Asynchronous evolutionary shape optimization based on high-quality surrogates: application to an air-conditioning duct
Abstract
Multi-processor HPC tools have become commonplace in industry and research today. Evolutionary
algorithms may be elegantly parallelized by broadcasting a
whole population of designs to an array of processors in a
computing cluster or grid. However, issues arise due to
synchronization barriers: subsequent iterations have to wait
for the successful execution of all jobs of the previous
generation. When other users load a cluster or a grid,
individual tasks may be delayed and some of them may
never complete, slowing down and eventually blocking the
optimization process. In this paper, we extend the recent
‘‘Futures’’ concept permitting the algorithm to circumvent
such situations. The idea is to set the default values to the
cost function values calculated using a high-quality surrogate model, progressively improving when ‘‘exact’’
numerical results are received. While waiting for the exact
result, the algorithm continues using the approximation and
when the data finally arrives, the surrogate model is
updated. At convergence, the final result is not only an
optimized set of designs, but also a surrogate model that is
precise within the neighborhood of the optimal solution.
We illustrate this approach with the cluster optimization of
an A/C duct of a passenger car, using a refined CFD legacy
software model along with an adaptive meta-model based
on Proper Orthogonal Decomposition (POD) and diffuse
approximation.