This document describes a hack that I have used to implement SD/FAST in C++ and in MATLAB. The motivation behind this was to find a simple way to use different models, or copies of the same model at the same time. The MATLAB script reads the output of SD/FAST and creates several new files that contain the source for the C++ and MATLAB interfaces.

The Files

Download a copy of all the files needed to run SD/FAST++ on an SD/FAST model here: sdfastplus.zip (updated 7/15/2011)

Below is a description of all of the files associated with this script.

• SD/FAST Input File

  This is the standard model description file used by SD/FAST. The only requirement is that you DO NOT use a prefix.

• SD/FAST Output Files

  SD/FAST outputs 4 files:

  • information file (*_i) - gives you an overview of the model topology
  • dynamics file (*_d.c) - c code for dynamics calculations
  • simplified analysis routines (*_s.c) - c code for analysis, like integration
  • standard library file (sdlib.c) - common functions, like vector operations

  SD/FAST++ only uses the dynamics file. sdlib.c is the same for every model. I do not provide these files, you need to get them yourself.

• SD/FAST++ Files

  These are the files that are used in conjunction with SD/FAST++ to make the magic:

  • sdfastplus.m - the script that reads SD/FAST outputs and creates the SD/FAST++ files
  • template.h - a template for the class definitions
  • template.cpp - a template for the class implementations
  • make_template.m - a template for the mex make file
  • template_mex.cpp - a template for the mex interface file
  • sdlib.h - definitions for the common library functions
  • SDModel.h - an abstract base class for all models
  • SDModel_common.cpp - common functions that work across models, like forward dynamics
  • SDModel_common.h - definitions of the common functions
• SD/FAST++ Output Files

  There are several files that SD/FAST++ outputs:

  • model.h - the class definition file for the model object
  • model.cpp - copies of the dynamics functions, now member functions of the class
  • make_model.m - a make file that makes the mex interface
  • model_mex - a mex file that returns a pointer to a model object

Instructions

1. Installation
   1. Unzip the files from sdfastplus.zip to a directory
   2. Add this directory to your MATLAB path
2. Compiling a model
   1. Write a model description file - "model"
   2. Run SD/FAST - "sdfast -lc -ge model"
   3. Open MATLAB and run the script (make sure the sdfastplus directory is in the path) - "sdfastplus('model')"
   4. Run the model mex make file - "make_model"
3. An example matlab interface
   1. Create a matlab mex interface file (example: model_impulse.cpp - others are included in the zip file)
   2. Make sure you include "SDModel.h" and "SDModel_common.h"
   3. Compile the mex interface file - mex model_impulse.cpp [SDFAST++Dir]\SDModel.cpp [SDFAST++Dir]\SDModel_common.cpp [SDFAST++Dir]\sdlib.c -I[SDFAST++Dir]
   4. Create a model object and get the pointer - "m = model_mex;"
   5. Pass the pointer into your mex interface function - "x_new = model_impulse(m,x_0,body,force);"