tf.py_func , custom tensorflow function getting applied to only the first element in the tensor - python-2.7

Question

I am new to tensorflow and was playing around with a deep learning network. I wanted to do a custom rounding off on all the weights after each iteration. As the round function in tensorflow library doesn't give you the option to round the values down to a certain number of decimal points.
So I wrote this
import numpy as np
import tensorflow as tf
from tensorflow.python.framework import ops
np_prec = lambda x: np.round(x,3).astype(np.float32)
def tf_prec(x,name=None):
with ops.name_scope( "d_spiky", name,[x]) as name:
y = tf.py_func(np_prec,
[x],
[tf.float32],
name=name,
stateful=False)
return y[0]
with tf.Session() as sess:
x = tf.constant([0.234567,0.712,1.2,1.7])
y = tf_prec(x)
y = tf_prec(x)
tf.global_variables_initializer
print(x.eval(), y.eval())
The output I got was this
[ 0.234567 0.71200001 1.20000005 1.70000005] [ 0.235 0.71200001 1.20000005 1.70000005]
So the custom rounding off worked only on the first item in the tensor and I am not sure about what I am doing wrong. Thanks in advance.

Answer 1

The error here because of the following line,
np_prec = lambda x: np.round(x,3).astype(np.float32)
you are casting the output to np.float32. You can verify the error by the following code,
print(np.round([0.234567,0.712,1.2,1.7], 3).astype(np.float32)) #prints [ 0.235 0.71200001 1.20000005 1.70000005]
The default output of np.round is float64. Moreover, you also have to change the Tout argument in tf.py_func to float64.
I have given the following code with the above fix and commented where necessary.
import numpy as np
import tensorflow as tf
from tensorflow.python.framework import ops
np_prec = lambda x: np.round(x,3)
def tf_prec(x,name=None):
with ops.name_scope( "d_spiky", name,[x]) as name:
y = tf.py_func(np_prec,
[x],
[tf.float64], #changed this line to tf.float64
name=name,
stateful=False)
return y[0]
with tf.Session() as sess:
x = tf.constant([0.234567,0.712,1.2,1.7],dtype=np.float64) #specify the input data type np.float64
y = tf_prec(x)
y = tf_prec(x)
tf.global_variables_initializer
print(x.eval(), y.eval())
Hope this helps.