I write, therefore I am
With this variation on a famous statement by the philosopher Descartes, I would like to express that the act of writing about what happens in my life is important to me.
Some snowAround 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.
New bikeThis 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.
You are what you doThis 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 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. 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.
Persistent 'balanced' treeIn 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.
Random Street Tile PatternI 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.
BooksAt 17:00:48, I bought the following two book from bookshop Broekhuis for € 5.00 each:
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.
360° videoAt TkkrLab we unpacked a Christmas gift from RevSpace. Someone had brought a Ricoh Theta V camera and used it to record a 360° video.
Saturday, December 30, 2017
WinterGo: Second dayIn the morning, I played against Francien. I played slower than last year, but I still missed some important moves and lost too many stones because I did not watch out enough. I played black and lost with 16.5 points. On the right the state of the board at the end of the game. White had captured 24 black stones and black had captured 13 white stones.
In the afternoon, I attended a game exposition of
- AlphaGo Master vs Fan Tingyu. I did not fall asleep, which I guess means
it was a good exposition, because usually I do fall asleep during go workshops.
WinterGo: First dayI played my first game of Go in almost a year. I played quite agressive, to my own surprise. I made several invasions and almost killed a black group in one of the corners. But in the end the black player found a good move, to which I did not know the answer, tipping the scales in his favour, forcing me to resign. On the right of the status of the board, just before he made his last move to kill a lot of white stones.
the Street Tile Pattern in an attempt to generate 'large' random patterns. This evening, I succeeded in doing so with the latest version of the program, but I am not very satisfied with the patterns being generated, because they have a certain bias.
BookAt 11:03:13, I bought the book Je bent wat je doet written by Roos Vonk in Dutch and published by Maven Publishing in April 2014, ISBN:9789491845017, from bookshop Broekhuis for € 11.50. the Street Tile Patterns. I established that each state can be reached from each state. If this would not be the case, it would have some implications for the infinite non-repeating Street Tile Patterns. I wrote a small program to see if the states could be used to generate a random pattern (within a square) without using back-tracking, and it turned out that it was not possible. I guess there must be a method to connect the DFA with itself to determine how to generate from a given sequence (matching the DFA) a sequence below it that also matches the DFA.
89 statesI took a new approach to the Street Tile Patterns and wrote another program. The idea was to implement an alternative method to calculate the 'states' of the DFA underlying the grammar. After I implemented it, I tried different depth, discovering it found more and more states. But then I realized, that many states might be equivalent. I found a method to determine equivalent states, and discovered that depth six, no more states were found, thus concluding that there are 89 states. I spend some time analysing the states with an idea to put them into a diagram. This evening, I spend analyzing some of the generated sequences on which I based the grammars, and discovered that all those sequences make use of a rather limited subset of states. I need some more time to construct a diagram.
Monday, December 18, 2017
Street tile grammarThis weekend, I continued my research on the grammar for the horizontal continuation for an infinite street tile pattern. The program I had been working on, crashed due to heap exhaustion. I already had discovered that I could reproduce the result of November 12 with the smaller number of states, if I would work go up, instead by going down, which actually comes down to using the upside-down encoding, like:
A AB D DE DEF A AB ABC GH GHI DE DEF AB ABCBut it did not bring me much further. As a next step, I decided to develop a version that does not store illegale chains, after I verified that it did not matter. This program was able to find all illegale sequences of lengths smaller than sixteen. I worked on developing a grammar to encompass all sequences. This resulted in the following regular expression (spread over multiple lines for readability):
[ABC]A(ABC)*AA |([ABC]AAD|[HI]D)(A?ABA?D)*(AAA|G) |(([ABC]AAD|[HI]D)(ABD)?AA|[HI]AB)DDEFD(ABG|AA(DAB)?(DAAA|DG)) |(([ABC]AAD|[HI]D)AABC|[HI]AB)(AADEAA|AABA)(ABG|ABCA(DAAA|DG)) |[HI]ABG |[DEFHI]A[DG]I searched the internet for an online converter to DFA. I found Regex => NFA => DFA by CyberZHG. It uses a slightly different notation, so I rewrote the above expression into: (A|B|C)A(ABC)*AA|((A|B|C)AAD|(H|I)D)((A|ϵ)AB(A|ϵ)D)*(AAA|G)|(((A|B|C)AAD|(H|I)D)(ABD|ϵ)AA|(G|H|I)AB)DDEFD(ABG|AA(DAB|ϵ)(DAAA|DG))|(((A|B|C)AAD|(H|I)D)AABC|(H|I)AB)(AADEAA|AABA)(ABG|ABCA(DAAA|DG))|(H|I)ABG|(D|E|F|H|I)A(D|G). It returend a nice graph, but it seemed not to be the most compact representation.
Below some of the long sequences of the different parts of the grammar are given together with the lines that can be inferred from them:
Saturday, December 16, 2017
Friday, December 15, 2017
Thursday, December 14, 2017
< H2>Wednesday, December 13, 2017
Tuesday, December 13, 2017
Hail, snow and rainAround four in the afternoon, it started to hail. The hail was quite fine, but still hurted when touching the skin. After about twenty minutes the hail changed into snow. About an hour later it changed to rain. In the west of the country there were a lot of traffic jams and problems with trains. In the middle of the country 44 cm of snow was measured at one location.
Snow and rainIn the afternoon it snowed. At the end of the afternoon, it started to rain. While biking around the city I encountered three instances where cars (and one city bus) had hid each other. In all cases, the damage seems minimal. I also one time encountered a car slipping. In the evening, most of the snow on the roads had disappeared.
AmsterdamI left at 8:16 from Enschede, hoping to arrive at 10:30 in Amsterdam. But half way between Apeldoorn and Amersfoort the train stopped in the middle of nowhere. It was announced that the overhead line had broken ahead of us, and that the train had to return to Apeldoorn. We were adviced to go back to Deventer and travel further over Zwolle. There were some more delays and it was only at 12:52 that I arrived in Amsterdam. It was snowing, but the snow did not stay.
While on the train, I finished reading the book The Seducer's Diary by Søren Kierkegaard, which I started reading on November 18 and bought on December 14, 2013. I found the story to be completely unbelievable, including its form.
In Amsterdam I went to bookshop Scheltema, where at 14:37, I bought the following two books:
Trip to China 2010
-- contact -- Frans
My life as a hacker
The Art of Programming
HTML to LaTeX
eXtreme Programming Programs Hamilton cycles