parfor loop throws error for bigger matrices : Index must not exceed 0
3 visualizzazioni (ultimi 30 giorni)
Mostra commenti meno recenti
Hello, I am a newbie in parallel computing.
I am doing some calculation to genereate a 4D data. It worked fined while calculating a 4D matrix of small size(for e.g 2 × 3 × 4 × 100). But it then threw an error when the matrix sized was increased to 5 × 101 × 1001 × 101.
Below is my minimal code script.
'A' is the 4D matrix to be generated. The calculations necessary are done by my function 'bem4DParallel'.
So, at the innermost loop, a 1D array A_L is calculated. It is then stored in the 2D matrix A_K. This is done parallely for different values of k.
Then it is stored in 3D matix A_J and then finally in the 4D matrix A.
Computations for input_3 are parallelized. I didn't parallelize the innemost loop because to there is a dependency of the variable. That is, calculation of A_L(l) in the innermonst loop required the value of A_L(l-1). That's why I am passing the whole A_L array in the function while calculating.
% script name: main4DParallel.m
% inputs
input_1 = 0:5:20;
input_2 = 0:100;
input_3 = 500:1500;
input_4 = 0:0.01:2;
% 4D matrix to be calculated
A = zeros( length(input_1), length(input_2), length(input_3), length(input_4) );
for i = 1:length(input_1)
arg_1 = input_1(i);
A_J = zeros(length(input_2), length(input_3), length(input_4));
for j = 1:length(input_2)
arg_2 = input_2(j);
A_K = zeros(length(input_3), length(input_4));
% parallel computing
parfor k = 1:length(input_3)
arg_3 = input_3(k);
A_L = zeros(1,length(input_4));
for l = 1:length(input_4)
a = bem4DParallel(arg_1, arg_2, arg_3, input_4(l), A_L, l);
A_L(l) = a;
end
A_K(k,:) = A_L;
end
A_J(j,:,:) = A_K;
end
A(i,:,:,:) = A_J;
end
The script runs for some time(about 12 hours) and then gives the following error:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1444332/image.png)
'main4DParallel' is the name of this script. And line 103 corresponds to the line where we have parfor k = 1:length(input_3)
After stopping, the values of the looping variables in the workspace are:
i = 1, j = 3. And there exists no k and l values.
Matrices:
A_L does not exist
2D matrix 'A_K' exist. And also data are present upto a row of 24. (Is it something to do with number of matlab workers?)
3D Matrix 'A_J' exist and contains value upto
A_J(2,:,:)
Make sense, because after stopping, j is at a value of 3
4D matrix A is completely empty.
Please let me know what I am doing wrong.
Thanks in advance
4 Commenti
Neelabh Jyoti Saharia
il 28 Lug 2023
Modificato: Neelabh Jyoti Saharia
il 28 Lug 2023
Harald
il 28 Lug 2023
Hi,
the next problem is that l does not exist in the function doSum. Let's assume that you want to use loopVar, so
m = Matrix(loopVar-1);
The next problem is that the loop over l starts at 1, meaning that you are falsely going to extract the 0-Element of Matrix. So, let me drop the "-1". Then, the provided example runs fine for me.
If that does not resolve the problem, I am afraid that it will be in bem4DParallel, and I recommend the following:
- Before returning the output, verify that it has the expected data type and dimension (double and scalar, I suppose).
- Wrap a try/catch - statement around the body of the function. In the catch portion, save the workspace of the function to a file. This will let you debug what the inputs were that led to the erroneous output, and thus fix the problem.
Best wishes,
Harald
Risposte (0)
Vedere anche
Categorie
Scopri di più su Startup and Shutdown in Help Center e File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!