Indian Pacific, Wednesday 1st February 2006


The mobile displays Network Search and it is a moment of joy for me. It means the train is leaving modern world. Two days to go till Adelaide. The desert is yet to come.

The window shows giant wheat fields, getting more and more dry. The on board radio plays country music, the tune of the Indian Pacific: The Indian Pacific spans the land. Well, I'm not going all the way. I'll disembark in Adelaide, halfway after 2.666 kilometres.


Perth is behind me. It is a bit of a puzzling town for me. Perth is a bit similar to my town of birth: Rotterdam.

South Perth

South Perth is a different story. Of course these BBQ huts are perfect as SUMit side office. A bit of shade, tranquility, nice river view, a fine breeze and a table serving as office desk. I'll have to adjust my last weeks conclusion about Heirisson Island. South Perth's park does win my points.

Sudoku Solver

9 2 6 7
3 2
6 2 1 5
7 1
7 8 6 4
1 9
4 9 3 1
7 5
6 3 2 7
The paper has Sudoku puzzles. Solving a Sudoku puzzle resembles shift roster design. The Sudoku puzzles are difficult for me, not because of the logic, but because they stress my short term memory to much. I have no memory for numbers, so the whole bunch of them dance chaotically through my brain.

Constraint propagation
Every cell has a domain
of possible numbers.
A domain sized one
has a value
limiting other
A computer memory and a bit of constraint propagation come to the rescue. Constraint propagation is a roster design method, learned years ago in Malaysia. Constraint propagation makes Sudoku puzzles easy to solve.

So yes, South Perth is the place where rosters step aside for a moment. A few hours later the Sudoku Solver is working. No, it does not solve the whole Sudoku puzzle for you. But it does a fine job of doing the tedious administration for you, shows the possible values of each cell.

I know, it is a simple tool, not very advanced. But it does leave you something to puzzle. Newspaper Sudoku puzzles now take only a few minutes to solve. Just click to copy the numbers from the paper and see the solution coming in view.

Out of reach

In South Perth I could service customers in the evening, when office hours in the Netherlands just started. I won't make it tonight. My evening shift will start, but it will be a quiet one for sure, with the results of my work confined to the laptop for the moment, just as this story. There is no room for Internet in the desert's domain.

The train leaves the wheat fields. The uninhabited word starts. Network search, what a wonderful, relaxing text.

Till next nut,