A Sudoku Solver in a few Lines of Code – Or the Power of Recursive Programming

In this post I want to demonstrate the power of recursive programming by programming a sudoku solver in Python. The complete sourcecode can also be downloaded here. Although I like solving Sudokus by hand, I’m far away from being a professional Sudoku solver. Usually I get the medium-ones solved, however, since I always want to… Read more A Sudoku Solver in a few Lines of Code – Or the Power of Recursive Programming

Fun with Mandelbrot

I’ve always been intrigued by the Mandelbrot set and the nice images one can render with just that simple recursive formula z=z2 + c. Back in the eighties I rendered images in 320×200 pixels on my Commodore 64, then on my Amiga 500, later on a Macintosh and finally on my subsequent PCs. Where I… Read more Fun with Mandelbrot

Switch Github Repository from https to ssh

Since github.com is about to disallow basic authentication using login and password over http/https connections, you should switch to connect via ssh providing a public ssh-key together with a passphrase. In this post I describe the steps necessary when using git for windows, however the steps are probably more or less identical if you’re running… Read more Switch Github Repository from https to ssh

Open Windows Explorer from shell and vice-versa

If at work you “have” to work with windows clients and are using linux shell-like tools like git, you probably know this problem: You want to open a shell from the Windows File Explorer, then do some actions, change directories and then again open a Windows File Explorer from the shell at your current location.… Read more Open Windows Explorer from shell and vice-versa

Graph Notation

There are different types of graph notations. Here I’d like to present a nice and compact way in the form of a Vertex Lists and Edge Lists, which I came across during my studies at the MSE in Zurich. [Note: All graph images shown in this post have been taken from graphical representations of graphs… Read more Graph Notation

Solve TSP Instance using Google OR-Tools

If you happen to have to solve TSPs or some special type of VRPs – i.e. capacitated or with timewindows and other constraints – you might want to have a look at Google OR-Tools. The library contains a wide variety of heuristics for different problems primarly based on google’s excellent constraint programming solver. The library… Read more Solve TSP Instance using Google OR-Tools

Calculate an MST with Ant Colony Optimization in Python

Ant Colony Optimization is an old but still often applied construction heuristic to develop solutions using nature inspired behavior. The heuristic mimics the behavior of ants when finding shortest paths to between their nests and some kind of attraction, i.e. a food-source. The main idea are the pheromone trails, which ants leave behind, when travelling… Read more Calculate an MST with Ant Colony Optimization in Python

Tabu Search in R

Here I’ll show you a way, how to do Tabu Search with Steepest Descent with best improvement in R. Tabu Search is a local improvement heuristic used to improve existing solutions. Such heuristics are also called local search heuristics. How does Local Search work? Local search can be described in words as follows: Take initial… Read more Tabu Search in R

RStudio Console hanging?

If you should ever experience a non responsive RConsole within RStudio on windows, try this: Terminate RStudioMake sure, RStudio Go to this folder: C:\Users\{your_user_abbreviation}\AppData\Local Delete this folder:RStudio-Desktop Restart RStudio Now chances are high, that your console is again working fine. What I had observed Suddenly, after having installed a new package in RStudio I wanted… Read more RStudio Console hanging?

Configure multiple Users for GUROBI Cloud

What is the Objective If you are a small to medium scale solution provider for optimization solutions and want to provide solutions using the world’s best solver, then you should go for GUROBI cloud, since prices are most attractive and management of multiple users is quite simple. You will have to pay something like –… Read more Configure multiple Users for GUROBI Cloud