Methods in Making a Simple Program More Efficient

Hi,

I would like to speed up the execution of my program. It's abbreviated as follows:

Definition of myScript.m is as follows:

%start of myScript.m
...
for m=1:1000
myFunction(m)
end
...
%end of myScript.m

Definition of myFunction(m):

%start of myFunction.m
function output=myFunction(m)
... %code that uses m
internalVar=takeALongTimeFunction() %does not use m
end
%end of myFunction.m

The function takeALongTimeFunction() does not have an input argument, takes a long time to execute, and returns the same result for each call to myFunction(m). How can I speed up the execution of the entire program?

Thanks,

David

Answer 1

[per isakson]

Try

    clear takeALongTimeFunction
    tic, takeALongTimeFunction, toc
    tic, takeALongTimeFunction, toc

it should return something like

    ans =
        17
    Elapsed time is 7.004011 seconds.
    ans =
        17
    Elapsed time is 0.000456 seconds.

where

    function    out = takeALongTimeFunction()

        persistent result_of_last_time

        if not( isempty( result_of_last_time ) )
            out = result_of_last_time;
            return
        end

        out = 17;
        pause( 7 )

        result_of_last_time = out;
    end

[Sean de Wolski]

I would even suggest saving the result to disk, then if the persistent variable is empty && and the matfile with the result doesn't exist, then do the computation.

[David C]

Thanks to you both for these great ideas!