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

조회 수: 3(최근 30일)
Deepa Maheshvare 2021년 2월 19일
댓글: Deepa Maheshvare 2021년 2월 19일
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 ?

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### 채택된 답변

Walter Roberson 2021년 2월 19일
Put back the
% f = zeros('like', x);
##### 댓글 수: 1표시숨기기 없음
Deepa Maheshvare 2021년 2월 19일
f = zeros(size(x), 'like', x) ;
This helped! thank you . f = zeros('like', x); didn't work for me.

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