X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=mjo%2Fcone%2Frearrangement.py;h=0bbf95bb7603bed819d4b9e91a4b148856dc464c;hb=928b7d49fda98ff105c92293b5797bb7a2b9873a;hp=6ea993c3b1b441980e648ee2e1a6d4ebaf964c57;hpb=edbce26685b7e62d04da8f037e51621551292225;p=sage.d.git diff --git a/mjo/cone/rearrangement.py b/mjo/cone/rearrangement.py index 6ea993c..0bbf95b 100644 --- a/mjo/cone/rearrangement.py +++ b/mjo/cone/rearrangement.py @@ -1,13 +1,6 @@ -# Sage doesn't load ~/.sage/init.sage during testing (sage -t), so we -# have to explicitly mangle our sitedir here so that "mjo.cone" -# resolves. -from os.path import abspath -from site import addsitedir -addsitedir(abspath('../../')) - from sage.all import * -def rearrangement_cone(p,n): +def rearrangement_cone(p,n,lattice=None): r""" Return the rearrangement cone of order ``p`` in ``n`` dimensions. @@ -26,14 +19,47 @@ def rearrangement_cone(p,n): INPUT: - - ``p`` -- The number of components to "rearrange." + - ``p`` -- The number of components to "rearrange." + + - ``n`` -- The dimension of the ambient space for the resulting cone. - - ``n`` -- The dimension of the ambient space for the resulting cone. + - ``lattice`` -- (default: ``None``) an ambient lattice of rank ``n`` + to be passed to the :func:`Cone` constructor. OUTPUT: A polyhedral closed convex cone object representing a rearrangement - cone of order ``p`` in ``n`` dimensions. + cone of order ``p`` in ``n`` dimensions. Each generating ray will + have the integer ring as its base ring. + + If a ``lattice`` was specified, then the resulting cone will live in + that lattice unless its rank is incompatible with the dimension + ``n`` (in which case a ``ValueError`` is raised). + + ALGORITHM: + + The generators for the rearrangement cone are given by [Jeong]_ + Theorem 5.2.3. + + REFERENCES: + + .. [GowdaJeong] Muddappa Seetharama Gowda and Juyoung Jeong. + Spectral cones in Euclidean Jordan algebras. + Linear Algebra and its Applications, 509, 286-305. + doi:10.1016/j.laa.2016.08.004 + + .. [HenrionSeeger] Rene Henrion and Alberto Seeger. + Inradius and Circumradius of Various Convex Cones Arising in + Applications. Set-Valued and Variational Analysis, 18(3-4), + 483-511, 2010. doi:10.1007/s11228-010-0150-z + + .. [Jeong] Juyoung Jeong. + Spectral sets and functions on Euclidean Jordan algebras. + University of Maryland, Baltimore County, Ph.D. thesis, 2017. + + SETUP:: + + sage: from mjo.cone.rearrangement import rearrangement_cone EXAMPLES: @@ -53,20 +79,116 @@ def rearrangement_cone(p,n): sage: rearrangement_cone(5,5).lineality() 4 + All rearrangement cones are proper when ``p`` is less than ``n`` by + [Jeong]_ Proposition 5.2.1:: + + sage: all( rearrangement_cone(p,n).is_proper() + ....: for n in range(10) + ....: for p in range(1, n) ) + True + + The Lyapunov rank of the rearrangement cone of order ``p`` in ``n`` + dimensions is ``n`` for ``p == 1`` or ``p == n`` and one otherwise, + by [Jeong]_ Corollary 5.2.4:: + + sage: all( rearrangement_cone(p,n).lyapunov_rank() == n + ....: for n in range(2, 10) + ....: for p in [1, n-1] ) + True + sage: all( rearrangement_cone(p,n).lyapunov_rank() == 1 + ....: for n in range(3, 10) + ....: for p in range(2, n-1) ) + True + TESTS: - todo. - should be permutation invariant. - should have the expected lyapunov rank. - just loop through them all for n <= 10 and p < n? + All rearrangement cones are permutation-invariant by [Jeong]_ + Proposition 5.2.1:: - """ + sage: n = ZZ.random_element(2,10).abs() + sage: p = ZZ.random_element(1,n) + sage: K = rearrangement_cone(p,n) + sage: P = SymmetricGroup(n).random_element().matrix() + sage: all( K.contains(P*r) for r in K ) + True + + The smallest ``p`` components of every element of the rearrangement + cone should sum to a nonnegative number (this tests that the + generators really are what we think they are):: + + sage: def _has_rearrangement_property(v,p): + ....: return sum( sorted(v)[0:p] ) >= 0 + sage: all( _has_rearrangement_property( + ....: rearrangement_cone(p,n).random_element(), + ....: p + ....: ) + ....: for n in range(2, 10) + ....: for p in range(1, n-1) + ....: ) + True - def d(j): - v = [1]*n # Create the list of all ones... - v[j] = 1 - p # Now "fix" the ``j``th entry. - return v + The rearrangenent cone of order ``p`` is contained in the rearrangement + cone of order ``p + 1`` by [Jeong]_ Proposition 5.2.1:: - V = VectorSpace(QQ, n) - G = V.basis() + [ d(j) for j in range(n) ] - return Cone(G) + sage: n = ZZ.random_element(2,10) + sage: p = ZZ.random_element(1,n) + sage: K1 = rearrangement_cone(p,n) + sage: K2 = rearrangement_cone(p+1,n) + sage: all( x in K2 for x in K1 ) + True + + The rearrangement cone of order ``p`` is linearly isomorphic to the + rearrangement cone of order ``n - p`` when ``p`` is less than ``n``, + by [Jeong]_ Proposition 5.2.1:: + + sage: n = ZZ.random_element(2,10) + sage: p = ZZ.random_element(1,n) + sage: K1 = rearrangement_cone(p,n) + sage: K2 = rearrangement_cone(n-p, n) + sage: Mp = (1/p)*matrix.ones(QQ,n) - identity_matrix(QQ,n) + sage: Cone( (Mp*K2.rays()).columns() ).is_equivalent(K1) + True + + The order ``p`` should be between ``1`` and ``n``, inclusive:: + + sage: rearrangement_cone(0,3) + Traceback (most recent call last): + ... + ValueError: order p=0 should be between 1 and n=3, inclusive + sage: rearrangement_cone(5,3) + Traceback (most recent call last): + ... + ValueError: order p=5 should be between 1 and n=3, inclusive + + If a ``lattice`` was given, it is actually used:: + + sage: L = ToricLattice(3, 'M') + sage: rearrangement_cone(2, 3, lattice=L) + 3-d cone in 3-d lattice M + + Unless the rank of the lattice disagrees with ``n``:: + + sage: L = ToricLattice(1, 'M') + sage: rearrangement_cone(2, 3, lattice=L) + Traceback (most recent call last): + ... + ValueError: lattice rank=1 and dimension n=3 are incompatible + + """ + if p < 1 or p > n: + raise ValueError('order p=%d should be between 1 and n=%d, inclusive' + % + (p,n)) + + if lattice is None: + lattice = ToricLattice(n) + + if lattice.rank() != n: + raise ValueError('lattice rank=%d and dimension n=%d are incompatible' + % + (lattice.rank(), n)) + + I = identity_matrix(ZZ,n) + M = matrix.ones(ZZ,n) - p*I + G = identity_matrix(ZZ,n).rows() + M.rows() + return Cone(G, lattice=lattice)