Drop MPI-2 support (#3643)

CMakeLists.txt

@@ -671,6 +671,12 @@ if (HDF5_ENABLE_PARALLEL)
   find_package(MPI REQUIRED)
   if (MPI_C_FOUND)
     set (H5_HAVE_PARALLEL 1)
+
+    # Require MPI standard 3.0 and greater
+    if (MPI_VERSION LESS 3)
+      message (FATAL_ERROR "HDF5 requires MPI standard 3.0 or greater")
+    endif ()
+
     # MPI checks, only do these if MPI_C_FOUND is true, otherwise they always fail
     # and once set, they are cached as false and not regenerated
     set (CMAKE_REQUIRED_LIBRARIES "${MPI_C_LIBRARIES}")

configure.ac

@@ -2654,6 +2654,20 @@ if test "X${ALLOW_UNSUPPORTED}" != "Xyes"; then
   fi
 fi
 
+# Requires MPI standard 3.0 and greater
+if test "X${enable_parallel}" = "Xyes"; then
+  AC_MSG_CHECKING([whether MPI meets the minimum 3.0 standard])
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+       #include <mpi.h>
+       #if MPI_VERSION < 3
+       #error, found MPI_VERSION < 3
+       #endif]])],
+       [AC_MSG_RESULT([yes])],
+       [AC_MSG_RESULT([no])
+       AC_MSG_ERROR([HDF5 requires MPI standard 3.0 or greater])]
+  )
+fi
+
 AC_MSG_CHECKING([for parallel support files])
 case "X-$enable_parallel" in
   X-|X-no|X-none)

release_docs/RELEASE.txt

@@ -332,6 +332,12 @@ Bug Fixes since HDF5-1.14.0 release
 ===================================
     Library
     -------
+
+    - Dropped support for MPI-2
+
+      The MPI-2 supporting artifacts have been removed due to the cessation
+      of MPI-2 maintenance and testing since version HDF5 1.12.
+
     - Fixed a bug with the way the Subfiling VFD assigns I/O concentrators
 
       During a file open operation, the Subfiling VFD determines the topology

src/H5Dmpio.c

@@ -3645,7 +3645,6 @@ H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk
                                         int H5_ATTR_NDEBUG_UNUSED mpi_size, unsigned char ***chunk_msg_bufs,
                                         int *chunk_msg_bufs_len)
 {
-#if H5_CHECK_MPI_VERSION(3, 0)
     H5D_filtered_collective_chunk_info_t *chunk_table       = NULL;
     H5S_sel_iter_t                       *mem_iter          = NULL;
     unsigned char                       **msg_send_bufs     = NULL;
@@ -3867,20 +3866,12 @@ H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk
          * post a non-blocking receive to receive it
          */
         if (msg_flag) {
-#if H5_CHECK_MPI_VERSION(3, 0)
             MPI_Count msg_size = 0;
 
             if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&status, MPI_BYTE, &msg_size)))
                 HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements_x failed", mpi_code)
 
             H5_CHECK_OVERFLOW(msg_size, MPI_Count, int);
-#else
-            int msg_size = 0;
-
-            if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&status, MPI_BYTE, &msg_size)))
-                HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code)
-#endif
-
             if (msg_size <= 0)
                 HGOTO_ERROR(H5E_DATASET, H5E_BADVALUE, FAIL, "invalid chunk modification message size");
 
@@ -4033,13 +4024,6 @@ H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk
 #endif
 
     FUNC_LEAVE_NOAPI(ret_value)
-#else
-    FUNC_ENTER_PACKAGE
-    HERROR(
-        H5E_DATASET, H5E_WRITEERROR,
-        "unable to send chunk modification data between MPI ranks - MPI version < 3 (MPI_Ibarrier missing)")
-    FUNC_LEAVE_NOAPI(FAIL)
-#endif
 } /* end H5D__mpio_share_chunk_modification_data() */
 
 /*-------------------------------------------------------------------------