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Performance using temporary boolean filter

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mutt on 5 Feb 2013
In a situation where I need to use a logical filter (simply a vector of logical) 3 times in succession, am I likely to get a performance improvement by creating a temporary variable to hold the filter and then referring to that where necessary as opposed to just repeating the filter expression explicitly? e.g. I could define say: filter=(floor(x)==y); then do something to A(filter), B(filter) and C(filter) or I could do something to A(floor(x)==y), B(floor(x)==y) and C(floor(x)==y)

Accepted Answer

Jan on 5 Feb 2013
A(floor(x)==y) creates the temporary array floor(x)==y explicitly. Therefore doing this three times needs more resources than making the comparison once only. Therefore A(filter) etc. is faster.

More Answers (1)

Ryan Livingston
Ryan Livingston on 5 Feb 2013
The performance depends on many things. But it is likely that assigning filter will decrease the number of operations needed to be performed. Namely,
will only be calculated once.
Try both examples and run your code through the profiler to see how it affects things:


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