c***********************************************************************
c     common block containing the constants controlling different 
c     algorithms 
c*** 
      DOUBLE PRECISION omega, mingrad, epsc, norm_old,
     % mineps  
      INTEGER cycles, ncycle, npre, npost, 
     % relax_times, relax_times_old, printres, ZOP
      COMMON /DIFF/ mingrad, epsc
      COMMON /CYCLING/ norm_old, mineps, omega, cycles, npre, npost, 
     % relax_times, relax_times_old, ncycle,printres,
     % ZOP