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 result's output files can be read
       and one or more of those files contains erroneous or
       invalid or incorrect output, i.e. bad file syntax)
   {
     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 three categories above. There are M of these. If the syntax pass
 has been skipped, then M == N.

 if (M < wu.min_quorum)
 {
   don't modify canonicalid;
   don't 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