[Numpy-discussion] distance matrix speed
David Douard
david.douard at logilab.fr
Fri Jun 16 03:53:37 EDT 2006
Hi,
On Fri, Jun 16, 2006 at 08:28:18AM +0200, Johannes Loehnert wrote:
> Hi,
>
> def dtest():
> A = random( [4,2])
> B = random( [1000,2])
>
> # drawback: memory usage temporarily doubled
> # solution see below
> d = A[:, newaxis, :] - B[newaxis, :, :]
Unless I'm wrong, one can simplify a (very) little bit this line:
d = A[:, newaxis, :] - B
> # written as 3 expressions for more clarity
> d = sqrt((d**2).sum(axis=2))
> return d
>
--
David Douard LOGILAB, Paris (France)
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