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Neural network libraries.
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Neural Network Libraries

Neural Network Libraries is a deep learning framework that is intended to be used for research,
development and production. We aim to have it running everywhere: desktop PCs, HPC
clusters, embedded devices and production servers.

  • Neural Network Console, a Windows GUI app for neural network developement, has been released.
  • The GitHub repository of CUDA extension of Neural Network Libraries can be found here.


Installing Neural Network Libraries is easy:

pip install nnabla

This installs the CPU version of Neural Network Libraries. GPU-acceleration can be added by installing the CUDA extension with pip install nnabla-ext-cuda.


Easy, flexible and expressive

The Python API built on the Neural Network Libraries C++11 core gives you flexibility and
productivity. For example, a two layer neural network with classification loss
can be defined in the following 5 lines of codes (hyper parameters are enclosed
by <>).

import nnabla as nn
import nnabla.functions as F
import nnabla.parametric_functions as PF

x = nn.Variable(<input_shape>)
t = nn.Variable(<target_shape>)
h = F.tanh(PF.affine(x, <hidden_size>, name='affine1'))
y = PF.affine(h, <target_size>, name='affine2')
loss = F.mean(F.softmax_cross_entropy(y, t))

Training can be done by:

import nnabla.solvers as S

# Create a solver (parameter updater)
solver = S.Adam(<solver_params>)

# Training iteration
for n in range(<num_training_iterations>):
    # Setting data from any data source
    x.d = <set data>
    t.d = <set label>
    # Initialize gradients
    # Forward and backward execution
    # Update parameters by computed gradients

The dynamic computation graph enables flexible runtime network construction.
Neural Network Libraries can use both paradigms of static and dynamic graphs,
both using the same API.

x.d = <set data>
t.d = <set label>
drop_depth = np.random.rand(<num_stochastic_layers>) < <layer_drop_ratio>
with nn.auto_forward():
    h = F.relu(PF.convolution(x, <hidden_size>, (3, 3), pad=(1, 1), name='conv0'))
    for i in range(<num_stochastic_layers>):
        if drop_depth[i]:
            continue  # Stochastically drop a layer
        h2 = F.relu(PF.convolution(x, <hidden_size>, (3, 3), pad=(1, 1), 
                                   name='conv%d' % (i + 1)))
        h = F.add2(h, h2)
    y = PF.affine(h, <target_size>, name='classification')
    loss = F.mean(F.softmax_cross_entropy(y, t))
# Backward computation (can also be done in dynamically executed graph)

Portable and multi-platform

  • Python API can be used on Linux and Windows
  • Most of the library code is written in C++11, deployable to embedded devices


  • Easy to add new modules like neural network operators and optimizers
  • The library allows developers to add specialized implementations (e.g., for
    FPGA, ...). For example, we provide CUDA backend as an extension, which gives
    speed-up by GPU accelerated computation.


  • High speed on a single CUDA GPU
  • Memory optimization engine
  • Multiple GPU support



Getting started

  • A number of Jupyter notebook tutorials can be found in the tutorial folder.
    We recommend starting from by_examples.ipynb for a first
    working example in Neural Network Libraries and python_api.ipynb for an introduction into the
    Neural Network Libraries API.

  • We also provide some more sophisticated examples in the examples folder.

  • C++ API examples are avaiailable in exampels/cpp.

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