Convert numpy array type and values from Float64 to Float32

Question

I am trying to convert threshold array(pickle file of isolation forest from scikit learn) of type from Float64 to Float32

for i in range(len(tree.tree_.threshold)):
    tree.tree_.threshold[i] = tree.tree_.threshold[i].astype(np.float32)

​ Then Printing it

for value in tree.tree_.threshold[:5]:
    print(type(value))
    print(value)

the output i am getting is :

<class 'numpy.float64'>
526226.0
<class 'numpy.float64'>
91.9514312744
<class 'numpy.float64'>
3.60330319405
<class 'numpy.float64'>
-2.0
<class 'numpy.float64'>
-2.0

I am not getting a proper conversion to Float32. I want to convert values and their type to Float32, Did anybody have any workaround this ?

Solution 1

Actually i tried hard but not able to do as the 'sklearn.tree._tree.Tree' objects is not writable.

It is causing a precision issue while generating a PMML file, so i raised a bug over there and they gave an updated solution for it by not converting it in to the Float64 internally.

For more info, you can follow this link: Precision Issue

Solution 2

The problem is that you do not do any type conversion of the numpy array. You calculate a float32 variable and put it as an entry into a float64 numpy array. numpy then converts it properly back to float64

Try someting like this:

a = np.zeros(4,dtype="float64") 
print a.dtype
print type(a[0])
a = np.float32(a)
print a.dtype
print type(a[0])

The output (tested with python 2.7)

float64
<type 'numpy.float64'>
float32
<type 'numpy.float32'>

a is in your case the array tree.tree_.threshold

Solution 3

You can try this:

tree.tree_.threshold[i]=tree.tree_.threshold[i].astype('float32',casting='same_kind’)

Comments

[Akshay Tilekar]

can you explain about np.zeroes parameters, specially "4"

[Glostas]

it was the fasted way of created a numpy array that is filled with something... here zeros. The 4 is just the number of zeros. I choose 4 because I like the number...

[Akshay Tilekar]

------------------------------------------------------------‌​--------------- AttributeError Traceback (most recent call last) <ipython-input-125-d20ee23285ad> in <module>() ----> 1 tree.tree_.threshold = np.zeros(4,dtype="float64") 2 print (tree.tree_.threshold.dtype) 3 tree.tree_.threshold= float32(tree.tree_.threshold) 4 print (a.dtype) AttributeError: attribute 'threshold' of 'sklearn.tree._tree.Tree' objects is not writable

[Akshay Tilekar]

getting same error: AttributeError Traceback (most recent call last) <ipython-input-139-0ba8c9d97878> in <module>() ----> 1 tree.tree_.threshold = np.zeros(4,dtype="float64") 2 print (tree.tree_.threshold.dtype) 3 print (tree.tree_.threshold[0].dtype) 4 tree.tree_.threshold= float32(a) 5 print (tree.tree_.threshold.dtype) AttributeError: attribute 'threshold' of 'sklearn.tree._tree.Tree' objects is not writable

[Glostas]

well, if its not a writable object, you cannnot overwrite it. Therefore the solution wont work. It only works if you use a new numpy array which you probably don't want.

[Akshay Tilekar]

yes, i want to modify the existed one.Is there any way to modify it ?

[Glostas]

you can try tree.tree_.threshold.dtype="float32"

[Akshay Tilekar]

no, it is not allowing me to do it causing an error "ValueError: new type not compatible with array."