check_exponent.c

/****************************************************************************
**
*A  check_exponent.c            ANUPQ source                   Eamonn O'Brien
**
*Y  Copyright 1995-2001,  Lehrstuhl D fuer Mathematik,  RWTH Aachen,  Germany
*Y  Copyright 1995-2001,  School of Mathematical Sciences, ANU,     Australia
**
*/

#include "pq_defs.h"
#include "pcp_vars.h"
#include "constants.h"
#include "pq_functions.h"
#include "exp_vars.h"

/* determine whether trial value is upper bound on exponent of the
   group; do this by checking that all test words are trivial */

Logical check_exponent(int trial_exponent,
                       struct exp_vars *exp_flag,
                       struct pcp_vars *pcp)
{
   int known_exponent;

   initialise_exponent(exp_flag, pcp);
   exp_flag->check_exponent = TRUE;
   exp_flag->all_trivial = TRUE;

   known_exponent = pcp->extra_relations;
   if (known_exponent)
      return known_exponent == trial_exponent;
   pcp->extra_relations = trial_exponent;

   /* now generate and power all test words */
   extra_relations(exp_flag, pcp);

   /* restore existing exponent law */
   pcp->extra_relations = known_exponent;

   /* if trivial flag is true, we have (upper bound on) exponent */
   return exp_flag->all_trivial;
}