finMath lib documentation
net.finmath.montecarlo.assetderivativevaluation

## Class HestonModel

• All Implemented Interfaces:
AbstractModelInterface

public class HestonModel
extends AbstractModel
This class implements a Heston Model, that is, it provides the drift and volatility specification and performs the calculation of the numeraire (consistent with the dynamics, i.e. the drift). The model is $dS(t) = r^{\text{c}} S(t) dt + \sqrt{V(t)} S(t) dW_{1}(t), \quad S(0) = S_{0},$ $dV(t) = \kappa ( \theta - V(t) ) dt + \xi \sqrt{V(t)} dW_{2}(t), \quad V(0) = \sigma^2,$ $dW_{1} dW_{2} = \rho dt$ $dN(t) = r^{\text{d}} N(t) dt, \quad N(0) = N_{0},$ The class provides the model of (S,V) to an AbstractProcessInterface via the specification of $$f_{1} = exp , f_{2} = identity$$, $$\mu_{1} = r^{\text{c}} - \frac{1}{2} V^{+}(t) , \mu_{2} = \kappa ( \theta - V^{+}(t) )$$, $$\lambda_{1,1} = \sqrt{V^{+}(t)} , \lambda_{1,2} = 0 ,\lambda_{2,1} = \xi \sqrt{V^+(t)} \rho , \lambda_{2,2} = \xi \sqrt{V^+(t)} \sqrt{1-\rho^{2}}$$, i.e., of the SDE $dX_{1} = \mu_{1} dt + \lambda_{1,1} dW_{1} + \lambda_{1,2} dW_{2}, \quad X_{1}(0) = \log(S_{0}),$ $dX_{2} = \mu_{2} dt + \lambda_{2,1} dW_{1} + \lambda_{2,2} dW_{2}, \quad X_{2}(0) = V_{0} = \sigma^2,$ with $$S = f_{1}(X_{1}) , V = f_{2}(X_{2})$$. See AbstractProcessInterface for the notation. Here $$V^{+}$$ denotes a truncated value of V. Different truncation schemes are available: FULL_TRUNCATION: $$V^{+} = max(V,0)$$, REFLECTION: $$V^{+} = abs(V)$$. The model allows to specify two independent rate for forwarding ($$r^{\text{c}}$$) and discounting ($$r^{\text{d}}$$). It thus allow for a simple modelling of a funding / collateral curve (via ($$r^{\text{d}}$$) and/or the specification of a dividend yield.
Author:
Christian Fries
The interface for numerical schemes., The interface for models provinding parameters to numerical schemes.
• ### Constructor Detail

• #### HestonModel

public HestonModel(double initialValue,
double riskFreeRate,
double volatility,
double discountRate,
double theta,
double kappa,
double xi,
double rho,
HestonModel.Scheme scheme,
AbstractRandomVariableFactory randomVariableFactory)
Create a Heston model.
Parameters:
initialValue - Spot value.
riskFreeRate - The risk free rate.
volatility - The log volatility.
discountRate - The discount rate used in the numeraire.
theta - The longterm mean reversion level of V (a reasonable value is volatility*volatility).
kappa - The mean reversion speed.
xi - The volatility of the volatility (of V).
rho - The instantaneous correlation of the Brownian drivers (aka leverage).
scheme - The truncation scheme, that is, either reflection (V → abs(V)) or truncation (V → max(V,0)).
• #### HestonModel

public HestonModel(double initialValue,
double riskFreeRate,
double volatility,
double discountRate,
double theta,
double kappa,
double xi,
double rho,
HestonModel.Scheme scheme)
Create a Heston model.
Parameters:
initialValue - Spot value.
riskFreeRate - The risk free rate.
volatility - The log volatility.
discountRate - The discount rate used in the numeraire.
theta - The longterm mean reversion level of V (a reasonable value is volatility*volatility).
kappa - The mean reversion speed.
xi - The volatility of the volatility (of V).
rho - The instantaneous correlation of the Brownian drivers (aka leverage).
scheme - The truncation scheme, that is, either reflection (V → abs(V)) or truncation (V → max(V,0)).
• #### HestonModel

public HestonModel(double initialValue,
double riskFreeRate,
double volatility,
double theta,
double kappa,
double xi,
double rho,
HestonModel.Scheme scheme)
Create a Heston model.
Parameters:
initialValue - Spot value.
riskFreeRate - The risk free rate.
volatility - The log volatility.
theta - The longterm mean reversion level of V (a reasonable value is volatility*volatility).
kappa - The mean reversion speed.
xi - The volatility of the volatility (of V).
rho - The instantaneous correlation of the Brownian drivers (aka leverage).
scheme - The truncation scheme, that is, either reflection (V → abs(V)) or truncation (V → max(V,0)).
• ### Method Detail

• #### getInitialState

public RandomVariableInterface[] getInitialState()
Description copied from interface: AbstractModelInterface
Returns the initial value of the state variable of the process Y, not to be confused with the initial value of the model X (which is the state space transform applied to this state value.
Returns:
The initial value of the state variable of the process Y(t=0).
• #### getDrift

public RandomVariableInterface[] getDrift(int timeIndex,
RandomVariableInterface[] realizationAtTimeIndex,
RandomVariableInterface[] realizationPredictor)
Description copied from interface: AbstractModelInterface
This method has to be implemented to return the drift, i.e. the coefficient vector
μ = (μ1, ..., μn) such that X = f(Y) and
dYj = μj dt + λ1,j dW1 + ... + λm,j dWm
in an m-factor model. Here j denotes index of the component of the resulting process. Since the model is provided only on a time discretization, the method may also (should try to) return the drift as $$\frac{1}{t_{i+1}-t_{i}} \int_{t_{i}}^{t_{i+1}} \mu(\tau) \mathrm{d}\tau$$.
Parameters:
timeIndex - The time index (related to the model times discretization).
realizationAtTimeIndex - The given realization at timeIndex
realizationPredictor - The given realization at timeIndex+1 or null if no predictor is available.
Returns:
The drift or average drift from timeIndex to timeIndex+1, i.e. $$\frac{1}{t_{i+1}-t_{i}} \int_{t_{i}}^{t_{i+1}} \mu(\tau) \mathrm{d}\tau$$ (or a suitable approximation).

int component,
RandomVariableInterface[] realizationAtTimeIndex)
Description copied from interface: AbstractModelInterface
This method has to be implemented to return the factor loadings, i.e. the coefficient vector
λj = (λ1,j, ..., λm,j) such that X = f(Y) and
dYj = μj dt + λ1,j dW1 + ... + λm,j dWm
in an m-factor model. Here j denotes index of the component of the resulting process.
Parameters:
timeIndex - The time index (related to the model times discretization).
component - The index j of the driven component.
realizationAtTimeIndex - The realization of X at the time corresponding to timeIndex (in order to implement local and stochastic volatlity models).
Returns:
• #### applyStateSpaceTransform

public RandomVariableInterface applyStateSpaceTransform(int componentIndex,
RandomVariableInterface randomVariable)
Description copied from interface: AbstractModelInterface
Applies the state space transform fi to the given state random variable such that Yi → fi(Yi) =: Xi.
Parameters:
componentIndex - The component index i.
randomVariable - The state random variable Yi.
Returns:
New random variable holding the result of the state space transformation.
• #### getNumeraire

public RandomVariableInterface getNumeraire(double time)
Description copied from interface: AbstractModelInterface
Return the numeraire at a given time index. Note: The random variable returned is a defensive copy and may be modified.
Parameters:
time - The time t for which the numeraire N(t) should be returned.
Returns:
The numeraire at the specified time as RandomVariable
• #### getNumberOfComponents

public int getNumberOfComponents()
Description copied from interface: AbstractModelInterface
Returns the number of components
Returns:
The number of components
• #### getRandomVariableForConstant

public RandomVariableInterface getRandomVariableForConstant(double value)
Description copied from interface: AbstractModelInterface
Return a random variable initialized with a constant using the models random variable factory.
Parameters:
value - The constant value.
Returns:
A new random variable initialized with a constant value.
• #### getCloneWithModifiedData

public HestonModel getCloneWithModifiedData(Map<String,Object> dataModified)
Description copied from interface: AbstractModelInterface
Returns a clone of this model where the specified properties have been modified. Note that there is no guarantee that a model reacts on a specification of a properties in the parameter map dataModified. If data is provided which is ignored by the model no exception may be thrown.
Parameters:
dataModified - Key-value-map of parameters to modify.
Returns:
A clone of this model (or this model if no parameter was modified).
• #### getRiskFreeRate

public RandomVariableInterface getRiskFreeRate()
Returns the risk free rate parameter of this model.
Returns:
Returns the riskFreeRate.
• #### getVolatility

public RandomVariableInterface getVolatility()
Returns the volatility parameter of this model.
Returns:
Returns the volatility.