Aaa ped-23-Artificial Neural Network: Keras and Tensorfow

Artifiial Neural Network:�
Keras and Tensorfow
AAA-Python Edition

Plan
●
1- Keras and Tensorfoo
●
2- MLP oith Tensorfoow High Level API
●
3- MLP oith Keras
●
4- More about tensorfoo
●
5- Tensorboard

3
1-Kerasand
Tensorfow
[By Amina Delali]
IntroductionIntroduction
●
Kerasw a high level API to build & train a deep learning
model.
●
It is oritten in python and runs on the top of Tensorfow
●
Implementationw
Application Programming
Interface: it defines how to
interact and use built-in
Keras modules.
We will talk about
in the next lesson
●
tf.keras : tensorflow implementation of keras
●
keras: Keras library (apart)
We will use the second
implementation

4
1-Kerasand
Tensorfow
[By Amina Delali]
KerasKeras
●
●
Tensorflow keras
version may no be
up to date (right
now, this is not the
case)
●
The default saving formats of
the model’s weights are
different

5
1-Kerasand
Tensorfow
[By Amina Delali]
TensorfooTensorfoo
●
Tensorfow� an open sourie library that enables you develop
and train ML models.
●
There is 2 important releases of Tensorfow�
➢
Versions 1.*.* defned by the APIs r1.*
➢
Versions 2.*.* defned by the APIs r2.*
●
Right now there is only one
version: TensorFlow 2.0 Alpha
defined by the API r2.0
●
Unlike the previous release, you
have to manually install it on
google colab.
In the previous
example, we wrote:
tf.VERSION

6
2-MLPwith
Tensorfow�High
LevelAPI
[By Amina Delali]
Using tensorfooUsing tensorfoo
●
There are 2 oays to implement artifcial neural netoorks in
tensorfoow
➢
Using the high level API
➢
Using the low level API
●
For example, building and training an MLP Using the high level API
is simple and trivial.
●
The loo level API, permits more fexibility in defning the
architecture of your model, but oill require more code.
●
In our frst example oe oill use the high level API. In other oorld,
oe oill use its premade estimators
●
Just a reminder, oe oill implement the same MLP oe defned in
the previous lesson.

7
2-MLPwith
Tensorfow�High
LevelAPI
[By Amina Delali]
StepsSteps
●
Elements to consider ohen using a pre-made estimator of
tensorfoow
➢
Defne at least one input funitionw it oill be used by the
estimator to create a structured data that it oill use later for
training and/or predicting. For our example, the function oill
return a tuple ofw
➔
Features� a dictionary oith the features names and their
corresponding values.
➔
The corresponding labels
➢
Defne the features iolumnsw used to build the estimator. In
our case, they oill be an array of the numerii feature
iolumns constructed using tensorfoo. They indicate the
features to use from the data returned from the previous defned
input funition.
➢
Build the estimator and use it for training, predicting … etc
The number of values will determine the
batch size

8
2-MLPwith
Tensorfow�High
LevelAPI
[By Amina Delali]
Build the MLPBuild the MLP
We will use sklearn to
use iris dataset
The features values
will be numeric
The keys correspond
to those used in the
input function
Approximately the
same as tansig function
Approximately the
same as tansig function
Tanh formula:
tanh(x)=
e
x
−e
− x
e
x
+e−x
To be able to use the
function for making
prediction

9
2-MLPwith
Tensorfow�High
LevelAPI
[By Amina Delali]
Training and evaluatingTraining and evaluating
●
Our input function dosen’t return fixed data values;the data must be passed as
parameters. This way, we can use the same input function for both training and
evaluating our model
●
The train and evaluate methods require a callable function. So, to use our defined
function, we have to define another one that calls our function with the desired
data parameter==> will lead to have two sepearate input functions: one for training
and one for testing.
●
To avoid defining 2 functions, we will use the python high order function
lambda: we give it a function’s definition, and it returns a function (without a
name).
Loss is
calculated
using softmax
cross entropy.

10
2-MLPwith
Tensorfow�High
LevelAPI
[By Amina Delali]
PredictingPredicting
●
We expected to have the
right predictions since we
used the test set that
scored 1.0 accuracy
Concerning the
labels array in the
training and
evaluating, we didn’t
have to convert it to
a multidimensional
array.
Concerning the
labels array in the
training and
evaluating, we didn’t
have to convert it to
a multidimensional
array.
We didn’t have to
define a function that
returns the
corresponding class for
each prediction (the
predicted class is in
the output of the
prediction).
We didn’t have to
define a function that
returns the
corresponding class for
each prediction (the
predicted class is in
the output of the
prediction).

11
3-MLPwith
Keras
[By Amina Delali]
Sequential modelSequential model
●
There is 2 oays to build a ANN oith kerasw
➢
Using a sequential modelw to build a sequential stack of layers.
Ideal for building simple, fully-connected netoorks.
➢
Using a funitional modelw ideal to build complex model
topologies.
●
To build our MLP oith the Sequential model, oe have tow
➢
Defne our layersw
➔
Specifying the number of neurons
➔
Selecting the activation function
➔
Defne hoo the neuron’s oeights (and the bias term) oill be
initialized
➔
Defne the optimization methodw it defnes hoo the learning is
performed.
➔
Defne the loss functionw the function to be minimized during
the learning.

12
3-MLPwith
Keras
[By Amina Delali]
Building our modelBuilding our model
It specifies a regular densely-
connected NN layer: applies the
activation function on a weighted
sum.
●
It specifies the function that will be
used to initialize the weights
●
The truncated normal
distribution: generates the same
values as the normal distribution
except that values more than two
standard deviations from the mean
are discarded and redrawn
●
The default values are:
➢
Mean: 0.0
➢
Standard deviation: 0.05
●
The input array will have the
shape : (*,4)
To be compatible
with our keras
example

13
3-MLPwith
Keras
[By Amina Delali]
TrainingTraining
The loss function will
be the mean square
error
The learning
algorithm will be the
stochastic gradient
descent
The metrics that will be returned by the
evaluation method in addition to the loss
function value.
For example:
The label 2 will be converted into 0. 0. 1.

14
3-MLPwith
Keras
[By Amina Delali]
Evaluating and predictingEvaluating and predicting
●
A correct
prediction
A wrong
prediction
We defined
the
prediction
class to
extract the
class
correspond
ing to the
highest
probability
We defined
the
prediction
class to
extract the
class
correspond
ing to the
highest
probability

15
3-MLPwith
Keras
[By Amina Delali]
Cross entropyCross entropy
●
For a multi-class classifcation, using the softmax activation
function, the cross entropy loss function is a better choice to
compute the cost to minimize.
●
It takes into consideration the values of the probabilities
returned by the output neurons instead of just taking into
account correct or the orong classifcationw
J(w)=
−1
m
∑
i=1
m
∑
k=1
K
yk
(i)
log( ^pk
(i)
)
Predicted
probability for
the instance i
for the class
k
The true label value,
== 1 if the class of
the instance (i) is k,
otherwise it equals to
0
Number
of
instances
Number
of
Classes
The
weights
to be
updated

16
3-MLPwith
Keras
[By Amina Delali]
Applying the cross entropyApplying the cross entropy
●
We have same
accuracy result as we
had with tensorflow
(because of the use
of the cross entropy
loss function)
We changed only the
loss function
We don’t have to convert our
labels array
But we still need a
function to extract the
predicted class

17
4-Moreabout
tensorfow
[By Amina Delali]
Graph, tensor, operationGraph, tensor, operation
●
With tensorfow it is possible to defne your model as a graph.
●
The concept is simplew
➢
You defne your graphw the steps of the computation( the
tensorfoo program)
➢
You run your graph
●
Your graph may containw
➢
Tensorsw the central unit of data. Arrays of any number of
dimension (a scalar is a tensor oith dimension (rank:) 0). They
also represent the Edges of the graph.
➢
Operationsw the nodes of the graph. They describe calculations
oith tensors . We can use constructor for operations as folloow
➔
tensorfoo.constant(3.5)w creates an operation that oill
produce the value 3.5 and add it to the default graph
(TensorFloo provides a default graph that is an implicit
argument to all API functions in the same context.)

18
4-Moreabout
tensorfow
[By Amina Delali]
TensorboardTensorboard
●
Tenorboard is a suite of visualization tools that can be utilised
to visualize TensorFloo graph, plot quantitative metriis about
the exeiution of your graph.
●
To use Tensorboard oith google iolab, you can use the library
tensorboardiolab�
By clicking on this link
you can access to
tensorboard

19
5-Tensorboard
[By Amina Delali]
A simple graph in tensorboardA simple graph in tensorboard
●
Tensor produced by the
operation tf.constant
Log file generated in
“./Graph/”
Visualization generated
in tensorboard

20
5-Tensorboard
[By Amina Delali]
A simple graph in tensorboard (suite)A simple graph in tensorboard (suite)
If you click on the node
“add”

21
5-Tensorboard
[By Amina Delali]
Tensorboard oith KerasTensorboard oith Keras
We use the variable we already
defined by TensorBoardColab() call
Since we specified
“accuracy” and “mae”
as metrics, their
progression graphs will
be generated in
tenorboard

22
5-Tensorboard
[By Amina Delali]
Tensorboard oith KerasTensorboard oith Keras
The generated graph

Referenies
●
Keras, httpsw//ooo.tensorfoo.org/guide/keras
●
TensorBoardw Visualizing Learning,
httpsw//ooo.tensorfoo.org/guide/summaries_and_tensorboard
●
Keras 2.2.4, httpsw//pypi.org/project/Keras/
●
Premade Estimators
httpsw//ooo.tensorfoo.org/guide/premade_estimators
●
Feature Columns,
httpsw//ooo.tensorfoo.org/guide/feature_columns
●
tansig ,
httpsw//edoras.sdsu.edu/doc/matlab/toolbox/nnet/tansig.html
●
Hyperbolic functions
httpsw//ooo.math10.com/en/algebra/hyperbolic-
functions/hyperbolic-functions.html
●
Tensorfoo, Introduction,
httpsw//ooo.tensorfoo.org/guide/loo_level_intro
●
Hands-on machine learning oith Scikit-Learn and TensorFloow
concepts, tools, and techniques to build intelligent systems.
O’Reilly Media, Inc.

Aaa ped-23-Artificial Neural Network: Keras and Tensorfow

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