X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo%2Feja%2Feja_utils.py;h=b6b0a0327c19842ce654023b00bf6e0b9af539a1;hb=1e9700cdd04434465ffcad148d078f7fa361e426;hp=cf75e325697dcefb3bf682b855f8d83e3e4f89e2;hpb=c16c11d5b4cd015b6d7516a175a92f46e03bd2d7;p=sage.d.git diff --git a/mjo/eja/eja_utils.py b/mjo/eja/eja_utils.py index cf75e32..b6b0a03 100644 --- a/mjo/eja/eja_utils.py +++ b/mjo/eja/eja_utils.py @@ -1,76 +1,4 @@ from sage.modules.free_module_element import vector -from sage.rings.number_field.number_field import NumberField -from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing -from sage.rings.real_lazy import RLF def _mat2vec(m): return vector(m.base_ring(), m.list()) - -def gram_schmidt(v): - """ - Perform Gram-Schmidt on the list ``v`` which are assumed to be - vectors over the same base ring. Returns a list of orthonormalized - vectors over the smallest extention ring containing the necessary - roots. - - SETUP:: - - sage: from mjo.eja.eja_utils import gram_schmidt - - EXAMPLES:: - - sage: v1 = vector(QQ,(1,2,3)) - sage: v2 = vector(QQ,(1,-1,6)) - sage: v3 = vector(QQ,(2,1,-1)) - sage: v = [v1,v2,v3] - sage: u = gram_schmidt(v) - sage: all( u_i.inner_product(u_i).sqrt() == 1 for u_i in u ) - True - sage: bool(u[0].inner_product(u[1]) == 0) - True - sage: bool(u[0].inner_product(u[2]) == 0) - True - sage: bool(u[1].inner_product(u[2]) == 0) - True - - TESTS: - - Ensure that zero vectors don't get in the way:: - - sage: v1 = vector(QQ,(1,2,3)) - sage: v2 = vector(QQ,(1,-1,6)) - sage: v3 = vector(QQ,(0,0,0)) - sage: v = [v1,v2,v3] - sage: len(gram_schmidt(v)) == 2 - True - - """ - def proj(x,y): - return (y.inner_product(x)/x.inner_product(x))*x - - v = list(v) # make a copy, don't clobber the input - - # Drop all zero vectors before we start. - v = [ v_i for v_i in v if not v_i.is_zero() ] - - if len(v) == 0: - # cool - return v - - R = v[0].base_ring() - - # First orthogonalize... - for i in xrange(1,len(v)): - # Earlier vectors can be made into zero so we have to ignore them. - v[i] -= sum( proj(v[j],v[i]) for j in range(i) if not v[j].is_zero() ) - - # And now drop all zero vectors again if they were "orthogonalized out." - v = [ v_i for v_i in v if not v_i.is_zero() ] - - # Just normalize. If the algebra is missing the roots, we can't add - # them here because then our subalgebra would have a bigger field - # than the superalgebra. - for i in xrange(len(v)): - v[i] = v[i] / v[i].norm() - - return v