dawson Engler of MIT, Stanford and now Coverity. Professor Engler's magic/xgcc project was an awesome feat, one of the coolest tools I've ever seen (or at least, seen its output -- the project was never released, and presumably formed the base of Coverity's armamentarium), and served the open source community well with its discovery of flaws in the Linux kernel and other large code bases (the open source community, of course, helped out by correcting magic's many errors and assisting in its refinement).

Allegations that Coverity's "patented analysis" is actually a ruthlessly managed legion of teenage Ukranian programmers, raised on pure rainwater, grain alcohol, methamphetamines and steroid shakes in sweatshop conditions have been denied as "baseless conjecture and libel" by Coverity officials, but that's what you get for not opening your code.

2009-05-01

at long last, a line of puerile computer scientist trading cards


let's try this again, players. btw, while i admire spunk, the traditional means of communicating disagreement is a reasonable letter to the editor.

chaitin's book

If you've never had the pleasure of reading G. J. Chaitin, the Algorithmic Information Theory text I referenced is freely available. Thanks a lot, Professor Chaitin! This kind of thing is really appreciated, simply because a pdf can be searched.

automatic extraction of parallelism

[Be forewarned: I'm about to appeal to a number of fields I don't know in much depth. Experts might find one suggestion or another bewildering. As opposed to spending much time trying to figure out what I mean, you can likely assume it to be gibberish -- assuming you're indeed a suitable expert, and not just a jackass.]

I have been marinating on this today, putting on my algorithmic information theory hat following the semester's close. As it turned out, PLD and automated theorem proving hats were also needed.

Think of decompositions as a language to be recognized by some turing machine. We have all the decidable languages at our disposal; can dependence-free decomposition be described by a DL?

An hour's review of the research suggests that:
  1. there's a ton of PLD research into this at a formal languages / program transformation standpoint. most of it makes use of toy languages that'll work great for half a page examples in some obscure journal. LogP is a great example of this kind of thing.
  2. from a dynamics standpoint, you have hoare and milner and all that hoary old communicating processes stuff. it's a great mathematical description of processes as they're running but not applicable, or at least not applied, to program analysis. deriving a milner system or any other pi-calculus description from program text seems a nonstarter in the Entscheidungsproblem sense
  3. quentin stout's seminal busy beaver work seems a great place to start putting the nails in any behavioral analysis argument and thus also anything involving "so we start simulating...." nosir, no we don't
  4. EXPTIME is a class not very well known outside the complexity and AI communities, but a reduction to this class would work for our purposes. Yu Ding's work on description logic satisfiability could be a good starting point.
  5. so let's turn to the AIT folks (this gets a bit esoteric). i've read chaitin's book, and it doesn't have anything really relevant, save all the mathematical tools necessary for talking about program size. how far can we push Chaitin's arithmetization process? this is for data- and not task-based parallelism. can we reduce to some Kolmolgorov description and pair it with some number theory / analysis (think Banerjee's Inequality) to isolate information-theoretic chunks of parallelism?
  6. yeah, heuristics (ala the FFTW paper and countless others). pretty much anything with heuristics is kinda lame IMHO, because the underlying assumptions change more quickly than the code. a spiritual dead end.
The problem seems sorely in need of really firm theoretical underpinnings. A good place to start: 2006's "Extracting Kolmogorov Complexity with Applications to Dimension Zero-One Laws." The miles between AIT's current state and the power we'd need to do anything interesting suggest that (a) there's fundamental results to be had for the taking here and (b) it'll be tough.

What would be just as useful, theoretically, is determining that AIT models *can't* address certain parallelisms, or at a more fundamental level that some decomposition languages can't be described by a type-0 Chomsky grammar. Of course, what we really want is to find a suitable DL, or preferably a parameterized set of such languages generated from a description, in some operator syntax, because then we could *apply* it.

Operator syntaxes! If we can decompose a program into, say, primitive recursive functions and SSA -- well, from Chaitin we already know changes that can be made assuming exponential time. Thus, we don't need a decidable language for the source; we could merely recognize safe and parallel transformations of said IR, if we had a language for THOSE, and rather than try to solve HOW to do it just start testing structured or random transformations upon the source!

To be more practical, you of course can't EXPTIME-ly generate all modifications within a finite distance, but I bet randomized methods could be used to find (with a high degree of probability) any "seed points" with a spark of parallelism, the local space around which more targeted (possibly genetic?) algorithms could search. Think of them as jeweled raindrops of parallelism forming in our stormy, branch-heavy cloud of code.

Either way, recognizing transformations as opposed to recognizing source patterns could be a very key insight here. I should go talk to Prof. Lipton, who ran one hell of a Randomized Algorithms class this semester.

Holla with your thoughts!