Error using Parfor "Unable to classify the variable 'Sort'"

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Erin Pratt
Erin Pratt 2021-7-23
回答： Edric Ellis 2025-1-30，12:01
Please help, pulling my hair out;
The following code is meant to sift through arrays Sort and Sort2 looking for intersections, and then if it finds one it reassigns that line (k) to all zeros. Sort is 16.777E6 x 24, and Sort2 is 24x24 matrix. k runs from 1 to Np = 16.777E6. This segment of the whole program takes considerable time with very, very large versions of Sort, so I am trying to use parfor to speed things up. I assumed this could be done because the results of any line Sort(k) do not affect any other line of Sort(k).
The error specifically says "Error using Solver_V (line 647)
Error: Unable to classify the variable 'Sort' in the body of the parfor-loop. For more information, see Parallel for Loops in MATLAB, "Solve Variable Classification Issues in
parfor-Loops".
The offending portion of code is below, and I included the full files for context.
Thank you so much!
parfor k=1:Np
for i=1:(Nu-1)
for j=(i+1):Nu
if Sort(k,i)*Sort(k,j)==1 && Sort2(i,j)==0
Sort(k,:)=zeros;
flag=1;
break
end
end
if flag==1
flag=0;
break
end
end
if mod(count2,10E6)==0
count2-count1
count2
end
count2=count2+1;
end

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采纳的回答

Raymond Norris
Raymond Norris 2021-7-23
Try this refactoring the for-loop a bit
parfor k=1:Np
flag = 0; %#ok<PFTUSW>
for i=1:(Nu-1)
for j=(i+1):Nu
% if Sort(k,i)*Sort(k,j)==1 && Sort2(i,j)==0
% Sort(k,:)=zeros;
% flag=1;
% break
% end
tmp_S = Sort(k,:);
if lFoundIntersection(tmp_S,i,j,Sort2)
Sort(k,:) = zeros;
flag = 1;
end
end
if flag==1
flag=0;
break
end
end
if mod(count2,10E6)==0
count2-count1
count2
end
count2=count2+1;
end
At the end of your script, add
function tf = lFoundIntersection(Sort,i,j,Sort2)
tf = Sort(:,i)*Sort(:,j)==1 && Sort2(i,j)==0;
end
I think you'll also need to comment out this
if mod(count2,10E6)==0
count2-count1
count2
end
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Erin Pratt
Erin Pratt 2021-7-23
Well, it did work. I ran it with a 13 node project, and it worked fine. When I moved to a 26 node project, I got the following error (the parfor statement went from 1 to 16E6 to now 1 to 1.07E9).
Error using distcomp.remoteparfor/rebuildParforController (line 212)
Unexpected failure to add interval 5.
Error in distcomp.remoteparfor/handleIntervalErrorResult (line 258)
obj.rebuildParforController();
Error in distcomp.remoteparfor/getCompleteIntervals (line 395)
[r, err] = obj.handleIntervalErrorResult(r);
Error in Solver_V (line 647)
parfor k=1:Np
Any idea why this would suddenly not work with a larger matrix?
Thanks again
Raymond Norris
Raymond Norris 2021-7-23
I would suggest two things:
  1. Make Solver_V a function and not a script. This will scope what variables are in the script's workspace.
  2. Change the parfor back to a for-loop with a 26 node project and see if it works. If not, resolve the issue and then go back to a parfor for a final test.

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更多回答（1 个）

Edric Ellis
Edric Ellis 2025-1-30，12:01
Ran in:
I just came here to mention that we tried to improve the error reporting for this case. Here's what happens now, hopefully it makes more sense.
parfor k=1:Np
for i=1:(Nu-1)
for j=(i+1):Nu
if Sort(k,i)*Sort(k,j)==1 && Sort2(i,j)==0
Sort(k,:)=zeros;
flag=1;
break
end
end
if flag==1
flag=0;
break
end
end
if mod(count2,10E6)==0
count2-count1
count2
end
count2=count2+1;
end
Error: The parfor-loop variable 'Sort' has multiple sliced accesses, but they do not all have the same list of subscripts. Each access to a sliced variable must use precisely the same list of subscripts. For more information, see Parallel for Loops in MATLAB, "Solve Variable Classification Issues in parfor-Loops".

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