mldivide does not support sparse inputs for code generation

Hey

Is there any function which can be replaced with 'mldivide'.

Actually I am trying to make generate C code for 'regionfill' command. But I think because of 'mldivide' inside the regionfill, it is not generating C code.

How can Isolve this problem?

Answer 1

[Rik]

You can try making a copy of this function, and editing it, so you avoid the sparse function, as that is causing the problem here:

i=[1 2 1];j=[1 1 2];s=[3 2 1];

D_original_code=sparse(i,j,s);

D=zeros(max(i),max(j));
D(sub2ind(size(D),i,j))=s;

isequal(D,full(D_original_code))

The tricky thing is that the sparse function is there for a reason: it makes things more efficient. You only need to hope either method (using full or filling a zeros) will not decrease the efficiency so much that generating C code and running the compiled code is not useful anymore.

Last note: don't edit the actual Matlab function, but create a copy. That might mean you are no longer allowed to share your compiled function, as it contains code by the Mathworks.

[JAI PRAKASH]

I think it is not gonna be easy for me :(

[Rik]

I think we discovered why it uses a sparse array...

Now your job becomes much more difficult: re-implementing mldivide, looking through its code (or using third party solvers). What is that pcg line? You could try if that one supports sparse arrays.

[JAI PRAKASH]

pcg is an alternative to mldivide.

This pcg solves faster than mldivide but unfortunately does not supported by Matlab Coder.

So I think thats why regionfill is also not supported by matlab coder.