receive upper halo   500+rank+nzdoms	      500 - 542
send    upper halo   400+rank                 400 - 432

recv    right halo  200+rank+1                801 - 233    200
send    right halo  100+rank                  700 - 132    100

send line buf 1000+200*(rank+1)+ime
recv line buf 1000+200*rank+ime              1000 - 7800

recv left halo 600+rank+1                    
send left halo 600+rank                        600 - 632
