function x = cs_utsolve (U,b) %#ok %CS_UTSOLVE solve a sparse lower triangular system U'*x=b. % x = cs_utsolve(U,b) computes x = U'\b, U must be upper triangular with a % zero-free diagonal. b must be a full vector. % % 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_ltsolve (L, cs_utsolve (U, b(q))) ; % x = L' \ (U' \ b(q)) ; % x (p) = x ; % norm (A'*x-b) % % See also CS_LSOLVE, CS_LTSOLVE, CS_USOLVE, MLDIVIDE. % CXSparse, Copyright (c) 2006-2022, Timothy A. Davis. All Rights Reserved. % SPDX-License-Identifier: LGPL-2.1+ error ('cs_utsolve mexFunction not found') ;