Monthly Archives: April 2007

More on Flash Video…

My brother mocked my use of ffmpeg to create flash video as I did a couple of days ago. He sent me this set of command line options for the Swiss Army knife of video encoders: mencoder. I went ahead and encoded the classic civil defense film “Duck and Cover”, and then used the flvtool2 to add indexing.

Here is the result:

Here is a little shell script that shows the options. I used mencoder as installed fresh from a new Fiesty Fawn Ubuntu installation. If you install rubygems, you can then type “sudo gem install flvtool2” to get flvtool2 installed (it is in /var/lib/gems/1.8/bin/flvtool2, which is not in my path, but it’s there), and it seems to work well too.

Anyway, Kevin wanted me to test it, and it seems to work.

Overpass Collapses, Many People Annoyed for Months

I dropped in at work over the weekend (we are in the final death throes of production on Ratatouille, so I’m basically doing 7 days a week for the next couple of weeks) and noticed that the traffic along 80 was pretty bad. I didn’t think too much of it, but apparently the cause was a collapsed overpass very near Pixar. A tanker truck apparently exploded and burned on one of the overpasses, and the deck above it collapsed. It’s quite the mess, and will likely take months to fix. I went over to an adjacent overpass and took this photo. It’s ugly. Really ugly.

Struggling with Milhouse…

My checkers program has developed some annoying quirks (read: bugs) and I haven’t made any good progress in figuring them out, except to assertain that most of them appear to be centered around the use of transposition tables (when I disable the transposition tables, my program is much better behaved). Because I didn’t know what was wrong, the code has been mangled in a way I don’t like. Oh well. Rather than mangle it further, I thought I’d dig up some more reading material. The links o’ gold today are T. A. Marlsand’s older papers, including a review on game-tree pruning that seems to answer many questions. Good stuff.

Oh well. I’ll work on it this weekend.

Historic Paper on Transposition Tables

Today was a miserable day for my checkers program. I suspected that some of the cases that were causing me some difficulty in the puzzles that I have attempted to date were caused by some problems with my alphabeta search. To resolve this, I coded up some simpler versions and a simple version of minimax. Indeed, I found that these worked reasonably well, but that my transposition table code bolluxed things. I obviously didn’t have the brain cells firing on all cylinders, so here it is, 12:35AM and I’m scanning the web for papers that might help. I found that Zobrist’s original paper on transposition tables was available for download.

Here it is: Tech Report TR88

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Progress with Milhouse

My Checkers Program is Not Endorsed by the SimpsonsMy checkers playing program milhouse is currently advancing at a good clip. I’ve added iterative deepening and a transposition table, and probably will add a history heuristic for move reordering to improve the search further. I’ve also started typing in a bunch of problems from Pike’s Little Giant Encyclopedia of Checkers Puzzles, and used them as test cases. It’s able to solve lots of them, but also stumbles on a few. I’m not certain that the basic alphabeta framework is completely bugfree (in fact, I’m pretty sure it is not) but it is still somewhat gratifying to find it solve problems like the one below:

EXECUTING PUZZLE From D. Oldbury, WHITE TO MOVE FIRST
        +--------+
        | - - - -|
        |- w r R |
        | - w w -|
        |r w w - |
        | - w w R|
        |r - w - |
        | - r w -|
        |- r - r |
        +--------+

1.      ...     27-24 [10001]
2.      20x27 [-10001]
2.      ...     14-9 [10001]
3.      7x14 [-10001]
3.      ...     15-11 [10001]
4.      1x10 [-10001]
4.      ...     11-7 [10001]
5.      13x6 [-10001]
5.      ...     18x2 [10001]
6.      25x18 [-10001]
6.      ...     23x14 [10001]
7.      10x17 [-10001]
7.      ...     19-16 [10001]
8.      3x10 [-10001]
8.      ...     2-6 [10001]
9.      12x19 [-10002]
9.      ...     6x13 [10003]

        +--------+
        | - - - -|
        |- - - - |
        | - - - -|
        |- - - - |
        | - - - W|
        |- - - - |
        | - - - -|
        |- - - - |
        +--------+

transposition: 61096470 lookups, 7241926 finds, 
    53839352 stores, 1048576 entries

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Lennart Augustsson on Automatic Differentiation

Lennart has a nice writeup on automatic differentiation in Haskell. I keep trying to come up with a reason to learn more about Haskell, and examples like this (which are difficult or at least less understandable in C or C++) go quite some way in convincing me that I should invest the time to understand how lazy, functional, polymorphic languages like Haskell can change the way I write programs.

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Baseball and Programming…

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