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Update MPI-HPX table
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@dimitraka
dimitraka committed Sep 7, 2023
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78 changes: 52 additions & 26 deletions docs/sphinx/manual/migration_guide.rst
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Expand Up @@ -42,6 +42,8 @@ Some general steps that can be used to migrate code to |hpx| code are the follow

Compile the converted code with the |hpx| library and run it using the appropriate HPX runtime environment.

.. _openmp:

|openmp|
========

Expand Down Expand Up @@ -656,6 +658,8 @@ directive in |openmp|. This synchronization is achieved using :cpp:func:`hpx::wa
If the `nowait` clause is used in the `sections` directive, then you can just remove
the :cpp:func:`hpx::wait_all` function while keeping the rest of the code as it is.

.. _tbb:

|tbb|
=====

Expand Down Expand Up @@ -966,7 +970,7 @@ parallel_scan
[](const int& left, const int& right) { return left + right; });

:cpp:func:`hpx::inclusive_scan` with `hpx::execution::par` as execution policy
can be used to perform a prefix scan in parallel. The management of intermediate
can be used to perform a prefix scan in parallel. The management of intermediate
results is seamlessly handled internally by |hpx|, eliminating the need
for explicit consideration. `input.begin()` and `input.end()` refer to the beginning
and end of the sequence of elements the algorithm will be applied to respectively.
Expand Down Expand Up @@ -1046,12 +1050,41 @@ task_group
feature. Therefore, utilizing :cpp:func:`hpx::experimental::task_group` provides an
equivalent functionality to `tbb::task_group`.

.. _mpi:

|mpi|
=====

|mpi| is a standardized communication protocol and library that allows multiple processes or
nodes in a parallel computing system to exchange data and coordinate their execution.

List of |mpi|-|hpx| functions
-----------------------------

.. table:: |hpx| equivalent functions of |mpi|

======================================== ===================================================================================================================
|mpi| function |hpx| equivalent
======================================== ===================================================================================================================
:ref:`MPI_Allgather` :cpp:class:`hpx::collectives::all_gather`
:ref:`MPI_Allreduce` :cpp:class:`hpx::collectives::all_reduce`
:ref:`MPI_Alltoall` :cpp:class:`hpx::collectives::all_to_all`
:ref:`MPI_Barrier` :cpp:class:`hpx::distributed::barrier`
:ref:`MPI_Bcast` :cpp:class:`hpx::collectives::broadcast_to()` and :cpp:class:`hpx::collectives::broadcast_from()` used with :code:`get()`
:ref:`MPI_Comm_size <MPI_Send_MPI_Recv>` :cpp:class:`hpx::get_num_localities`
:ref:`MPI_Comm_rank <MPI_Send_MPI_Recv>` :cpp:class:`hpx::get_locality_id()`
:ref:`MPI_Exscan` :cpp:class:`hpx::collectives::exclusive_scan()` used with :code:`get()`
:ref:`MPI_Gather` :cpp:class:`hpx::collectives::gather_here()` and :cpp:class:`hpx::collectives::gather_there()` used with :code:`get()`
:ref:`MPI_Irecv <MPI_Send_MPI_Recv>` :cpp:class:`hpx::collectives::get()`
:ref:`MPI_Isend <MPI_Send_MPI_Recv>` :cpp:class:`hpx::collectives::set()`
:ref:`MPI_Reduce` :cpp:class:`hpx::collectives::reduce_here` and :cpp:class:`hpx::collectives::reduce_there` used with :code:`get()`
:ref:`MPI_Scan` :cpp:class:`hpx::collectives::inclusive_scan()` used with :code:`get()`
:ref:`MPI_Scatter` :cpp:class:`hpx::collectives::scatter_to()` and :cpp:class:`hpx::collectives::scatter_from()`
:ref:`MPI_Wait <MPI_Send_MPI_Recv>` :cpp:class:`hpx::collectives::get()` used with a future i.e. :cpp:function:`setf.get()`
======================================== ===================================================================================================================

.. _MPI_Send_MPI_Recv:

MPI_Send & MPI_Recv
-------------------

Expand Down Expand Up @@ -1153,6 +1186,8 @@ To understand this example, let's focus on the `hpx_main()` function:

Having said that, we conclude to the following table:

.. _MPI_Gather:

MPI_Gather
----------

Expand Down Expand Up @@ -1282,6 +1317,8 @@ gather operation by sending data to the root locality. In more detail:
- The `get()` member function of the `overall_result` future is used to wait for the gather operation
to complete for this locality.

.. _MPI_Scatter:

MPI_Scatter
-----------

Expand Down Expand Up @@ -1409,6 +1446,8 @@ the data from the root locality. In more detail:

- `HPX_TEST_EQ` is a macro provided by the |hpx| testing utilities to test the collected values.

.. _MPI_Allgather:

MPI_Allgather
-------------

Expand Down Expand Up @@ -1506,6 +1545,7 @@ detail:

- The `get()` function waits until the result is available and then stores it in the vector called `r`.

.. _MPI_Allreduce:

MPI_Allreduce
-------------
Expand Down Expand Up @@ -1593,6 +1633,8 @@ detail:

- The `get()` function waits until the result is available and then stores it in the variable `res`.

.. _MPI_Alltoall:

MPI_Alltoall
-------------

Expand Down Expand Up @@ -1697,6 +1739,8 @@ detail:

- The `get()` function waits until the result is available and then stores it in the variable `r`.

.. _MPI_Barrier:

MPI_Barrier
-----------

Expand Down Expand Up @@ -1778,6 +1822,8 @@ detail:
Each thread waits until all other threads also reach this point before any of them can proceed
further.

.. _MPI_Bcast:

MPI_Bcast
---------

Expand Down Expand Up @@ -1889,6 +1935,8 @@ the root locality. In more detail:

- The `get()` member function of the `result` future is used to wait for the result.

.. _MPI_Exscan:

MPI_Exscan
----------

Expand Down Expand Up @@ -1975,6 +2023,7 @@ For num_localities = 2 this code will print the following message:

- The `get()` member function of the `overall_result` future is used to wait for the result.

.. _MPI_Scan:

MPI_Scan
--------
Expand Down Expand Up @@ -2055,6 +2104,8 @@ For num_localities = 2 this code will print the following message:

- The `get()` member function of the `overall_result` future is used to wait for the result.

.. _MPI_Reduce:

MPI_Reduce
----------

Expand Down Expand Up @@ -2153,28 +2204,3 @@ root locality. In more detail:

- The `get()` member function of the `overall_result` future is used to wait for the remote
reduction operation to complete. This is done to ensure synchronization among localities.

List of |mpi|-|hpx| functions
-----------------------------

.. table:: |hpx| equivalent functions of |mpi|

========================= =============================================================================================
|openmpi| function |hpx| equivalent
========================= =============================================================================================
MPI_Allgather `hpx::collectives::all_gather`
MPI_Allreduce `hpx::collectives::all_reduce`
MPI_Alltoall `hpx::collectives::all_to_all`
MPI_Barrier `hpx::distributed::barrier`
MPI_Bcast `hpx::collectives::broadcast_to()` and `hpx::collectives::broadcast_from()` used with `get()`
MPI_Comm_size `hpx::get_num_localities`
MPI_Comm_rank `hpx::get_locality_id()`
MPI_Exscan `hpx::collectives::exclusive_scan()` used with `get()`
MPI_Gather `hpx::collectives::gather_here()` and `hpx::collectives::gather_there()` used with `get()`
MPI_Irecv `hpx::collectives::get()`
MPI_Isend `hpx::collectives::set()`
MPI_Reduce `hpx::collectives::reduce_here` and `hpx::collectives::reduce_there` used with `get()`
MPI_Scan `hpx::collectives::inclusive_scan()` used with `get()`
MPI_Scatter `hpx::collectives::scatter_to()` and `hpx::collectives::scatter_from()`
MPI_Wait `hpx::collectives::get()` used with a future i.e. `setf.get()`
========================= =============================================================================================

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