MATLAB: Fastest way to AND or OR together columns of a matrix

jitlogical operationMATLABoptimization

I'm using 2017b and I need to test whether each row of a matrix meets an inequality constraint. This test is done millions of times in my code, so I'm trying to make it as fast as possible. I'm wondering if there is any faster way to do it than this

testdata = rand(1000,26);  % setup some fake data
testref = rand(1,26)/20;   % setup a fake test reference
result = sum(testdata >= testref,2)==26;   % Actual test; can this be faster?

Best Answer

try

result = all(testdata >= testref,2)

It is quite faster.

Elapsed time is 0.000445 seconds.

Elapsed time is 0.000294 seconds.

Elapsed time is 0.000426 seconds.

Elapsed time is 0.000254 seconds.

Elapsed time is 0.000406 seconds.

Elapsed time is 0.000255 seconds.

Related Solutions

MATLAB: Gets imellipse slower and slower in a loop

Because the axes is getting "full" - not quite sure how else to describe it. Put the command "cla" before the call to imellipse and you'll see the times stay short no matter how many times you call it.

MATLAB: Are the times took for consequent tocs not consistent

I would personally use multiple tic tocs instead of tic then multiple tocks. tic tocs are meant to be used as a pair, that's the primay function. Although your usage is supported, it's probably be so by logistics in an obscure way, (e.g. 1st toc release resources and 2nd toc need to dig the last used tic ID from somewhere.) If one uses multiple tocs for less critical timings (several milliseconds) it will be fine. In your case you are measurement is back to front. In addition, the documentation says it is much more accuracte to loop over multiple calculations between the tic and the toc if the calculations take too short of a time.

If you modify your code to include the tic IDs the picture changes, supporting my 'logistics' theory. Now the 1st toc uses slightly more time than the second, than the 3rd, and similar from then on. 2nd still uses more than the 3rd probably as it still have to check through why am I being called a 2nd time and set stage for the 3rd and so on.

for i = 1:k
    ID = tic;
    tocs(i,1) = toc(ID); 
    tocs(i,2) = toc(ID); % the second toc!
    tocs(i,3) = toc(ID); 
    tocs(i,4) = toc(ID);
    tocs(i,5) = toc(ID);
    tocs(i,6) = toc(ID);
    pause(0.001); % this also affects the results.
end

If you run paired tic tocs:

for i = 1:k
    pause(0.001); 
    for j=1:6
    tic;
    tocs(i,j) = toc; 
    end
end
elapsed = tocs;

Then, only the first toc take longer than the rest, which is forgiveable.

In anycase, you would not use tic toc for measuring very fast timings like this. If you need to do so, use:

tic
for i=1:1000
%some fast code%
end
time = toc;
time = time/1000;

Best Answer

Related Solutions

MATLAB: Gets imellipse slower and slower in a loop

MATLAB: Are the times took for consequent tocs not consistent

Related Question