to speed up 'for' loop

2012 8 1
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0 个投票

hello,
i have a loop with the following format:
for n = 1:length(x)
if ....
.....
elseif ....
.......
end
end
I suspect that it takes too long and my program is stuck. the length of 'x' currently 1200 cells and it might vary. How can I speed this up?
thanks,

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Oleg Komarov
Oleg Komarov 2012-8-1
编辑：Oleg Komarov 2012-8-1
You haven't posted the relevant info.
What are you specifically doing inside the loop, what type of inputs, size you have, have you preallocated?
W/o this info is hard to say.
Michael Adelman
Michael Adelman 2012-8-2
I check if the value is correct or not and according the value in the cell i decide how to update the cell. The update is: to add or Substract to current value.
Rick Rosson
Rick Rosson 2012-8-2
Please post the actual and complete code...
Michael Adelman
Michael Adelman 2012-8-3
Hello Rick,
I'm sorry but I really can't post the actual code. The loop as I described is very simple and do check for the value of the cell and then do a substitution or addition to the current value.

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Walter Roberson
Walter Roberson 2012-8-1

0 个投票

Processing 1200 items in an array would normally take too little time to measure meaningfully, unless the processing for each one takes a long time (in which case that is the problem rather than the for loop.)
I suggest you use the profiler to measure the performance. You could temporarily change the upper bound to something smaller than length(x)
You may wish to consider using waitbar()

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Michael Adelman
Michael Adelman 2012-8-3

0 个投票

Hello Walter,
Thank you , using a profiler really gave me a lot of information that I wan't aware of it before.
I'll continue to analyze the code and then ask more specific questions.
waitbar() is not a good use for me, since the code must work in real time telemetry and no wait/delay are allowed (as little as possible).

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