## I write, therefore I amWith 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. | |||

## Saturday, March 23, 2019## Learning ChineseBecause we have plans to make a trip to China this year, I have decided to learn some Chinese. I have installed the ChineseSkill Android app and finished some of the basic lessons, but since this morning, I get a message that I am out of pandas and I have no idea how to get more. Maybe because I have no payment method installed. Maybe I have to take a look at some other Android apps. I am also thinking about making my own flashcards and go over them when I bike to my office or listen to language learning mp3's. I found the video 200 Chinese Phrases for Beginners from the Learn Chinese 360 YouTube channel, which seems to be an interesting starting point to improving listening. This morning, I also started reading the Dutch bookHet karakter van China (known in English
under the title China: Empire Of Living Symbols) by
Cecilia
Lindqvist, which might be a good way to learn Chinese characters.
## One flowerAt the end of the afternoon, one flower of our magnolia had opened a little. Expect that many more flowers will open in the coming days.## BikeriderEarly this evening, I bought the drawingBikerider from Maria Britze after her exhibition Colourtramp at
B93 came to an end today.
## Wednesday, March 20, 2019## EstimatingYesterday evening, I made some modification to my Exact Cover program, such that it can be used to estimate the number of solutions of the Octopuszle. This morning, I made some modifications of the program. The idea of the 'sample' mode is that it will run for two minutes using a random selection of vectors from the column with a minimum value of vectors. While doing so, it measures the distance of the solutions spaces that has been covered under the assumption that each selection covers an equal part of the solution space. It also counts the number of solutions that were found. These two can be used to estimate the total number of solutions. However, the assumption is not correct and does influence the result. This morning, while biking to my office, I realized that there is an easy way to estimate an upper limit on the estimation. There are 256! ways of putting the pieces within the 16 by 16 square. Now, what is the chance that all pieces fit. There are a total of 2.(2.16^{2}-16.15) + 2.(2.16^{2}-15^{2})
relationships that have to meet. If we assume that all the chances are
independent, which is probably not the case, than the number of solutions are
about 2.409128076060726988778E+170 (found by calculating the expression
256!/(2^(2*(2*16*16-15*16)+2*(2*16*16-15*15))) with Keisan Online Calculator. I have no idea which statisical method I should
use to look at the numbers produced by the sample mode, but if I just have a
look at the numbers, it seems to return a number around 10^{163}
solutions. This is close to the theoretical maximum number of solutions.
## Saturday, March 16, 2019## Exhibitions and bookI went to XPO to see the exhibitionA Blue,
A Purple, Aloë vera, Aster, Banaan, Cupcake, Engeland, Hibiscus, Pilli
Pilli, Prinsessen Roze, Selectie and Ultiem by Evangeline Clark. She was there herself and I talked a little with her. I
think about buying Pilli Pilli. Next, I went to bookshop Broekhuis, where at 16:08:40, I bought the book De edele kunst
van not giving a fuck written by Mark Manson, translated from the English
The Subtle Art of Not Giving a F*ck into Dutch by Annoesjka
Oostindiër and Henk Popken, published by Bruna Uitgevers in
2017, ISBN:9789400509023, for € 20.99. I walked through the city and went
to have a look at the exhibition Monsterproject at Concordia. In a
bookshelve, I discovered a copy of Jaarboek 09/10. I made some inquiries
as to if it was on sale, but it was not. I did get some tip about another place
where the AKI yearbooks can be found.
## Octopuszle solutionsA large part of the day, I worked on a program to generate an exact cover problem for solving The China Labyrinth within a more compact, hexagon shaped, enclosure. As usual, a one off error, was the last bug that kept the program from running. Below one of the solutions is given.
I noticed how this solution consists of three parts (counting the empty piece as a separate part), and it only has one loop (circling the empty piece), which seems to be a counter example of the statement that I quoted yesterday. Maybe the proof is not as solid as it was thought. Because there are so many solutions to the puzzle, I thought that maybe an algorithm that would search for solutions at random would give a more varied number of solutions. When I started working on this, I discovered a bug in the algorithm, that was introduced when I did some experimentations on reducing while solving. When I fixed it, the program returned many solutions per second. I decided to also give it a try at Octopuszle and for that too it produced many more solutions than before. Below ten random solutions are given.
## Friday, March 15, 2019## The China LabyrithWhile thinking about better ways to solve the Octopuszle, I decided to take one of the diagonals away, and try to fit the 64 remaining pieces into a 8 by 8 grid. Even then, the program did not find many solutions per hour. I let the program run some time until it found 1900 solutions. I did think about some ideas to find more solutions. I did realize that the remaining puzzle was actually The China Labyrith inside a rhombus. After realizing this and remembering the statement: "It was soon discovered and proven that the number of seperate groups (the blank counting as one group) will always equal the number of loops (holes in the solution)", it became clear to me that one of my approaches to find more solutions, was never going to work. Also it is clear that the one piece with no lines, cannot be at the edge, but must always be in the middle. This evening, I worked at the visualization of one of the solutions, also to verify that my mapping to an exact cover was actually correct. The visualization uses one of the lines generated by the exact cover algorithm.
## Saturday, March 9, 2019## BookAt 15:58, I bought the bookScience * Art written by Ans van Berkum and
Tom Blekkenhorst in English and published by The Fentener van Vlissingen Fund,
ISBN:9789090013596, from charity shop Het Goed
for € 2.50.
## Magnolia seedThis morning, I noticed that some of the outer shells of the flowers of our magnolia had cracked, a sign that it might start flowering within some weeks, which would be rather early this year. I decided to have a look at the one seed that I had discovered last year and kept in our shed, only to discover that it was covered with mold. In the afternoon, told Annabel about. She went to inspect the magnolia and discovered two other withered pods that had contain one or two seeds. Annabel noticed that it is not so difficult to grow a magnolia from a cutting. I told her, that I rather grow one from a seed. This fall, I will look more carefull for seeds and hopefully treat them better.## Friday, March 8, 2019## Link## Wednesday, March 6, 2019## ColourtrampI went to the opening of the exhibitionColourtramp by Maria
Britze at B93. I found her newest work,
drawings made with colour pencils, the most interesting, and I was not the
only one in that regard. I want to buy one of these drawings.
## Link- Ghidra: A software reverse engineering (SRE) suite of tools developed by NSA's Research Directorate in support of the Cybersecurity mission
## Monday, March 3, 2019## Paarse Dag 2This evening, I went to collect the art workPaarse Dag 2 made by
Simone Zacharias, which I had first seen
on Saturday, February 2. Again, a work with
both figurative and abstract elements, just like most of the other works that I
bought in recent years. It seems that purely abstract is too abstract for me.
I also like the colours in this work, as purple ('Paars' in Dutch) is my
favourite colour.
## Link## Saturday, March 2, 2019## The naked truthIn the afternoon, I went to Rijksmuseum Twenthe for the exhibitionDe Naakte Waarheid
(The Naked Truth. I found the following works notable (in the order I
saw them):
*Digital artifacts*2014 by Bart Hess*Adam en Eva*1914-16 by Jan Sluijters*Fallen Angel*2011 by Christiaan Zwanikken*De Prediker (zelfportret)*1937 by Carel Willink*Het slachtoffer van de ellende*1892 by Marie de Roode-Heijermans*Body Builder (Profile)*1976-1978 by Andy Warhol (four photographs sewed together)- 4 nudes 1889-1915 by George Hendrik Breitner
*023. Dreads*1998,*066. Babes*2005, and*156. Good Morning*2018 by Ellie Uyttenbroek and Ari Versluis*Halfnaakt (vrouw van de schilder)*about 1912 by Jan Sluijters*Halfnaakt*1964 by Aat Veldhoen*Paring*1962 by Aat Veldhoen*Selfmade: Duisternis (3)*Heleen van Royen*PSP Ontwapened*by George Noordanus and Hendrik Jan Koldeweij- Phil Bloom with newspaper, fragment from HOEPLA, episode 2.
*A History of Sex (Rietveld)*1996 by Andres Serrano*A History of Sex (Eline)*1996 by Andres Serrano*A History of Sex (Leo's Fantasy)*1996 by Andres Serrano*Chair*1969 by Allen Jores*The Palace of Automorphic Delight*2009 by Terry Rodgers*Veneration (The Chapel)*2017 by Levi van Veluw*Study for Racional*2004-2007 by Yoan Capote*Easy to remember*2011 by Lorna Simpson*Blue*2016 by Ingrid Baars*Mother and Child*2008 by Luo Fahui*Falaises près de Pourville*1882 by Claude Monet*Freeing*(the body) by Marina Abramović*Untitled (C.M. #10)*2015 by Juul Kraijer*Untitled (L.P. #7)*2015 by Juul Kraijer*Paring*1962 by Aat Veldhoen*Copulation*1961 by Aat Veldhoen*Zonder titel/Untitled*(4x) 2015 by L.A. Raeven*10 meters of sound*by Philip Vermeulen
Afterwards, I went into the city. At bookshop
Broekhuis there was an exhibition with works by Jeanine Wubbels. I also went to photo gallary Objektief to see the
exhibition ## Tuesday, February 26, 2019## Hexagon numbersThis afternoon, I thought about the hexagon numbers not with triangles but with hexagons on the corners of the triangles. That is because I wanted to know if there is a hexagon with 64 smaller hexagons. If every side should have more than one hexagon, the smallest configuration you can create, consists of seven hexagon. The following sizes, above seven, are not possible: 8, 9, 11, 15, and 17. There are several ways to make a hexagon with 64 hexagons and the most round shape seems to have sides of lengths going round: four, seven, four, fife, six and five.## 19.2° CelciusThis morning, between seven and eight, the temperature was still around -1° Celsius, but around four in afternoon, it reached 19.2° Celsius. Very likely a record, probably also for the whole month of February.## Link## Saturday, February 23, 2019## Links- A Heavily-Commented Linux Kernel Source Code
- Commentary on the Sixth Edition UNIX Operating System
- Physically Based Rendering: From Theory To Implementation by Matt Pharr, Wenzel Jakob, and Greg Humphreys.
## Thursday, February 21, 2019## Alita: Battle AngelAnnabel and I went to see the movie Alita: Battle Angel. We both did not have high expectations of this movie, but we both enjoyed it very much hoping that a sequel will be made soon.## Wednesday, February 20, 2019## Link- LOFAR Surveys: a new window on the Universe in Astronomy & Astrophysics.
## Tuesday, February 19, 2019## Octopuszle 4x4Yesterday, I got an idea for finding solutions for the Octopuszle. The idea is to split the large puzzle in four by four smaller puzzles. If you look at only the horizontal and vertical lines, then there are 652 solutions of all possible pieces within four by four pieces. I discovered that there are no solutions when you only look at the diagonal lines. This night, I ran the Exact Cover solver to figure out how many solutions there are for filling a four by four square with all of the pieces, such that there is exactly all the pieces are used when ignoring the diagonals. The answer was 170,917,888. Today, while biking, I concluded that there might not by any solution at all, simply because of the pieces that are needed at the border. Not suprisingly, 170,917,888 is equal to 652 times two to the power 18. I have no idea how to proceed from here.## Saturday, February 16, 2019## Come together in a dreamI went to the opening of the exhibitionCome
together in a dream by Emmy
Zwagers at XPO. I liked her work acryl op paper 300x400 2017. I
understand that for her the process of making the work is as important as the
result.
## Thursday, February 14, 2019## Exact Cover to SATThinking about the Octopluszle and the lack of succes of making any progress, I decided to see if converting the problem into a Boolean satisfiability problem would be an option, knowing that there is a lot of research going on SAT solvers. I came across Solving Exact Cover via SAT, which happens to be from the same person who tried to solve the Octopuszle with an Exact Cover solver almost a year before. We could conclude from this, that he did not make much progress and that the Octopuszle is indeed a very hard puzzle.## Wednesday, February 13, 2019## OctopuszleLast Monday, I came across the China Labyrinth and the Octopuszle. Yesterday, I wrote a program to generate an Exact Cover for this problem and last night I ran my Exact Cover solver on it, but it did not find any solutions. Today, I discovered that others tried it before and did find solutions using a Python 3 Exact Cover solver. This was also refered to in a Hacker News thread aboutOrganicity in abstract strategy games.
Anneke Treep discussed it in the March and July 1990 issues of Cubism For Fun newsletter.
## Saturday, February 10, 2019## UbuntuI have installed Unbutu onjohan. I
installed it on the disconnected hard-drive that I put in place as an
anti-virus back-up. It appeared that this drive was also seen as the first
drive. So, now johan is a dual-bootable PC. I noticed that Firefox
does not run very smooth under Unbutu and that it having similar problems with
playing videos, like it has under Windows XP. I would think that it is related
to my graphics card not being fully supported anymore.
## Friday, February 8, 2019## Memoral service Martin MedemaYesterday, I got news that Martin Medema died during the night of Monday to Tuesday and that there would be a short memoral service this morning. I doubted a long time whether I should go, because it was on Friday, June 12, 2009 that I met him for the last time. I met him shortly after I arrived at the University of Twente, usually at (board) game club Fanaat. I am happy that I did go. I discovered that until recently (when he became ill), he was a frequent guest at Fanaat. Almost half of the attendees where current members of Fanaat, students of the University. But there were also some people from the early eighties, some of which had not seen Martin for much longer than me. Arjan and Erik, as long time members of Fanaat, also attended. (The only person, I had expected to see, did not come.) Someone from the eighties had brought a seven hexes segment and placed it on the coffin with six wooden round stones of different colour on top of it. These are used in the game Atlantis. After the nephew of Martin said some words, several other people said some words, often telling how Martin had taught them important lessons in life, about trusting and living an alternative, nomadic life-style.## Thursday, February 7, 2019## ExhibitionsThis evening, I went to see the exhibitionI owned a tree by Linda Vilka
at the Tankstation in Enschede. Later, I also went to Concordia and saw the
exhibition Inktspot of a hunderd political cartoons from Dutch
newspapers. I also played a little with some musical art works that are part
of the exhibition Ik zie ik zie wat jij niet hoort (I see what you do
not hear), which is geared towards children.
## Wednesday, February 6, 2019 |
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