How to force MATLAB Coder to not combine two functions into one?

I am using MATLAB Coder to generate C code which will have to be maintained (as C code), so I am looking for ways to improve the readability of the generated code. Consider the following test function:

function [result] = coder_test(a,b)
    x = my_mult(a,b);
    result = my_svd(x);
end

function [ U ] = my_svd( x )
    [U,~,~] = svd(x);
end

function [ x ] = my_mult(a,b)
    x = a*b;
end

where coder_test is the entry-point and the dimensions of a and b are 3x4 and 4x3 respectively. The generated code is:

   // snip about 650 lines of code defining the 3x3 SVD, called by eml_xgesvd below

   void coder_test(const double a[12], const double b[12], double result[9])
   {
     double b_a[9];
     int i0;
     int i1;
     int i2;
     double unusedU1[9];
     double s[3];
     for (i0 = 0; i0 < 3; i0++) {
       for (i1 = 0; i1 < 3; i1++) {
         b_a[i0 + 3 * i1] = 0.0;
         for (i2 = 0; i2 < 4; i2++) {
           b_a[i0 + 3 * i1] += a[i0 + 3 * i2] * b[i2 + (i1 << 2)];
         }
       }
     }

     eml_xgesvd(b_a, result, s, unusedU1);
   }

We can see here that in the generated code, the SVD is moved out of the main function coder_test (and into the function eml_xgesvd), presumably because it is in a separate function in the Matlab code. However, the code to multiply the matrices A and B is still in the function coder_test, even though I moved the multiply into a separate function my_mult in the Matlab code.

To improve readability I would like a way to ensure that in the generated code, the matrix multiply is actually in a separate function. In other words, I would like it to generate something like:

   // snip about 650 lines of code defining the 3x3 SVD, called by eml_xgesvd below

   void my_mult(const double a[12], const double b[12], double x[9])
   {
     for (i0 = 0; i0 < 3; i0++) {
       for (i1 = 0; i1 < 3; i1++) {
         b_a[i0 + 3 * i1] = 0.0;
         for (i2 = 0; i2 < 4; i2++) {
           b_a[i0 + 3 * i1] += a[i0 + 3 * i2] * b[i2 + (i1 << 2)];
         }
       }
     }
   }

   void coder_test(const double a[12], const double b[12], double result[9])
   {
     double b_a[9];
     int i0;
     int i1;
     int i2;
     double unusedU1[9];
     double s[3];

     my_mult(a,b,b_a);
     eml_xgesvd(b_a, result, s, unusedU1);
   }

Is there a way to get MATLAB Coder to do this, or is the only way to do this to manually change the generated code?

Answer 1

[Rick Rosson]

Insert the following line of code in any MATLAB a function that you want to have as a separate function in the generated C code:

   coder.inline('never');