Source code for cvxpy.atoms.affine.trace

Copyright 2013 Steven Diamond

This file is part of CVXPY.

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from cvxpy.atoms.affine.affine_atom import AffAtom
import cvxpy.lin_ops.lin_utils as lu
import numpy as np

[docs]class trace(AffAtom): """The sum of the diagonal entries of a matrix. Parameters ---------- expr : Expression The expression to sum the diagonal of. """ def __init__(self, expr): super(trace, self).__init__(expr) @AffAtom.numpy_numeric def numeric(self, values): """Sums the diagonal entries. """ return np.trace(values[0]) def validate_arguments(self): """Checks that the argument is a square matrix. """ shape = self.args[0].shape if self.args[0].ndim != 2 or shape[0] != shape[1]: raise ValueError("Argument to trace must be a square matrix.") def shape_from_args(self): """Always scalar. """ return tuple() @staticmethod def graph_implementation(arg_objs, shape, data=None): """Sum the diagonal entries of the linear expression. Parameters ---------- arg_objs : list LinExpr for each argument. shape : tuple The shape of the resulting expression. data : Additional data required by the atom. Returns ------- tuple (LinOp for objective, list of constraints) """ return (lu.trace(arg_objs[0]), [])