
.. _tutorial_printing_drawing:

==============================
Printing/Drawing Theano graphs
==============================


Theano provides the functions :func:`theano.printing.pprint` and
:func:`theano.printing.debugprint` to print a graph to the terminal before or
after compilation. :func:`pprint` is more compact and math-like,
:func:`debugprint` is more verbose. Theano also provides :func:`pydotprint`
that creates an image of the function. You can read about them in
:ref:`libdoc_printing`.

.. note::


    When printing Theano functions, they can sometimes be hard to
    read.  To help with this, you can disable some Theano optimizations
    by using the Theano flag:
    ``optimizer_excluding=fusion:inplace``. Do not use this during
    real job execution, as this will make the graph slower and use more
    memory.

Consider again the logistic regression example:

>>> import numpy
>>> import theano
>>> import theano.tensor as T
>>> rng = numpy.random
>>> # Training data
>>> N = 400
>>> feats = 784
>>> D = (rng.randn(N, feats).astype(theano.config.floatX), rng.randint(size=N,low=0, high=2).astype(theano.config.floatX))
>>> training_steps = 10000
>>> # Declare Theano symbolic variables
>>> x = T.matrix("x")
>>> y = T.vector("y")
>>> w = theano.shared(rng.randn(feats).astype(theano.config.floatX), name="w")
>>> b = theano.shared(numpy.asarray(0., dtype=theano.config.floatX), name="b")
>>> x.tag.test_value = D[0]
>>> y.tag.test_value = D[1]
>>> # Construct Theano expression graph
>>> p_1 = 1 / (1 + T.exp(-T.dot(x, w)-b)) # Probability of having a one
>>> prediction = p_1 > 0.5 # The prediction that is done: 0 or 1
>>> # Compute gradients
>>> xent = -y*T.log(p_1) - (1-y)*T.log(1-p_1) # Cross-entropy
>>> cost = xent.mean() + 0.01*(w**2).sum() # The cost to optimize
>>> gw,gb = T.grad(cost, [w,b])
>>> # Training and prediction function
>>> train = theano.function(inputs=[x,y], outputs=[prediction, xent], updates=[[w, w-0.01*gw], [b, b-0.01*gb]], name = "train")
>>> predict = theano.function(inputs=[x], outputs=prediction, name = "predict")


Pretty Printing
===============

>>> theano.printing.pprint(prediction) # doctest: +NORMALIZE_WHITESPACE
'gt((TensorConstant{1} / (TensorConstant{1} + exp(((-(x \\dot w)) - b)))),
TensorConstant{0.5})'


Debug Print
===========

The pre-compilation graph:

>>> theano.printing.debugprint(prediction) # doctest: +NORMALIZE_WHITESPACE
    Elemwise{gt,no_inplace} [@A] ''
    |Elemwise{true_div,no_inplace} [@B] ''
    | |DimShuffle{x} [@C] ''
    | | |TensorConstant{1} [@D]
    | |Elemwise{add,no_inplace} [@E] ''
    |   |DimShuffle{x} [@F] ''
    |   | |TensorConstant{1} [@D]
    |   |Elemwise{exp,no_inplace} [@G] ''
    |     |Elemwise{sub,no_inplace} [@H] ''
    |       |Elemwise{neg,no_inplace} [@I] ''
    |       | |dot [@J] ''
    |       |   |x [@K]
    |       |   |w [@L]
    |       |DimShuffle{x} [@M] ''
    |         |b [@N]
    |DimShuffle{x} [@O] ''
      |TensorConstant{0.5} [@P]

The post-compilation graph:

>>> theano.printing.debugprint(predict) # doctest: +NORMALIZE_WHITESPACE
    Elemwise{Composite{GT(scalar_sigmoid((-((-i0) - i1))), i2)}} [@A] ''   4
     |CGemv{inplace} [@B] ''   3
     | |Alloc [@C] ''   2
     | | |TensorConstant{0.0} [@D]
     | | |Shape_i{0} [@E] ''   1
     | |   |x [@F]
     | |TensorConstant{1.0} [@G]
     | |x [@F]
     | |w [@H]
     | |TensorConstant{0.0} [@D]
     |InplaceDimShuffle{x} [@I] ''   0
     | |b [@J]
     |TensorConstant{(1,) of 0.5} [@K]


Picture Printing of Graphs
==========================

The pre-compilation graph:

>>> theano.printing.pydotprint(prediction, outfile="pics/logreg_pydotprint_prediction.png", var_with_name_simple=True)
The output file is available at pics/logreg_pydotprint_prediction.png

.. image:: ./pics/logreg_pydotprint_prediction.png
   :width: 800 px

The post-compilation graph:

>>> theano.printing.pydotprint(predict, outfile="pics/logreg_pydotprint_predict.png", var_with_name_simple=True)
The output file is available at pics/logreg_pydotprint_predict.png

.. image:: ./pics/logreg_pydotprint_predict.png
   :width: 800 px

The optimized training graph:

>>> theano.printing.pydotprint(train, outfile="pics/logreg_pydotprint_train.png", var_with_name_simple=True)
The output file is available at pics/logreg_pydotprint_train.png

.. image:: ./pics/logreg_pydotprint_train.png
   :width: 1500 px
