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Mixed (up)
In the evening, I went to the opening of the
exhibition Mixed (up) at B93 with photographs by Esmee van Zeeventer and Patric
Jonkman. I talked a bit with Esmee and told her that I am interested in
buying a copy of the (small) book she wants to make with some of her
photographs. I also talked with one of her former teachers about photography
and art.
Checking maze
I am working on a program for generating mazes and I wanted to implement an
algorith to check if a maze is 'nice', meaning that from every 'room' you can
reach any other 'room' and that there is exactly one route between any two
rooms, or in other words, that you cannot walk in a circle. (In graph theory
the nice maze is similar to a tree graph.) I was thinking about all kinds of rather complicated
algorithms to check these properties, until I realized that there was a very
simple algorithm. This algorithm depends on the property that you can walk
through a maze by following the wall on your right (or left) side. With a
closed maze, you will return to where you started. If the maze is nice, you
will visit every passages (between two rooms) in both directions. The number
of passages for a nice mazes is one less than the number of rooms and thus
easy to calculate. If the maze is not nice the number of passages you pass
while following the wall will be lower than twice the number of passages. If
some rooms are not reachable from each other, you will not visite them during
the walk, and thus the number of passages you count will be lower. If all the
rooms are connected, but you can walk in a circle, than you will never be able
to walk around and touch all the walls, meaning that you will only follow some
passages in one direction and not two directions. Thus the number of passages
you pass will also be lower.
Palingdrom date
Today is a palindrome date when
written according to the (D)D(M)M(YYY)Y format: 9102019. The
previous such date was October 8, 2018
and the next will be January 10, 2101.
Moleskin daily planner
At 17:26:43, I bought a Moleskin daily planner for
2020 from Bookshop Broekhuis for
€ 21.99.
Museumnacht Enschede
Annabel and I went to the Museum Night Enschede.
We had dinner at a local food hall. First we went to Concordia. We looked around a bit. The
music from DJ Southern Depot was a little overshadowing everything. Did look
a little at VJ The Cmen. Next we went to Sickhouse. Here we saw (the last half) of Patric Jonkman performing with his (relatively small) modular synth to
silent movie The Cabinet of Dr. Caligari and Thom Floris performing to chapter 1 of the silent movie Häxan. From this we went to Rijksmuseum
Twente. I showed Annabel the painting by Claude Monet. I sat on the ground while listening to the performance of
Lotte Pen and immediately slipped into
a meditative state. She performed: Triptych, Chronon,
Patternalism, and Tabernacle (if I remember correctly). We looked
around a little more and paid short visits to the
AKI and Tetem art place before going to
De Museum Fabriek. There we joined the last demo of the oldest
Zeiss Mark I
planetarium projector, which is in the process of being restored. It was
damaged during a fire in 1976 and had been in a storage room for a long time.
It was only last year that the restoration started. It is not finished yet.
Many of the projectors are not aligned correctly yet and need to be adjusted.
(In 1968, I saw this planetarium in The Hague together with my father, my
brother and two of my sisters.) We drank some tea in the cafe of the museum
before we went home at midnight.
Unravel
In the afternoon, I visited XPO to have a look
at the exhibition Unravel with work Rhizoma by Melle Foortjes and the work 111 days in Jerusalem by Judith
Glimmerveen. The exhibition is part of the Fotomanifestation Enschede. They are two students from AKI.
I was thinking about generating mazes in a rectangle of squares that have the
property that non of squares with four squares to the left, the right, the
top and the bottom, has no walls, e.g., is like a cross. One way to
generate these is thus to allow such cross squares and apply an algoritm to
elimintate them one by one. We assume only nice mazes, which are mazes where
every two squares can be accessed through exactly one route, or in other
words where the passages form a tree graph according to graph theory. I think
the following algorithm works. As long as there is a still cross square, pick
a cross square that is furthers away from the top left corner, where distances
is calculated by adding the distance in horizontal and vertical direction.
Now change either the passages to the top or the left into a wall, which makes
that the square is no longer a 'cross' square. With doing this, some squares
will no longer be reachable from the top left square. Now, either the square
to the left or to the top will be included into these squares. Note that this
square is closer to the top left square. Possibly there is even another square
even closer that now no longer can be reached from the top left corner. Pick
one of these squares. Now it must be that this square has only passages to the
right and the bottom and that if there is a square to the left or the top, it
must be reachable from the top left corner. Turn the wall into a passage for
either the top or the left square. This might turn the square into a cross
square, but that cross square is closer to the top left corner. Each step, will
either remove a cross square or replace it by a cross square closer to the top
left corner. (An implementation of the algorith could make some smart choices
to prevent the latter case.) Because there is only a limited set of squares
that might have to changed into a cross square, and this set becomes smaller
whenever the last cross square at a certain distance is eliminated, the
algorith must come to a halt, resulting in a maze that does not have cross
squares.
Rule 30
When I read about Rule 110
being Turing
complete, I adapted a program that I wrote for Rule 30 such that it works for Rule 110. The results looked promissing.
Yesterday evening, I spend some time to write some JavaScript code to display the results. When today, I applied this to the
results for Rule 110, the results where somewhat disappointing. A lot of
repetitive patterns and some of the expected patterns did not appear. Below
the visualisation of repeating patterns up to the area of 100. (A manually
removed some dupplicates, so the list might be incomplete.)
Today, I read that Stephen Wolfram announced The Wolfram Rule 30
prizes, which are about the randomness of Rule 30. I think that all three
questions are true, but very very hard to prove.
Books and exhibition
At 16:27, I bought the book On the Road written by Jack Kerouac in
English and published by Penguin Books in 1998,
ISBN:9780140274158, from charity shop Het Goed
for € 1.30. In the evening, I visited the last day of
the exhibition Mixed (up) at B93. Around 18:25, I bought
the artist book Street Poetry I. (5/30) from Esmee van Zeeventer for € 15.00 and also the artist book
Crisis Sale (57/100) from Patric
Jonkman.
In to the city
While biking to the city, I stopped at Kringloop
Enschede. At 15:57, I bought the following two books:
 De tweede helft: beeldende kunst na 1945 written by Ad de Visser in
Dutch, published by SUN in 1998,
ISBN:9789063037833, for € 3.00.
 Pier+ocean: construction in the art of the seventies : an exhibition
written by Gerhard von Graevenitz and Norman Dilworth in English and
published by Arts Council of Great Britain in 1980,
ISBN:9780728702394, for € 1.00.
I went to Concordia to watch the short movie: Fake Fiction, which is
part of the exhibition Untitled Surface by Filip Markiewicz. On
Sunday, September 29, I already saw this
exhibition and watched part of the movie. Now I took time to see it from the
start to the end only to discover that I already saw almost the whole movie.
Nevertheless, it was an interesting experiecnce. After having eaten an ice
cream (temperature reached 19.9°C at the weather station at Twenthe
Airport), I went to bookshop Broekhuis, where
at 17:12:58, I bought the book Famous For 15 Minutes: My Years With Andy
Warhol written by Ultra Violet in English and published by Methuen London in 1989,
ISBN:0413615308, for € 12.50.
This months interesting links
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