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Subject: Re: [OMPI users] using MPI through Qt
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2011-03-01 11:39:41


Eye RCS 51 wrote:

> Hi,
>
> In an effort to make a Qt gui using MPI, I have the following:
>
> 1. Gui started in master node.
>
> 2. In Gui, through a pushbutton, a global variable x is assigned some
> value; let say, x=1000;
>
> 3. I want this value to be know to all nodes. So I used broadcast in
> the function assigning it on the master node and all other nodes.
>
> 4. I printed values of x, which prints all 1000 in all nodes.
>
> 5. Now control has reached to MPI_Finalize in all nodes except master.
>
> Now If I want to reassign value of x using pushbutton in master node
> and again broadcast to and print in all nodes, can it be done??

Not with MPI if MPI_Finalize has been called.

> I mean, can I have an MPI function which through GUI is called many
> times and assigns and prints WHILE program is running.

You can call an MPI function like MPI_Bcast many times. E.g.,

MPI_Init();
MPI_Comm_rank(...,&myrank);
while (...) {
   if ( myrank == MASTER ) x = ...;
   MPI_Bcast(&x,...);
}
MPI_Finalize();

There are many helpful MPI tutorials that can be found on the internet.

>
> OR simply can I have a print function which is printing noderank value
> in all nodes whenever pushbutton is pressed while program is running.
>
> command i used is "mpirun -np 3 ./a.out".