Time Comparison and Tic Toc

I am having a little trouble using the tic toc function. (For background, I wanted to visualize the difference in calculation times between vectorized equations and for-loops, make a function, called timecompare that takes in a function handle ,fh, and a vector, x, at which to evaluate my function.)

My function timecompare should evaluate my function handle in two ways: (1) using a for-loop to evaluate fh at each element of x, and (2) by simply inputting the whole vector into fh. The structure is function is:

two inputs:

1) A function handle, fh.

2) An array of values, x, at which to evaluate the function handle.

three outputs:

1) time1, the total time it takes to evaluate fh at each value of x using a for-loop.

2) time2, the total time it takes to evaluate fh at each value of x by inputting the whole array into your function.

3) flag, which has a value of 1 if time1 > time2, or a value of 2 if time2 > time1.

Your function header should be:

     function [time1, time2] = timecompare(fh,x)
  tic  
  for ii = 1:length(x)
  feval(fh,x(ii))
  end
  time1 = toc;
  tic
  feval(fh,x)
 end
    plot(fh)

clearly I am doing something in my code and it’s probably because I am not too familiar with tic toc. How should I go about fixing my code?

Answer 1

[Arthur]

With tic toc you measure the time elapsed between the 'tic' and 'toc' command. So for instance

tic
%you code here
elapsedTime = toc

I guess your code should be something like this:

function [time1, time2] = timecompare(fh,x)

tic
for ii = 1:length(x)
feval(fh,x(ii))
end
time1 = toc;

tic
feval(fh,x)
time2 = toc;

[Matt]

thanks! This is a dumb question, but i am trying to test out my code, so my lab advisor emailed me this:

fh=@cos;

[time1, time2, flag]=timecompare(@cos,1:1000)

when I tried running fh=@cos; I got nothing for the output

when I run that AND [time1, time2, flag]=timecompare(@cos,1:1000), I get

Error using timecompare Too many output arguments.

Error in TestCasesLab9 (line 2) [time1, time2, flag]=timecompare(@cos,1:1000)

am I interpreting his test case wrong? If not, is there something wrong in the code?

[John Petersen]

You got the error because you added another argument that you haven't included inside your function. Where did "flag" come from?

[Arthur]

Ah yes my answer didn't include the flag. I was hoping you could include that yourself. A simple if statement.