int check_set(
  vector<RESULT> results,
  DB_WORKUNIT&   wu,
  int&           canonicalid,
  double&        credit,
  bool&          retry
);

Define N := length of result vector, and let M := N.

check_set() will ALWAYS be called with N>=wu.min_quorum.

check_set() will ALWAYS be called with ALL results satisfying
    result.outcome == RESULT_OUTCOME_SUCCESS
    result.validate_state == VALIDATE_STATE_INIT

check_set() should NEVER modify wu [although it is not declared
    const]

[1] Syntax pass (optional)

 for (all N results) {

   if (one or more of the output files can be read and one or
       more of those files contains erroneous or invalid or
       incorrect output, i.e. the file syntax is wrong)
   {
     set result.outcome=RESULT_OUTCOME_VALIDATE_ERROR; 
     set result.validate_state=VALIDATE_STATE_INVALID;
     decrement counter: M = M-1;
   } // erroneous or incorrect or invalid output files

   else if (result has a potentially recoverable error,
	    i.e. NFS directory not mounted, server
	    is unreachable, upload server unreachable)
   {
     dont not modify result.validate_state;
     dont not modify result.outcome;
     decrement counter M = M-1;
     set retry=true;
   } // recoverable error
   
   else if (every output file of the result is unreadable or
	    fails to exist)
   {
     set result.outcome=RESULT_OUTCOME_VALIDATE_ERROR;
     set result.validate_state=VALIDATE_STATE_INIT;
     decrement counter: M = M-1;
   } // all result output files unreadable or nonexistent
   
 } // end of syntax pass loop over all N results

 Define REMAINING RESULTS to be those that do NOT fall into one of
 the two categories above. There are M of these. If the syntax pass
 has been skipped, then M == N.

 if (M < wu.min_quorum)
 {
   dont modify canonicalid;
   dont modify credit;
   leave retry as set above;
   leave result.outcome unchanged for M remaining results;
   leave result.validate_state unchanged for M remaining results;
   return 0;
 } // fewer than min_quorum results remain

 At any point in this process, if a major error occurs, check_set
 should return nonzero.  This will cause the validator to exit.  If
 this happens, it does not matter how you have set or modified
 result.outcome, result.validate_state, retry, credit, or canonicalid.

// END OF OPTIONAL SYNTAX PASS


[2] Comparison pass (required).  We have
    M>=wu.min_quorum REMAINING RESULTS results with
      result.outcome == RESULT_OUTCOME_SUCCESS
      result.validate_state == VALIDATE_STATE_INIT

   All the output files of all of these results are
   readable.  All of the output files for a given result
   are, when taken "in isolation" apparently valid.  If
   these conditions are not met then you must do the
   "syntax pass" above.

   if (one of these results is determined to be THE correct
       [canonical] result)
   {

     for correct result {
       set result.validate_state=VALIDATE_STATE_VALID;
       set canonicalid=result.id;
     } // canonical result

     for (the REMAINING M - 1 results)
     {
       // NOTE: what is below can be done by calling
       // check_pair(result, canonical_result)
       if (result is correct, matches canonical)
       {
	 result.validate_state=VALIDATE_STATE_VALID;
       }
       else
       {
         result.validate_state=VALIDATE_STATE_INVALID;
       }
     } // loop over remaining M-1 results

     set credit;

     leave retry as set from the syntax pass above;

     return 0;
   } // found canonical result
   else
   {
     // You are UNABLE to determine if one of the M REMAINING RESULTS
     // is correct, so:
    
     do not modify result.outcome for ANY of M remaining results;
     do not modify result.validate_state for ANY of M remaining results;
     do not set credit;
     do not set canonicalid;
     leave retry as set from the syntax pass;
     return 0;
    
   } // did not find canonical result
    
 At any point in this process, if a major error occurs, check_set
 should return nonzero.  This will cause the validator to exit.  If
 this happens, it does not matter how you have set result.outcome,
 result.validate_state, retry, credit, or canonicalid for ANY of the
 results.
    
// end of Comparison pass