rcm

Source: tests/multifrontal/symbolic/rcm.cpp

// ========================================================================= //
// This file is part of MyraMath, copyright (c) 2014-2019 by Ryan A Chilton  //
// and distributed by MyraCore, LLC. See LICENSE.txt for license terms.      //
// ========================================================================= //

// Containers.
#include <myramath/dense/intRange.h>
#include <myramath/sparse/Pattern.h>
#include <myramath/sparse/PatternRange.h>
#include <myramath/sparse/Permutation.h>

// Algorithms.
#include <myramath/sparse/laplacian2.h>
#include <myramath/sparse/permute.h>
#include <myramath/multifrontal/symbolic/rcm.h>

// Reporting.
#include <tests/myratest.h>

// For std::max.
#include <algorithm>

using namespace myra;

namespace {

// Helper function to compute the bandwidth of a Pattern.
int bandwidth(const Pattern& A)
  {
  int bw = 0;
  for (auto aij = A.begin(); aij != A.end(); ++aij)
    bw = std::max(bw, std::abs(aij.i()-aij.j()) );
  return bw;
  }

}

ADD_TEST("rcm","[symbolic]")
  {
  Pattern A = stencil2(100,10);
  Permutation P = rcm(A);
  Pattern B = permute(P,A);
  int bandwidth_A = bandwidth(A);
  int bandwidth_B = bandwidth(B);
  myra::out() << "bandwidth(A) = " << bandwidth_A << std::endl;
  myra::out() << "bandwidth(B) = " << bandwidth_B << std::endl;
  REQUIRE(bandwidth_B < bandwidth_A);
  }

Results: [PASS]

bandwidth(A) = 100
bandwidth(B) = 11

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