@sdeverywhere/cli

This package contains the sde command line interface for the SDEverywhere suite of tools.

SDEverywhere can be used to translate System Dynamics models from Vensim to C and WebAssembly.

For more details on the full suite of tools and libraries provided in SDEverywhere, refer to the top-level README in the SDEverywhere repository.

For instructions on using the sde command line tool provided in this package, refer to the "Usage" section below.

Quick Start

The best way to get started with SDEverywhere is to follow the Quick Start instructions. If you follow those instructions, the @sdeverywhere/cli package and sde tool will be added to your project automatically, in which case you can skip the next section and jump straight to the "Usage" section below.

Install

If you are building a JavaScript-based library or application, it is recommended that you install the cli package locally (in the devDependencies section of your package.json file). This allows you to use a version of the cli package that is specific to your project:

npm install --save-dev @sdeverywhere/cli

If you are using SDEverywhere only to generate C code (using the more advanced sde commands listed below), then it is acceptable to install the package "globally":

npm install -g @sdeverywhere/cli

Usage

If you installed the cli package globally (see "Install" section above), you can run the sde command directly.

If you installed the cli package locally (i.e., you followed the "Quick Start" instructions and/or installed it as a dev dependency in your package.json), you can run the sde command via npx, for example:

npx sde <args>

Basic commands

Note: A string surrounded by curly braces {like this} indicates a placeholder that you should fill in with the appropriate value.

Use sde -h to see a list of all commands.

Use sde {command} to see options for a command.

It is usually easiest to run these commands from the directory where the .mdl file is located. The {model} placeholder can be the model filename, for instance arrays.mdl, or simply the model name arrays.

If you are not running from the model directory, you can give a full pathname to locate the .mdl file anywhere on the system.

By default, SDEverywhere will create a build directory in your model directory to hold the generated code and the compiled model. If you run the model, it will also create an output directory by default. You can specify other directories with command options.

Generate C code that outputs all variables with no inputs

sde generate --genc {model}

Generate C code that uses a specified set of inputs and outputs

sde generate --genc --spec {model}_spec.json {model}

Start a local development builder/server

The sde dev command is great for local development of a web application. It will start a builder process that rebuilds your app and runs QA checks against your model any time you save changes to your mdl file. You can leave the builder running while developing your model in Vensim. The app and model-check tabs in your browser will refresh automatically whenever you save changes in Vensim or make edits to your application code.

See examples/hello-world for a simple example of an sde.config.js file. You can also follow the Quick Start instructions for examples/sir, which will generate a more complete example of an sde.config.js file.

sde dev [--config sde.config.js] [--verbose]

Generate a JS bundle that can be deployed on a web server

After using the sde dev command described above, you can use sde bundle to generate a production-ready version of your web application that can be deployed on any web server.

sde bundle [--config sde.config.js] [--verbose]

Advanced commands

List a model's variables

sde generate --list {model}

Preprocess a model to remove macros and tabbed arrays

NOTE: For most users it is not necessary to run the preprocessor manually because the transpiler runs the preprocessor automatically prior to parsing.

sde generate --preprocess {model}

Compile the C code into an executable in the build directory

sde compile {model}

Run the executable and capture output into a text file in the output directory

sde exec {model} {arguments}

Convert the SDEverywhere output file to a DAT file in the output directory

sde log --dat output/{model}.txt

Compare a previously exported Vensim DAT file to SDEverywhere output

sde compare {model}.dat output/{model}.dat

Generate C code and compile it in the build directory

sde build {model}

Build C code and run the model

sde run {model}

Run the model and compare its output to a previously exported Vensim DAT file

sde test {model}

Delete the build and output directories

sde clean {model}

Print variable dependencies

sde causes {model} {C variable name}

Convert variable names to C format

sde names {model} {Vensim names file}

Print the SDEverywhere home directory

sde which

Configuration files

NOTE: The following sections refer to "model specification files" (or "spec files" as a shorthand). These JSON spec files are generally used by the lower-level sde commands, such as sde generate. We are gradually adding support for a more flexible configuration file format (sde.config.js) that works with newer commands such as sde dev and sde bundle. We hope to unify these configuration file formats soon to eliminate any confusion about which file format can be used with which command (see related issue #327).

Specify input and output variables

Most applications do not require all variables in the output. And we usually want to designate some constant variables as inputs. In SDEverywhere, this is done with a model specification JSON file. The conventional name is {model}_spec.json.

First, create a model specification file that gives the Vensim names of input and output variables of interest. Be sure to include Time first among the output variables.

{
  "inputVarNames": ["Reference predators", "Reference prey"],
  "outputVarNames": ["Time", "Predators Y", "Prey X"]
}

Specify external data sources

Add a directData section to the spec file to have SDEverywhere read data from an Excel file into lookups with a variable name prefix. There is an example in the directdata sample model.

"directData": {
  "?data": "data.xlsx"
}

Generating, compiling, running, and testing the C code

To generate C code using the --spec argument, enter the following command:

sde generate --genc --spec {model}_spec.json {model}

SDE allows for validation against Vensim output. Before running the C file, it is useful to generate the Vensim data so you can ensure the C code is valid and reproduces the same results as Vensim. To make the Vensim output, run the model in 64-bit Vensim and export the run in DAT format to the {model}.dat file in the model directory.

The sde test command generates baseline C code that outputs all variables with no inputs. It then compiles the C code and runs it. The output is captured and converted into DAT format in the output/{model}.dat file. This is compared to Vensim run exported to a {model}.dat file in the model directory. All values that differ by a factor of 1e-5 or more are listed with the variance.

sde test {model}

Setting inputs

SDEverywhere generates code that runs the model using the constants defined in the model. To explore model behavior, the user changes the values of constants we call "input variables" and runs the model again.

There is a setInputs implementation in the generated code that gets called at initialization. It takes a string with serialized input values and sets variable values from it. The serialization format depends on the needs of your application. You can replace setInputs if you want to use a different serialization form. The input variables are listed in the inputVars section of the spec file. Look at the arrays model for an example.

The generated format minimizes the amount of data on the wire for web applications. It parses index-value pairs sent in a compact format that looks like this: 0:3.14 6:42. That is, the values are separated by spaces, and each pair has an index number, a colon, and a floating point number.

The zero-based index maps into a static array of input variable pointers held in the function. These are used to set the value directly into the static double variable in the generated code.

License

SDEverywhere is distributed under the MIT license. See LICENSE for more details.