opm-simulators/tests/test_graphcoloring.cpp

#include <config.h>

#include <dune/common/fmatrix.hh>
#include <dune/istl/bcrsmatrix.hh>
#include <dune/istl/paamg/graph.hh>

#include <opm/autodiff/GraphColoring.hpp>

#define BOOST_TEST_MODULE GraphColoringTest
#define BOOST_TEST_MAIN

#include <boost/test/unit_test.hpp>

BOOST_AUTO_TEST_CASE(TestWelschPowell)
{
    using Matrix = Dune::BCRSMatrix<Dune::FieldMatrix<double,1,1>>;
    using Graph = Dune::Amg::MatrixGraph<Matrix>;
    int N = 10;
    Matrix matrix(N*N, N*N, 5, 0.4, Matrix::implicit);
    for( int j = 0; j < N; j++)
    {
        for(int i = 0; i < N; i++)
        {
            auto index = j*10+i;
            matrix.entry(index,index) = 1;

            if ( i > 0 )
            {
                matrix.entry(index,index-1) = 1;
            }
            if ( i  < N - 1)
            {
                matrix.entry(index,index+1) = 1;
            }

            if ( j > 0 )
            {
                matrix.entry(index,index-N) = 1;
            }
            if ( j  < N - 1)
            {
                matrix.entry(index,index+N) = 1;
            }

        }
    }
    matrix.compress();

    auto colorsTuple = Opm::colorVerticesWelshPowell(Graph(matrix));
    const auto& colors = std::get<0>(colorsTuple);
    auto noColors = std::get<1>(colorsTuple);
    auto firstCornerColor = colors[0];
    BOOST_CHECK(noColors == 2);

    // Check for checkerboard coloring

    for( int j = 0, index = 0; j < N; j++)
    {
        auto expectedColor = firstCornerColor;

        for(int i = 0; i < N; i++)
        {
            BOOST_CHECK(colors[index]==expectedColor);
            index++;
            expectedColor = (expectedColor + 1) % 2;
        }
        firstCornerColor=(firstCornerColor + 1) % 2;
    }
}