parfor slicing variables suggestions

I'm wondering what was the best way to split a big matrix (500000 x 1000) into 20 matrices of size 25000 x 1000. The aim is to use parfor to try to speed up the code

A and B have the same size

As you can see, I tried to split directly A and B but it gives me warning with broadcast variables (see commented part).

So I changed and the way i did it now, I'm loosing precious time to convert with mat2cell and cell2mat. It takes around 15% ot total computation time.

Do you have any suggestion ?

I did the following:

nbSlices=20;
SplitSize=size(S,1) / nbSlices * ones(nbSlices,1);
split_A=mat2cell(A,SplitSize,1000);
split_B=mat2cell(B,SplitSize,1000);
parfor ix=1:nbSlices
    %A2=A(ix*nbSlices-nbSlices+1:ix*nbSlices,:);
    %B2=B(ix*nbSlices-nbSlices+1:ix*nbSlices,:);
    Res(ix)=Compute(cell2mat(split_A(ix)),cell2mat(split_B(ix)))
end