A parallel computational model for sensitivity analysis in optimization for robustness

  • Authors:
  • Radu Serban

  • Affiliations:
  • Center for Applied Scientific Computing, Lawrence Livermore National Laboratory, Livermore, California, USA

  • Venue:
  • Optimization Methods & Software
  • Year:
  • 2009

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Abstract

We present an efficient method for computing, in a parallel distributed environment, gradients of functionals depending on the solution sensitivities of dynamical systems described by ordinary differential equations. This work was motivated by the need to compute cost function gradients for dynamically constrained optimization for robustness, i.e. the problem of finding the model parameters of a given dynamical system that lead to minimum solution sensitivity. The proposed approach for this particular second-order sensi-tivity problem falls into the class of the so-called 'adjoint-over-forward' methods and is based on solving the continuous forward sensitivity equations (for evaluating the cost functional) and their continuous adjoint systems (for evaluation of the gradient of the cost functional). Efficiency is ensured by: (i) a suitable distribution over processors of the individual sensitivity systems, both forward and adjoint so that inter-process communication is minimized; and (ii) use of an iterative solver combined with a block-diagonal preconditioner for the solution of the linear systems arising in the implicit integration of the resulting ordinary differential equations (ODE) systems. The proposed algorithm was implemented as an extension of the cvodes solver in sundials [P. Brown, K. Grant, A. Hindmarsh, S. Lee, R.S.D. Shumaker, and C. Woodward. SUNDIALS: SUite of Nonlinear and DIfferential/ALgebraic equation Solvers, ACM Trans. Math. Software, 31(3) (2005), pp. 363-396], but it can be used in conjunction with any sensitivity-enabled ODE integrator that provides adjoint sensitivity capabilities and (if based on implicit integration methods) support for iterative linear algebra.