Pasky’s Log

A couple of weeks ago, I have created my own fairly elaborate setup of the Conky system monitor. I have been wanting to fix up some of the weather display aspects, but I’m realistically not getting around to that anytime soon.

So, I have pushed it out to Github now.

I’m still working on YodaQA and there is quite some interest in it in my mailbox. One thing leads to another and our startup Ailao already has a few first customers, we work together on various related semantic NLP / search projects.

In YodaQA, we have a much neater web interface as well as a mobile app as the natural way to interact with a QA system is using your voice. Plus, on a limited domain (movies), we are getting pretty close to crossing the 80% mark for accuracy on simpler questions, entering the “magic zone” where people might start really trusting the system. A few essential blocks for that are still in the pipeline, though.

I’ll try to post a bit more about YodaQA and other work we are doing in the coming weeks / months (as well as some of my hobby projects, of course).

For a course of Jan Šedivý, I prepared a presentation on building apps around the semantic web and linked data. See it here for an intro to the tech, it also includes two silly web mashups that might be inspiring.

I was working on Question Answering last year. Guess what, I’m still on it!

I threw away my first prototype BlanQA and started building a second system, YodaQA. It currently has reasonable performance of answering about a third of trivia questions properly and listing the correct answer in top five candidates for half of the questions – without doing any googling or binging.

A few weeks ago, I published the first paper on YodaQA. With a few fellow scientists, we also re-started the qa-oss Google Group on open source question answering systems.

Today, I finally made a proper homepage for YodaQA and launched a live demo of the system. It’s pretty primitive, but hopefully will serve as a proof of concept.

So what’s the strongest program you can make with minimum effort and code size while keeping maximum clarity? Chess programers were exploring this for long time, e.g. with Sunfish, and that inspired me to try out something similar in Go over a few evening recently:

https://github.com/pasky/michi

Unfortunately, Chess rules are perhaps more complicated for humans, but much easier to play for computers! So the code is longer and more complicated than Sunfish, but hopefully it is still possible to understand it for a Computer Go newbie over a few hours. I will welcome any feedback and/or pull requests.

Contrary to other minimalistic UCT Go players, I wanted to create a program that actually plays reasonably. It can beat many beginners and on 15×15 fares about even with GNUGo; even on 19×19, it can win about 20% of its games with GNUGo on a beefier machine. Based on my observations, the limiting factor is time – Python is sloooow and a faster language with the exact same algorithm should be able to speed this up at least 5x, which should mean at least two ranks level-up. I attempt to leave the code also as my legacy, not sure if I’ll ever get back to Pachi – these parts of a Computer Go program I consider most essential. The biggest code omission wrt. strength is probably lack of 2-liberty semeai reading and more sophisticated self-atari detection.

P.S.: 6k KGS estimate has been based on playtesting against GNUGo over 40-60 games – winrate is about 50% with 4000 playouts/move. Best I can do… But you can connect the program itself to KGS too:

http://www.gokgs.com/gameArchives.jsp?user=michibot

My Firefox (or rather Iceweasel) is prone to constantly spinning and eating about 50-70% CPU on average when should be supposed to just sit idle. I tried to find the root cause, but Javascript profiler sees nothing and other forays didn’t end up with much (I discovered that spinning progress wheel when some tab is forever loading amounts to about 20% CPU, though). Not sure if always, but sometimes it spins within WebGLImageConverter::run() (no callgraph, sorry).

So in the end I decided to treat the symptoms instead. Cleaning my CPU fan helped with the noise, but the main problem is that running firefox brings my battery life to about 1/2 to 1/3. So one obvious solution would be to just stop the damn process when I don’t use it. I typically don’t do background downloads while on battery (or otherwise), so that means I want it stopped when the window is inactive – not in focus. This is surprisingly exotic idea, apparently, and not easy to do in most window managers.

I even tried switching to awesome or i3 window managers which should make this easy, but I’m psychologically not up to that; I think I’m too conservative, but I decided not to stick with that. I use the MATE desktop environment with marco window manager. Perhaps switching to sawfish would be a good option, but in the end I just decided to write a shell script that will periodically assess the situation and suspend or resume firefox as needed. Of course this introduces extra wakeups and ambient CPU load, but when powertop reports that my GoogleTalkPlugin (running at all times for whatever reason) wakes up 150 times per second, the powersaving situation on Linux is still too messy – so who cares?

Here goes the script, in the hope that it will be useful for someone else too. Run it in a terminal or backgrounded in your ~/.xprofile, it will stop the firefox process when out of focus for more than 10s and on battery, and resume it within a second when switching back. In practice, I found these timings completely acceptable so far, and didn’t notice any ill effects of constant STOP/CONT either.

firefox-suspender.sh:

#!/bin/bash
#
# firefox-suspender: Periodically check whether firefox is out of focus
# and STOP it in that case after a time delay; if in focus but stopped,
# send SIGCONT.
#
# (c) Petr Baudis <pasky@ucw.cz>  2014
# MIT licence if this is even copyrightable
 
loop_delay=1    # [s]
stop_delay=10   # [s]
 
last_in_focus=$(date +%s)
firefoxpid=
state=running
 
while true; do
  sleep $loop_delay
 
  # Get active window id
  window=$(xprop -root _NET_ACTIVE_WINDOW)
  window=${window#*# }
  # What kind of window is it?
  class=$(xprop -id "$window" WM_CLASS)
  # echo Active window $window, class $class
 
  if [[ "$class" =~ Navigator ]]; then
    # Firefox!  We know it is running.  Make sure we
    # have its pid and update the last seen date.
    # If we stopped it, resume again.
    if [ "$state" = stopped ]; then
      echo "$(date)  Resuming firefox @ $firefoxpid"
      if kill -CONT $firefoxpid; then
        state=running
      else
        firefoxpid=
      fi
    fi
    last_in_focus=$(date +%s)
    if [ -z "$firefoxpid" ]; then
      firefoxpid=$(pidof iceweasel)
    fi
    if [ -z "$firefoxpid" ]; then
      firefoxpid=$(pidof firefox)
    fi
 
    continue
  fi
 
  # Not Firefox!  If it's running, we are on battery and
  # it's been long enough, stop it now.
  if [ "$state" != running ]; then
    continue
  fi
 
  read battery </sys/class/power_supply/BAT0/status
  if [ "$battery" != Discharging ]; then
    continue
  fi
 
  if [ $(($(date +%s) - last_in_focus)) -ge $stop_delay ]; then
    echo "$(date)  Stopping firefox @ $firefoxpid"
    if ! kill -STOP $firefoxpid; then
      firefoxpid=
    fi
    state=stopped
  fi
done

An improved version of this script: https://github.com/mkoura/browser-suspender

In part of my research, I have been heavily involved with building portfolios of optimization algorithms. Optimization algorithms stay at the root of many computational tasks, from designing laser mirror systems to neural network training. We want to find a minimum (or maximum) of some mathematical function, and for some functions it’s easier than for others.

For very many fairly hairy functions, the best state-of-art optimization algorithm is based on genetic algorithms and it’s called CMA-ES. It also has a very nice Python implementation by its original author, Nikolaus Hansen.

CMA-ES is still not as good as it could be on some functions with many local optima, but its performance can be much improved by establishing a restart strategy that will repeatedly restart it with varying population size and parameters. The best performing restart strategy is BIPOP-CMA-ES and unfortunately, it had no Python implementation so far. I took care of that more than a month ago, but since it’s taking some time to get my modifications upstreamed, if anyone would find that useful,

here is a patch for CMA-1.1.02 adding BIPOP restart strategy

I recently switched to xterm-256color in my konsole, but I found that vim looks exceedingly ugly, unfortunately. The colors were all washed out and difficult to read with reduced brightness. I decided to explore some alternative color schemes, including popular ones like solarized etc., but they just don’t work for me – I have the default color scheme burned into my mind and I really like its high contrast even though I can easily stare at it for 12+ hours in a row. It also works great even in adverse light coditions on a notebook.

In the end, I didn’t find any dark vim color scheme that would just look like its default 16-color color scheme. (Light background color scheme looks mostly the same in 16 and 256 colors by default.) So I had to create my own – 256like16.vim, drop it in ~/.vim/colors. You may want to edit yours to add some more bolds to make it look exactly like the 16-color scheme, but I ended up liking this one more, after all.

(You will need to install colorsupport.vim so that GUI color settings are used in the 256-color terminal. This particular script worked by far the best for me, and :ColorSchemeBrowse is also great when exploring schemes.)

Call me old-fashioned but I’m still using xterm on my desktop computer (where I use just fluxbox as my window manager) – it suits me just fine, but for one thing that I finally managed to solve. xterm by default ignores the clipboard, and none of the previously published solutions cut it for me, until now.

In X11, we have two commonly used selection buffers – PRIMARY and CLIPBOARD:

• PRIMARY is used when you simply highlight text in most applications, without pressing anything, and you can paste from it using the middle mouse button; it is of fleeting nature and used for quick cut’n’paste; and it doesn’t work well with all applications, e.g. libreoffice doesn’t put highlighted stuff there at least in some contexts and non-textarea HTML5 text edit widgets usually can’t handle the middle button for pasting.
• CLIPBOARD is used when you use ctrl-c or ctrl-v and can be used even with the evil applications above, but the problem is it’s not supported by xterm well!

In most terminal emulators, you can use the clipboard either using menus or shift-ctrl-c / shift-ctrl-v. However, in xterm, the best you can do is either…

• Make it use CLIPBOARD just instead of PRIMARY and in the same manner – the moment you select any text in xterm, it will plaster it over whatever else was in the CLIPBOARD before, without any explicit action. This sucks.
• Have a different set of bindings for selection to PRIMARY and CLIPBOARD. This is a lot better, but I’m out of modifiers since I use shift to cut’n’paste in terminal applications that use mouse themselves (e.g. elinks).

So, my solution is to bring in the shift-ctrl-c / shift-ctrl-v bindings! In your ~/.Xresources or ~/.Xdefaults, add

XTerm*VT100.*translations:      #override \
        Shift Ctrl C: select-end(CLIPBOARD, CUT_BUFFER0) \n\
        Shift Ctrl V: insert-selection(CLIPBOARD, CUT_BUFFER0)

(and don’t forget to xrdb ~/.Xresources afterwards).

Now, you can use shift-ctrl-v for pasting from CLIPBOARD, and almost use shift-ctrl-c for copying to clipboard. There is a catch – you must press shift-ctrl-c while you are still holding the mouse button, i.e you press left mouse button, drag your selection, then before releasing it, press shift-ctrl-c; thankfully, that can be done by one hand without too much cramping.

It’s a bit inconvenient because of this bug, and doesn’t quite work with left and right selection; maybe I will sometime get around to adding true clipboard support to xterm code, but I think this is good enough for me at this point. :)

A few hours ago, I have read about Spritz, a new speed-reading app, and I was quite impressed by the idea. I know the underlying concept is not new and I didn’t even try out Spritz itself (they announce their idea but not release the software, huh?), but this was the first time I have heard about it and I really liked it!

So I decided to implement my own terminal version of this idea, acting as a regular command-line filter. Find the new tool speedread at:

https://github.com/pasky/speedread

(Yes, it may not work well for beletry. Or slides. Yes, it may not work well for emails that you want to just skim for keywords. But then there’s the other 80% of text I need to chew through that does not fall in either category. I’ll have to continue trying it out for longer but it might be really useful.)

Meanwhile, I have also learned about OpenSpritz, a web-based implementation of Spritz. Can be a good match for speedread!

I don’t send email from my notebook often, dealing with my correspondence on my server machine via ssh. When I need to do it, it’s usually when I’m sending Git patches or something like that. I didn’t meet much trouble with sending it directly, but SMTP servers of Debian-involved people are some of the most picky one can meet and I decided it’ll be best if I switch the exim4 on my notebook to smarthost mode where all mail is relayed via my main server.

So that should be trivial to do, right? Wrong, apparently. I figured I’d use SMTP auth, but it just seems mind-bogglingly complicated to configure if you don’t want to spend an evening on it. The client part is fairly easy (probably both on exim4 and postfix), but setting up postfix server to do SMTP auth (for just a single person) is really silly stuff. Maybe not so crazy if you use PAM / shadow for authentication, but that means that on my notebook, I’d have to store (in plaintext) my server password anyone could use to log in – no way. It seems I could switch to Dovecot and somehow pass it a simple password to use, but at that point my patience ran out and I just backed off a litle.

Why not just use ssh for smarthost SMTP transport? Authentication via ssh is something everyone understands nowadays, it does the best job there, no silly passwords involved and you can just pipe SMTP through it. You wouldn’t do that at in a company setting with Windows notebooks, but for a single geek, it seems ideal.

Someone already did set up ssh as exim transport, but that’s for exim3. So here follows a super-quick HOWTO to do this with exim4:

• Set up ssh key on client:

  sudo -u Debian-exim /bin/bash
  ssh-keygen # go with the default, and empty password, this will be used in an automated way
  ssh me@server.example.org # to fill up known_hosts; it will fail yet
  cat ~/.ssh/id_rsa.pub # this is my public key
  exit # ..the sudo
  

• Set up ssh key on server – paste the public key printed by the cat above to ~me/.ssh/authorized_keys and prepend command="nc -w1 localhost smtp",no-agent-forwarding,no-port-forwarding,no-X11-forwarding to the key line. This key can now be used only for mail relaying.
• Do dpkg-reconfigure exim4-config and configure smarthost mode. Also use it to find out whether you are using split or big configuration. You will also probably want to enable “mailname hiding”, otherwise your return-path will contain an unroutable address.
• Set up ssh transport in exim4 – add the following to the config file:

  ssh_pipe:
    debug_print = "T: ssh_pipe for smarthost delivery"
    driver = pipe
    path = "/bin:/usr/bin:/usr/local/bin"
    command = "ssh me@server.example.org nc -w1 localhost smtp"
    use_bsmtp
    message_prefix = "HELO mynotebook.example.org\r\n"
    delivery_date_add
    envelope_to_add
  

  (it would be nicer if we used the actual smarthost configuration option value and our notebook’s hostname instead of hardcoded strings, I guess).

• In the smarthost: section of the configuration file, replace transport = remote_smtp_smarthost with transport = ssh_pipe.
• /etc/init.d/exim4 reload and voilá, sending mail from anywhere should work now!

I *wish* setting up roaming SMTP nodes would be way easier nowadays and I wouldn’t have to eventually spend about 90 minutes on this stuff…