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How I can optimize my code for a stack construct?

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Nazar Adamchuk
Nazar Adamchuk on 19 Apr 2021 at 14:46
Commented: Rik on 19 Apr 2021 at 15:35
In reality I have nine variables with scalar values. For them, I have built a stack construct (last in first out) with following logic: push (only for three variabled from nine, as an example)
stack(end+1:end+3) = [value1, value2, value3];
read and pop is
value3 = stack(end); stack = [];
value2 = stack(end); stack = [];
value1 = stack(end); stack = [];
In my script I call these code lines over 8 million time each and that is why I wish the time could be less. Can you help me to optimize the code lines and decrease the speed?

Answers (1)

Rik
Rik on 19 Apr 2021 at 14:51
Dynamically growing a variable is generally slow, because Matlab needs to copy the entire array.
You could pre-allocate a stack and use a counter to keep track of the position in the stack.
  2 Comments
Rik
Rik on 19 Apr 2021 at 15:35
Matlab is copying the array for you: if you add an element to a vector Matlab will allocate a new block of memory, copy all the data (appending your new elements), and free the old memory blocks.
%these two operations are the exact same:
stack(end+1:end+3) = [value1, value2, value3];
stack = [stack, value1, value2, value3];

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