Fast FIFO Array/Other Datatype
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Matthew Mellor
on 14 Jun 2016
Edited: Andrew Ward
on 27 Nov 2018
I'm trying to plot something in real time using an FIFO array. I'm implementing the array using the advice someone else here gave me (thank you!) of the following sort:
array = {1,2,3,4};
array = array(2:end)
array{end+1} = 5
Unfortunately this is a bit too slow for what I'm trying to do :(. Could anyone suggest either an efficient FIFO array-like data structure? Or just a faster way?
2 Comments
Adam
on 14 Jun 2016
You could probably also use a containers.Map though I don't know what its speed would be like compared to your approach or Walter's answer which is probably faster since it uses a raw array without memory copying.
Accepted Answer
Walter Roberson
on 14 Jun 2016
array(1:end-1) = array(2:end);
array{end} = newvalue;
This avoids having to grow the array.
2 Comments
More Answers (1)
Andrew Ward
on 27 Nov 2018
Edited: Andrew Ward
on 27 Nov 2018
Nmax=50000;
A1=1:Nmax;
Ap=A1;
%%
%Method 1 concatenate array with element - Slow
tic
for i=1:Nmax
A1=[A1(2:end),Nmax+i];
end
toc
%%
%% Method 2 overwite ellemnts followed by a circular shift - Fastest -
% avoids taking a sub portion of the array
% which I think is costly, just replaces the value, 1,2,3,4
% becomes 5,2,3,4, so to get it in order you need to
% do the circular shift at the end.
tic
A2=1:Nmax;
for i=1:Nmax
ic=mod(i,Nmax+1);
A2(ic)=Nmax+i;
end
A2=circshift(A2,-i);
toc
sum(A2~=A1)
%% Method from above, still slow
A3=Ap;
tic
for i=1:Nmax
A3(1:end-1)=A3(2:end);
A3(end)=Nmax+i;
end
toc
sum(A3~=A1);
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