Lines

There exist 5 different types of lines. They are defined as follows:

• solution ('s ' line)

  These lines are mandatory and start with the two following characters: lower case s followed by a space (ASCII code 32). These two characters are followed by one of the following answers:

  UNSUPPORTED:

  for CSP, Max-CSP and WCSP.

  SATISFIABLE:

  for CSP, Max-CSP and WCSP.

  UNSATISFIABLE:

  for CSP.

  UNKNOWN:

  for CSP, Max-CSP and WCSP.

  OPTIMUM FOUND:

  for Max-CSP and WCSP.

  It is of utmost importance to respect the exact spelling of these answers. Any mistake in the writing of these lines will cause the answer to be disregarded. Solvers are not required to provide any specific exit code corresponding to their answer.

  It is important to note that UNSUPPORTED is used when the solver recognises a constraint that is not implemented.

  See Subsections 7.2 and 7.3 about their use.

• values ('v ' line)

  These lines are mandatory and start with the two following characters: lower case v followed by a space (ASCII code 32) and followed by a solution of the problem.

  Here, a solution is a sequence of numbers (only), which are separated by one or more space symbols. The $i^{th}$ number in the solution corresponds to the ``assignment'' to the $i^{th}$ variable of the problem in the original problem specification in standard input format. (Note that this may have consequences for solvers that introduce auxiliary variables, rename variables, or change their order.)

• diagnostic ('d ' line)

  These lines are optional and start with the two following characters: lower case d followed by a space (ASCII code 32). Then, a keyword followed by a value must be given on this line. See section 7.4 for details about the diagnostics.

• comment ('c ' line)

  Such lines are optional and start with the two following characters: lower case c followed by a space (ASCII code 32). These lines are optional and may appear anywhere in the solver output. They contain any information that authors want to output. They are recorded by the evaluation environment for later viewing but are otherwise ignored. At most one megabyte of solver output will be recorded. So, if a solver is very verbose, some comments may be lost.

  Submitters are advised to avoid outputting comment lines which may be useful in an interactive environment but otherwise useless in a batch environment. For example, outputting comment lines with the number of constraints read so far only increases the size of the logs with no benefit.

  If a solver is really too verbose, the organisers will ask the submitter to remove some comment lines.

• objective cost ('o ' line) (for Max-CSP and WCSP, only)

  These lines start with the two following characters: lower case o followed by a space (ASCII code 32). These two characters are followed by one integer.

  See Subsection 7.3 about its use.

Important: Any line must be terminated by a Line Feed character: the usual Unix line terminator ' $\backslash$n' (ASCII code 10). A 'v ' line which does not end with that terminator will be ignored because it will be considered that the solver was interrupted before it could output a complete solution. Also, it is important that you don't forget to flush the output as soon as you have printed a 's ' line or a 'v ' line.