Toc returns loop time instead of total script time

Hi

I have a script with a large loop nested inside another loop, and i would like to time the progress of the loop, using the tic/toc commands.

The code is like this:

tic

--some code and small loops--

for i=1:lengthi

for j=1:lengthj

clc

disp(['Iteration: ' num2str((i-1)*lengthj+j) ' of ' num2str(lengthi*lengthj)]);

toc

--some code--

end

end

toc

however, when I run the code, toc seems to display the time since last toc, instead of the time since tic. The problem is not exclusive to this piece of code, I have noticed it before with other scripts.

Any thoughts or experience with this?

-Nicolas

[Nicolas Schnedler-Meyer]

I've tried replacing tic with tstart=tic, and then toc(tstart) later, and that works as intended.

but i still don't know why it doesn't work otherwise.

[Greig]

What version are you using?

I encounter something similar in 2014a with a particular piece of code, but I could never replicate in another code. I spent ages looking for other tics or clears, but was pretty sure there were none.

[Nicolas Schnedler-Meyer]

It happens both in version 2014b and 2015a.

Answer 1

[pfb]

Hi,

I've tried this

 tic;
 for k=1:10
  pause(2);
  toc;
 end
 pause(2);
 toc;

on both R2012b and R2014b and the output is what I expect: after each toc 2 seconds are passed

 Elapsed time is 2.000970 seconds.
 Elapsed time is 4.002267 seconds.
 [...]
 Elapsed time is 22.011765 seconds.

[Nicolas Schnedler-Meyer]

Well, that works for me too, but not in the aforementioned script

[pfb]

And, just for the sake of stating the obvious, there is no "tic" or similar in "-- some code --", right?

Have you tried different measures of time? Like using "clock" and "etime"?

Like

 t0=clock;

 % --- some code

 et = etime(t0,clock);
 fprintf('Elapsed time is %1.3f seconds\n',et);

[Nicolas Schnedler-Meyer]

there's no tic in "-- some code --", no.

Haven't tried other measures, I'm just mystified by toc not working properly..

[pfb]

I can understand that... It's puzzling.

I'd just try and look whether etime and clock are similarly affected by this thing, or else if this is a problem with tic and toc alone...

Answer 2

[Ilham Hardy]

Apart from tic and toc, there is also profile command to check the bottleneck of the script/function.

Answer 3

[Jan]

Do you have a 'clear all' anywhere in your code?

[Nicolas Schnedler-Meyer]

No, only a "clc"

Answer 4

[Philip Borghesani]

Clear all and clc will not clear tic time.

There must be another call to tic. For this reason I recommend always using the t0=tic; t=toc(t0) form of these functions.

To find other calls to tic try dbstop in tic or write your own version of tic that checks for other uses.

A foolproof way to find the call to tic with no output is to fix your outer loop to call t0=tic and place this tic.m in your current directory:

function t0=tic
   if nargout==0
      dbstack
      keyboard
   end
   t0=builtin('tic');
end