How I can optimize my code for a stack construct?

1 次查看（过去 30 天）
Nazar Adamchuk
Nazar Adamchuk 2021-4-19
评论： Rik 2021-4-19
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?

请先登录，再回答此问题。

回答（1 个）

Rik
Rik 2021-4-19
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 个评论
Nazar Adamchuk
Nazar Adamchuk 2021-4-19
I am not copying the array, I am appending the elements to the array. That would be copying:
stack = [stack value1 value2 value3]
Rik
Rik 2021-4-19
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];

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by