public static void nwspgr(Func <int, double[], double[], ClenshawCurtis.ccResult> rule,
Func <int, int> rule_order, int dim, int k, int r_size, ref int s_size,
ref double[] nodes, ref double[] weights)
//****************************************************************************80
//
// Purpose:
//
// NWSPGR generates nodes and weights for sparse grid integration.
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 19 April 2013
//
// Author:
//
// Original MATLAB version by Florian Heiss, Viktor Winschel.
// C++ version by John Burkardt.
//
// Reference:
//
// Florian Heiss, Viktor Winschel,
// Likelihood approximation by numerical integration on sparse grids,
// Journal of Econometrics,
// Volume 144, 2008, pages 62-80.
//
// Parameters:
//
// Input, void RULE ( int n, double x[], double w[] ), the name of a function
// which is given the order N and returns the points X and weights W of the
// corresponding 1D quadrature rule.
//
// Input, int RULE_ORDER ( int l ), the name of a function which
// is given the level L and returns the order N of the corresponding 1D rule.
//
// Input, int DIM, the spatial dimension.
//
// Input, int K, the level of the sparse rule.
//
// Input, int R_SIZE, the "size" of the sparse rule.
//
// Output, int &S_SIZE, the size of the sparse rule, after
// duplicate points have been merged.
//
// Output, double NODES[DIM*R_SIZE], the nodes of the sparse rule.
//
// Output, double WEIGHTS[R_SIZE], the weights of the sparse rule.
//
{
int i;
int j;
int level;
int n;
int q;
for (j = 0; j < r_size; j++)
{
for (i = 0; i < dim; i++)
{
nodes[i + j * dim] = 0.0;
}
}
for (j = 0; j < r_size; j++)
{
weights[j] = 0.0;
}
//
// Create cell arrays that will contain the points and weights
// for levels 1 through K.
//
int[] n1d = new int[k];
int[] x1d_off = new int[k + 1];
int[] w1d_off = new int[k + 1];
x1d_off[0] = 0;
w1d_off[0] = 0;
for (level = 1; level <= k; level++)
{
n = rule_order(level);
n1d[level - 1] = n;
x1d_off[level] = x1d_off[level - 1] + n;
w1d_off[level] = w1d_off[level - 1] + n;
}
int n1d_total = x1d_off[k];
//
// Calculate all the 1D rules needed.
//
double[] x1d = new double[n1d_total];
double[] w1d = new double[n1d_total];
for (level = 1; level <= k; level++)
{
n = n1d[level - 1];
double[] x = new double[n];
double[] w = new double[n];
ClenshawCurtis.ccResult result = rule(n, x, w);
x = result.x;
w = result.w;
typeMethods.r8cvv_rset(n1d_total, x1d, k, x1d_off, level - 1, x);
typeMethods.r8cvv_rset(n1d_total, w1d, k, w1d_off, level - 1, w);
}
//
// Construct the sparse grid.
//
int minq = Math.Max(0, k - dim);
int maxq = k - 1;
//
// Q is the level total.
//
int[] lr = new int[dim];
int[] nr = new int[dim];
int r = 0;
for (q = minq; q <= maxq; q++)
{
//
// BQ is the combinatorial coefficient applied to the component
// product rules which have level Q.
//
int bq = typeMethods.i4_mop(maxq - q) * typeMethods.i4_choose(dim - 1, dim + q - k);
//
// Compute the D-dimensional row vectors that sum to DIM+Q.
//
int seq_num = Comp.num_seq(q, dim);
int[] is_ = Comp.get_seq(dim, q + dim, seq_num);
//
// Allocate new rows for nodes and weights.
//
int[] rq = new int[seq_num];
for (j = 0; j < seq_num; j++)
{
rq[j] = 1;
for (i = 0; i < dim; i++)
{
level = is_[j + i * seq_num] - 1;
rq[j] *= n1d[level];
}
}
//
// Generate every product rule whose level total is Q.
//
int j2;
for (j2 = 0; j2 < seq_num; j2++)
{
for (i = 0; i < dim; i++)
{
lr[i] = is_[j2 + i * seq_num];
}
for (i = 0; i < dim; i++)
{
nr[i] = rule_order(lr[i]);
}
int[] roff = typeMethods.r8cvv_offset(dim, nr);
int nc = typeMethods.i4vec_sum(dim, nr);
double[] wc = new double[nc];
double[] xc = new double[nc];
//
// Corrected first argument in calls to R8CVV to N1D_TOTAL,
// 19 April 2013.
//
for (i = 0; i < dim; i++)
{
double[] xr = typeMethods.r8cvv_rget_new(n1d_total, x1d, k, x1d_off, lr[i] - 1);
double[] wr = typeMethods.r8cvv_rget_new(n1d_total, w1d, k, w1d_off, lr[i] - 1);
typeMethods.r8cvv_rset(nc, xc, dim, roff, i, xr);
typeMethods.r8cvv_rset(nc, wc, dim, roff, i, wr);
}
int np = rq[j2];
double[] wp = new double[np];
double[] xp = new double[dim * np];
typeMethods.tensor_product_cell(nc, xc, wc, dim, nr, roff, np, ref xp, ref wp);
//
// Append the new nodes and weights to the arrays.
//
for (j = 0; j < np; j++)
{
for (i = 0; i < dim; i++)
{
nodes[i + (r + j) * dim] = xp[i + j * dim];
}
}
for (j = 0; j < np; j++)
{
weights[r + j] = bq * wp[j];
}
//
// Update the count.
//
r += rq[j2];
}
}
//
// Reorder the rule so the points are in ascending lexicographic order.
//
QuadratureRule.rule_sort(dim, r_size, ref nodes, ref weights);
//
// Suppress duplicate points and merge weights.
//
r = 0;
for (j = 1; j < r_size; j++)
{
bool equal = true;
for (i = 0; i < dim; i++)
{
if (!(Math.Abs(nodes[i + r * dim] - nodes[i + j * dim]) > double.Epsilon))
{
continue;
}
equal = false;
break;
}
switch (equal)
{
case true:
weights[r] += weights[j];
break;
default:
{
r += 1;
weights[r] = weights[j];
for (i = 0; i < dim; i++)
{
nodes[i + r * dim] = nodes[i + j * dim];
}
break;
}
}
}
r += 1;
s_size = r;
//
// Zero out unneeded entries.
//
for (j = r; j < r_size; j++)
{
for (i = 0; i < dim; i++)
{
nodes[i + j * dim] = 0.0;
}
}
for (j = r; j < r_size; j++)
{
weights[j] = 0.0;
}
//
// Normalize the weights to sum to 1.
//
double t = typeMethods.r8vec_sum(r, weights);
for (j = 0; j < r; j++)
{
weights[j] /= t;
}
}