How to define input types in Matlab Coder for a function that has a varying number of input?

Question

I have a function let's say sq_dist(). This function can be called like this sq_dist(a,b) or sq_dist(a). This function includes slow operations and thus I am trying to make a Mex version of it hoping that it will run faster. I am using the Matlab Coder GUI to do so. In order to define input types (in the define input screen) i use a function that calls sq_dist(a,b) and sq_dist(a) to automatically determine input. This gives me an error: Error determining type for input sq_dist:b. Index exceeds matrix dimensions. Here is my function:

n = 50; 
dim = 50; 
a = rand(n, dim);  
b = rand(n, dim); 

u = sq_dist(a, b); 
v = sq_dist(a);

So, since sq_dist can be called in different ways I am not sure how to define its input in the Coder.

If i manually set the input to double :inf x :inf for a and b the mex file is compiled but i get a runtime error: Function 'sq_dist' called with wrong number of arguments: expected 2, received 1.

4Oh4 · Accepted Answer · 2016-07-27 23:36:44Z

1

In short, you cannot do what you want to do (with current version 2016a) for the top-level function - this has to have a defined number of inputs and outputs. Even if you use the 'varargin' parameter in the function definition, MATLAB Coder will generate the function with a fixed number of inputs based on the example arguments you provide.

If you have a particular function that has a variable number of input arguments, you can put a wrapper function (with a fixed number of input arguments) around the outside, and make the wrapper the top-level function.

Rules here: http://uk.mathworks.com/help/simulink/ug/rules-for-using-variable-length-argument-lists-for-code-generation.html

answered Jul 27, 2016 at 23:36

4Oh4

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