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Diary, October 2019

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Wednesday, October 2, 2019

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.

Monday, October 7, 2019

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.

Wednesday, October 9, 2019

Palingdrom date

Today is a palindrome date when written according to the (D)D-(M)M-(YYY)Y format: 9-10-2019. The previous such date was October 8, 2018 and the next will be January 10, 2101.

Thursday, October 10, 2019

Moleskin daily planner

At 17:26:43, I bought a Moleskin daily planner for 2020 from Bookshop Broekhuis for € 21.99.

Saturday, October 12, 2019

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 C-men. 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.

Sunday, October 13, 2019


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.

Crossless mazes

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.

Wednesday, October 23, 2019

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.)

This text is displayed if your browser does not support HTML5 Canvas.

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.

Friday, October 25, 2019

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.

Saturday, October 26, 2019

In to the city

While biking to the city, I stopped at Kringloop Enschede. At 15:57, I bought the following two books: 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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