From 975e8deba0f5b53f0dc6d8e37d0d1aa36bd1a858 Mon Sep 17 00:00:00 2001
From: Vicente Bolea <vicente.bolea@kitware.com>
Date: Tue, 17 Oct 2023 15:53:52 -0400
Subject: [PATCH] MPI_DP: do not call MPI_Init (#3847)

---
 source/adios2/toolkit/sst/dp/mpi_dp.c | 66 ++++++++-------------------
 1 file changed, 20 insertions(+), 46 deletions(-)

diff --git a/source/adios2/toolkit/sst/dp/mpi_dp.c b/source/adios2/toolkit/sst/dp/mpi_dp.c
index 612985c146..d82fc189b4 100644
--- a/source/adios2/toolkit/sst/dp/mpi_dp.c
+++ b/source/adios2/toolkit/sst/dp/mpi_dp.c
@@ -42,8 +42,6 @@
 #define QUOTE(name) #name
 #define MACRO_TO_STR(name) QUOTE(name)
 
-static pthread_once_t OnceMpiInitializer = PTHREAD_ONCE_INIT;
-
 /*****Stream Basic Structures ***********************************************/
 
 typedef struct _MpiReaderContactInfo
@@ -235,40 +233,6 @@ static void MpiReadReplyHandler(CManager cm, CMConnection conn, void *msg_v, voi
 static void MpiReadRequestHandler(CManager cm, CMConnection conn, void *msg_v, void *client_Data,
                                   attr_list attrs);
 
-/**
- * Initialize MPI in the mode that it is required for MPI_DP to work.
- *
- * It can be called multiple times.
- */
-static void MpiInitialize()
-{
-    int IsInitialized = 0;
-    int provided;
-
-    MPI_Initialized(&IsInitialized);
-    if (!IsInitialized)
-    {
-        MPI_Init_thread(NULL, NULL, MPI_THREAD_MULTIPLE, &provided);
-    }
-    else
-    {
-        MPI_Query_thread(&provided);
-    }
-
-    if (provided != MPI_THREAD_MULTIPLE)
-    {
-        int rank;
-        MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-        if (!rank)
-        {
-            fprintf(stderr,
-                    "MPI init without MPI_THREAD_MULTIPLE (Externally "
-                    "initialized:%s)\n",
-                    IsInitialized ? "true" : "false");
-        }
-    }
-}
-
 /*****Public accessible functions********************************************/
 
 /**
@@ -286,8 +250,6 @@ static DP_RS_Stream MpiInitReader(CP_Services Svcs, void *CP_Stream, void **Read
                                   struct _SstParams *Params, attr_list WriterContact,
                                   SstStats Stats)
 {
-    pthread_once(&OnceMpiInitializer, MpiInitialize);
-
     MpiStreamRD Stream = calloc(sizeof(struct _MpiStreamRD), 1);
     CManager cm = Svcs->getCManager(CP_Stream);
     SMPI_Comm comm = Svcs->getMPIComm(CP_Stream);
@@ -327,8 +289,6 @@ static DP_RS_Stream MpiInitReader(CP_Services Svcs, void *CP_Stream, void **Read
 static DP_WS_Stream MpiInitWriter(CP_Services Svcs, void *CP_Stream, struct _SstParams *Params,
                                   attr_list DPAttrs, SstStats Stats)
 {
-    pthread_once(&OnceMpiInitializer, MpiInitialize);
-
     MpiStreamWR Stream = calloc(sizeof(struct _MpiStreamWR), 1);
     CManager cm = Svcs->getCManager(CP_Stream);
     SMPI_Comm comm = Svcs->getMPIComm(CP_Stream);
@@ -798,16 +758,30 @@ static void MpiReleaseTimeStep(CP_Services Svcs, DP_WS_Stream Stream_v, long Tim
  */
 static int MpiGetPriority(CP_Services Svcs, void *CP_Stream, struct _SstParams *Params)
 {
-#if defined(MPICH)
-    // Only enabled when MPI_THREAD_MULTIPLE and using MPICH
+    int IsInitialized = 0;
     int provided = 0;
-    pthread_once(&OnceMpiInitializer, MpiInitialize);
-    MPI_Query_thread(&provided);
-    if (provided == MPI_THREAD_MULTIPLE)
+    int IsMPICH = 0;
+#if defined(MPICH)
+    IsMPICH = 1;
+
+    MPI_Initialized(&IsInitialized);
+    if (IsInitialized)
     {
-        return 100;
+        MPI_Query_thread(&provided);
+        // Only enabled when MPI_THREAD_MULTIPLE and using MPICH
+        if (provided == MPI_THREAD_MULTIPLE)
+        {
+            return 100;
+        }
     }
 #endif
+
+    Svcs->verbose(CP_Stream, DPTraceVerbose,
+                  "MPI DP disabled since the following predicate is false: "
+                  "(MPICH=%s AND MPI_initialized=%s AND MPI_THREAD_MULTIPLE=%s)",
+                  IsMPICH ? "true" : "false", IsInitialized ? "true" : "false",
+                  provided == MPI_THREAD_MULTIPLE ? "true" : "false");
+
     return -100;
 }