module default;
const N = 2..max;
global protocol TwoWayMesh(role Worker[1..N][1..N]) {
  Init() from __self to __self;
  rec Steps {
    LoopBegin() from __self to __self;
    LeftToRight(T) from Worker[r:1..N][c:1..N-1] to Worker[r][c+1];
    RightToLeft(T) from Worker[r:1..N][c:2..N]   to Worker[r][c-1];
    UpToDown(T) from Worker[r:1..N-1][c:1..N] to Worker[r+1][c];
    DownToUp(T) from Worker[r:2..N][c:1..N]   to Worker[r-1][c];
    LoopEnd() from __self to __self;
    continue Steps;
  }
  Finish() from __self to __self;
}