Python: Making numpy default to float32

25
votes

Is there any clean way of setting numpy to use float32 values instead of float64 globally?

3
pythonnumpynumbers
Closely related: stackoverflow.com/questions/5350342/… - Sven Marnach
Also an interesting discussion on scipy list: old.nabble.com/switching-to-float32-ts24203533.html#a24203533 - joris
Saw the nabble conversation but missed the float128 (thanks sven), and it appears they're both saying the same thing, 'No, not really'. On the Nabble discussion there was then mention of adding it to the cookbook which would be nice. I myself just did a few hacks similar to the float128 question sven mentioned (and answered). Pity - Bolster

3 Answers

13
votes

Not that I am aware of. You either need to specify the dtype explicitly when you call the constructor for any array, or cast an array to float32 (use the ndarray.astype method) before passing it to your GPU code (I take it this is what the question pertains to?). If it is the GPU case you are really worried about, I favor the latter - it can become very annoying to try and keep everything in single precision without an extremely thorough understanding of the numpy broadcasting rules and very carefully designed code.

Another alternative might be to create your own methods which overload the standard numpy constructors (so numpy.zeros, numpy.ones, numpy.empty). That should go pretty close to keeping everything in float32.

6
votes

This question showed up on the NumPy issue tracker. The answer is:

There isn't, sorry. And I'm afraid we're unlikely to add such a thing[.]

2
votes

For each function you can overload by:

def array(*args, **kwargs):
    kwargs.setdefault("dtype", np.float32)
    return np.array(*args, **kwargs)

As posted by njsmith on github