Simultaneous upper and lower bounds of American-style option prices with hedging via neural networks
Simultaneous upper and lower bounds of American-style option prices with hedging via neural networks
This paper introduces two neural network-based methods for simultaneously computing lower and upper bounds of American-style option prices, along with hedging strategies. The first method uses a series of neural networks, one per exercise time, to approximate continuation values and martingale increments via regression. The second method employs a single global network that takes time as an additional input, requiring an iterative training-updating procedure to refine stopping strategies. Both methods avoid nested Monte Carlo simulations, significantly reducing computational complexity. The dual formulation of the option price is leveraged to derive upper bounds, and the martingale representation directly yields hedging strategies without differentiation. Numerical experiments on vanilla American put options and max-call options in dimensions up to 10 demonstrate that the methods produce tight bounds and effective hedges. Algorithm variations, such as warm-start training and fresh data generation, further improve efficiency and memory usage. The hedging strategies can also serve as control variates to reduce variance in lower bound estimates.
Highlights
- 1Simultaneous computation of lower and upper bounds for American option prices using neural networks without nested Monte Carlo.
- 2Two algorithms: one using a series of neural networks and another using a single global network with time as input.
- 3Direct derivation of hedging strategies from the dual martingale representation, avoiding differentiation.
- 4Hedging strategy can be used as a control variate to reduce variance in lower bound estimates.
- 5Numerical experiments demonstrate effectiveness in high-dimensional settings with frequent exercise opportunities.
Methods
- MLeast Squares Monte Carlo (LSMC) modified with neural networks for regression of continuation values and martingale increments.
- MDual formulation of American option pricing to obtain upper bounds via martingale representation.
- MTwo neural network architectures: multiple networks (one per exercise time) and a single global network with time as input.
- MAlgorithm variations including warm-start training, partial data training, and fresh data generation to improve efficiency and memory usage.
Results
- RThe proposed methods produce tight lower and upper bounds for American option prices in both low- and high-dimensional settings.
- RWarm-start training reduces computation time and improves bound tightness (e.g., difference reduced from 0.0151 to 0.0108 for a 1D put option).
- RThe global network method achieves comparable accuracy to the multiple network method while reducing model complexity.
- RHedging strategies derived from the dual martingale are effective and can be used as control variates for variance reduction.
- RThe methods handle Bermudan options with up to 50 exercise opportunities in dimensions up to 10.
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