Re: [Numpy-discussion] Vectorizing computation

On 02/13/2015 01:03 PM, Francesc Alted wrote:

2015-02-13 12:51 GMT+01:00 Julian Taylor mailto:jtaylor.debian@googlemail.com>:

On 02/13/2015 11:51 AM, Francesc Alted wrote: > Hi, > > I would like to vectorize the next computation: > > nx, ny, nz = 720, 180, 3 > outheight = np.arange(nz) * 3 > oro = np.arange(nx * ny).reshape((nx, ny)) > > def compute1(outheight, oro): > result = np.zeros((nx, ny, nz)) > for ix in range(nx): > for iz in range(nz): > result[ix, :, iz] = outheight[iz] + oro[ix, :] > return result > > I think this should be possible by using an advanced use of broadcasting > in numpy. Anyone willing to post a solution?

result = outheight + oro.reshape(nx, ny, 1)

And 4x faster for my case. Oh my, I am afraid that my mind will never scratch all the amazing possibilities that broadcasting is offering :)

Thank you very much for such an elegant solution!

if speed is a concern this is faster as it has a better data layout for numpy during the computation, but the result may be worse layed out for further processing result = outheight.reshape(nz, 1, 1) + oro return np.rollaxis(result, 0, 3)