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Dairy, January 2018

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Wednesday, January 3, 2018


At 17:00:48, I bought the following two book from bookshop Broekhuis for € 5.00 each:

More random Street Tile Pattern

I came up with a simple trick in the program to generate more random Street Tile Patterns. I was not happy with first result, because it had a strong tendency to place large tiles under eachother with a one shift to the left. This resulted in many similar looking patches. The trick was to generate the pattern for the following lines from right-to-left. This results in a quite even distribution of the different types of tiles. The reason why the trick works, is that the top-right letter of the tile defines the tile, and generating from right-to-left, results in a even distribution of the possibilities when ever there is a choice between the different types of tiles.

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But on second look, I discovered that the trick does not work perfect, because the above pattern has several H shapes (rotated by 90°). This does not completely come as a surprise, but I right now, I have no clue how to fix it.

Thursday, January 4, 2018

Random Street Tile Pattern

I found a way to prevent the errors. I realized that there were squares of four values that did not match the allowed tiles. I added a check to the program enforcing this. Still there are some problems at the borders, which I hide by showing only part of them. More research will be needed to address these issue.

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Sunday, January 7, 2018

Persistent 'balanced' tree

In the past weeks, I worked on the implementation of a persistent tree data structure. I first wanted to base it on a red-black tree, but then decided on a kind of 'balanced' trees using an extra height indicator. The idea is that this would also allow less optimal height differences in favour of sharing larger parts between versions, by only performing the balancing in the parts that made version specific. This afternoon, I finished a first version, which works correctly and keeps the tree reasonable balanced under deletion, but does not implement the idea of sharing larger parts between versions. I still would like to perform some performance analyses to see if it can be optimized. All the code is in a single file, which also includes all the testing procedures and some debugging code.

Monday, January 8, 2018

You are what you do

This morning, I finished reading the Dutch book Je bent wat je doet (You are what you do) by Roos Vonk, which I started reading on December 20, 2017, the day I bought the book. Roos Vonk is a Dutch professor of social psychology. What I like about the book, compared to other self-help books, is that it contains many references to scientific experiments to support the advice that it gives. It is also a very practical book. Although I have finished reading the book, I am going to study again, trying to make a summary of the main points in order to apply them to my own life.

Four colour theorem: edge marking

The Four colour theorem states that faces of a planar graph can be coloured with four colours. Given four colours, there are 24 ways to permute them. Because of this, there must be another method to represent a colouring with less freedom. For each planar graph with degree three it is possible to define an equivalence relationship between a face colouring and an edge colouring with three colours. Given three colours, there are six ways to permute them. Which gives reason to believe there is a more compact way to represent a colouring. And there is indeed, because with each edge colouring it is the case that at each vertex the three edges are assigned a different colour. By assigning a number to the edge colours, the colours will appear either clockwise or anti-clockwise around each vertex. This can be represented by assigning one of two 'colours' to each vertex. One could exchange these, meaning that there must still be a more compact method for representing a face colouring of a planar graph with degree three. This can done by marking the edges for which the edge colours around the vertices of the edge run in a different direction. It appears that for a marked edge, the colours of the faces on the 'opposite side' of the two vertices are always the same, while for an unmarked edge they are always different. The edge marking also has the property that each face has an even number of edges with a marking. But that is about everything that can be stated in general. Depending on the number of edges of a face, there are certain patterns of edge markings that are allowed, but there are no simple rules to describe which patterns can occur.

The Philosophy of Andy Warhol

This evening, I finished reading the book The Philosophy of Andy Warhol by Andy Warhol, which I started reading on December 9. 2017 after I bought it on November 26. I found this a rather boring book. It is rather similar to A, A novel in the sense that it present every day talk as something special. It has long transcripts of telephone calls with B, who according to Pat Hackett is Brigid Berlin. It is definitely not about philosophy, at most about Warhol's attitude to life.

Tuesday, January 9, 2018

New bike

This morning, I went to get my new bike, a Vilo de ville B 200 in the colour apple green. Instead of a chain drive it has a belt drive, which is more durable, maintenance free, very silent, and has less friction.

Wednesday, January 17, 2018

Some snow

Around seven in the morning, I saw some snow on the cars, but not on the ground. Around eight, I saw that it was snowing. When went outside around half past eight, it was snowing. I measured 1.5 cm of snow on the table outside. Around ten, the snow already started to melt. It snowed on and off during the day. In the evening there were still some patches of snow, mostly on (high) grass.

This months interesting links

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