Best Practices for Efficiency

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.

Answer 1

[Image Analyst]

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?

[Groat]

Yes, I'm sure it's these three lines. I've even just added the code below at the beginning of my script and get a similar problem (over 10 million repetitions, the time for each line is 25 seconds)

for i = 1:10000000
  parameter1 = 8;
  parameter2 = 3; 
  parameter3 = 1; 
end

How can I know if i'm using the parallel toolbox?

[Image Analyst]

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]

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?