In message <77as23f1fhj3...@mid.uni-berlin.de>, Diez B. Roggisch wrote:
>> But reduce()? I can't see how you can parallelize reduce(). By its
>> nature, it has to run sequentially: it can't operate on the nth item
>> until it is operated on the (n-1)th item.
>
> That depends on the operation in question. Addition for example would
> work. My math-skills are a bit too rusty to qualify the exact nature of
> the operation, commutativity springs to my mind.
Associativity:
((A op B) op C) = (A op (B op C))
So for example
A op B op C op D
could be grouped into
(A op B) op (C op D)
and the two parenthesized subexpressions evaluated concurrently. But this
would only give you a speedup that was logarithmic in the number of op's.
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