[OMPI users] Cannot create X11 window in Rank 0 node(master) ?

[Ashika Umanga Umagiliya]

Hi all,

I have written mandelbrot rendering using X11.I have two nodes with OpenMPI.
In my code, the rank 0 node(master) does the data collection from 
salves, Window creation using X11 and render the graph.(using 
XCreateSimpleWindow() ). Slave nodes calculate and send data to master.

But when I execute my application by :
#mpirun -np 4 -host biggserver ./mandel

its gives error :

"cannot connect to X server '(null)'"


Isn't the rank 0 given to the machine which we initially run the MPI 
application?
If so,why the application says it cannot connect to X server?Since rank 
0 is my workstation?

When I run this using a single node , it works well.

Any tips?

thanks in advance,
umanga