EXTERNAL

SUB anneal (x(), y(), iorder(), ncity)

    LIBRARY "link", "ran3", "irbit1"
    DECLARE FUNCTION alen, ran3, irbit1

    ! The function alen and the subroutines revcst, revers,
    ! trncst, trnspt, and metrop are in the file "link"

    DIM n(6)

    LET nover = 100 * ncity
    LET nlimit = 10 * ncity
    LET tfactr = .9
    LET path = 0
    LET t = .5
    FOR i = 1 to ncity - 1
        LET i1 = iorder(i)
        LET i2 = iorder(i + 1)
        LET path = path + alen (x(i1), x(i2), y(i1), y(i2))
    NEXT i
    LET i1 = iorder(ncity)
    LET i2 = iorder(1)
    LET path = path + alen (x(i1), x(i2), y(i1), y(i2))
    LET idum = -1
    LET iseed = 111
    FOR j = 1 to 100
        LET nsucc = 0
        FOR k = 1 to nover
            DO
               LET n(1) = 1 + int(ncity * ran3(idum))
               LET n(2) = 1 + int((ncity - 1) * ran3(idum))
               IF n(2) >= n(1) then LET n(2) = n(2) + 1
               LET nn = 1 + mod(n(1) - n(2) + ncity - 1, ncity)
            LOOP while nn < 3

            LET idec = irbit1(iseed)
            IF idec = 0 then
               LET n(3) = n(2) + int(abs(nn - 2) * ran3(idum)) + 1
               LET n(3) = 1 + mod(n(3) - 1, ncity)

               CALL trncst (x(), y(), iorder(), ncity, n(), de)
               CALL metrop (de, t, ans)

               IF ans=-1 then
                  LET nsucc = nsucc + 1
                  LET path = path + de

                  CALL trnspt (iorder(), ncity, n())

               END IF
            ELSE

               CALL revcst (x(), y(), iorder(), ncity, n(), de)
               CALL metrop (de, t, ans)

               IF ans=-1 then
                  LET nsucc = nsucc + 1
                  LET path = path + de

                  CALL revers (iorder(), ncity, n())

               END IF
            END IF
            IF nsucc >= nlimit then EXIT FOR
        NEXT k
        PRINT
        PRINT "t =";
        PRINT using "####.######": t;
        PRINT "   Path length =";
        PRINT using "####.######": path
        PRINT "Successful moves: "; nsucc
        LET t = t * tfactr
        IF nsucc = 0 then EXIT SUB
    NEXT j

END SUB