Is it possible to determine whether or not it is the first pass of a loop
entirely from within the loop, i.e. without adding extra statements outside
the loop?
The context is that I've been thinking about how to avoid reallocating
arrays on each loop, for instance something like this will reallocate a
bunch of arrays on each iteration:
X = starting_value
for i = 1:10
# update A, B, U
...
X += d * ((A+c*B) \ U)
end
What I'd like to do is simply place a macro statement such as:
X = starting_value
for i = 1:10
# update A, B, U
...
@reuse X += d * ((A+c*B) \ U)
end
which would:
1) On the first pass, break out all the computations and create bindings to
the intermediate arrays
2) On every subsequent pass, reuse the intermediate arrays.
Now I have some rough infrastructure for (2) in InplaceOps.jl, but I have
no idea how to determine whether or not I'm on the first pass, without
allocating variables outside the loop (which seems to be impossible from a
macro invoked inside the loop). Any ideas?
Simon
