Why am I not able to run this code?

Question

Deepa Maheshvare 2021-2-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/748697-why-am-i-not-able-to-run-this-code

评论： Walter Roberson 2021-2-19

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', 1, 'thresh', 1e-8, 'fac', []);
J = odenumjac(fun,{0 x0}, f0, joptions); 
sparsity_pattern = sparse(J~=0.);
options = odeset('Stats', 'on', 'JPattern', sparsity_pattern);
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(1,1) = 0;     
f(2:9,1) = mat1*x + mat2*x;
f(10,1) = 2*(x(end-1) - x(end));
end

I've defined the `options` for `odenumjac` and it still throws the error

Not enough input arguments.

Am I missing something?

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Answer 1

KALYAN ACHARJYA 2021-2-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/748697-why-am-i-not-able-to-run-this-code#answer_626337

在 MATLAB Online 中打开

Here

J = odenumjac(fun,{0 x0}, f0, joptions); 
^..............^ function without input arguments 

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Deepa Maheshvare 2021-2-18

在 MATLAB Online 中打开

@Walter Roberson

Thanks so much. That helps!

Unfortunately, I still couldn't compute the sparsity pattern successfullly.

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', 1, 'thresh', 1e-8, 'fac', []);
J = odenumjac(@fun,{0 x0}, f0, joptions); 
sparsity_pattern = sparse(J~=0.);
options = odeset('Stats', 'on', 'JPattern', sparsity_pattern);
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
fprintf('size of x: %d %d\n', size(x))
f(1,1) = 0;
f(2:9,1) = mat1*x + mat2*x;
f(10,1) = 2*(x(end-1) - x(end));
end

The above is the updated code and following issue occurs

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 Untitled>fun (line 47)
f(2:9,1) = mat1*x + mat2*x;
Error in odenumjac (line 143)
    Fdel = feval(F,Fargs_expanded{:});
Error in Untitled (line 31)
J = odenumjac(@fun,{0 x0}, f0, joptions);
 

I see that the size of `x` changes in the second iteration.

>> test
size of x: 10 1
size of x: 10 10

I'm not sure why this happens. Suggestions on how this issue can be fixed will be of great help.

KALYAN ACHARJYA 2021-2-19

编辑：KALYAN ACHARJYA 2021-2-19

在 MATLAB Online 中打开

For this issue

Error in Untitled>fun (line 47)
f(2:9,1) = mat1*x + mat2*x;

Once I tried to reproduce the error with a little modification to the function file, I could not find any such issue. Note that here I only partially executed the main code upto the following line

f0 = fun(0, x0);

Function file: Input t is not used within the function

function f = fun(~,x)
global mat1 mat2
f(1,1) = 0;     
f(2:9,1) = mat1*x + mat2*x;
f(10,1) = 2*(x(end-1) - x(end));
end

Walter Roberson 2021-2-19

在 MATLAB Online 中打开

joptions = struct('diffvar', 2, 'vectvars', 1, 'thresh', 1e-8, 'fac', []);

That 'vectvars', 1 option says that your function is vectorized over the first variable, t,

%   ODENUMJAC takes advantage of vectorization, i.e., when several values F 
%   can be obtained with one function evaluation. Set OPTIONS.VECTVAR 
%   to the indices of vectorized arguments: VECTVAR = [2] indicates that 
%   F(t,[x1 y2 ...]) returns [F(t,x1) F(t,x2) ...], while VECTVAR = [1,2] 
%   indicates that F([t1 t2 ...],[x1 x2 ...]) returns [F(t1,x1) F(t2,x2) ...]. 

So you have declared that it an pass in multiple t values and the function will return a result for each of the t values -- but your code does not in fact handle that situation.

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