Am 12.12.2011 um 15:04 schrieb LASAGNA DAVIDE: > Hi, > > I have written a class for polynomials with negative > exponents like: > > p(x) = a0 + a1*x**-1 + ... + an*x**-n > > The code is this one: > > class NegativeExpPolynomial( object ): > def __init__ ( self, coeffs ): > self.coeffs = np.array( coeffs ) > > def __call__( self, x ): > return sum( (c*x**(-i) for i, c in enumerate( > self.coeffs ) ) ) > > where coeffs = [a0, a1, ..., an]. > > I find that the way i evaluate the polynomial is kind of > *slow*, especially for polynomial with order larger than > ~200 and for arrays x large enough.
I fear that such high orders create a lot of troubles since evaluating them is very sensitive to numerical errors. > Do you have suggestions on how to speed up this code? > Your polynomials with negative exponents are equivalent to a polynomial with positive exponents, but evaluated at 1/x. Therefore you can make use of the efficient polynomial functions of numpy. Try np.polyval(self.coeffs, x) Gregor _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
