private static void test04()
//****************************************************************************80
//
// Purpose:
//
// TEST04 works with a CCS sparse matrix with many repeated index pairs.
//
// Discussion:
//
// To complete this test, I want to compare AST * X and ACC * X.
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 23 July 2014
//
// Author:
//
// John Burkardt
//
{
Console.WriteLine("");
Console.WriteLine("TEST04");
Console.WriteLine(" Convert a sparse matrix from ST to CCS format.");
Console.WriteLine(" ST: sparse triplet, I, J, A.");
Console.WriteLine(" CC: compressed column, I, CC, A.");
Console.WriteLine(" The ST matrix is the Wathen finite element matrix.");
Console.WriteLine(" It has many repeated index pairs.");
Console.WriteLine(" To check, compare ACC*X - AST*X for a random X.");
//
// Get the size of the ST matrix.
//
const int nx = 3;
const int ny = 3;
int nst = SparseTriplet.wathen_st_size(nx, ny);
Console.WriteLine("");
Console.WriteLine(" Number of ST values = " + nst + "");
//
// Set the formal matrix size
//
const int m = 3 * nx * ny + 2 * nx + 2 * ny + 1;
//
// Set a random vector.
//
int seed = 123456789;
double[] x = UniformRNG.r8vec_uniform_01_new(m, ref seed);
//
// Allocate space.
//
int[] ist = new int[nst];
int[] jst = new int[nst];
//
// Create the ST matrix.
//
seed = 123456789;
double[] ast = SparseTriplet.wathen_st(nx, ny, nst, ref seed, ref ist, ref jst);
int i_min = typeMethods.i4vec_min(nst, ist);
int i_max = typeMethods.i4vec_max(nst, ist);
int j_min = typeMethods.i4vec_min(nst, jst);
int j_max = typeMethods.i4vec_max(nst, jst);
SparseTriplet.st_header_print(i_min, i_max, j_min, j_max, m, m, nst);
//
// Compute B1 = AST * X
//
double[] b1 = SparseTriplet.st_mv(m, m, nst, ist, jst, ast, x);
//
// Get the CCS size.
//
int ncc = SparseTriplet.st_to_ccs_size(nst, ist, jst);
Console.WriteLine(" Number of CCS values = " + ncc + "");
//
// Create the CCS indices.
//
int[] icc = new int[ncc];
int[] ccc = new int[m + 1];
SparseTriplet.st_to_ccs_index(nst, ist, jst, ncc, m, ref icc, ref ccc);
//
// Create the CCS values.
//
double[] acc = SparseTriplet.st_to_ccs_values(nst, ist, jst, ast, ncc, m, icc, ccc);
//
// Compute B2 = ACC * X.
//
double[] b2 = CompressedColumnStorage.ccs_mv(m, m, ncc, icc, ccc, acc, x);
//
// Compare B1 and B2.
//
double r = typeMethods.r8vec_diff_norm(m, b1, b2);
Console.WriteLine(" || ACC*X - AST*X|| = " + r + "");
}
