Team Coprin

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Inria / Raweb 2004
Project: Coprin

Project : coprin

Section: Scientific Foundations


The scientific objective of the COPRIN project is to develop and implement systems solving and optimization algorithms based on constraints propagation methods, interval analysis and symbolic computation, with interval arithmetic as the primary tool.

The results obtained with these algorithms are certified in the sense that all solutions will be obtained and can be calculated with an arbitrary accuracy. Furthermore some of our algorithms will allow us to deal with systems involving uncertain coefficients.

A system will be constituted by a set of relations that may use all the usual mathematical operators and functions (hence we may deal, for example, with the relation sin(x + y) + log(cos(ex) + y2)$ \le$0).

We are interested in real-valued constraint satisfaction problems ((f(X) = 0, f(X)$ \le$0)), in optimization problems and in the proof of the existence of properties (for example it exists X such that f(X) = 0 or it exists two values X1, X2 such that f(X1)>0 and f(X2)<0)

Solutions will be searched within a finite domain (called a box) which may be either continuous or mixed (i.e. for which some variables must belong to a continuous range while other variables may only have value within a discrete set). An important point is that we aim to find all the solutions within the domain as soon as the computer arithmetic will allow it: in other words we are looking for certified solutions.

Our approach is to develop various operators that will be applied in sequence on a box:

  1. exclusion operators: these operators determine that there is no solution to the problem within a given box

  2. contractors: these operators may reduce the size of the box i.e. decrease the width of the allowed ranges for the variables

  3. existence operators: they allow one to determine that there is a unique solution within a given box and are usually associated to a numerical scheme that enable to compute this solution in a safe way

If a given box is not rejected by the exclusion operators and is not modified by the other operators, then we will bisect one of the variables in order to create two new boxes that will be processed later on. Methods for choosing the bisected variable are also clearly within the scope of the project.

Our research aims to develop operators that can be used for any problem or are specific to a given class of problem, especially problems that are issued from application domains for which we have internally an expertise (such as mechanism theory and software engineering). Furthermore we will study symbolic computation based methods:


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