# lacaml / examples / nag / nag_gesv.ml

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44``` ```(* File: nag_gesv.ml Copyright (C) 2013- Christophe Troestler email: Christophe.Troestler@umons.ac.be WWW: http://www.umh.ac.be/math/an/ This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA *) (* Example from http://www.nag.com/lapack-ex/node5.html *) open Format open Lacaml.D open Lacaml.Io let a = Mat.of_array [| [| 1.80; 2.88; 2.05; -0.89 |]; [| 5.25; -2.95; -0.95; -3.80 |]; [| 1.58; -2.69; -2.90; -1.04 |]; [|-1.11; -0.66; -0.59; 0.80 |] |] let b = Vec.of_array [| 9.52; 24.35; 0.77; -6.22 |] let () = (* Solves [a * x = b]. Solution in [x] which must initially hold [b]. *) let x = copy b in let ipiv = Lacaml.Common.create_int32_vec (Mat.dim1 a) in gesv a (Mat.from_col_vec x) ~ipiv; (* Print solution and details of factorisation. *) printf "Solution: X = @[%a@]@\n" pp_rfvec x; printf "Details of factorization: @[%a@]@\n" pp_fmat a; printf "Pivot indices: @[%a@]@\n" pp_rivec ipiv; ```
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