Generator

      PROGRAM MAIN
      COMMON /VALUES/ M_SIZE
      CALL ENTER_SIZE
      CALL GENERATE_MATRIX

      END

      SUBROUTINE ENTER_SIZE
      COMMON /VALUES/ M_SIZE

      PRINT *, 'ENTER SIZE OR TAB 0 TO READ SIZE OF MATRIX FROM FILE'
      READ *, M_SIZE

      IF(M_SIZE.GT.0) GOTO 5
      OPEN(1, FILE = 'N1N2.txt', ERR = 9)
      READ(1,*) M_SIZE
    5 PRINT *, M_SIZE

      CLOSE(1)
      GOTO 1
    9 STOP 'ERROR: SOMETHING WENT WRONG WITH N1N2.txt'
    1 END

      SUBROUTINE GENERATE_MATRIX
      COMMON /VALUES/ M_SIZE

C     ================= GENERATE VECTOR & DIAG =================
      OPEN(1, FILE = 'vec.txt', ERR = 99)
      OPEN(2, FILE = 'di.txt', ERR = 99)
      DO I = 1, M_SIZE
        WRITE(1, 3) MOD(I, 3)
        WRITE(2, 3) MOD(I, 10)
      ENDDO
      CLOSE(1)
      CLOSE(2)

C     ================= GENERATE PROFILE AND LT =================
      OPEN(3, FILE = 'ia.txt')
      OPEN(4, FILE = 'al.txt')
      WRITE(3, 3) 1
      IT = 1
      IK = 1
      DO WHILE (IK .LT. M_SIZE)
        IF (MOD(IT,3) .EQ. 0) GOTO 33
        WRITE(3, 3) IT
        IK = IK + 1
33      IT = IT + 1
      ENDDO
      WRITE(3, 3) IT

      DO I = 1, IT
        WRITE(4, 3) MOD(I, 10)
      ENDDO
      CLOSE(3)
      CLOSE(4)

      GOTO 11
C     ===============================================================
    3 FORMAT(I2)
   99 STOP 'ERROR: SOMETHING WENT WRONG WITH INPUT FILE'
   11 END