Nested loops within PARFOR loop

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Jeremy
Jeremy on 9 Nov 2012
I am having issues using parfor. Getting the following error: The PARFOR loop cannot run due to the way variable 'ed' is used.
ed is some nm by 6 matrix that I am trying to fill in with certain values. BIN is a vector used to convert from binary to decimal.
If anyone has used PARFOR for parallel computing and could help it would be greatly appreciated (trying to reduce the run time which is currently at ~4 hrs).
Thanks,
-Jeremy
parfor i=1:popSize
O=0;
for j=1:nm
for k=1:ng
if edi(j,4)==k && pop(i,(k*7-6):(k*7))*BIN<=nsd && pop(i,(k*7-6):(k*7))*BIN~=0
ed(j,4:6)=sd(pop(i,(k*7-6):k*7)*BIN,2:4);
elseif pop(i,(k*7-6):(k*7))*BIN>nsd || pop(i,(k*7-6):(k*7))*BIN==0
O=1;
break
end
end
end
end
  1 Comment
Jan
Jan on 9 Nov 2012
"O=0" is really confusing. Please do not use an uppercase "oh" as name of a variable.

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Answers (1)

Jan
Jan on 10 Nov 2012
Please use the profiler to find the bottlenecks. What is sd and pop?
Avoid calculating pop(i,(k*7-6):k*7)*BIN 4 times: Store the value in a temporary variable instead:
for i=1:popSize
P = 0;
for j=1:nm
c1 = edi(j, 4);
for k=1:ng
c2 = pop(i,(k*7-6):(k*7))*BIN;
if c1 == k && c2 <=nsd && c2 ~= 0
ed(j, 4:6) = sd(c2, 2:4);
elseif c2 > nsd || c2 == 0
P = 1;
break
end
end
end
end
Do you need "P" anywhere?!
  1 Comment
Jeremy
Jeremy on 12 Nov 2012
Edited: Jeremy on 12 Nov 2012
This is part of a genetic algorithm to optimize a certain structural analysis problem where pop is the binary population matrix, where I am attempting to retrieve different index values for sd. sd is a definition of different section values (area, moment of inertia, weight) and contributes to the definition of an element. Each index value for sd is defined by a 7 bit byte, of which there are several bytes in each row of pop.
P is used to ensure that the value gotten in c2 is within the dimensions of sd. As any byte could lead to a value greater than the number of rows in sd, I do not want it to try and access a non-existent point in sd.
Thank you for the advice on c1 and c2, I will definitely implement that. Any ideas as to why the parfor loop isn't working?

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