[Numpy-discussion] A numpy accumulator...

Tom K. tpk@kraussfamily....
Mon Oct 5 21:49:15 CDT 2009



Christopher Barker wrote:
> 
> 
> What do folks think? is this useful? What would you change, etc?
> 

Chris - I really like this and find it useful.  I would change the name to
something like "growable" or "ArrayList" - accumulator seems like an object
for cumulative summation.  I think the right amount to grow is 2x - this
provides an amortized O(log n) append.  If the array doesn't have to grow,
the cost is 1 - no copies - whereas if you have to grow, the cost is n
copies.  Is 2x optimal?  Perhaps the configurable grow ratio is a good
thing, although giving a knob means people are going to set it wrong.

I would also vote "+1" for an ND version of this (growing only a single
dimension).  Keeping 2x for each of n dimensions, while conceivable, would
be 2**n extra memory, and hence probably too costly.

Cheers,
  Tom K.

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