> For the complete documentation index, see [llms.txt](https://nelson-9.gitbook.io/nelson/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nelson-9.gitbook.io/nelson/markdown/en/mpi/mpi_barrier.md).

# MPI\_Barrier

Blocks until all processes in the communicator have reached this routine.

## 📝 Syntax

* r = MPI\_Barrier(Comm)

## 📥 Input argument

* Comm - a MPI\_Comm object.

## 📤 Output argument

* r - integer value: MPI\_SUCCESS (0) or MPI\_ERR\_COMM (5).

## 📄 Description

This function is used as a synchronization point for all processes in a group. All processes are blocked until every process calls MPI\_Barrier.

## 💡 Example

mpiexec(\[modulepath('mpi'), '/examples/help\_examples/MPI\_Barrier.m'], 4)

```matlab

if ~MPI_Initialized()
  MPI_Init();
end
my_rank = MPI_Comm_rank ();
num_ranks = MPI_Comm_size();
comm = MPI_Comm_object('MPI_COMM_WORLD');
sleep(my_rank);
MPI_Barrier(comm);
disp(['I am ', int2str(my_rank), ' of ', int2str(num_ranks)]);
if MPI_Initialized()
  MPI_Finalize();
end

```

## 🔗 See also

[MPI\_Initialized](/nelson/markdown/en/mpi/mpi_initialized.md).

## 🕔 History

| Version | 📄 Description  |
| ------- | --------------- |
| 1.0.0   | initial version |