LibSPN-Keras: a Keras library for Sum-Product Networks.
Project description
LibSPN Keras
LibSPN Keras is a library for constructing and training Sum-Product Networks. By leveraging the
Keras framework with a TensorFlow backend, it offers both ease-of-use and scalability. Whereas the
previously available libspn
focused on scalability, libspn-keras
offers scalability and
a straightforward Keras-compatible interface.
What are SPNs?
Sum-Product Networks (SPNs) are a probabilistic deep architecture with solid theoretical foundations, which demonstrated state-of-the-art performance in several domains. Yet, surprisingly, there are no mature, general-purpose SPN implementations that would serve as a platform for the community of machine learning researchers centered around SPNs. LibSPN Keras is a new general-purpose Python library, which aims to become such a platform. The library is designed to make it straightforward and effortless to apply various SPN architectures to large-scale datasets and problems. The library achieves scalability and efficiency, thanks to a tight coupling with TensorFlow and Keras, two frameworks already in use by a large community of researchers and developers in multiple domains.
Dependencies
Currently, LibSPN Keras is tested with tensorflow>=2.0
and tensorflow-probability>=0.8.0
.
Installation
pip install libspn-keras
Note on stability of the repo
Currently, the repo is in an alpha state. Hence, one can expect some sporadic breaking changes.
Feature Overview
- Gradient based training for generative and discriminative problems
- Hard EM training for generative problems
- Hard EM training with unweighted weights for generative problems
- Soft EM training (experimental) for generative problems
- Deep Generalized Convolutional Sum-Product Networks
- SPNs with arbitrary decompositions
- Fully compatible with Keras and TensorFlow 2.0
- Input dropout
- Sum child dropout
- Image completion
- Model saving
- Discrete inputs through an
IndicatorLeaf
node - Continuous inputs through
NormalLeaf
,CauchyLeaf
orLaplaceLeaf
. Each of these distributions support both univariate as well as multivariate inputs.
Examples / Tutorials
- Image Classification: A Deep Generalized Convolutional Sum-Product Network (DGC-SPN) with
libspn-keras
in Colab - Image Completion: A Deep Generalized Convolutional Sum-Product Network (DGC-SPN) with
libspn-keras
in Colab. - Randomly structured SPNs for image classification
- Understanding region SPNs
- More to come, and if you would like to see a tutorial on anything in particular please raise an issue!
Check out the way we can build complex DGC-SPNs in a layer-wise fashion:
from libspn_keras import layers
from tensorflow import keras
sum_kwargs = dict(
accumulator_initializer=keras.initializers.TruncatedNormal(
stddev=0.5, mean=1.0),
logspace_accumulators=True
)
sum_product_network = keras.Sequential([
layers.NormalLeaf(
input_shape=(28, 28, 1),
num_components=16,
location_trainable=True,
location_initializer=keras.initializers.TruncatedNormal(
stddev=1.0, mean=0.0)
),
# Non-overlapping products
layers.Conv2DProduct(
depthwise=True,
strides=[2, 2],
dilations=[1, 1],
kernel_size=[2, 2],
padding='valid'
),
layers.Local2DSum(num_sums=16, **sum_kwargs),
# Non-overlapping products
layers.Conv2DProduct(
depthwise=True,
strides=[2, 2],
dilations=[1, 1],
kernel_size=[2, 2],
padding='valid'
),
layers.Local2DSum(num_sums=32, **sum_kwargs),
# Overlapping products, starting at dilations [1, 1]
layers.Conv2DProduct(
depthwise=True,
strides=[1, 1],
dilations=[1, 1],
kernel_size=[2, 2],
padding='full'
),
layers.Local2DSum(num_sums=32, **sum_kwargs),
# Overlapping products, with dilations [2, 2] and full padding
layers.Conv2DProduct(
depthwise=True,
strides=[1, 1],
dilations=[2, 2],
kernel_size=[2, 2],
padding='full'
),
layers.Local2DSum(num_sums=64, **sum_kwargs),
# Overlapping products, with dilations [4, 4] and full padding
layers.Conv2DProduct(
depthwise=True,
strides=[1, 1],
dilations=[4, 4],
kernel_size=[2, 2],
padding='full'
),
layers.Local2DSum(num_sums=64, **sum_kwargs),
# Overlapping products, with dilations [8, 8] and 'final' padding to combine
# all scopes
layers.Conv2DProduct(
depthwise=True,
strides=[1, 1],
dilations=[8, 8],
kernel_size=[2, 2],
padding='final'
),
layers.SpatialToRegions(),
# Class roots
layers.DenseSum(num_sums=10, **sum_kwargs),
layers.RootSum(
return_weighted_child_logits=True,
logspace_accumulators=True,
accumulator_initializer=keras.initializers.TruncatedNormal(
stddev=0.0, mean=1.0)
)
])
sum_product_network.summary()
Which produces:
Model: "sequential"
_________________________________________________________________
Layer (type) Output Shape Param #
=================================================================
normal_leaf (NormalLeaf) (None, 28, 28, 16) 25088
_________________________________________________________________
conv2d_product (Conv2DProduc (None, 14, 14, 16) 4
_________________________________________________________________
local2d_sum (Local2DSum) (None, 14, 14, 16) 50176
_________________________________________________________________
conv2d_product_1 (Conv2DProd (None, 7, 7, 16) 4
_________________________________________________________________
local2d_sum_1 (Local2DSum) (None, 7, 7, 32) 25088
_________________________________________________________________
conv2d_product_2 (Conv2DProd (None, 8, 8, 32) 4
_________________________________________________________________
local2d_sum_2 (Local2DSum) (None, 8, 8, 32) 65536
_________________________________________________________________
conv2d_product_3 (Conv2DProd (None, 10, 10, 32) 4
_________________________________________________________________
local2d_sum_3 (Local2DSum) (None, 10, 10, 64) 204800
_________________________________________________________________
conv2d_product_4 (Conv2DProd (None, 14, 14, 64) 4
_________________________________________________________________
local2d_sum_4 (Local2DSum) (None, 14, 14, 64) 802816
_________________________________________________________________
conv2d_product_5 (Conv2DProd (None, 8, 8, 64) 4
_________________________________________________________________
spatial_to_regions (SpatialT (1, 1, None, 4096) 0
_________________________________________________________________
dense_sum (DenseSum) (1, 1, None, 10) 40960
_________________________________________________________________
root_sum (RootSum) (None, 10) 10
=================================================================
Total params: 1,214,498
Trainable params: 1,201,930
Non-trainable params: 12,568
_________________________________________________________________
TODOs
- Structure learning
- Advanced regularization e.g. pruning or auxiliary losses on weight accumulators
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