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# squash(+Vars, ++Precision, ++LinLog)

Refine the intervals of Vars by the squashing algorithm.
*Vars*
- Collection (a la collection_to_list/2) of variables
*Precision*
- Minimum required precision (float)
*LinLog*
- Domain splitting method (lin or log)

## Description

Use the squash algorithm on Vars. This is a deterministic reduction of
the intervals of variables, done by searching for domain restrictions
which cause failure, and then reducing the domain to the complement of
that which caused the failure. This algorithm is appropriate when the
problem has continuous solution intervals (where locate would return many
adjacent solutions).

Precision is the minimum required precision, i.e. the maximum size of the
resulting intervals (in either absolute or relative terms). Note that
the arc-propagation threshold (set by set_threshold/1,2), needs to be one
or several orders of magnitude smaller than Precision, otherwise the
solver may not be able to achieve the required precision.

The LinLog parameter guides the way domains are split. If it is set to
`lin` then the split is linear (i.e. the arithmetic mean of the bounds is
used). If it is set to `log`, the split is logarithmic (i.e. the geometric
mean of the bounds is used). Note that if `log` is used, there will be
roughly the same number of representable floating point numbers on either
side of the split, due to the logarithmic distribution of these numbers.

If the intervals of variables at the start of the squashing algorithm are
known not to span several orders of magnitude, the somewhat cheaper
linear splitting may be used. In general, log splitting is recommended.

## See Also

locate / 2, locate / 3, locate / 4, set_threshold / 1, get_threshold / 1, eclipse_6 : collection_to_list / 2, lists : collection_to_list / 2