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## Appendix A Dynamically Linked Functions

Octave has the possibility of including compiled code as dynamically linked extensions and then using these extensions as if they were part of Octave itself. Octave can call C++ code through its native oct-file interface or C code through its mex interface. It can also indirectly call functions written in any other language through a simple wrapper. The reasons to write code in a compiled language might be either to link to an existing piece of code and allow it to be used within Octave, or to allow improved performance for key pieces of code.

Before going further, you should first determine if you really need to use dynamically linked functions at all. Before proceeding with writing any dynamically linked function to improve performance you should address ask yourself

- Can I get the same functionality using the Octave scripting language only?
- Is it thoroughly optimized Octave code? Vectorization of Octave code, doesn't just make it concise, it generally significantly improves its performance. Above all, if loops must be used, make sure that the allocation of space for variables takes place outside the loops using an assignment to a matrix of the right size, or zeros.
- Does it make as much use as possible of existing built-in library routines? These are highly optimized and many do not carry the overhead of being interpreted.
- Does writing a dynamically linked function represent useful investment of your time, relative to staying in Octave?

Also, as oct- and mex-files are dynamically linked to Octave, they introduce the possibility of Octave crashing due to errors in the user code. For example a segmentation violation in the user's code will cause Octave to abort.