Fighting with computers

Computers are not always friendly.

Sunday, May 27, 2007

Losing the weekend fight

Over the weekend I've lost several battles:
  • First one was against my TV computer. The Asrock motherboard died last week, so I bought a replacement but it was an Elitegroup VIA KM400-M. To make a long story short I tell you this mobo does not play right with my Nexus-S PCI card. Of course, figuring that out took me a good part of the weekend. I sent a support request to the manufacturer, but given the way the manage their website I'm afraid I am in for a big dissapointment.

  • Second, I turned to my desktop to scan some pages I realized that my Ubuntu upgrade to Feisty also did bring an annoying bug that made my Acer S2W 3300U scanner not to work properly. It turns out it is a new bug that can be avoided by using the scanbuttond application (weird but true, this daemon-like application prevents the scanner to be powered down which is what causes the bug). Finally I managed to get the work done, but I'm exhausted. Those of you with your shine Vista and the same scanner are not lucky either as it seems not to work.
I ended up recovering an old P3 motherboard I put on a piece of cardboard under the TV set (as its size does not fit inside my TV computer case). I hope this week nothing will break.

Wednesday, May 23, 2007

Weird CUPS printing problem

Since I installed Ubuntu's Feisty Fawn my user impressions have been very good. However, some days ago I experience a weird problem when my system began to work erratically. I was not expecting it so it took me some time till I realized my filesystem was full. I did not understand why that was happening as the last time I checked there where more than 7GB of free space on that partition. But the first trouble sign was that print jobs where not printed.

After some confusion I realized I had 7GB /var/log/cups/error_log file. So that was the cause of my trouble. Inside the file I had millions of lines with the error message "Too many open files". It was clear there was a problem with the printing system.

I googled for that and I learned there were not one but two different reports of a similar problem. Just restarting the printing system was restoring the service (but not deleting the error_log file).

As soon as I removed the error_log file and restarted cups I was back on, but I join the bug process and it seems that now the problem is fixed (but the fix is still manual though I guess it will be soon included in the automatic system updates). In the mean time, you can use the proposed patch. Happy printing!!

Tuesday, May 22, 2007

OpenOffice fonts in Feisty

A colleague of mine who tried the new Ubuntu 7.04 was not happy with the OpenOffice Impress tool (I'd say he was not very impressed) because certain pages were rendered using larger fonts that in the original page. This odd behavior was forcing him to patch slides that were ok for previous versions of OpenOffice.

I haven't experienced the problem myself, but I told him to have a look at Launchpad to see if there was a bug report on this and, if not, to file his own bug report. It turned out that a very helpful guy reported a similar problem, its cause and several suggestions to fix it.


It turns out there is nothing wrong with OpenOffice but last version of Ubuntu fails to do the right substitution with some fonts. This bug was not happening on previous Ubuntu versions though. As my friend's problem was due to the use of some TrueType fonts from Microsoft (a document migrated from PowerPoint) I suggested to install the package msttcorefonts and that fixed the problem.

Saturday, May 19, 2007

eBay experiences

A few days ago I bought one item from a seller on eBay. Seller looked good. But two days after I sent my payment I got an eBay warning message telling me the seller's account has been canceled and advising me not to send any money. Unfortunately the money was already sent so there was not much I could do.

Checking the seller's account feedback page revealed that the flow of feedback messages had stopped as users cannot leave feedback on a canceled account (not sure this is a good idea) even if buyers are already getting what they paid for (or a brick in a box). Let me elaborate on this: Blocking a seller account should prevent the seller to do "any more harm" (ie. to sell any new item) but the feedback information is useful mostly for buyers, so you are here punishing the buyers if they cannot post feedback for a blocked account.

Some days later my product arrived ok and I was surprised when I can see I can leave feedback for this seller. In fact, it seems the seller is back to business with the same userid. Maybe there was some sort of misunderstanding that was cleared out. Good for the seller I guess.

However I found pretty annoying that eBay failed to let me know this too. They were capable of warning me about a seller I was buying from who got his account locked, but they failed to tell me the same account was reinstated later. I am not happy with this behavior. To tell the truth I've got the feeling eBay is running downhill in customer service. I hope you do not have to deal with the silly automated answers they use to provide.

Friday, May 11, 2007

New life to the Traveling Salesman Problem


I learned about this problem when I was a CS student: A salesman has to visit a set of cities and then returns home. The problem is to find the fastest/cheapest/shortest way of doing so. It is a NP-hard problem as the solution space is n! (for a n-city problem) that is impossible to be examined fully in a lifetime. It can be entertaining to do by hand, but there are many programs that may help you, like Concorde.
My interest for TSP was sparked as a possible solution to the optimization problem for the drawings made with my home-made painting machine. It is not a new problem but I was not aware of the best solution possible. I was lucky enough contacting Michael Trick who, right off the bat, gave me a nice and elegant solution.
I need to determine the right order for drawing a set of n lines but each line may be drawn in one direction or backwards. The solution to the problem needs to determine the drawing order of the lines plus the drawing direction for each one that makes the total drawing time minimum.
The solution Michael suggested was to use both endpoints of each line to create a TSP problem with 2*n cities and to use a negative cost for the edge connecting the two endpoints of each lines [and the Euclidean distance for the rest of edges]. It worked like a charm and I am really grateful for his help.
Other things I learned along this problem is that TSP problem has even been used to create an interesting form of art.

Friday, May 04, 2007

A good moment for a backup


After doing a full backup of my trusty Ubuntu 6.06 system at home I decided to give it a shot to the new Ubuntu 7.04 (aka Feisty Fawn). I just decided not to be on the cutting edge and I did the install only after other users were reporting successful installs. So far I've updated a couple of my systems, the first one, an ASUS pundit worked like a charm and the graphics card was detected ok. The second system, with an ASROCK mobo with an ATI Xpress 200 graphics card was not so lucky and though the install worked I needed to do some black magic to get the graphics working at the right resolution and, more important, to get 3D acceleration.

Why is 3D needed now? Well, it is not really needed but after so many comments about all the "experimental" graphic features nicely included in the last Ubuntu I decided it will be nice to try it out (don't worry I am not posting any video to youtube).

The bottom line is that the new 7.04 feels a better Ubuntu than ever before, with a simple installation even if you are a beginner and the eye candy with transparency, windows that wobble when you move them and the (compiz) rotating cube thing make it funnier too. I particularly like the effect by means of which a window you are dragging to the edge of the current viewport forces the desktop to rotate to the next virtual desktop. It is a cool metaphor to help you organize your desktop windows.

As with 6.06, you can get free Ubuntu 7.04 CD-ROMs delivered to your home (for free). It comes with OpenOffice 2.2, the GIMP and many other programs but, this time playing multimedia files, like mp3 or divx, while not out of the box, will work after you download some additional codecs the first time you try to play that type of files. It is done nice and easy. The other thing I that looked better but I failed to get working at first sight was Flash plug-in (the automated install triggered by my first visit to youtube failed). I needed to use synaptic to install the flashplugin-nonfree package.

My advice is that you should give this new Ubuntu a try (you can use the Live version of the install CD), I like it a lot, and many of the tools I use like Inkscape or Texmacs are now in their latest release in this distro.