Client to worker communication in Matlab

9 次查看（过去 30 天）
Anurag Kamal
Anurag Kamal 2019-6-13
回答： Sahil Islam 2024-3-25
Is there a way to let the cleint send data back to parallel workers in Matlab. Using a queue make the data sending from worker to the client easy, but vice versa is proving diffcult.
I am trying to use a ascii file that is written by the client for the workers to read, but simulataneous accessing of the file is giving me an error.
Error using startSimulation>mainCore (line 440)
"File temp/current.txt is in use by another process or thread. You should be able to load data once the other process or thread has released the file."
Is there a way to wait for the file to be readable (waitfor doesn't work), or implemeting a easy semaphore code to do this? I am open to implementing any ideas, there has to be a communication between client and workers both ways.
  2 个评论
Edric Ellis
Edric Ellis 2019-6-13
It would be helpful if you could post a minimal reproduction to demonstrate the problem. I presume you must be using parfeval to trigger execution on the workers - because otherwise the client would be blocked executing the parfor or spmd block otherwise... Could you perhaps only schedule the parfeval calls after the client has completed?
Anurag Kamal
Anurag Kamal 2019-6-13
Well, I am using parfor, adn this is how the pseudo code looks like
mainscript()
initialize queue;
aftereach(queue,@purgefunc)
parfor i=1:3
results(i)=start_sim(params, queue)
end
end mainscript()
purgefunc(data)
if data==!
plot(results)
end if
end purgefunc
startsim(params, queue)
while t<tf // final simulation time
send.queue(data)
end
end
Now as the loop on workers is continuously running, how do I send data from client to worker.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（3 个）

Walter Roberson
Walter Roberson 2019-6-13
https://www.mathworks.com/help/parallel-computing/parallel.pool.pollabledataqueue.html
"You can construct the queue on the workers and send it back to the client to enable communication in the reverse direction. However, you cannot send a queue from one worker to another. Use spmd, labSend, or labReceive instead."
  1 个评论
Anurag Kamal
Anurag Kamal 2019-6-13
if the workers are in a loop, how can they send a variable back to the client. Sending the pollable queue by the queue doesn't work, I tried it.

请先登录，再进行评论。

Davey Gregg
Davey Gregg 2021-3-24
I have been hitting my head against this problem for a while too. There does not seem to be an easy way to do this. I found this way works - it's not ideal because it takes some time to bounce the command to the hard drive and get it back. But it will let you send a command to the workers from anywhere beit the main client, a function, or even a seperate script. Basically you write a file to tempdir where you can save your command and then have the workers access the file to receive it.
%Make a matObj file in the temp directory
G = 1;
matObj = matfile([tempdir,'G.mat'],'Writable',true);
matObj.G = G;
% Setup a queue to receive data from workers
dataOut = parallel.pool.DataQueue;
afterEach(dataOut,@sendIT);
spmd (4)
if labindex == 1
t = 1;
while G == 1
G = matObj.G; % Access the matObj to recieve data from client
pause(1);
t = t+1;
if t == 5
disp('sent')
send(dataOut,0)
end
end
end
end
delete([tempdir,'G.mat']);
% update matObj with command from client
function sendIT(data)
matObj = matfile([tempdir,'G'],'Writable',true);
matObj.G = data;
end
Sahil Islam
Sahil Islam 2024-3-25
%load("data.txt);
data = readtable("data.txt);
data = table2array(data);
Instead of loading, using 'readtable' solved the problem for me.

类别

在 Help Center 和 File Exchange 中查找有关 Parallel Computing Fundamentals 的更多信息

标签

产品


版本

R2018b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by