Target Language Compiler

Inlining Fortran (F-MEX) S-Functions

The capabilities of Fortran MEX S-functions can be fully inlined using a TLC block target file. With a simple F MEX S-function version of the ubiquitous "timestwo" function, this interface can be illustrated. Here is the sample Fortran S-function code:

• C
  C     FTIMESTWO.FOR
  C     $ Revision: 1.1$
  C
  C     A sample FORTRAN representation of a 
  C     timestwo S-function.
  C     Copyright 1990-2000 The MathWorks, Inc.
  C
  C=====================================================
  C     Function:  SIZES
  C       
  C     Abstract:
  C       Set the size vector.
  C
  C       SIZES returns a vector which determines model 
  C       characteristics.  This vector contains the 
  C       sizes of the state vector and other
  C       parameters. More precisely,
  C       SIZE(1)  number of continuous states
  C       SIZE(2)  number of discrete states
  C       SIZE(3)  number of outputs
  C       SIZE(4)  number of inputs
  C       SIZE(5)  number of discontinuous roots in 
  C                the system
  C       SIZE(6)  set to 1 if the system has direct 
  C                feedthrough of its inputs, 
  C                otherwise 0
  C
  C=====================================================
  C
        SUBROUTINE SIZES(SIZE)
  C     .. Array arguments ..
        INTEGER*4        SIZE(*)
  C     .. Parameters ..
        INTEGER*4       NSIZES
        PARAMETER       (NSIZES=6)
  
        SIZE(1) = 0
        SIZE(2) = 0
        SIZE(3) = 1
        SIZE(4) = 1
        SIZE(5) = 0
        SIZE(6) = 1
  
        RETURN
        END
  
  C
  C=====================================================
  C
  C     Function:  OUTPUT
  C
  C     Abstract:  
  C       Perform output calculations for continuous 
  C       signals.
  C
  C=====================================================
  C     .. Parameters ..
        SUBROUTINE OUTPUT(T, X, U, Y)
        REAL*8           T
        REAL*8           X(*), U(*), Y(*)
  
        Y(1) = U(1) * 2.0
  
        RETURN
        END
  
  C
  C=====================================================
  C
  C     Stubs for unused functions.
  C
  C=====================================================
  
        SUBROUTINE INITCOND(X0)
        REAL*8           X0(*)
  C --- Nothing to do.
        RETURN
        END
  
        SUBROUTINE DERIVS(T, X, U, DX)
        REAL*8           T, X(*), U(*), DX(*)
  C --- Nothing to do.
        RETURN
        END
  
        SUBROUTINE DSTATES(T, X, U, XNEW)
        REAL*8           T, X(*), U(*), XNEW(*)
  C --- Nothing to do.
        RETURN
        END
  
        SUBROUTINE DOUTPUT(T, X, U, Y)
        REAL*8           T, X(*), U(*), Y(*)
  C --- Nothing to do.
        RETURN
        END
        
        SUBROUTINE TSAMPL(T, X, U, TS, OFFSET)
        REAL*8           T,TS,OFFSET,X(*),U(*)
  C --- Nothing to do.
        RETURN
        END
        
        SUBROUTINE SINGUL(T, X, U, SING)
        REAL*8           T, X(*), U(*), SING(*)
  C --- Nothing to do.
        RETURN
        END
  

Copy the above code into file ftimestwo.for in a convenient working directory.

Putting this into an S-function block in a simple model will illustrate the interface for inlining the S-function. Once your Fortran MEX environment is set up, prepare the code for use by compiling the S-function in a working directory along with the file simulink.for from matlabroot/simulink/src/. This is done with the mex command at the MATLAB command prompt:

• mex -fortran ftimestwo.for simulink.for
  

And now reference this block from a simple Simulink model set with a fixed step solver and the grt target.

The TLC code needed to inline this block is a modified form of the now familiar timestwo.tlc. In your working directory, create a file named ftimestwo.tlc and put this code into it.

• %implements "ftimestwo" "C"
  
  %function Outputs(block, system) Output
    /* %<Type> Block: %<Name> */
    %%
    /* Multiply input by two */
    %assign rollVars = ["U", "Y"]
    %roll idx = RollRegions, lcv = RollThreshold, block, ... 
  "Roller", rollVars
      %<LibBlockOutputSignal(0, "", lcv, idx)> = \
      %<LibBlockInputSignal(0, "", lcv, idx)> * 2.0;
    %endroll
  %endfunction
  

Now you can generate code for the ftimestwo Fortran MEX S-function. The resulting code fragment specific to ftimestwo is

• /* S-Function Block: <Root>/F-MEX S-Function */
    /* Multiply input by two */
    rtB.F_MEX_S_Function = rtB.Gain * 2.0;
  

Inlining M-File S-Functions

TLC Coding Conventions