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TensorFlow @ PyData SG

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Google just released a fantastic-looking deep learning library called TensorFlow, complete with tutorials, and model-zoo-like examples.

Fortunately, the framework is very reminiscent of Theano, and has a Python front-end over a computation graph construction machine in C++ / CUDA (no OpenCL as far as I can tell).

Because it's new, and Python-related, I gave a "Lightning Talk" at the November meeting of the Singapore PyData group.

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If there are any questions about the presentation please ask below, or contact me using the details given on the slides themselves.

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#Slide Notes (outline)

These are the notes I put together for myself before preparing the slides. Almost everything made it into the presentation, but only because I split the positives into 2 slides, and the not-so-positives into 4 slides...

Positives

  • Cross-platform : CPUs, GPUs, Android, iOS (soon), etc

  • Open Source (Apache 2)

    • and Google actively reviews and responds to PRs

  • Theano-like definition and optimisation of calculation graph

    • backend in C++

  • Python is first-class citizen (other is C++)

  • TensorBoard (images?)

  • Hiring tool

"Lowlights"

There are several points worth highlighting:

  • Nvidia devices supported much have 'Compute Capability' >= 3.5

    • This includes 900-series cards, and Titan, and the 'K cards'
    • But not 700-series (apart from 750), nor Amazon EC GPUs
      • "A g2.2xlarge is a downclocked GK104 (797 MHz), that would make it 1/4 the speed of the recently released TitanX and 2.7x slower than a GTX 980."

  • Not many ops available in GPU

    • Vector embedding example can't be run on GPU, for instance
      • Theano can do this

  • No OpenCL

  • Memory hungry - far prefers a 16Gb machine to an 8Gb one

  • Inefficient operations

    • No in-place ReLU, for instance

  • C++ build environment requires bazel which is a Java-based horror story

  • PR submission process is via (painful) Gerrit rather than GitHub

  • Legacy Nvidia drivers :

    • 7.0 (rather than 7.5) for the main driver
    • 6.5 (rather than 7.0+) for cuDNN, which is now 'archive', so not even supported

  • No distributed computation (yet), even though that's what Google uses

  • Only Python and C++ APIs (others will be 'community implemented')

  • Incorporates something like fuel (from blocks) as a data-feed engine

  • Whole approach requires implementing many 'client' operations on the TensorFlow 'server' side

  • Currently targets Python 2.7 (though 3.3+ looks like it's coming soon)

  • Would definitely benefit from 'deep learning library' like lasagne

    • theras author has already stated that they'll target TensorFlow
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