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Re: Fast forward-backward (write-read)

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Virgil Stokes <vs@it.uu.se> writes:
> Finally, to my question --- What is a fast way to write these
> variables to an external file and then read them in backwards?

Seeking backwards in files works, but the performance hit is
significant.  There is also a performance hit to scanning pointers
backwards in memory, due to cache misprediction.  If it's something
you're just running a few times, seeking backwards the simplest
approach.  If you're really trying to optimize the thing, you might
buffer up large chunks (like 1 MB) before writing.  If you're writing
once and reading multiple times, you might reverse the order of records
within the chunks during the writing phase.  

You're of course taking a performance bath from writing the program in
Python to begin with (unless using scipy/numpy or the like), enough that
it might dominate any effects of how the files are written.

Of course (it should go without saying) that you want to dump in a
binary format rather than converting to decimal.

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Thread

Fast forward-backward (write-read) Virgil Stokes <vs@it.uu.se> - 2012-10-23 16:31 +0200
  Re: Fast forward-backward (write-read) Paul Rubin <no.email@nospam.invalid> - 2012-10-23 09:17 -0700
    Re: Fast forward-backward (write-read) Paul Rubin <no.email@nospam.invalid> - 2012-10-23 09:22 -0700
    Re: Fast forward-backward (write-read) Tim Chase <python.list@tim.thechases.com> - 2012-10-23 11:53 -0500
      Re: Fast forward-backward (write-read) Paul Rubin <no.email@nospam.invalid> - 2012-10-23 09:58 -0700
    Re: Fast forward-backward (write-read) Virgil Stokes <vs@it.uu.se> - 2012-10-23 19:06 +0200
  Re: Fast forward-backward (write-read) rusi <rustompmody@gmail.com> - 2012-10-24 08:11 -0700
    Re: Fast forward-backward (write-read) Virgil Stokes <vs@it.uu.se> - 2012-10-25 11:00 +0200

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