MATLAB Programming

Techniques for Improving Performance
This statement preallocates a 100-by-100 matrix of int8 first by creating a
full matrix of doubles, and then converting each element to int8. Thiscosts
time and uses memory unnecessarily.
The next statement shows how to do this more efficiently:
A = zeros(100, 'int8');
Coding Loops in a MEX-File
If there are instances where you cannot vectorize and must use a for or
while loop, consider coding the loop in a MEX-file. In this way, the loop
executes much more quickly since the instructions in the loop do not have to
be interpreted each time they execute.
See “Introducing MEX-Files” in the External Interfaces documentation.
Assigning to Variables
For best performance, keep the following suggestions in mind when assigning
values to variables.
Changing a Variable’s Data Type or Dimension
Changing the data type or array shape of an existing variable slows MATLAB
down as it must take extra time to process this. When you need to store data
of a different type, it is advisable to create a new variable.
This code changes the type for X from double to char, which has a negative
impact on performance:
X = 23;
.
-- other code --
.
X = 'A';
.
-- other code --
% X changed from type double to char
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