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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.

Friday, January 28, 2022


At 17:31, I collected the book Cain's Jawbone written by Edward Powys Mathers in English and published by Unbound in 2021, ISBN:9781800180796, which I had bought on Tuesday, January 18, 2022 at 10:22 from bookshop Broekhuis for € 14.95.

Thursday, January 27, 2022

Buning - Djokja

I discovered that the edition of Ulysses that I bought yesterday is much more worth than what the half Euro I paid for it. I do not have the first volume. The two volumes together are worth about € 50.00. On the first title page it has a round paper sticker with the words 'Buning' and 'Djokja'. This could be a bookstore label of a Buning bookshop in Yogyakarta. Some simalar bookstore labels can be found on the (Dutch) page Librariana Deel 28 (2011) / Boek- en leescultuur in Nederlands Indië by Lisa Kuitert. But it could also be some personal label, because it is also found on the back of a watercolour Javanese scene by the artist Jan Christiaan Poortenaar. Anyway, it looks like the book has been in Yogyakarta. I wonder how it arrived her in Enschede.

Wednesday, January 26, 2022


At 12:15, I bought the following books from charity shop Het Goed:


Tuesday, January 25, 2022


Today, I am 22,000 days old. I have decided to celebrate this day on a smaller scale than the day I was 20,000 days old. I have bought some tompouce for us and some stroopwafels to treat my colleagues tomorrow when I will be in the office again.

Addition: A colleague of mine suggested the term kilo days.


Monday, January 24, 2022


I made the test at 16 Personalities and according to the test I am a INTP with the following details: 72% introvert, 63% intuitive, 59% thinking, 57% prospecting, and 51% assertive. This matches with what I concluded on August 16, 2002. It looks like this test is a range version of the Myers–Briggs Type Indicator, which has been critized that there is little evidence for dichotomies.

Sunday, January 23, 2022

Border poles

This afternoon, Conny and I continued our search for border poles. We first visited Dutch trigonometric point 299308 which is located at X-RD 266010.3554 Y-RD 485167.1394 52° 20' 35.47425" North, 7° 00' 58.74302" East. We found it at 14:27. We look around the area before going to the border. There we encountered the following border poles: We searched for the two poles 33, but failed to find them.

Saturday, January 22, 2022

Palindrome date

Today is a palindrome date when written according to the D(D)-M(M)-YY format: 22-11-22 and the YY.(M)M.(D)D formats: 22.1.22. The previous such date was November 12, 2021.

Fotocollectief Photophever

This afternoon, I visited Bookshop Broekhuis where at the top floor, I saw the exhibition from Fotocollectief Photophever. I liked some of the pictures by Marek Hardens.

Monday, January 17, 2022


Last Saturday, the lock-down with respect to non-essential shops came to an end. This morning, I could not resist my urge to visit charity shop Het Goed on my way to the office. At 10:10, I bought the following books:

Sunday, January 16, 2022

Border poles

It is since last year September 2 that Conny and I went looking for border poles. This afternoon, we continued our search. We were surprised to find several border poles that we missed last year as they were clearly visible now. For sure the amount of overgrowth is much less than in the four months ago. (I had entered the location of the border poles we wanted to find in a GPX file and unloaded it to my Galaxy Tab 3 tablet.) We encountered the following border poles:


Saturday, January 15,2022


Friday, January 14, 2022

2-state 4-color BLB

Last Wednesday, I read the blog Another New Record in Self-Cleaning Turing Machines, which is about a new record breaking 2-state 4-color Turing Machine that is a Blanking Beaver, a kind of Busy Beaver. In the past two days, I have been trying to analyze it. This evening, I found that it calculates the following Collatz like sequence:
    n = 1; m = 1;
    while (true)
        if ((n % 2) == 1)
            if (m == 2)
                n = 1;
                n = 2 + 5 * (n + m) / 2;
            m = 1;
            n = 1 + 5 * n / 2;
The steps it took me to find this can be found in this program. I started with an interpretting implementation for the Turing machine using a compressed representation of the tape. The idea that in case a number of cells are given the same 'colour' (symbol) to represent it as a single cell with a number representing the count. The implementation is found in the function interpretter. I ran this to get an idea of the patterns that occured. At one point, I replaced the count (in the printout) by a star character and discovered some repeating patterns. I decided to write a version where the turing machine is hard code. See the function hard_coded1. At one point, I made it print out the transitions from state with colour under the head to next state and next colour under the head. This showed that there were only a limited number of transitions. I used this to construct the function hard_coded2 where they are shown in the comments. I added labels for all state-colour combinations and a goto statements for the transistions. In the function hard_coded3 I reordered the statements such that state-colour combinations that often occured to follow each other appeared below each other. I also added while-loops for repeating state-colour combinations, which I rewrote in a more compact form. (The while-loops can be found as comments in the code.) This resulted in less output to be printed, but I took care that the lines in the input still matched those generated with the earlier functions, to make sure I had not introduced errors. I studied the output and noticed some repeating patterns. This lead to the implementation of hard_coded4 function that tries to reimplement the behaviour starting from the 'A'-state, '0'-colour combination. I already had noticed that there was a slight difference depending on the number of ones on the left tape were odd or even. (It took me some effort to get the number of intermediates steps calculated correctly.) However, it did not result in the expected cleaning of the tape. This lead to the development of the function hard_coded5 which does not make a difference between whether the number of ones is odd or even, but stops a little earlier. Now it did produce the expected cleaning of the tape (not exactly). Through analyzing the output produced by this function, I wrote the calc function, which is also shown above. The calculation of the n variable is derived from the code of hard_coded5 and the calculation of the m variable is based on analyzes of the output.


Wednesday, January 12, 2022


Tuesday, January 11, 2022


I have been looking at the Tropy application to see if I could use it for my research on Peter Struycken. It has some interesting features. It allows you organize your images and allows you to add meta data and notes to these, including selections of them. You can export the data as JSON and the notes are stored with a subset of HTML, which makes it possible to parse them. I want to extract data from the images and have a way to relate, to correlate, and to condens them into well established and supported facts. I also want to go from the facts back to the data and the images they are based on. It seems that Tropy does not support this. This afternoon, I discovered that it is possible to define templates and base these on all kinds ontologies. I had some look at Linked Open Vocabularies and the GND ontology. These are based on Resource Description Framework. (On Hacker News there was some discussion about the semantic web.) I find this model a little limited and rather cumbersome to work with. I thinking about representing the data in the images with (nested) bullet lists in the notes and write some software to extract these.


Friday, January 7, 2022

Paintings and such

Today, we spend some time cleaning the former home of my mother now that we are in the process of selling the house. I took some paintings and objecs with me. Among them:

Wednesday, January 5, 2022

Memory upgrade

I got a 2Gbyte DDR3 SDRAM memory module from a fellow TkkrLab member and installed it in FJF2 following the YouTube video How to upgrade ram of Acer Aspire One D270. Easy! Do it yourself. I ran some memory test to check the memory module before closing it. Reconnecting the keyboard (twice) was the hardest part.

Tuesday, January 4, 2022


Sunday, January 2, 2022


Saturday, January 1, 2022

13.5° Celsius

The temperature at Twenthe Airport has gone up to 13.5° Celsius, which breaks the previous record of 12.9° on this date in 2012.

Friday, December 31, 2021

Brewing the Sublime

I finished reading the book Brewing the Sublime by Philip Vermeulen which I started reading two days ago, and which I bought earlier this month on the second. It is a small book with a lot of interesting notes with links. There is not an online version with the links. I started my own list:
  1. Sane man by Bill Hicks
  2. Beyond the Finite: The Sublime in Art and Science by Roald Hoffmann and Iain Boyd Whyte


13.8° Celsius

The temperature at Twenthe Airport has gone up to 13.8° Celsius, which breaks the previous record of 13.7° on this date in 2017. But what is more remarkable is that that temperature was reached two times during last night. The temperature did not drop below 12.5° Celsius.

Thursday, December 30, 2021

14.1° Celsius

Today, Conny and I went for a walk from our home. We did not know whether it would started to rain, so we did not plan to make a long walk at first. But while walking, we decided to go further, because it did not look like it was going to rain and the weather felt warm. At some point, we realized we had dressed ourselves too warm. At home I discovered that during out walk, the temperature at Twenthe Airport had gone up to 14.1° Celsius, which breaks the previous record of 13.0° for the temperature on this date in 1925. This is probably going to be our last walk for this year. Although there is a ban on fireworks this year, we still expect that a lot of illegal fireworks will be ignited tomorrow during the day and the night.

Tuesday, December 28, 2021


Saturday, December 25, 2021

Advent of Code 2021

This evening, I finished all the puzzles of Advent of Code 2021. My programs can be found in this github repository:. I was the 5774th person to finish all the puzzles. Up to and including Thursday, I woke up early every day to compete in the contest against my colleagues. About thirthy of them started out and were about five others still running in the competition. However, on Thurday, I realized that I was taking it far too seriously and I decided to quit the competition with my colleagues, removing myself from the private leaderboard. In the evening, I managed to finish the puzzles of Thursday. Yesterday, I spend at least half of my hours being awake and a some hours into the night to work on yesterdays puzzle without being able to finish the puzzle. Today around noon, I had a quick look at todays puzzle, which did not look so hard. But it was only around nine in the evening that I continued working on the puzzles and managed to finish yesterdays puzzle and todays puzzle (only one). This years winner is Brian Chen with the alias betaveros. On second place is Andrew He.

Wednesday, December 22, 2021

Palindrome date and double date

Today is a palindrome date when the date is written in the format MM/DD/YY: 12/22/21, and a double date when written in the format DD-MM-YY: 22-12-21.

Tuesday, December 21, 2021


Sunday, December 19, 2021

Snailfish numbers

Day 18 of this years Advent of Code is about Snailfish numbers. I decided to use a tree representation for my solution, but while I was doing this, I several times complementated to use a flat representation when I was struggling to implement an iterator that walks over the leaves of the tree. It took me 2:20:41 to finish the first puzzle and another ten minutes to solve the second puzzle. Yesterday afternoon, I tried to implement the algorithm using an array to store the numbers together with their depth. But it took me even more time. Then I thought a bit more about it. I realized that the explosions could be done in one pass. I also realized that a split at depth four, leads to a single explosion, which combined lead to a 'distrution' of the value to surrounding values, and which can be done in a single step. I also realized that with some clever moving around this can also be done in a single pass. Today, I worked on a third solution using a double linked list. Because the depth of the numbers is limited to at most four it is a limited depth binary tree, which can be represented by 31 cells. If you decided to use -1 for the representation of a pair, it is possible to use an array of 31 integers. (I used an array of size 32 out of convenience.) The idea is to asume that you have a tree with fullest depth and then you number the nodes, from left to right, starting with 1. During the addition, you temporary need an tree with five levels and thus 63 cells. This evening, I finished the fourth solution with this. I tested the solutions on the example input given at the end of the description for the first puzzle. The code can be found in the program 2021day18.cpp. With the command line option -t, the program gives some detailed output.

Saturday, December 18, 2021


This evening, our government announced that there will be another lockdown starting early tomorrow morning till at least January 14. Although the number of people testing positive on Covid-19 has dropped in the past two weeks by more than a quarter and even the number of people in the hospital has dropped (the number of people in IC only slightly), there is great fear that the Omicron variant will cause those number to increase quickly. Today, I saw the data that from November 29 to and including December 5, about 0.2% of the examined samples were the omicron variant. During that period about 152349 people tested positive, which means that during that period about 300 people were already infected with the omicron variant. Yesterday, it was reported that in the capital city, Amsterdam, about 25% of the examend samples where of the Omicron variant.

Friday, December 17, 2021


Sunday, December 12, 2021

Hexagonal mazes

Last week, I was going through some old paper, and I found to sheets with hexagonal mazes. Today, I found them (at least one of them) on the website of Olin Shivers. I visited his website before on January 29, 1997, when he was still working at MIT. The mazes can be found on the page Maze generation. He mentions that Robert Givan finished the largest maze by hand. There are good reasons to believe that this is Bob Givan working at Purdue University.

Saturday, December 11, 2021

Palindrome date and double date

Today is a palindrome date when the date is written in the format MM/DD/YY: 12/11/21, and a double date for that format. It is also a double date when written in the format YY.MM.DD: 21.12.11.

Matching brackets

Day 10 of Advent of Code 2021 is about brackets. There are four types of brackets (using ()[]{}<>) and the puzzles have to do with checking if they are matching. This can fail because there are some brackets missing at the end or because there is a mismatch. I decided to use a stack for my implementation of puzzles instead of using a recursive function. I felt that it was the right decision for finishing the puzzles. When I was done, I started thinking about repairing a mismatched sequence of brackets and what would be the minimum number of brackets to insert. It took me some time to come up with an algorithm. It is implemented in the program day10_s.cpp. What it first does is replacing all matched brackets (inside-out) with underscore characters. Next it uses a recursive function to try all possible matchings. For the input given, this runs fast enough, but the complexity is (at least) cubic to the length of the input. Memoization (using a sqaure amouth of memory to the length of the input) can be used to reduce it to at most cubic. I made some searches and made some inquiries (on Twitter, Hacker News, dan Reddit) but did not get any further. I suppose that some research on this must have been done in the past. I suspect that the two type brackets problem is easier than the three or more types of brackets problem.

Wednesday, December 8, 2021

Friday, December 10, 2021


January 2022
December 2021
November 2021
October 2021
September 2021
August 2021
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Califlower fractal




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