[Numpy-discussion] extremely slow array indexing?

Robert Kern robert.kern at gmail.com
Thu Nov 30 11:28:45 CST 2006

Fang Fang wrote:
> Hi,
> I am writing code to sort the columns according to the sum of each
> column. The dataset is huge (50k rows x 300k cols), so i have to read
> line by line and do the summation to avoid the out-of-memory problem.
> But I don't know why it runs very slow, and part of the code is as
> follows. Can anyone point out what needs to be modified to make it run
> fast? thanks in advance!

Nothing leaps out. Generally, it's difficult (or impossible) to answer such
questions without running code. Can you distill the time-consuming part into a
small, self-contained script with fake data that we can run?

Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco

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