/// <summary>
/// accumulates the derivative of DG field <paramref name="f"/>
/// (along the <paramref name="d"/>-th axis) times <paramref name="alpha"/>
/// to this field, i.e. <br/>
/// this = this + <paramref name="alpha"/>* \f$ \frac{\partial}{\partial x_d} \f$ <paramref name="f"/>;
/// </summary>
/// <param name="f"></param>
/// <param name="d">
/// 0 for the x-derivative, 1 for the y-derivative, 2 for the
/// z-derivative
/// </param>
/// <param name="alpha">
/// scaling of <paramref name="f"/>;
/// </param>
/// <param name="optionalSubGrid">
/// An optional restriction to the domain in which the derivative is
/// computed (it may, e.g. be only required in boundary cells, so a
/// computation over the whole domain would be a waste of computational
/// power. A proper execution mask would be see e.g.
/// <see cref="GridData.BoundaryCells"/>.)
/// <br/>
/// if null, the computation is carried out in the whole domain.
/// </param>
/// <param name="bndMode">
/// if a sub-grid is provided, this determines how the sub-grid
/// boundary should be treated.
/// </param>
/// <remarks>
/// The derivative is calculated using Riemann flux functions
/// (central difference);<br/>
/// In comparison to
/// <see cref="Derivative(double, DGField, int, CellMask)"/>, this method
/// should be slower, but produce more sane results, especially for
/// fields of low polynomial degree (0 or 1);
/// </remarks>
virtual public void DerivativeByFlux(double alpha, DGField f, int d, SubGrid optionalSubGrid = null, SubGridBoundaryModes bndMode = SubGridBoundaryModes.OpenBoundary)
{
int D = this.Basis.GridDat.SpatialDimension;
if (d < 0 || d >= D)
{
throw new ArgumentException("spatial dimension out of range.", "d");
}
MPICollectiveWatchDog.Watch(csMPI.Raw._COMM.WORLD);
EdgeMask emEdge = (optionalSubGrid != null) ? optionalSubGrid.AllEdgesMask : null;
CellMask emVol = (optionalSubGrid != null) ? optionalSubGrid.VolumeMask : null;
SpatialOperator d_dx = new SpatialOperator(1, 1, QuadOrderFunc.Linear(), "in", "out");
d_dx.EdgeQuadraturSchemeProvider = g => new Quadrature.EdgeQuadratureScheme(true, emEdge);
d_dx.VolumeQuadraturSchemeProvider = g => new Quadrature.CellQuadratureScheme(true, emVol);
var flux = CreateDerivativeFlux(d, f.Identification);
d_dx.EquationComponents["out"].Add(flux);
d_dx.Commit();
var ev = d_dx.GetEvaluatorEx(
new CoordinateMapping(f), null, this.Mapping);
if (optionalSubGrid != null)
{
ev.ActivateSubgridBoundary(optionalSubGrid.VolumeMask, bndMode);
}
ev.Evaluate <CoordinateVector>(alpha, 1.0, this.CoordinateVector);
}
/// <summary>
/// Calculates the DG-projection (with respect to the DG-basis
/// of this field, <see cref="Basis"/>) of
/// <paramref name="alpha"/>*<paramref name="a"/>/<paramref name="b"/>
/// and, depending on the value of <paramref name="accumulateResult"/>,
/// either adds or assigns it to this field.
/// </summary>
/// <param name="a">1st multiplicand</param>
/// <param name="b">2nd multiplicand</param>
/// <param name="alpha">scaling for <paramref name="a"/>*<paramref name="b"/></param>
/// <param name="accumulateResult">
/// Tells this method whether to accumulate (true) or not (false)
/// </param>
/// <param name="cm">
/// optional restriction to computational domain
/// </param>
virtual public void ProjectQuotient(
double alpha, DGField a, DGField b, CellMask cm, bool accumulateResult)
{
if (!object.ReferenceEquals(a.Basis.GridDat, this.Basis.GridDat))
{
throw new ArgumentException("field is associated to another grid.", "a");
}
if (!object.ReferenceEquals(b.Basis.GridDat, this.Basis.GridDat))
{
throw new ArgumentException("field is associated to another grid.", "b");
}
if (!accumulateResult)
{
if (a == this)
{
a = (DGField)a.Clone();
if (b == this)
{
b = a;
}
}
else if (b == this)
{
b = (DGField)b.Clone();
}
this.Clear();
}
SpatialOperator fracOp = new SpatialOperator(new string[] { "a", "b" },
new string[] { "res" },
QuadOrderFunc.Linear());
//QuadOrderFunc.NonLinear(2));
fracOp.EdgeQuadraturSchemeProvider = g => new EdgeQuadratureScheme(true, EdgeMask.GetEmptyMask(g));
fracOp.VolumeQuadraturSchemeProvider = g => new CellQuadratureScheme(true, cm);
fracOp.EquationComponents["res"].Add(new QuotientSource());
fracOp.Commit();
CoordinateVector coDom = this.CoordinateVector;
var ev = fracOp.GetEvaluatorEx(
new CoordinateMapping(a, b), null, coDom.Mapping);
ev.Evaluate <CoordinateVector>(alpha, 1.0, coDom);
}