MultiDimensionalIndexing.C

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//-----------------------------------------------------------------------bl-
//--------------------------------------------------------------------------
//
// QUESO - a library to support the Quantification of Uncertainty
// for Estimation, Simulation and Optimization
//
// Copyright (C) 2008-2017 The PECOS Development Team
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the Version 2.1 GNU Lesser General
// Public License as published by the Free Software Foundation.
//
// 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. 51 Franklin Street, Fifth Floor,
// Boston, MA  02110-1301  USA
//
//-----------------------------------------------------------------------el-

// This class
#include <queso/MultiDimensionalIndexing.h>

// QUESO
#include <queso/asserts.h>

namespace QUESO
{

  unsigned int MultiDimensionalIndexing::coordToGlobal( const std::vector<unsigned int>& coord_indices,
                                                        const std::vector<unsigned int>& n_points )
  {
    // Make sure the dimension is consisent
    queso_assert_equal_to( coord_indices.size(), n_points.size() );

    // The input objects implicitly carry the dimension with them
    unsigned int dim = coord_indices.size();

    /* Mapping is: i + j*n_i + k*n_i*n_j + l*n_i*n_j*n_k + ...
       Initialize global_index to "i".
       Then loop and build up each term.*/
    queso_assert_less( coord_indices[0], n_points[0] );

    unsigned int global_index = coord_indices[0];

    for( unsigned int d = 1; d < dim; d++ )
      {
        queso_assert_less( coord_indices[d], n_points[d] );

        // Accumulate the current term
        unsigned int idx = coord_indices[d];

        for( int local_d = d-1; local_d >=0; local_d -= 1)
          {
            idx *= n_points[local_d];
          }

        global_index += idx;
      }

    return global_index;
  }

  void MultiDimensionalIndexing::globalToCoord( unsigned int global,
                                                const std::vector<unsigned int>& n_points,
                                                std::vector<unsigned int>& coord_indices )
  {
    // The input object implicitly carry's the dimension
    unsigned int dim = n_points.size();

    coord_indices.resize(dim);

    /* coordToGlobal computes: i + j*n_points[0] + k*n_points[0]*n_points[1] + ...
       so we use integer arithmetic and work backwards. */
    unsigned int tmp = global;

    for( int d = dim-1; d > 0; d -= 1 )
      {
        unsigned int np = compute_npoints_factor( n_points, d );
        coord_indices[d] = tmp/np;
        tmp -= coord_indices[d]*np;
      }

    // What's left should be our starting index
    coord_indices[0] = tmp;

    // Sanity check: the indices we determined should map back to the global
    queso_assert_equal_to( global, coordToGlobal(coord_indices,n_points) );
  }

  unsigned int MultiDimensionalIndexing::compute_npoints_factor( const std::vector<unsigned int>& n_points,
                                                                 unsigned int term )
  {
    unsigned int value = 1;

    for( unsigned int d = 0; d < term; d++ )
      {
        value *= n_points[d];
      }

    return value;
  }

} // end namespace QUESO