Why does the same function generate different results when coder.extrinsic is ON or OFF?

In the attached file, there is a simulink block that:

• Calls a TestFunction directly
• Calls the TestFunction through a wrapper

at the end the result of the two function calls are compared.

If the following line:

coder.extrinsic('wrapper');

is commented, the two function calls give the same results. However, if that line is not commented very small differences arise.

Where do these difference come from? And more importantly, how can I get exactly the same result by having following line not commented?

coder.extrinsic('wrapper');

I have performed the test under Matlab 2013a 32bit and 2014a 32bit.

Answer 1

[Angelo Yeo]

This is because math kernel libraries for code-gen fmincon and MATLAB engine's are different. This is explained in the doc "fmincon".

https://www.mathworks.com/help/optim/ug/fmincon.html#refsect-extended-capabilities:~:text=Code%20generation%20targets%20do%20not%20use%20the%20same%20math%20kernel%20libraries%20as%20MATLAB%20solvers.%20Therefore%2C%20code%20generation%20solutions%20can%20vary%20from%20solver%20solutions%2C%20especially%20for%20poorly%20conditioned%20problems.