We present a novel numerical method for solving McKean-Vlasov forward-backward stochastic differential equations (MV--FBSDEs) with common noise, combining Picard iterations, elicitability and deep learning. The key innovation involves elicitability to derive a path-wise loss function, enabling efficient training of neural networks to approximate both the backward process and the conditional expectations arising from common noise -- without requiring computationally expensive nested Monte Carlo simulations. The mean-field interaction term is parameterized via a recurrent neural network trained to minimize an elicitable score, while the backward process is approximated through a hybrid feedforward and recurrent network representing the decoupling field. We validate the algorithm on a systemic risk inter-bank borrowing and lending model, where analytical solutions exist, demonstrating accurate recovery of the true solution. We further extend the model to quantile--mediated interactions, showcasing the flexibility of the elicitability framework beyond conditional means or moments. Finally, we apply the method to a non-stationary Aiyagari-Bewley-Huggett economic growth model with endogenous interest rates, illustrating its applicability to complex mean-field games without closed-form solutions.
Algorithm 5 Estimating Z and Z0 through elicitability with fixed (X,Y,m)
Figure 1. Architecture of the hybrid approximator.
d
K
X
Y
Z
Z0
S
d=1
k=5
3.54 (
1.99 )
8.22 (
5.97 )
16.80 (
11.2 )
19.70 (
3.54 )
3.82 (
2.03 )
k=50
0.54 (
0.46 )
1.08 (
1.00 )
2.08 (
2.18 )
3.84 (
1.84 )
0.45 (
0.56 )
k=100
0.59 (
0.44 )
1.53 (
0.94 )
1.71 (
1.30 )
1.76 (
1.11 )
0.36 (
0.45 )
k=250
0.41 (
0.34 )
0.81 (
0.81 )
1.59 (
1.13 )
0.60 (
0.60 )
0.47 (
0.44 )
d=5
k=5
11.10 (
6.94 )
31.50 (
17.2 )
45.20 (
25.0 )
45.40 (
7.45 )
12.60 (
8.18 )
k=50
2.29 (
1.35 )
4.95 (
2.92 )
3.67 (
3.09 )
5.17 (
2.21 )
3.01 (
2.08 )
Table 1. MEE results ( ×10−2 ) for different values of K and dimensions. In parentheses, the standard deviation of the Euclidean norm of errors by path and time.
Figure 2. Comparison between analytic solution and approximated solution on two sample paths for the systemic risk with common noise experiment. Solid lines are the numerical solutions, and dotted lines represent the analytical solution. Each color pair (orange and blue, green and red) represents a particular path of each variable of the system.
Figure 3. The same sample path at iterations 1,2,4,8,16 and 32. As iteration increases, the color becomes darker.
Figure 4. Modified systemic risk model where interaction is mediated through the 60% quantile. Respective paths (subjected to the same Brownian motion) of the original, mean interaction systemic risk model are shown in lighter shades. Note that the Xt variable is greater in the quantile interaction model.
Figure 7. Marginal propensity to consume as a function of Kt and rt , for time t=0.5 .
This paper develops an a posteriori error analysis framework for decoupled neural approximations of fully coupled forward--backward stochastic differential equations (FBSDEs). It provides an a posteriori error-analysis for the idealized discrete adapted trajectory. The main feature of the proposed formulation is the use of an auxiliary control process in the forward coefficients, which may differ from the backward component approximated by the neural network. This decoupling is useful in practical deep learning implementations, but it creates a control mismatch that must be included in the error analysis. We first establish a continuous-time stability estimate for fully coupled FBSDEs under perturbations of the drift, diffusion, generator, terminal condition, and auxiliary control input. We then transfer this estimate to the discrete-time setting and derive computable a posteriori error bounds depending only on the terminal defect, the pathwise residual, and the control mismatch. When the auxiliary control is identified with the backward approximation, the mismatch term vanishes and the bound reduces to the standard two-term form. Numerical experiments on a linear--quadratic FBSDE with an explicit reference solution and a multidimensional Burgers-type FBSDE without a reference solution illustrate the diagnostic role of the proposed indicators and the contribution of the mismatch penalty to the consistency and reproducibility of the numerical approximations.
Xichuan Zhang
Intelligent Game and Decision Lab, Beijing 100091, China
In this paper, we introduce two neural-network-based numerical schemes for solving systems of coupled ergodic Backward Stochastic Differential Equations (eBSDEs), motivated by the approximation of optimal strategies within the framework of forward utilities in a regime-switching stochastic factor model. Our approach builds on the representation of such models through systems of eBSDEs introduced in [HLT20]. We first establish a link between the solution of the system of ergodic BSDEs and that of an associated multidimensional BSDE with random terminal time, given by the hitting time of the positive recurrent stochastic factor. Building on this representation, we introduce a locally additive deep learning scheme obtained by minimizing aggregated local error terms. We then present a new Deep Galerkin Method (DGM) inspired algorithm that minimizes the residual of the associated ergodic PDE system, relying on a representation of the ergodic cost. Finally, we apply this framework to regime-switching forward utilities in a stochastic factor model. We first derive a general consistency SPDE that characterizes regime-switching forward utilities and retrieve their representation with systems of ergodic BSDEs in the homothetic case. Numerical experiments demonstrate the performance of the proposed methods, with a particular focus on the impact on forward preferences of taking into account regime switches.
Guillaume Broux-Quemerais, Sarah Kaakai, Anis Matoussi +1
LMM · 1Laboratoire Manceau de Mathématiques & FR CNRS No 2962, Institut du Risque et de l’Assurance, Le Mans Université · LAGA +1
In this article, we introduce a deep learning based approximation algorithm for SPDEs. Our approach employs neural networks to approximate the solutions of SPDEs along given realizations of the driving noise process. If applied to a set of simulated noise trajectories, it yields empirical distributions of SPDE solutions, from which functionals like the mean and variance can be estimated. We test the performance of the method on stochastic heat equations with additive and multiplicative noise as well as stochastic Black-Scholes equations with multiplicative noise and Zakai equations from nonlinear filtering theory. In all cases, the proposed algorithm yields accurate results with short runtimes in up to 100 space dimensions.
Christian Beck, Sebastian Becker, Patrick Cheridito +2
Department of Mathematics, ETH Zurich · School of Data Science and School of Artificial Intelligence,2025 The Chinese University of Hong Kong, Shenzhen (CUHK-Shenhen) · Applied Mathematics: Institute for Analysis and Numerics, University of Münster +1