Hi, On Wed, May 11, 2011 at 8:28 AM, Elfnor <elf...@gmail.com> wrote:
> > Hi > > The following code produces the desired result but has a slow triple loop > iterating over the matrix multiplication. > > I'm sure it can be eliminated with a neat indexing trick but I can't figure > out how. > > Any suggestions please? > ----------------------------- > import numpy > #define domain of function > x = numpy.linspace(-5,5,64) > y = numpy.linspace(-5,5,64) > z = numpy.linspace(-5,5,64) > > #calculate f at each point in domain > a = 5.0 > b = 3.0 > c = 2.0 > #ellipsoid > E = numpy.array([[1/a**2, 0 , 0 , 0 ], > [ 0 ,1/b**2 , 0 , 0 ], > [ 0 , 0 ,1/c**2, 0 ], > [ 0 , 0 , 0 , -1 ]]) > > f = numpy.zeros((x.size,y.size,z.size)) > > for i,xi in enumerate(x): > for j,yj in enumerate(y): > for k,zk in enumerate(z): > X = numpy.array([xi,yj,zk,1]) > f[i,j,k] = numpy.dot(numpy.dot(X.T,E),X) > ----------------------------------- > Something like this: n= 64 u= np.linspace(-5, 5, n)[None, :] u0= u.repeat(n** 2)[None, :] u1= u.repeat(n)[None, :].repeat(n, axis= 0).reshape(1, -1) u2= u.repeat(n** 2, axis= 0).reshape(1, -1) U= np.r_[u0, u1, u2, np.ones((1, n** 3))] f= (np.dot(E, U)* U).sum(0).reshape(n, n, n) Regards,eat > > Thanks Eleanor > -- > View this message in context: > http://old.nabble.com/Need-to-eliminate-a-nested-loop-tp31591457p31591457.html > Sent from the Numpy-discussion mailing list archive at Nabble.com. > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion >
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