public MultiPathGenerator(StochasticProcess process, TimeGrid times, GSG generator, bool brownianBridge)
{
brownianBridge_ = brownianBridge;
process_ = process;
generator_ = generator;
next_ = new Sample <IPath>(new MultiPath(process.size(), times), 1.0);
Utils.QL_REQUIRE(generator_.dimension() == process.factors() * (times.size() - 1), () =>
"dimension (" + generator_.dimension()
+ ") is not equal to ("
+ process.factors() + " * " + (times.size() - 1)
+ ") the number of factors "
+ "times the number of time steps");
Utils.QL_REQUIRE(times.size() > 1, () => "no times given");
}
protected override IPathGenerator <IRNG> pathGenerator()
{
int dimensions = process_.factors();
TimeGrid grid = timeGrid();
IRNG generator = (IRNG)FastActivator <RNG> .Create().make_sequence_generator(dimensions * (grid.size() - 1), seed_);
return(new PathGenerator <IRNG>(process_, grid, generator, brownianBridge_));
}
private Sample <IPath> next(bool antithetic)
{
if (brownianBridge_)
{
Utils.QL_FAIL("Brownian bridge not supported");
return(null);
}
Sample <List <double> > sequence_ =
antithetic
? generator_.lastSequence()
: generator_.nextSequence();
int m = process_.size();
int n = process_.factors();
MultiPath path = (MultiPath)next_.value;
Vector asset = process_.initialValues();
for (int j = 0; j < m; j++)
{
path[j].setFront(asset[j]);
}
Vector temp;
next_.weight = sequence_.weight;
TimeGrid timeGrid = path[0].timeGrid();
double t, dt;
for (int i = 1; i < path.pathSize(); i++)
{
int offset = (i - 1) * n;
t = timeGrid[i - 1];
dt = timeGrid.dt(i - 1);
if (antithetic)
{
temp = -1 * new Vector(sequence_.value.GetRange(offset, n));
}
else
{
temp = new Vector(sequence_.value.GetRange(offset, n));
}
asset = process_.evolve(t, asset, dt, temp);
for (int j = 0; j < m; j++)
{
path[j][i] = asset[j];
}
}
return(next_);
}