| |
| //@HEADER |
| // ************************************************************************ |
| // |
| // HPCCG: Simple Conjugate Gradient Benchmark Code |
| // Copyright (2006) Sandia Corporation |
| // |
| // Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive |
| // license for use of this work by or on behalf of the U.S. Government. |
| // |
| // 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 2.1 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 |
| // Questions? Contact Michael A. Heroux (maherou@sandia.gov) |
| // |
| // ************************************************************************ |
| //@HEADER |
| |
| ///////////////////////////////////////////////////////////////////////// |
| |
| // Routine to compute the 1-norm difference between two vectors where: |
| |
| // n - number of vector elements (on this processor) |
| |
| // v1, v2 - input vectors |
| |
| // residual - pointer to scalar value, on exit will contain result. |
| |
| ///////////////////////////////////////////////////////////////////////// |
| |
| #include <cmath> // needed for fabs |
| using std::fabs; |
| #include "compute_residual.hpp" |
| |
| int compute_residual(const int n, const double * const v1, |
| const double * const v2, double * const residual) |
| { |
| double local_residual = 0.0; |
| |
| for (int i=0; i<n; i++) { |
| double diff = fabs(v1[i] - v2[i]); |
| if (diff > local_residual) local_residual = diff; |
| } |
| #ifdef USING_MPI |
| // Use MPI's reduce function to collect all partial sums |
| |
| double global_residual = 0; |
| |
| MPI_Allreduce(&local_residual, &global_residual, 1, MPI_DOUBLE, MPI_MAX, |
| MPI_COMM_WORLD); |
| *residual = global_residual; |
| #else |
| *residual = local_residual; |
| #endif |
| |
| return(0); |
| } |