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###

Accuracy

Two criterion are used to determine if a box
possibly includes a solution of the system:

- the largest width of the components of the box is lower than
`epsilon` and the functions intervals for this box all contain 0
- the largest width of the function
intervals is lower than
`epsilonf` and they contain all 0. You
must be aware that this test is only used if there is no inequality in
the system. **In that case it is compulsory to have an **`epsilon` not equal to 0 otherwise the procedure may lead to an
infinite loop.

If we use only the first criteria (i.e. we put `epsilonf`=0)
the largest width of the solution intervals will be `epsilon`. A
consequence is that the unknowns should be normalized in order that
all the intervals in the `TestDomain` have roughly the same
width.
If we use only the second criteria the width of the solution intervals
cannot be determined and the functions should be roughly normalized
(see the example in section 15.1.3 for the importance of the
conditioning).

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Jean-Pierre Merlet
2012-12-20