From 2be323c9987abe603f88056aecae02ef0a01cd2e Mon Sep 17 00:00:00 2001
From: Kirill Suvorov <kirill.suvorov@intel.com>
Date: Mon, 13 Nov 2023 17:02:41 +0000
Subject: [PATCH] FEAT-#392: Send a warning if shared object storage is enabled
 but the MPI library does not support it.

Signed-off-by: Kirill Suvorov <kirill.suvorov@intel.com>
---
 docs/troubleshooting.rst                          |  9 +++++++++
 unidist/core/backends/mpi/core/common.py          | 15 ++++++++++++++-
 .../core/backends/mpi/core/shared_object_store.py |  4 +++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/docs/troubleshooting.rst b/docs/troubleshooting.rst
index 74804fc4..64893341 100644
--- a/docs/troubleshooting.rst
+++ b/docs/troubleshooting.rst
@@ -202,3 +202,12 @@ To get more information about the flags refer to `Open MPI's mpiexec`_ command d
 
 .. _`Open MPI's mpiexec`: https://www.open-mpi.org/doc/v3.1/man1/mpiexec.1.php
 .. _`issue`: https://github.com/modin-project/unidist/issues
+
+
+Shared object store is not supported in C/W model if the using MPICH version is less than the 4.2.0 version.
+------------------------------------------------------------------------------------------------------------
+Unfortunately, this version of MPICH has a problem with shared memory in the Controller/Worker model.
+
+**Solution**
+You can run your script using the SPMD model, or use other MPI implementations 
+such as Open MPI, Intel MPI, or MPICH above version 4.2.0.
\ No newline at end of file
diff --git a/unidist/core/backends/mpi/core/common.py b/unidist/core/backends/mpi/core/common.py
index 2bb8af80..0ed7861a 100755
--- a/unidist/core/backends/mpi/core/common.py
+++ b/unidist/core/backends/mpi/core/common.py
@@ -6,6 +6,7 @@
 
 import logging
 import inspect
+import warnings
 import weakref
 
 from unidist.config.backends.mpi.envvars import MpiSpawn
@@ -463,10 +464,15 @@ def versiontuple(v):
     return versiontuple(mpich_version) >= versiontuple(target_version)
 
 
-def is_shared_memory_supported():
+def is_shared_memory_supported(send_warning=False):
     """
     Check if the unidist on MPI supports shared memory.
 
+    Parameters
+    ----------
+    send_warning: bool, default: False
+        The need for warning as a flag.
+
     Returns
     -------
     bool
@@ -480,6 +486,9 @@ def is_shared_memory_supported():
         return False
 
     if MPI.VERSION < 3:
+        warnings.warn(
+            "The too old version of MPI is used. Shared object store can not be used."
+        )
         return False
 
     # Mpich shared memory does not work with spawned processes prior to version 4.2.0.
@@ -488,6 +497,10 @@ def is_shared_memory_supported():
         and MpiSpawn.get()
         and not check_mpich_version("4.2.0")
     ):
+        warnings.warn(
+            "Shared object store is not supported in C/W model if the using MPICH version is less than the 4.2.0 version."
+            + "Please read more about this problem in the `Troubleshooting` chapter of the Unidist documentation."
+        )
         return False
 
     return True
diff --git a/unidist/core/backends/mpi/core/shared_object_store.py b/unidist/core/backends/mpi/core/shared_object_store.py
index 2a5aa236..356d2db7 100644
--- a/unidist/core/backends/mpi/core/shared_object_store.py
+++ b/unidist/core/backends/mpi/core/shared_object_store.py
@@ -106,8 +106,10 @@ def __init__(self):
         # Length of service shared memory buffer in items
         self.service_info_max_count = None
 
+        mpi_state = communication.MPIState.get_instance()
+
         # Initialize all properties above
-        if common.is_shared_memory_supported():
+        if common.is_shared_memory_supported(send_warning=mpi_state.is_root_process()):
             self._allocate_shared_memory()
 
         # Logger will be initialized after `communicator.MPIState`