DYNSYS

System Dynamics Toolkit

Modeling language

The Dynsys modeling language describes quantitative System Dynamics models using stocks, flows and parameters. The following tokens in the language are used to describe entitites in the model.

STOCK FLOW PARAMETER

Every entity has a unique description used as identifier. It is written within double-quotes like STOCK "Potential Adopters" 100. The token 100 sets the initial quantitiy of the stock to 100 units (Dynsys is as of writing a unit-less model).

Flows are edges between entities that may increase or decrease a stock. Their impact is described using the TO and FROM keywords together with the identifiers of a STOCK or PARAMETER. For example:

FLOW "New adopters" FROM "Potential adopters" TO "Adopters"

FLOWs and PARAMETERs may be influenced by another FLOW and/or PARAMETER. These influencing edges are described using indentation in a new line after the according entity. For example to describe a positive influence from "Potential adopters" to "Innovators" use the following notation:

PARAMETER "Innovators"
    positive FROM "Potential adopters"

Requirements

Get gcc for debian 9

$ sudo apt update
$ sudo apt install build-essential

OR

equivalent for macOS

$ export HOMEBREW_NO_ANALYTICS=1
$ brew update
$ brew upgrade
$ brew info gcc
$ brew install gcc
$ brew cleanup
$ gcc -v

Test for gcc and make

$ which gcc
$ gcc -v
$ which make
$ make -v

Compile and Execute

$ chmod +x compile-and-execute.sh
$ ./compile-and-execute.sh

Execute the binary

$ ./Dynsys

Contribute

Feel free to contribute by creating tickets and pull requests.

richardbrammer / DYNSYS