Dag Sverre Seljebotn, 04.04.2011 12:17:
CEP up at http://wiki.cython.org/enhancements/prange
"""
Variable handling
Rather than explicit declaration of shared/private variables we rely on
conventions:
* Thread-shared: Variables that are only read and not written in the
loop body are shared across threads. Variables that are only used in the
else block are considered shared as well.
* Thread-private: Variables that are assigned to in the loop body are
thread-private. Obviously, the iteration counter is thread-private as well.
* Reduction: Variables that only used on the LHS of an inplace
operator, such as s above, are marked as targets for reduction. If the
variable is also used in other ways (LHS of assignment or in an expression)
it does instead turn into a thread-private variable. Note: This means that
if one, e.g., inserts printf(... s) above, s is turned into a thread-local
variable. OTOH, there is simply no way to correctly emulate the effect
printf(... s) would have in a sequential loop, so such code must be
discouraged anyway.
"""
What about simply (ab-)using Python semantics and creating a new inner
scope for the prange loop body? That would basically make the loop behave
like a closure function, but with the looping header at the 'right' place
rather than after the closure.
Also, in the example, the local variable declaration of "tmp" outside of
the loop looks somewhat misplaced, although it's precedented by
comprehensions (which also have their own local scope in Cython).
Stefan
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