errors.py

   1 """
   2 Errors that can occur when solving a linear game.
   3 """
   4
   5 from cvxopt import matrix
   6
   7
   8 class GameUnsolvableException(Exception):
   9     """
  10     Every linear game has a solution (this follows from a general
  11     min-max theorem). If we can't solve the conic program associated
  12     with a linear game, then something is wrong with either the model of
  13     the input.
  14     """
  15     def __str__(self):
  16         tpl = 'Solution failed with result "{:s}."\n' \
  17               'CVXOPT returned:\n{!s}'
  18         return tpl.format(self._solution_dict['status'],
  19                           self._pretty_print_dict(self._solution_dict))
  20
  21
  22     def __init__(self, solution_dict):
  23         """
  24         Create a new GameUnsolvableException object.
  25
  26         INPUT:
  27
  28         - ``solution_dict`` -- the solution dictionary returned from the
  29           cone program.
  30
  31         """
  32         self._solution_dict = solution_dict
  33
  34
  35     def _pretty_print_dict(self, solution_dict):
  36         """
  37         Return a pretty-printed string representation of a CVXOPT
  38         solution dictionary.
  39         """
  40         result = ''
  41         for (k,v) in solution_dict.items():
  42             if isinstance(v, matrix):
  43                 # Display matrices on their own lines, indented.
  44                 result += '  {:s}:'.format(k)
  45                 colvec = '\n{!s}'.format(v)
  46                 result += '\n    '.join(colvec.splitlines())
  47                 result += '\n'
  48             else:
  49                 result += '  {:s}: {!s}\n'.format(k,v)
  50
  51         return result