# matlab coder report Size mismatch (size [0 x 0] ~= size [1 x 2])

조회 수: 50 (최근 30일)
zhou caiwei 2022년 8월 15일
댓글: Walter Roberson 2023년 2월 13일
I tried to use matlab coder to convert my matlab file into C\C++ source file. In my *.m file,I defined a dynamic array:
...
coord_list = [];
I_list = [];
...
for i=1:n
....
coordinate = yy;
I = zz;
coord_list = [coord_list;coordinate];
I_list = [I_list;I]
end
The error occurs like:
??? Size mismatch (size [0 x 0] ~= size [1 x 2]).
The size to the left is the size of the left-hand side of the assignment.
How could I fix this bug? how should I modify my matlab code so that It meets the requirements of C\C++ style for matlab-coder?
##### 댓글 수: 1이전 댓글 -1개 표시이전 댓글 -1개 숨기기
Chiluveru 2023년 2월 13일
hi Raghu,
I am alsp facing same issue like the error below:
Size mismatch (size [1 x 0] ~= size [16 x 0]).
need your help for solving it

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### 채택된 답변

Chunru 2022년 8월 15일
...
coord_list = zeros(n, m1); % m1 is the length of yy below
I_list = zeros(n, m2); % m2 is the lenght of zz
...
for i=1:n
....
coordinate = yy;
I = zz;
coord_list(i, :) = coordinate;
I_list(i, :) = I;
end
##### 댓글 수: 14이전 댓글 12개 표시이전 댓글 12개 숨기기
Bruno Luong 2022년 8월 17일
편집: Bruno Luong 2022년 8월 17일
Your code is too long for me to look in detail. I notice that the code is not even optimized (growing array, call function in the loop, some common calculation is repeated, some constant quantity is computed inside the loop, etc...)
My recommendation is working on your matlab code before feed it to the coder.
zhou caiwei 2022년 8월 18일
you are right, I think I should optimize my code.Is there any reference materials?

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### 추가 답변 (1개)

Raghu Boggavarapu 2022년 8월 25일
Hi,
MATLAB Coder supports growing an array only by concatenation, growing an array by index is not supported. Please see: https://in.mathworks.com/help/coder/ug/limitations-with-variable-size-support-for-code-generation.html
If you wish to assign varying sized arrays to same variable, you can use coder.varize .
Also if you would like to optimize the MEX runtime, you can try disabling IntegrityChecks and ResponsivenessChecks in the MEX coder config.
##### 댓글 수: 3이전 댓글 1개 표시이전 댓글 1개 숨기기
Chiluveru 2023년 2월 13일
need help to solve the above error
Walter Roberson 2023년 2월 13일
You are assigning an empty array with 16 rows to a variable that was first assigned an empty array with one row.
When you use MATLAB Function Blocks in Simulink, then unless you use coder.varsize then the first assignment to a variable sets the limits on how large the variable is. This is different from regular MATLAB as regular MATLAB adjusts sizes as needed.

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