A few months ago, am not sure how, but Nat talked me into getting a widescreen laptop. I no longer remember what were the touted benefits of it, but this warpig of a machine is both buggy and heavy.

Since the warpig is just too heavy to carry home every day (and also requires a base station hooked up to high-def output to stay at 2.4 GHz of speed) I just leave it at work and use my five year old computer at home to surf the internets. When I bought the machine I remember distinctively describing it to friends as "a silent computer". Five years later every time I load a new web page the fans make as much noise as the construction site across the street. Was I deaf back then, or did the fans become dirty and loud?

I am a fan of Google IG, and recently I discovered that they have a tiny IDE that you can add to your Google IG page. So I decided to try to write a Silverlight Sudoku application entirely using that tiny editor in my old computer at home:

I actually cheated a little and used Emacs here and there every once in a while.

But I ended up with this cute Sudoku/Silverlight application that has exactly one puzzle:

I am very proud of my one-puzzle Sudoku because it has some of the features that I like from Big Bang's Sudoku (click to flag, double click to set the value, hints) and some cute and simple animations that I wrote in xaml and shows my allegiance to the clean and simple configuration religion:

I published it on IG as "Moonlight Sudoku". To add it to your IG home page, go here and click "Add to Google".

Now the only problem with it is that it seems to work just fine with Firefox but seems to have problems with IE and Safari. I must be doing something wrong with Javascript, but I have no idea what it could be. If you can find the bug, let me know so I can make it work on other browser.

My toy sudoku only has one puzzle, this is clearly a design decision to prevent people from becoming addicted to Moonlight Sudoku. But if you know of a source of http-fetchable Sudoku puzzles, let me know, as I might want to revisit this design decision to include more puzzles.

You can download the self-contained module (ig + html + xaml + js) from here. You might also need the Silverlight.js file.

In clear violation of David Mamet's advise to the aspiring actor, I am now going to act surprised:

In other news, Firefox 3 RC1 came out, and the release notes have nothing to say about the bugs that prevent Silverlight from working with it.

Just opened a twitter account

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In my recent post about ZYpp, yum and smart speed and memory usage, I got this comment:

It would be also interesting to know how the new libzypp manages the “Case Studies” from http://svn.labix.org/smart/trunk/README

I don’t know, but could be that yum fixed “Case 2″ and libzypp “fails”? So the extra time and memory over libzypp taken by yum to make the dep resolution would be justified.

At first glance I thought the case was very vague, but actually it was really simple and concrete, so it was a good candidate to be tested with our test suite tools. Let’s look at it:

This is another real case, and is being reproduced in a controlled environment for tests with YUM, APT-RPM, and Smart.

The issue is, a package named A requires package BCD explicitly, and RPM detects implicit dependencies between A and libB, libC, and libD. Package BCD provides libB, libC, and libD, but additionally there is a package B providing libB, a package C providing libC, and a package D providing libD.

In other words, there’s a package A which requires four different symbols, and one of these symbols is provided by a single package BCD, which happens to provide all symbols needed by A. There are also packages B, C, and D, that provide some of the symbols required by A, but can’t satisfy all dependencies without BCD.

So, what is so special about this case?

The expected behavior for an operation asking to install A is obviously selecting BCD to satisfy A’s dependencies, on the other hand, YUM and APT fail to deliver that as a guaranteed operation, as is shown below.

Ok, there are a couple of things that must be said about this example.

• The dependencies of the package A are broken. Unless the package A depends on the libraries libA, libB and libC and some runtime “thing” provided by it, then BCD should be split in three packages. But as none of B, C, D provides any runtime “thing”, but they just “replace” it, this is not true. So either fix BCD or fix A to depend on the libraries only, the explicit BCD dependency is bogus.

• Debian’s apt-get won’t succeed here, because AFAIK Debian only has dependencies across packages, not on libraries. Actually I still wonder how smart could succeed here using a debian backend. I ignore if apt-rpm does support library dependencies.

• The result yum produces makes no sense too.

• So yes, this is the expected result, but the example is a really dumb package.

How to simulate dependencies using the ZYpp sat solver?. The magic is call deptestomatic. There are two versions of this tool, one provided by satsolver-tools, and another one provided by libzypp-testsuite. The one in sat-solver tools should be sufficient. The one in libzypp-testsuite has extra features like graphical display of dependencies.

So, we use the helix format for testcases, which was the format of the original RedCarpet testuite. A testcase is a xml file refering to one or more xml files describing repositories, and one repository represents the installed packages (in this case we can simulate with no installed packages and just one repository).

We start by creating a packages.xml.

And now, we define the test.xml describing the testcase.

If there are conflicts, the xml language has features to select solutions, but that is advanced stuff documented here. For our case, the test is really, simple, just install A.

Now run the test:

# deptestomatic test.xml

And you get the result:

>!> Installing A from channel test
>!> Solution #1:
>!> install A-2.0-1.noarch[test]
>!> install BCD-2.0-1.noarch[test]
>!> installs=2, upgrades=0, uninstalls=0

Which is the “smart” result. It only installs A and BCD, and not B, C and D (which is what yum does).

Learning to develop testcases and run them is an excellent way to help the development team to fix bugs without having to request extra information, so you can play yourself with the simulation before actually reporting it.

You can also generate testcases for day to day operations in a very simple way (no need to write xml):

• in the YaST (Qt) package selector, go to Extras, and choose generate solver testcase (after selecting your transactions, like installing or removing packages).
• Use zypper –debug-solver command (like zypper –debug-solver install foo )

Then you can run them with deptestomatic by referencing the test xml file. Note that you can reuse package lists (repositories) across tests. libzypp-testsuite and the sat-solver source includes a big list of testcases representing simple operations, distributions, upgrades, and distribution upgrades.

• Turned to valgrinding for my strange X kb problem; poked the X server, found a few trivial things. Lost a chunk of time when xorg-x11-driver-input.spec deleted all of /usr/src/packages/BUILD and then unpacked

• Couldn't sleep, up rather early, poked mail - bits of hacking.
• Amused by the metasploit motivational posters. Quick chat with the evo guys, read some code. More bug mail thrash. Pleased to measure oowriter launching in ~500ms (according to the RTL_LOGFILE timing debug in the main binary), at least wall-clock time of oowriter is around ~1 second for me in factory.
• Prodded my gdb bug again; why should prologue analysis be necessary to walk the %ebp chain ? valgrind manages to do a great job here in the same test case.
• Knocked off early. J. out to Laura's party - back to work for a bit. Dug at a really strange xkb / libxklavier bug: most amazing, still no progress on it.