[Numpy-discussion] A proposal to implement round in C Was: Rookie problems - Why is C-code much faster?
Mads Ipsen
mpi at osc.kiku.dk
Wed Feb 22 02:27:02 CST 2006
On Tue, 21 Feb 2006, Sasha wrote:
> > python -m timeit -s "from numpy import array; x = array([1.5]*1000)" "(x+0.5).astype(int).astype(float)"
> 100000 loops, best of 3: 18.8 usec per loop
> > python -m timeit -s
just want to point out that the function
foo(x) = (x+0.5).astype(int).astype(float)
is different from around. For
x = array([1.2, 1.8])
it works but for
x = array([-1.2, -1.8])
you get
around(x) = array([-1., -2.])
whereas foo(x) gives
foo(x) = array([0., -1.])
Using
foo(x) = where(greater(x,0),x+0.5,x-0.5).astype(int).astype(float)
will work.
// Mads
More information about the Numpy-discussion
mailing list