What's going wrong in the vectorization of my ode function?

Hi All,

I'm trying to setting `vectorization` = 'on' in the ode settings and I clearly don't understand what's going wrong

global mat1 mat2
mat1=[ 
       1    -2     1     0     0     0     0     0     0     0;
       0     1    -2     1     0     0     0     0     0     0;
       0     0     1    -2     1     0     0     0     0     0;
       0     0     0     1    -2     1     0     0     0     0;
       0     0     0     0     1    -2     1     0     0     0;
       0     0     0     0     0     1    -2     1     0     0;
       0     0     0     0     0     0     1    -2     1     0;
       0     0     0     0     0     0     0     1    -2     1;
       ];

mat2 = [
        1    -1     0     0     0     0     0     0     0     0;
        0     1    -1     0     0     0     0     0     0     0;
        0     0     1    -1     0     0     0     0     0     0;
        0     0     0     1    -1     0     0     0     0     0;
        0     0     0     0     1    -1     0     0     0     0;
        0     0     0     0     0     1    -1     0     0     0;
        0     0     0     0     0     0     1    -1     0     0;
        0     0     0     0     0     0     0     1    -1     0;
        ];



x0 = [1 0 0 0 0 0 0 0 0 0]';
tspan = 0:0.01:5;

f0 = fun(0, x0);
joptions = struct('diffvar', 2, 'vectvars', [], 'thresh', 1e-8, 'fac', []);
J = odenumjac(@fun,{0 x0}, f0, joptions); 
sparsity_pattern = sparse(J~=0.);
options = odeset('Stats', 'on', 'JPattern', sparsity_pattern, 'Vectorized', 'on');

ttic = tic();
[t, sol]  =  ode15s(@(t,x) fun(t,x), tspan , x0, options);
ttoc = toc(ttic)
fprintf('runtime %f seconds ...\n', ttoc)
plot(t, sol)

function f = fun(t,x)
global mat1 mat2
% f = zeros('like', x)
% size(f)
f(1,:) = 0;
f(2:9,:) = mat1*x + mat2*x;
f(10,:) = 2*(x(end-1) - x(end));
% df = [f(1, :); f(2:9, :); f(10, :)];
end

I've tried to vectorize f in fun and also set vectvars=2 to vectorize the jacobian calculation. However, there is a problem again when vectvars = 2 in joptions and/or 'Vectorized', 'on' in options defined for ode15s.

Unable to perform assignment because the size of the left side is 8-by-1 and the size of the right side is 8-by-10.

Error in cse_11_5_20>fun (line 44)
f(2:9,:) = mat1*x + mat2*x;

Error in odenumjac (line 143)
    Fdel = feval(F,Fargs_expanded{:});

Error in cse_11_5_20 (line 31)
J = odenumjac(@fun,{0 x0}, f0, joptions);

Suggestions on how to fix this error will be of great help. Could someone please have a look ?

Answer 1

[Walter Roberson]

Put back the

% f = zeros('like', x);

[Deepa Maheshvare]

f = zeros(size(x), 'like', x) ;

This helped! thank you . f = zeros('like', x); didn't work for me.