Using the C Math Library

Example Without Automated Memory Management

The function Explicit_Mem_Example() performs the same calculations as Automated_Mem_Example() in the previous example. Compare the use of temporary variables, nonnested calls to the MATLAB C Math Library functions, and calls to mxDestroyArray(). It contains twenty-six lines of code compared to Automated_Mem_Example()'s nine lines.

Note    You can still code to this interface. The MATLAB C Math Library continues to support it. However, you cannot call Explicit_Mem_Example() from a function that uses automated memory management. The routine that calls Explicit_Mem_Example(), whether it is main() or another function, cannot include calls to mlfEnterNewContext() and mlfRestorePreviousContext(). If automated memory management were in effect, the calls to the library functions in Explicit_Mem_Example() could unexpectedly delete the temporary arrays passed to them as input arguments.

mxArray *Explicit_Mem_Example(mxArray **z_out, mxArray *x_in,
                    mxArray *y_in)
{
    mxArray *result_local, *q_local;
    mxArray *temp1, *temp2, *temp3;

    /* In MATLAB: r = sqrt(sin(x) + cos(x)) */
    temp1 = mlfSin(x_in);
    temp2 = mlfCos(y_in);
    temp3 = mlfPlus(temp1, temp2);
    result_local = mlfSqrt(temp3);

    mxDestroyArray(temp1);
    mxDestroyArray(temp2);
    mxDestroyArray(temp3);

    /* In MATLAB: q = sqrt(cos(y) - sin(y)) */
    temp1 = mlfCos(y_in);
    temp2 = mlfSin(y_in);
    temp3 = mlfMinus(temp1, temp2);
    q_local = mlfSqrt(temp3);

    mxDestroyArray(temp1);
    mxDestroyArray(temp2);
    mxDestroyArray(temp3);

    /* In MATLAB: z = q * r - q^3 */
    temp1 = mlfScalar(3);
    temp2 = mlfPower(q_local, temp1);
    temp3 = mlfTimes(q_local, result_local);
    *z_out = mlfMinus(temp3, temp2);

    mxDestroyArray(temp1);
    mxDestroyArray(temp2);
    mxDestroyArray(temp3);

    mxDestroyArray(q_local);
  
    return result_local;
}

Example - Managing Array Memory (ex2.c)

Restrictions