The estimation of variance-based importance measures (called Sobol' indices)
of the input variables of a numerical model can require a large number of model
evaluations. It turns to be unacceptable for huge model involving a large
number of input variables (typically more than ten).
Complex computer codes, for instance simulating physical phenomena, are often
too time expensive to be directly used to perform uncertainty, sensitivity,
optimization and robustness analyses. A widely accepted method to circumvent
this problem consists in replacing cpu time expensive computer models by cpu
inexpensive mathematical functions, called metamodels. In this paper, we focus
on the Gaussian process metamodel and two essential steps of its definition
phase.
The global sensitivity analysis of a complex numerical model often requires
the estimation of variance-based importance measures, called Sobol indices.
Metamodel-based techniques have been developed in order to replace the cpu time
expensive computer code with an inexpensive mathematical function, predicting
the computer code output.
In some studies requiring predictive and CPU-time consuming numerical models,
the sampling design of the model input variables has to be chosen with caution.
For this purpose, Latin hypercube sampling has a long history and has shown its
robustness capabilities. In this paper we propose and discuss a new algorithm
to build a Latin hypercube sample (LHS) taking into account inequality
constraints between the sampled variables. This technique, called constrained
Latin hypercube sampling (cLHS), consists in doing permutations on an initial
LHS to honor the desired monotonic constraints.