Best Practices for Efficiency

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Groat
Groat 2015-2-28
评论： Stephen23 2015-3-1
Hi,
I have a function that's run around 10 million times, so I want to make sure I'm doing things as efficiently as possible.
I use three parameters which are constants. Currently within my function I have:
parameter1 = 3;
parameter2 = 4;
parameter3 = 39;
These parameters are not used anywhere else other than this function. However, when looking at profiler, each line is taking up a considerable time.
Is there a more efficient method to utilise these parameters in the function? For example, global variables, etc?
Any help is much appreciated.

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回答（1 个）

Image Analyst
Image Analyst 2015-2-28
Here's my time for the 3 lines:
Elapsed time is 0.000004 seconds.
Perhaps there's some setup time involved because you're using the parallel toolbox. Are you sure it's those 3 lines that's taking up all the time and not some other lines of code?
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Image Analyst
Image Analyst 2015-2-28
You're not. You'd need to use parfor instead of for. Type ver on the command line to see if you have the toolbox.
I don't have the toolbox but when I run the code
tic
for i = 1:10000000
parameter1 = 8;
parameter2 = 3;
parameter3 = 1;
end
toc
I get this:
Elapsed time is 0.028298 seconds.
Far, far from the 75 seconds or more that it's taking you. I think there's something you're not telling us or some code you're not sharing with us.
Stephen23
Stephen23 2015-3-1
When I run that loop (2010b on an old laptop) I get
Elapsed time is 0.114191 seconds.
Are the variables declared to be persistent or global?

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