Deep Learning Volatility

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Deep Learning Volatility

Blanka Horvath
Aitor Muguruza
Mehdi Tomas
Published on 1/28/2019
Options
Derivatives
Machine learning
Deep learning
Volatility effect
Volatility premium
Risk management

This paper presents a deep learning framework for pricing and calibration of stochastic volatility models, with a focus on rough volatility models that are notoriously slow to calibrate due to their reliance on Monte Carlo methods. The authors propose a two-step approach: first, a deep neural network is trained offline to approximate the mapping from model parameters to the implied volatility surface (or option prices) using supervised learning on numerically generated data. Second, the trained network serves as a fast surrogate for online calibration, reducing calibration time from minutes or hours to milliseconds. The method is demonstrated on several models including the rough Bergomi, Bergomi, Heston, and SABR models, showing that the neural network approximation achieves accuracy comparable to the original numerical method (e.g., Monte Carlo) for out-of-sample parameters. Key innovations include representing the implied volatility surface as a collection of pixels for efficient learning and handling piecewise constant forward variance curves in the rough Bergomi model. Numerical experiments on synthetic and historical SPX data confirm that the approach enables fast, accurate, and robust calibration, effectively removing the computational bottleneck that previously limited the industrial applicability of rough volatility models. The authors also discuss potential extensions to model recognition and hedging.

Highlights

  • 1Proposes a two-step neural network calibration method that moves expensive numerical pricing into an offline training phase, enabling millisecond calibration for rough volatility models.
  • 2Demonstrates accurate approximation of implied volatility surfaces for the rough Bergomi, Bergomi, Heston, and SABR models using deep neural networks.
  • 3Achieves calibration of the rough Bergomi model with piecewise constant forward variance curve in milliseconds, enabling practical use of rough volatility models in industry.
  • 4Shows that the neural network pricing functional generalizes well to unseen parameter combinations, with accuracy comparable to the original numerical approximation.
  • 5Introduces a pixel-like representation of implied volatility surfaces for efficient neural network training.

Methods

  • M
    Supervised deep neural network training to approximate the pricing functional from model parameters to option prices/implied volatilities.
  • M
    Two-step calibration: offline learning of pricing map via neural network, followed by online deterministic calibration using the learned map.
  • M
    Monte Carlo simulation for generating training data for rough volatility models (e.g., rough Bergomi).
  • M
    Gradient-based optimization for calibration using the neural network surrogate.

Results

  • R
    Neural network price approximation achieves accuracy within the same range as the original numerical approximation (e.g., Monte Carlo) for out-of-sample parameters.
  • R
    Calibration of rough Bergomi model to synthetic and historical SPX data is performed in milliseconds, compared to minutes or hours with traditional methods.
  • R
    The method is consistently applicable across multiple volatility models (rough Bergomi, Bergomi, Heston, SABR) and contract types (vanilla options).
  • R
    Calibration to 10 years of SPX data shows stable parameter evolution and fast execution.
  • R
    The neural network approach lifts the calibration bottleneck for rough volatility models, making them viable for industrial applications.
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