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

# Category: programming

## 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?

## Solve TSP using Pilot Method

This post shows a simple implementation using R to solve a given TSP (Traveling Salesperson Problem) instance using the Pilot Method. The whole R script can be accessed here on my gist. How does the Pilot Method work? The Pilot Method is a construction heuristic to build (i.e. initial) solutions. The method tries to avoid… Read more Solve TSP using Pilot Method

## Calling GUROBI from Matlab

In this post I’ll show you the steps you need to take, if you want to use the powerful GUROBI solver from Matlab in order to solve Mixed Integer Linear Programs. Install the GUROBI Solver Go to the Gurobi website, create an account and download the version applicable for your operating system here. Acquire and… Read more Calling GUROBI from Matlab

## Solve Optimization Tasks using GUROBI Cloud

What is the objective here? I will document the steps needed to setup Gurobi to solve a Linear Program in the cloud. For this example we will use a simple linear model and use Matlab to invoke the locally installed Gurobi solver, which in turn would forward it to a Gurobi Compute Server, which we… Read more Solve Optimization Tasks using GUROBI Cloud

## Run OSRM in Docker on Windows

After the OSRM routing service is no longer available on Windows we have a good reason to try to run it in a Docker container. However, there are some hurdles that have to be overcome in order to get your daemon up and running. SInce I’ve gone through this, I write down the necessary steps… Read more Run OSRM in Docker on Windows

## Set-Operations on data.frames

Have you been loooking for a nice way to determine differences of sets of dataframes in R? There is a very cool package, part of the tidyverse from Hadley Wickham. See here, how simple it is to perform this task in R, with dplyr installed: If you would like to preserve the information contained in… Read more Set-Operations on data.frames

## Change Local Library for R-Packages

You might have been wondering, that after having installed or updated your system to a new R version, the package installation Path within your RStudio still refers to your “old” location. In some situations, this might make sense. However, after changing to a completeley new version (main release number) of R, you might want to… Read more Change Local Library for R-Packages