I have a program running a loop I want to have two time counters, one for the loop, that will tell me how log did one iteration of the loop took, and one for the entire program. To the best of my knowledge tic and toc will work only once.
You're only familiar with this tic toc syntax:
tic; someCode; elapsed = toc;
But there is another syntax:
start = tic; someCode; elapsed = toc(start);
The second syntax makes the same time measurement, but allows you the option of running more than one stopwatch timer concurrently. You assign the output of tic to a variable tStart and then use that same variable when calling toc. MATLAB measures the time elapsed between the tic and its related toc command and displays the time elapsed in seconds. This syntax enables you to time multiple concurrent operations, including the timing of nested operations (matlab documentation of tic toc).
Here's how to use it in your case. Let's say that this is your code:
for i = 1:M
someCode;
end
Insert the tic and toc like this:
startLoop = tic;
for i = 1:N
startIteration = tic;
someCode;
endIteration = toc(startIteration);
end
endLoop = toc(startLoop);
You can also use the above syntax to create a vector for which the ith element is the time measurement for the ith iteration. Like this:
startLoop = tic;
for i = 1:N
startIteration(i) = tic;
someCode;
endIteration(i) = toc(startIteration(i));
end
endLoop = toc(startLoop);
You can use tic and toc to time nested operations, from the Matlab help for tic:
tStart=tic; any_statements; toc(tStart); makes the same time measurement, but allows you the option of running more than one stopwatch timer concurrently. You assign the output of tic to a variable tStart and then use that same variable when calling toc. MATLAB measures the time elapsed between the tic and its related toc command and displays the time elapsed in seconds. This syntax enables you to time multiple concurrent operations, including the timing of nested operations
I'm not able to try this right now, but you should be able to use multiple tic and toc statements if you store the tic values into variables.
Read Matlab's documentation on this, there is even a section on nesting them. Here is a rough example:
tStartOverall = tic;
...
tStartLoop = tic;
<your loop code here>
tEndLoop = toc(tStartLoop);
...
tEndOverall = toc(tStartOverall);
Related
I am collecting data from a potentiometer connected to an Arduino. In the script, I tell matlab to keep collecting data for 2 minutes. But I need to tell it that if the user does not move the potentiometer for 10 consecutive seconds, then it should stop the loop and move to the next session (write the data to an excel file). Does anybody have ideas on how to achieve this?
Probably tic and toc can help you.
tic starts a stopwatch timer. The function records the internal time at execution of the tic command.
toc reads the elapsed time from the stopwatch timer started by the tic function.
tic;
while toc < 10
% Do your loopy things
if variable_changed
tic; % Restart stopwatch
end
end
Furthermore to be sure tic won't interact with other processes you should store it's value like this:
% First start stopwatch
time_since_last_movement = tic;
while toc(time_since_last_movement) < 10
% Do your loopy things
if variable_changed
time_since_last_movement = tic; % Restart stopwatch
end
end
I received a computer with 4xGPU's Tesla K80 and I am trying the parfor loops from Matlab PCT to speed up FFT's calculation and it is yet slower.
Here is what I am trying:
% Pupil is based on a 512x512 array
parfor zz = 1:4
gd = gpuDevice;
d{zz} = gd.Index;
probe{zz} = gpuArray(pupil);
Essai{zz} = gpuArray(pupil);
end
tic;
parfor ii = 1:4
gd2 = gpuDevice;
d2{ii} = gd2.Index;
for i = 1:100
[Essai{ii}] = fftn(probe{ii});
end
end
toc
%%
Starting parallel pool (parpool) using the 'local' profile ... connected to 4 workers.
Elapsed time is 1.805763 seconds.
Elapsed time is 1.412928 seconds.
Elapsed time is 1.409559 seconds.
Starting parallel pool (parpool) using the 'local' profile ... connected to 8 workers.
Elapsed time is 0.606602 seconds.
Elapsed time is 0.297850 seconds.
Elapsed time is 0.294365 seconds.
%%
tic; for i = 1:400; Essai{1} = fftn( probe{1} ); end; toc
Elapsed time is 0.193579 seconds !!!
Why is opening 8 workers faster as in principle I stored my variables into 4gpu's only (out of 8)?
Also, how to use a Tesla K80 as a single GPU?
Merci, Nicolas
I doubt that parfor works for multi-GPU systems. If speed is critical and you want to take full advantage of your GPUs, I suggest to write your own little CUDA script using the cuFFT library:
http://docs.nvidia.com/cuda/cufft/#multiple-GPU-cufft-transforms
Here is how to write your mex file containing CUDA code:
http://www.mathworks.com/help/distcomp/run-mex-functions-containing-cuda-code.html
many thanks for your quick reply and for the links ! It is true that I was trying to avoid CUDA but it seems like the best option to spread FFTs.
Although I thought that parfor and spmd were great tools for multiple GPUs..
I need to filter 6 signals with 60000000 samples in each. So data are saved in matrix data(60000000,6). There are several aproaches how to do that:
data=randn(60000000,6);
b=ones(1,1000)/1000;
tic
R=filter(b,1,data);
toc
tic
for i=1:6
R2(:,i)=filter(b,1,data(:,i));
end
toc
tic
parfor i=1:6
R2(:,i)=filter(b,1,data(:,i));
end
toc
By documentation it is recommanded to use 1st form as the fastest one, but in my case it is the slowest.
Elapsed time is 172.235919 seconds.
Elapsed time is 45.354810 seconds.
Elapsed time is 59.250638 seconds.
In process explorer 1st form use only 1 thread of CPU. By documentation it should run on multiple threads in default. Have you experienced same problem?
I'm checking the running time of a function using tic/toc. I write the following in the command window (and execute it simultaneously):
tic
res = checkFunc('case2736sp',1:3000);
toc
Elapsed time is 0.080491 seconds.
where checkFunc returns a 2736x2500 full matrix.
What puzzles me is that I have to wait almost 20 seconds for the output saying the run time is only 80 ms.
Does anyone have a clue why this is?
It's possible that tic/toc's internal counter is getting reset somehow during execution. Try it like this:
t = tic
res = checkFunc('case2736sp',1:3000);
toc(t)
I have this function:
function example(y)
global TICTOC;
tic
TICTOC=5;
toc
end
and I expect TICTOC=5 change the result of toc, since TICTOC is a global variable in tic and toc functions; but this is not the case; Does anyone know the reason?
I like to know the answer, because I 'm worried to declare a global variable, which it's name has been declared global in some other functions, I'm not aware of.
I saw this function in matlab 2008b help
function tic
% TIC Start a stopwatch timer.
% TIC; any stuff; TOC
% prints the time required.
% See also: TOC, CLOCK.
global TICTOC
TICTOC = clock;
function t = toc
% TOC Read the stopwatch timer.
% TOC prints the elapsed time since TIC was used.
% t = TOC; saves elapsed time in t, does not print.
% See also: TIC, ETIME.
global TICTOC
if nargout < 1
elapsed_time = etime(clock, TICTOC)
else
t = etime(clock, TICTOC);
end
thanks.
I think you can use assignin command to send the TICTOC value to base and thus changing the global value.
I use the assignin command to send parameters from function to Base.
Regards
Dilip
I don't know why but I the answer of my question is No. I checked it and it seems that it is not being overwritten. The reason must be because tic, toc is a built in Matlab function