(* Create a trivial matching for the center pair: *)
          oldMatch := NEW(REF PZMatch.T, 1);
          oldMatch[0] := ctr;
          maxAdjust := MAX((NA+1) DIV 2, (NB+1) DIV 2)
  
 
PROCEDURE RefineCandidateMatching(
    READONLY a, b: PZSymbolChain.T;
    maxShift: LONG; 
    mp: MismatchOptions;     (* Mismatch formula parameters. *)
    step: LONG;
    minSteps: NAT;
    VAR (*OUT*) mismatch : LONG;
    VAR (*OUT*) length: LONG;
    VAR (*OUT*) nMatched: NAT;
    VAR (*OUT*) match: REF PZMatch.T;
    VAR (*WORK*) XYCost: REF PZMatch.CostMatrix;
  ) =
  VAR xCenter, yCenter: NAT;
      minAvgDist: REF LONGS;
  BEGIN
    WITH
      NA = NUMBER(a),
      NB = NUMBER(b),
      ac = (NA-1) DIV 2,
      bc = (NB-1) DIV 2
    DO
      IF minSteps <= (NA-1)+(NB-1) THEN
        PZSymbolChain.RefineMatch(
          a, b,


          loc := FLOAT(ac + bc, LONG),
          align := FLOAT(ac - bc, LONG),
          maxShift := maxShift,
          mp := mp,
          step := step,
          minChainSteps := minSteps,
          (*OUT*) mismatch := mismatch,
          (*OUT*) nMatched := nMatched,
          (*OUT*) match := match,
          (*OUT*) xCenter := xCenter,
          (*OUT*) yCenter := yCenter,
          (*OUT*) minAvgDist := minAvgDist,
          (*WORK*) XYCost := XYCost
        );
        WITH
          nm = NUMBER(match^),
          La = match[nm-1,0] - match[0,0],
          Lb = match[nm-1,1] - match[0,1]
        DO
          length := step * FLOAT(La + Lb, LONG)/2.0d0
        END;
      ELSE
        mismatch := LAST(LONG);
        length := 0.0d0;
        nMatched := 0;
        match := NEW(REF PZMatch.T, 1);
        match[0] := PZMatch.Pair{ac,bc}
      END
    END
  END RefineCandidateMatching;


          

          (* Expand the input candidate *)
          FOR j := 0 TO 1 DO
            WITH
              sOld = cOld.seg[j],
              chd = ch[sOld.cvx],
              step = chd.length / FLOAT(sOld.tot, LONGREAL),
              extra = CEILING(extraLength / step)
            DO
              <* ASSERT NUMBER(chd.c^) = sOld.tot *>
              sExp[j] := PZSegment.Expand(sOld, extra, extra);
              chainStep[j] := step
              <* ASSERT sExp[j].tot = sOld[j].tot *>
              <* ASSERT sExp[j].cvx = sOld[j].cvx *>
              <* ASSERT sExp[j].rev = sOld[j].rev *>
            END
          END;


PROCEDURE ReadAllCVCFiles(
    chainPrefix : TEXT;
    nChains, band: CARDINAL; 
  ): REF ARRAY OF PZSymbolChain.ReadData =
  <* FATAL Rd.Failure *>
  BEGIN 
   WITH 
     ch = NEW(REF ARRAY OF PZSymbolChain.ReadData, nChains )
   DO 
     FOR i := 0 TO nChains-1 DO  
        WITH 
          chainTag  = Fmt.Pad(Fmt.Int(i), 4, '0'),
          bandTag = Fmt.Pad(Fmt.Int(band), 3, '0'),
          fileName = 
            chainTag & "/" & chainPrefix & "-" & chainTag & "-f" & bandTag & "-c-u.cvc", 
          rd = FileRd.Open(fileName),
          data = PZSymbolChain.Read(rd)
        DO
          ch[i] := data;
          Rd.Close(rd);
        END;
      END;
     RETURN ch;
    END;  
  END ReadAllCVCFiles;



        IF pp.keywordPresent("-fractality") THEN
          o.fractality := pp.getNextLongReal(0.5d0, 2.0d0)
        ELSE
          o.fractality := 1.0d0
        END;
        
PROCEDURE ReduceSampleIndex(x: LONGREAL; m: CARDINAL): LONGREAL =
  (*
    Reduces the sample index "x" modulo the sample count "m". *)
  BEGIN
    WITH
      fm = FLOAT(m, LONGREAL)
    DO
      WHILE x < 0.0d0 DO x := x + fm END;
      WHILE x >= fm DO x := x - fm END;
      RETURN x
    END
  END ReduceSampleIndex;