This morning, the temperature was -2.5 degrees Celsius. There was already
some dry snow on the ground. Throughout the day
we got some more dry snow, which was easily blown away by the wind,
leading to all kinds of patterns on the ground. But the snow did not melt
away like in the past weeks.
Heavy snow fall
Yesterday evening, heavy snow fall was
forcasted for the Northern part of the country. When I looked outside
of the window this morning, I concluded that we did not get any
of it. On the news we heard that just 100 Km North of us,
they got 30 to 50 cm of snow fall in the last 24 hours.
But maybe we still get some later this day, because the
small low pressure area causing all of this snow fall is
drifting to the South a little.
Later during the day it started to snow again. At first
the snow did not stay on the ground, but I guess that by
midnight there was at least an inch of fresh snow.
This evening, I explained to Annabel
what a Latin Square is. First I let her make one of size three.
Then when she understood it, I asked her to complete one of size
nine, where I already had filled in some random squares. I told
her that it was difficult, but she still wanted to try it.
Last week, I read how Carla P. Gomes had come up with some clever idea how to
solve these. She has a nice
demo to explain it. I immediately had to think about
the Eternity Puzzle and how it was solved. I think that
the general approach to solving this kind of puzzles is
to choose that next step that will leave as many possible
next steps open. In that way your chance that you have are
making a "wrong" choice is minimized. (See also my page on
Discrete Piece Fitting Puzzles.)
When I looked out of the window every thing was beautifully white
with snow. All the trees and plants were
covered with a layer of snow and the ground was completely covered.
This morning, our outside thermometer showed -6.1 degrees Celsius.
In some other parts in the Netherlands (about 100 Km to the North-West)
the temperature dropped till -20.5 degrees Celsius. This is the coldest
day in March every recorded in the Netherlands. The drop in temperature
is caused by a combination of a clear sky, the absence of wind, and a
fresh layer of snow.
Solution to the Latin Square
Today, I spend some time to write a progam
to find a solution to the Latin Square puzzle that I gave to
Annabel last Wednesday.
This evening, she said she was going to find the solution within one
hour. Less than a quarter of an hour later, she found the solution
7 6 3 2 9 8 5 1 4
6 9 7 5 4 1 3 2 8
3 4 2 7 8 6 9 5 1
9 8 1 6 5 4 2 7 3
4 2 6 1 3 5 8 9 7
8 5 4 3 1 2 7 6 9
2 1 8 4 7 9 6 3 5
5 7 9 8 2 3 1 4 6
1 3 5 9 6 7 4 8 2
The red numbers are the number that I had filled in at random.
Just a little later, I found some obvious improvement for my program.
When I implemented it, the program
found a solution without performing any back-tracking. The first
solution it found was:
8 4 2 9 5 7 3 6 1
6 7 3 5 9 8 1 2 4
3 5 1 2 4 6 7 9 8
7 9 6 8 3 1 2 4 5
4 2 8 1 7 3 9 5 6
9 6 5 3 1 2 4 8 7
2 1 7 4 8 5 6 3 9
5 3 4 7 6 9 8 1 2
1 8 9 6 2 4 5 7 3
Snow again and curly kail
Around eight o'clock in the morning, it was 4.2 degrees Celsius below zero.
Also in the car it was very cold, and I decided to put on my gloves.
There are still some patches of snow left from the snow that fell in the
past week. Around noon it was about one degree above zero. Later in the
afternoon it started to snow, but because it was
already above zero, the snow immediately disappeared when it fell on the
Around three o'clock I decided to prepair the curly kail hotchpotch, with the idea that I would have some time
left before dinner. Pealing the potatoes was not so easy. But then I
discovered that the quality of the curly kail was not particularly good.
It had a lot of sand a brown leaves and there where it had been cut, it
had turn brown. Cleaning it, took a lot of time. I guess I would have
been better of if I had bought the more expensive curly kail from the
supermarket instead of going for the cheap curly kail from the open
air market, especially this late in the season. I did end up watching
some television but that was only because Li-Xia
gave a hand.
Software patents endorsed by European commission
It seems that the council
presidency adopts Software Patent Agreement against Council's rules.
This means that EU ministers endorse patent law that support software patents, although
the European parliament and many national parliaments have protested against
this. It seems that today is really a black day for democracy in Europe. We
will see what will happen at the second reading at the European parliament.
It looks like we now live in the Banana Republic
The program that I wrote last Saturday for solving Latin
Squares does generate many double solutions. Today, I discovered a simple
adaptation that only generates unique solutions. This version of the progam finds the first 100,000 solutions and
prints them one on each line, using one character per square.
I am thinking about implementing an Exact Cover algoritm using the same
heuristic. I am thinking about making use of dancing links. It is very easy to see that Latin Squares can be
mapped to Exact Cover problems, once you realize that a Latin Square
can be transformed into a binary cube, where the value placed in
each square is seen as number of the bit that is set in the z-axe.
For each direction of the cube there should be exactly one bit set
in each "square". So an Latin Square of size n (with no additional
restrictions), can be transformed into a exact cover problem with
3n2 positions and n3 vectors. This also shows
that each Latin Square can be transformed into 23 equvalent Latin
Squares, some of which may be the same as the original.
Three games against Ton
This evening, I played three games of Go against
Ton. The first game, Ton was given an eight stone handicap. And besides
one small correction at the end of the game, I won the game. With the
second game, where he got a seven stone handicap, I gave up after about
twenty moves, because I lost a whole corner. We decided to play another
game just for the fun, where he was given an eight stone handicap again.
I played this game very intuitively, meaning that I did not really spend
time to think about the consequences of my moves. In the beginning we
played a lot of territorium exchanges. I felt I was losing. Then somewhere
in the middle game, I missed an easy way to save a large black group of
mine, because I did not see a possibility for a cut. I did not even see
it when Rudy remarked that it was there. Because Ton had finished his
beer, he gave up. He remarked that I was slowly getting stronger and that
it would be possible that I could jump several ranks in the coming year.
Two weeks ago, Annabel did some IQ test (I
guess WISC-R), and last week she did a dyslexy test. Today, the results
arrived in the form of a letter. According to the test, her average IQ
is 113, better than average, but not really exceptional. But according
to the test her performance (non-verbal) IQ is 122 and her verbal IQ is
101. And that is quite substantial imbalance, especially for a girl,
because for girls the verbal IQ is usually higher than the performance
IQ. (Actually, this is exactly as I had predicted. Yesterday evening,
I told Li-Xia that the result would say that
her performance IQ is 120 and her verbal IQ is 95.) She also scored
positive on the dyslexy test. One can ask if this an aquired form of
dyslexy due to the imbalance. Although one should always be skeptical
with respect to the outcome of an intelligence test, her IQ profile
is rather rare. In case of an imbalance, which is defined as a difference
of more than 12 points, it is only in one out of eight cases that the
non-verbal IQ is higher than the verbal IQ.
Snow rain and curly kail
Today, I noticed some rather big snowflake
falling from the sky, but when I looked outside I saw it was also raining.
A strange combination rain and snow at the same time. When in
the afternoon, I went into the city, it happened again: snow
and rain at the same time. That is when I decided to call this
"snow rain". When I was about to leave home from the city and
half of the shops had closed, I decided to look in a supermarket
to see it they had nay curly kail. To my surprise they did, and
it was much cheaper than last year. Within five minutes, I bought
all the ingredients for making curly kail hotchpotch.
It was already getting close to dinner time when I came home and
Li-Xia already started preparing
dinner, when Annabel begged that I
would make the hotchpotch. She did convinced me, and I ended up
preparing the hotchpotch. This time it went much faster then
last Sunday because I did not have to wash the
curly kail again.
Knowing the time
When I came home, I heard that the teacher of Andy
had phoned Li-Xia to ask her if she could
come to catch him, because he was too ill. Andy had been a little
bit ill in the past days. He had some fever and has been coughing
a lot. He might also suffer from a ear infection as part of the deal.
When I asked Andy when he had come home, he immediately said "Half een"
(Dutch for half past twelve). And to my astonishment, that was a quite
Saddlebag for bike
Today, I lost the saddlebag I used for my bike. It is a cotton saddlebag
that I used to take off when I went inside. I must have forgotten to tie
it properly and lost it because I was in such a hurry to go to a meeting
with the teacher of Annabel and someone else about the test that Annabel
had with respect to her being dyslectic. I only discovered that it was
lost when I arrived at the school. I biked back a little bit and tears
came in to my eyes with the idea that it might be lost for good. I really
like this bag, because it was simply elegant. I returned because I had to
attend the meeting. At the school I phoned to my office to ask if I might
have simply forgotten. That was not the case. After the meeting, I biked
back to my office, but did not find it along the road. Also my hope that
I might have forgotten to put it on in the bike parking near the office
turned out to be idle. I am afraid that I will never find a bag like it
again. The bag also contained my Vision Poncho.
I will have to buy a new one.
This weekend both Annabel and Andy are away for two nights. Annabel is staying with a friend in
Hengelo, and Andy went to the weekend care for the second time. (The first
time was on the weekend from Friday, 18
till Sunday, 20 Februari.) Today, we
took it very quiet with getting up. Around eleven we went into the city.
We had thought about watching the movie "Ray" about Ray Charles. But then
as the time was coming closer, we were a little doubtful. When we finally
decided to go, we were a little late and missed the first ten minutes of
the movie. This is the second time Li-Xia and I went to see a movie with the two of us. (The first time was on February 11, 2004 when we went to see "Lord of the Rings: The
Return of the King".) We enjoyed the movie. But it is not a movie that I
would have missed seeing on the big screen. I found the end of the movie
a little chaotic. Afterwards we had some doner kebap (lamb meat) and falafel
at Camel restaurant. We were both tired and went to bed around half past nine.
Pruning the willow
Today, it was a very warm day for the time of the year.
During dinner, I suggested that I would start with the
pruning of our willow in the back garden. It is
two and half year ago that
we did it for the last time. When I started, I noticed
it was very easy to off most of the branches. I also
just a saw for some of the thicker branches. In less
than two hours I pruned the whole tree and we were able
to clear most of the rubbish. We stopped when it started
Annabel and I went to Go club to
play Go. We were the first ones to arrive.
Annabel played against Marcel on a 13x13 board. They played three
games. The first two (where Marcel had a nine and eight stone handicap)
games she won. The last (where Marcel had a seven stone handicap) she
lost, because she made some mistake. I played against Rudi. He got
a nine stone handicap. In the early part of the middle game, I made
a mistake, and gave away a group. Still, I only lost with about 25
points, which is not bad, if you realize that he is a 5 Dan player.
This months interesting links
February 2005 |
April 2005 |