andrea_gavana@tin.it writes:
Hello NG,
in one script, I generated a matrix "dx" which has a (200000, 10) shape. Well, everything is working fine (matrix multiplication, sum, exponentiation etc...), but I'm having problems in squaring all elements of this matrix.
Suppose I have:
import Numeric import random
dx = Numeric.ones((200000,10), Numeric.Float0, savespace=1) dx[:,:] = random.random()
It's faster to do import RandomArray dx = RandomArray.random((200000,10)).astype(Numeric.Float0) dx.savespace(1) (it won't use the same RNG as random, though)
td1 = dx*2.0 ---> This takes about 0.2 seconds td2 = dx**2.0 ---> This takes about 6 seconds
Why this difference? And why it is so slow the exponentiation? I have tried the same operation in Matlab and it was almost instantaneous. I don't want to stick with Matlab, noting the great job the Numeric developers have done.
Hmm, I don't see this, with either 23.8 or 24.0b2. What version of Numeric are you using, and on what platform? dx**2 uses the C 'pow' function on each element (so using 2 or 2.0 here doesn't make a difference), so may be your platform pow() is slow. dx*dx should be faster (it takes 80% of the time that dx**2 does on my machine). -- |>|\/|< /--------------------------------------------------------------------------\ |David M. Cooke http://arbutus.physics.mcmaster.ca/dmc/ |cookedm@physics.mcmaster.ca