Re: cPickle.load vs. file.read+cPickle.loads on large binary files

Newsgroups	comp.lang.python
Date	2015-11-18 02:31 -0800
References	(2 earlier) <54330891-6568-4469-93ae-7a7825961500@googlegroups.com> <mailman.392.1447773612.16136.python-list@python.org> <420ec4e9-6af6-49bd-a9f4-8b47ef1f136e@googlegroups.com> <n2fip9$ajg$1@ger.gmane.org> <mailman.406.1447837229.16136.python-list@python.org>
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Subject	Re: cPickle.load vs. file.read+cPickle.loads on large binary files
From	andrea.gavana@gmail.com

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Hi,

On Wednesday, November 18, 2015 at 10:00:43 AM UTC+1, Nagy László Zsolt wrote:
> > Perhaps there is a size threshold? You could experiment with different block 
> > sizes in the following f.read() replacement:
> >
> > def read_chunked(f, size=2**20):
> >     read = functools.partial(f.read, size)
> >     return "".join(iter(read, ""))
> >
> Under win32 platform, my experience is that the fastest way to read
> binary file from disk is the mmap module. You should try that too.

Thank you for your suggestion. I have tried that now, and with my naive approach I have done this:

    start = time.time()
    fid = open(filename, 'r+b')
    strs = mmap.mmap(fid.fileno(), 0, access=mmap.ACCESS_READ)[:]
    end = time.time()
    print 'mmap.read time:', end-start

And it takes about 2.7 seconds. Not a bad improvement :-) . Unfortunately, when the file is on a network drive, all the other approaches ran at around 25-30 seconds loading time, while the mmap one clocks at 110 seconds :-(

Andrea.

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cPickle.load vs. file.read+cPickle.loads on large binary files andrea.gavana@gmail.com - 2015-11-17 05:26 -0800
  Re: cPickle.load vs. file.read+cPickle.loads on large binary files Peter Otten <__peter__@web.de> - 2015-11-17 15:14 +0100
    Re: cPickle.load vs. file.read+cPickle.loads on large binary files andrea.gavana@gmail.com - 2015-11-17 06:20 -0800
      Re: cPickle.load vs. file.read+cPickle.loads on large binary files Chris Angelico <rosuav@gmail.com> - 2015-11-18 02:20 +1100
        Re: cPickle.load vs. file.read+cPickle.loads on large binary files andrea.gavana@gmail.com - 2015-11-17 07:31 -0800
          Re: cPickle.load vs. file.read+cPickle.loads on large binary files Peter Otten <__peter__@web.de> - 2015-11-17 16:57 +0100
            Re: cPickle.load vs. file.read+cPickle.loads on large binary files andrea.gavana@gmail.com - 2015-11-17 08:31 -0800
              Re: cPickle.load vs. file.read+cPickle.loads on large binary files Peter Otten <__peter__@web.de> - 2015-11-17 18:20 +0100
          Re: cPickle.load vs. file.read+cPickle.loads on large binary files Nagy László Zsolt <gandalf@shopzeus.com> - 2015-11-18 10:00 +0100
            Re: cPickle.load vs. file.read+cPickle.loads on large binary files andrea.gavana@gmail.com - 2015-11-18 02:31 -0800

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