Coder - Create constant for specifying array size

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amin ya
amin ya on 15 Mar 2019
Edited: amin ya on 16 Mar 2019
How can I create a constant variable in MATLAB (and its results the generated C code), so I can use it later in my code to specify the size of variables.
In C, we usually do this:
const int arraySize = 5;
int array[arraySize];
When I write the following in the MATLAB, coder just repalces arraySize with the actual number which is 5:
arraySize=5;
array=zeros(1,arraySize); % zeros is just used for specifying size
(This array size may be repeated throughout the different functions and code many times, so global probably may be related to this)
I want to use static memory allocation as long as it is possible.

Answers (1)

Fangjun Jiang
Fangjun Jiang on 15 Mar 2019
Please refer to the document
Code Generation for Variable-Size Arrays
web(fullfile(docroot, 'simulink/ug/what-is-variable-size-data.html'))
Control Memory Allocation for Variable-Size Arrays in a MATLAB FunctionBlock
web(fullfile(docroot, 'ecoder/ug/control-memory-allocation-for-variable-size-arrays-in-a-matlab-function-block.html'))
  1 Comment
amin ya
amin ya on 16 Mar 2019
This is not useful.
I want to have an array that its size is not hardcoded via number all over the code. This may be related to constant folding which I can not disable!
I want to specify the size at the beginning of the code like how we do in C code using one of the followings:
constant int arraySize=5
or
#define arraysize 5
--------------------------------------------------------------------------------
For example the generated code for my This example, where a is defined as a global constant int8(5),
function A=coder()
global a
A=zeros(a,a);
end
is this, which you see 5 is used in the code instead of being defined in the beginning
#include <string.h>
#include "coder.h"
void coder(double A[5][5])
{
memset(&A[0][0], 0, sizeof(double) << 16);
}
--------------------------------------------------------------------------------
I tried using the following but it does not allow me to use a in MATLAB calculations:
a=coder.opaque('const int16','5');
A=zeros(a,a);

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