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function x = cs_usolve (U,b) %#ok
%CS_USOLVE solve a sparse upper triangular system U*x=b.
% x = cs_usolve(U,b) computes x = U\b, U must be lower triangular with a
% zero-free diagonal. b must be a column vector. x is full if b is full.
% If b is sparse, x is sparse but nonzero pattern of x is NOT sorted (it is
% returned in topological order).
%
% Example:
% Prob = ssget ('HB/arc130') ; A = Prob.A ; n = size (A,1) ;
% b = rand (n,1);
% [L U p q] = cs_lu (A) ;
% x = cs_usolve (U, cs_lsolve (L, b(p))) ; % x = U \ (L \ b(p)) ;
% x (q) = x ;
% norm (A*x-b)
%
% See also CS_LSOLVE, CS_LTSOLVE, CS_UTSOLVE, MLDIVIDE.
% CXSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved.
% SPDX-License-Identifier: LGPL-2.1+
error ('cs_usolve mexFunction not found') ;
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