# How to speed up my code?

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Benson Gou on 18 Jun 2021
Commented: Benson Gou on 21 Jun 2021
Dear All,
I found my code spent a lot of cpu time on the following functions:
1. intersect, took 20.11 seconds, called 232074 times in my code.
My code:
C = intersect(A,B); where A and B are two column arrays.
2. unique, took 8.845 seconds, called 251736 times in my code.
My code:
BadMeas = unique([A; red2(B)']); where A and B are two column arrays, red2 is another row array.
3. ismember, took 7.117 seconds, called 269278 times in my code.
My code:
if ismember(selectedBus, InjBus_moreZeroLines)
for i = 1 : m
do the calculation
end
end
4. setdiff, called 13103 times in my code.
My code:
red = setdiff([1:length(A)],B);
A is an array and B is an array formed by integers.
I am wondering if there are faster functions to replace the above ones. Thanks.
Benson
Benson Gou on 18 Jun 2021
Hi, dpb,
Thanks a lot for your reply. I will do as you suggested. You have a good weekend!
Benson

Jan on 19 Jun 2021
if ismember(selectedBus, InjBus_moreZeroLines)
ismember replies a vector, if the inputs are vectors. The if command requires a scalar condition. So I guess, this can be abbreviated. Maybe this is faster:
if any(selectedBus == InjBus_moreZeroLines)
In the line:
red = setdiff([1:length(A)],B)
the square brackets are a waste of time. [ ] is the concatenation operator, but here you concatenate the vector 1:length(A) with nothing.
Maybe this is more efficient:
red = true(size(A));
red(B) = false;
Then use red for logical indexing, instead of numerical indices.
I assume there are faster repalcements for the called functions, but without knowing what the inputs are and the context, it is not possible to suggest modifications.
Benson Gou on 21 Jun 2021
Hi, Jan,
Best regards,
Benson