Thread Subject:

timing a loop

how do i time this loop
A=randn(500);
for i=1:500
     for j=1:500
   B(i,j)=sum(A(:,i).*A(:,j));
   end
end

i tried the following with tic toc but i get an enormous lines of timing. how do i get the single time taken for the whole process?

A=randn(500);
for i=1:500
     for j=1:500
  tic; B(i,j)=sum(A(:,i).*A(:,j)); toc
   end
end
Elapsed time is 0.000042 seconds.
Elapsed time is 0.000005 seconds.
Elapsed time is 0.000004 seconds.
Elapsed time is 0.000004 seconds.
...
...
...

Thanks

On 5/5/2012 2:30 PM, anyani himura wrote:
> how do i time this loop
> A=randn(500);
> for i=1:500
> for j=1:500
> B(i,j)=sum(A(:,i).*A(:,j));
> end
> end
>
> i tried the following with tic toc but i get an enormous lines of timing. how do i
>get the single time taken for the whole process?
>
> A=randn(500);
> for i=1:500
> for j=1:500
> tic; B(i,j)=sum(A(:,i).*A(:,j)); toc
> end
> end
> Elapsed time is 0.000042 seconds.
> Elapsed time is 0.000005 seconds.
> Elapsed time is 0.000004 seconds.
> Elapsed time is 0.000004 seconds.
> ...
> ...
> ...
>
> Thanks

Just put the tic/toc pair outside the loop?

-----------------------------
A=randn(500);
t0=tic;
for i=1:500
   for j=1:500
     B(i,j)=sum(A(:,i).*A(:,j));
   end
end
toc(t0)
---------------

"anyani himura" <colormason@att.net> wrote in message
news:jo3v48$asf$1@newscl01ah.mathworks.com...
> how do i time this loop A=randn(500);
> for i=1:500
> for j=1:500
> B(i,j)=sum(A(:,i).*A(:,j));
> end end
>
> i tried the following with tic toc but i get an enormous lines of timing.
> how do i get the single time taken for the whole process?

Don't put tic/toc around the body of the nested loops; put it around the
loops as a whole.

tic
> A=randn(500);
> for i=1:500
> for j=1:500
> B(i,j)=sum(A(:,i).*A(:,j));
> end end
toc

If for whatever reason you want to know how long each inner loop iteration
takes, call TOC with an output.

> A=randn(500);
times = zeros(500, 500);
> for i=1:500
> for j=1:500
tic;
> B(i,j)=sum(A(:,i).*A(:,j));
times(i, j) = toc;
> end end

--
Steve Lord
slord@mathworks.com
To contact Technical Support use the Contact Us link on
http://www.mathworks.com