for / parfor within if
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Is there a way to write something like:
if parallelloop
parfor i=1:n
else
for i=1:n
end
...iterations
end
where parallellop is a boolean.
This code is not accepted by Matlab because the same end for both parfor and for.
A solution I do not accept for many reasons would be:
if parallelloop
parfor i=1:n
...iterations
end
else
for i=1:n
...iterations
end
end
Another solution I would like to have is an #ifdef like approach, but is there any?
Thanks by advance.
2 Commenti
Philippe Lebel
il 21 Nov 2019
Modificato: Philippe Lebel
il 21 Nov 2019
what are the reasons why you dont want to put the end statments after the parfor and the for?
Risposte (1)
Jason Ross
il 21 Nov 2019
You can control if a loop is run with parallel workers or not by changing the number of workers. See "Test parfor-Loops by Switching Between Parallel and Serial Execution" in the parfor documentation. Note that even with 0 workers, the parfor is still nondeterministic.
To make your example work, you would set the number of workers to 0 if parallelloop is false.
4 Commenti
Jason Ross
il 22 Nov 2019
There have been a lot of changes since then -- the computational time issue might have been a bug, and fixed. The overall point I was getting at was that parfor is interpreted as a for in the absence of Parallel Computing Toolbox being present.
This also does make the implicit assumption that parfor introduces new functionality that would be incompatible with releases that don't know what parfor is, but that's going to be the case with pretty much any arbitrary software package.
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