Drop MPI-2 support (#3643) (#3802)

9 files changed, 71 insertions, 216 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0dd250c..19c6742 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -684,6 +684,12 @@ 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 "${MPI_C_LIBRARIES}")
diff --git a/configure.ac b/configure.ac
index 4033953..48e6ce3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2679,6 +2679,20 @@ if test "X${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)
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 4878b34..4e376f5 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -109,7 +109,10 @@ Bug Fixes since HDF5-1.14.3 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.
 
 
     Java Library
diff --git a/src/H5Dmpio.c b/src/H5Dmpio.c
index 5c2ee87..16243fa 100644
--- a/src/H5Dmpio.c
+++ b/src/H5Dmpio.c
@@ -4065,7 +4065,6 @@ H5D__mpio_share_chunk_modification_data(H5D_filtered_collective_io_info_t *chunk
                                         int mpi_rank, 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;
@@ -4300,20 +4299,12 @@ 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");
 
@@ -4466,13 +4457,6 @@ done:
 #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() */
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5FDmpio.c b/src/H5FDmpio.c
index ed704c2..7141550 100644
--- a/src/H5FDmpio.c
+++ b/src/H5FDmpio.c
@@ -11,7 +11,7 @@
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 /*
- * Purpose:     This is the MPI-2 I/O driver.
+ * Purpose:     This is the MPI I/O driver.
  */
 
 #include "H5FDdrvr_module.h" /* This source code file is part of the H5FD driver module */
@@ -363,12 +363,12 @@ H5FD__mpio_term(void)
  *              only in the parallel HDF5 library and is not collective.
  *
  *              comm is the MPI communicator to be used for file open as
- *              defined in MPI_FILE_OPEN of MPI-2. This function makes a
+ *              defined in MPI_FILE_OPEN of MPI. This function makes a
  *              duplicate of comm. Any modification to comm after this function
  *              call returns has no effect on the access property list.
  *
  *              info is the MPI Info object to be used for file open as
- *              defined in MPI_FILE_OPEN of MPI-2. This function makes a
+ *              defined in MPI_FILE_OPEN of MPI. This function makes a
  *              duplicate of info. Any modification to info after this
  *              function call returns has no effect on the access property
  *              list.
@@ -1222,20 +1222,13 @@ H5FD__mpio_read(H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNU
     MPI_Status   mpi_stat;            /* Status from I/O operation */
     MPI_Datatype buf_type = MPI_BYTE; /* MPI description of the selection in memory */
     int          size_i;              /* Integer copy of 'size' to read */
-#if H5_CHECK_MPI_VERSION(3, 0)
-    MPI_Count bytes_read = 0; /* Number of bytes read in */
-    MPI_Count type_size;      /* MPI datatype used for I/O's size */
-    MPI_Count io_size;        /* Actual number of bytes requested */
-    MPI_Count n;
-#else
-    int bytes_read = 0; /* Number of bytes read in */
-    int type_size;      /* MPI datatype used for I/O's size */
-    int io_size;        /* Actual number of bytes requested */
-    int n;
-#endif
-    bool use_view_this_time = false;
-    bool derived_type       = false;
-    bool rank0_bcast        = false; /* If read-with-rank0-and-bcast flag was used */
+    MPI_Count    bytes_read = 0;      /* Number of bytes read in */
+    MPI_Count    type_size;           /* MPI datatype used for I/O's size */
+    MPI_Count    io_size;             /* Actual number of bytes requested */
+    MPI_Count    n;
+    bool         use_view_this_time = false;
+    bool         derived_type       = false;
+    bool         rank0_bcast        = false; /* If read-with-rank0-and-bcast flag was used */
 #ifdef H5FDmpio_DEBUG
     bool H5FD_mpio_debug_t_flag = (H5FD_mpio_debug_flags_s[(int)'t'] && H5FD_MPIO_TRACE_THIS_RANK(file));
     bool H5FD_mpio_debug_r_flag = (H5FD_mpio_debug_flags_s[(int)'r'] && H5FD_MPIO_TRACE_THIS_RANK(file));
@@ -1393,11 +1386,7 @@ H5FD__mpio_read(H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNU
     /* Only retrieve bytes read if this rank _actually_ participated in I/O */
     if (!rank0_bcast || (rank0_bcast && file->mpi_rank == 0)) {
         /* How many bytes were actually read? */
-#if H5_CHECK_MPI_VERSION(3, 0)
         if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&mpi_stat, buf_type, &bytes_read))) {
-#else
-        if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_read))) {
-#endif
             if (rank0_bcast && file->mpi_rank == 0) {
                 /* If MPI_Get_elements(_x) fails for a rank 0 bcast strategy,
                  * push an error, but continue to participate in the following
@@ -1418,19 +1407,11 @@ H5FD__mpio_read(H5FD_t *_file, H5FD_mem_t H5_ATTR_UNUSED type, hid_t H5_ATTR_UNU
      *          of the data.  (QAK - 2019/1/2)
      */
     if (rank0_bcast)
-#if H5_CHECK_MPI_VERSION(3, 0)
         if (MPI_SUCCESS != MPI_Bcast(&bytes_read, 1, MPI_COUNT, 0, file->comm))
-#else
-        if (MPI_SUCCESS != MPI_Bcast(&bytes_read, 1, MPI_INT, 0, file->comm))
-#endif
             HMPI_GOTO_ERROR(FAIL, "MPI_Bcast failed", 0)
 
-            /* Get the type's size */
-#if H5_CHECK_MPI_VERSION(3, 0)
+    /* Get the type's size */
     if (MPI_SUCCESS != (mpi_code = MPI_Type_size_x(buf_type, &type_size)))
-#else
-    if (MPI_SUCCESS != (mpi_code = MPI_Type_size(buf_type, &type_size)))
-#endif
         HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code)
 
     /* Compute the actual number of bytes requested */
@@ -1486,19 +1467,13 @@ static herr_t
 H5FD__mpio_write(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED dxpl_id, haddr_t addr, size_t size,
                  const void *buf)
 {
-    H5FD_mpio_t *file = (H5FD_mpio_t *)_file;
-    MPI_Offset   mpi_off;
-    MPI_Status   mpi_stat;            /* Status from I/O operation */
-    MPI_Datatype buf_type = MPI_BYTE; /* MPI description of the selection in memory */
-#if H5_CHECK_MPI_VERSION(3, 0)
-    MPI_Count bytes_written;
-    MPI_Count type_size; /* MPI datatype used for I/O's size */
-    MPI_Count io_size;   /* Actual number of bytes requested */
-#else
-    int bytes_written;
-    int type_size; /* MPI datatype used for I/O's size */
-    int io_size;   /* Actual number of bytes requested */
-#endif
+    H5FD_mpio_t     *file = (H5FD_mpio_t *)_file;
+    MPI_Offset       mpi_off;
+    MPI_Status       mpi_stat;            /* Status from I/O operation */
+    MPI_Datatype     buf_type = MPI_BYTE; /* MPI description of the selection in memory */
+    MPI_Count        bytes_written;
+    MPI_Count        type_size; /* MPI datatype used for I/O's size */
+    MPI_Count        io_size;   /* Actual number of bytes requested */
     int              size_i;
     bool             use_view_this_time = false;
     bool             derived_type       = false;
@@ -1642,19 +1617,11 @@ H5FD__mpio_write(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED dxpl_id, h
     } /* end else */
 
     /* How many bytes were actually written? */
-#if H5_CHECK_MPI_VERSION(3, 0)
     if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&mpi_stat, buf_type, &bytes_written)))
-#else
-    if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_written)))
-#endif
         HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code)
 
-        /* Get the type's size */
-#if H5_CHECK_MPI_VERSION(3, 0)
+    /* Get the type's size */
     if (MPI_SUCCESS != (mpi_code = MPI_Type_size_x(buf_type, &type_size)))
-#else
-    if (MPI_SUCCESS != (mpi_code = MPI_Type_size(buf_type, &type_size)))
-#endif
         HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code)
 
     /* Compute the actual number of bytes requested */
@@ -1858,7 +1825,7 @@ H5FD__mpio_vector_build_types(uint32_t count, H5FD_mem_t types[], haddr_t addrs[
                 HMPI_GOTO_ERROR(FAIL, "MPI_Get_address for s_bufs[] - mpi_bufs_base failed", mpi_code)
 
                 /*... and then subtract mpi_bufs_base_Aint from it. */
-#if ((MPI_VERSION > 3) || ((MPI_VERSION == 3) && (MPI_SUBVERSION >= 1)))
+#if H5_CHECK_MPI_VERSION(3, 1)
             mpi_bufs[i] = MPI_Aint_diff(mpi_bufs[i], mpi_bufs_base_Aint);
 #else
             mpi_bufs[i] = mpi_bufs[i] - mpi_bufs_base_Aint;
@@ -2085,18 +2052,11 @@ H5FD__mpio_read_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t cou
     H5FD_mpio_xfer_t           xfer_mode;     /* I/O transfer mode */
     H5FD_mpio_collective_opt_t coll_opt_mode; /* whether we are doing collective or independent I/O */
     int                        size_i;
-#if MPI_VERSION >= 3
-    MPI_Count bytes_read = 0; /* Number of bytes read in */
-    MPI_Count type_size;      /* MPI datatype used for I/O's size */
-    MPI_Count io_size;        /* Actual number of bytes requested */
-    MPI_Count n;
-#else
-    int bytes_read = 0; /* Number of bytes read in */
-    int type_size;      /* MPI datatype used for I/O's size */
-    int io_size;        /* Actual number of bytes requested */
-    int n;
-#endif
-    bool rank0_bcast = false; /* If read-with-rank0-and-bcast flag was used */
+    MPI_Count                  bytes_read = 0; /* Number of bytes read in */
+    MPI_Count                  type_size;      /* MPI datatype used for I/O's size */
+    MPI_Count                  io_size;        /* Actual number of bytes requested */
+    MPI_Count                  n;
+    bool                       rank0_bcast = false; /* If read-with-rank0-and-bcast flag was used */
 #ifdef H5FDmpio_DEBUG
     bool H5FD_mpio_debug_t_flag = (H5FD_mpio_debug_flags_s[(int)'t'] && H5FD_MPIO_TRACE_THIS_RANK(file));
     bool H5FD_mpio_debug_r_flag = (H5FD_mpio_debug_flags_s[(int)'r'] && H5FD_MPIO_TRACE_THIS_RANK(file));
@@ -2226,11 +2186,7 @@ H5FD__mpio_read_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t cou
         /* Only retrieve bytes read if this rank _actually_ participated in I/O */
         if (!rank0_bcast || (rank0_bcast && file->mpi_rank == 0)) {
             /* How many bytes were actually read? */
-#if MPI_VERSION >= 3
             if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&mpi_stat, buf_type, &bytes_read)))
-#else
-            if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_read)))
-#endif
                 HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code)
         } /* end if */
 
@@ -2243,19 +2199,11 @@ H5FD__mpio_read_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t cou
          *          the bcast.  (NAF - 2021/9/15)
          */
         if (rank0_bcast)
-#if MPI_VERSION >= 3
             if (MPI_SUCCESS != MPI_Bcast(&bytes_read, 1, MPI_COUNT, 0, file->comm))
-#else
-            if (MPI_SUCCESS != MPI_Bcast(&bytes_read, 1, MPI_INT, 0, file->comm))
-#endif
                 HMPI_GOTO_ERROR(FAIL, "MPI_Bcast failed", 0)
 
-                /* Get the type's size */
-#if MPI_VERSION >= 3
+        /* Get the type's size */
         if (MPI_SUCCESS != (mpi_code = MPI_Type_size_x(buf_type, &type_size)))
-#else
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_size(buf_type, &type_size)))
-#endif
             HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code)
 
         /* Compute the actual number of bytes requested */
@@ -2275,13 +2223,8 @@ H5FD__mpio_read_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t cou
             do {
                 assert(i >= 0);
 
-#if MPI_VERSION >= 3
                 io_size    = MIN(n, (MPI_Count)s_sizes[i]);
                 bytes_read = (MPI_Count)s_sizes[i] - io_size;
-#else
-                io_size    = MIN(n, (int)s_sizes[i]);
-                bytes_read = (int)s_sizes[i] - io_size;
-#endif
                 assert(bytes_read >= 0);
 
                 memset((char *)s_bufs[i] + bytes_read, 0, (size_t)io_size);
@@ -2359,20 +2302,12 @@ H5FD__mpio_read_vector(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, uint32_t cou
 
                     HMPI_GOTO_ERROR(FAIL, "MPI_File_read_at failed", mpi_code)
 
-                    /* How many bytes were actually read? */
-#if MPI_VERSION >= 3
+                /* How many bytes were actually read? */
                 if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&mpi_stat, MPI_BYTE, &bytes_read)))
-#else
-                if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_read)))
-#endif
                     HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code)
 
-                    /* Compute the actual number of bytes requested */
-#if MPI_VERSION >= 3
+                /* Compute the actual number of bytes requested */
                 io_size = (MPI_Count)size;
-#else
-                io_size = (int)size;
-#endif
 
                 /* Check for read failure */
                 if (bytes_read < 0 || bytes_read > io_size)
@@ -3008,18 +2943,11 @@ H5FD__mpio_read_selection(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED d
     void    *mpi_bufs_base = NULL;
     char     unused        = 0; /* Unused, except for non-NULL pointer value */
 
-#if H5_CHECK_MPI_VERSION(3, 0)
     MPI_Count bytes_read = 0; /* Number of bytes read in */
     MPI_Count type_size;      /* MPI datatype used for I/O's size */
     MPI_Count io_size;        /* Actual number of bytes requested */
     MPI_Count n;
-#else
-    int bytes_read = 0; /* Number of bytes read in */
-    int type_size;      /* MPI datatype used for I/O's size */
-    int io_size;        /* Actual number of bytes requested */
-    int n;
-#endif
-    bool rank0_bcast = false; /* If read-with-rank0-and-bcast flag was used */
+    bool      rank0_bcast = false; /* If read-with-rank0-and-bcast flag was used */
 #ifdef H5FDmpio_DEBUG
     bool H5FD_mpio_debug_t_flag = (H5FD_mpio_debug_flags_s[(int)'t'] && H5FD_MPIO_TRACE_THIS_RANK(file));
     bool H5FD_mpio_debug_r_flag = (H5FD_mpio_debug_flags_s[(int)'r'] && H5FD_MPIO_TRACE_THIS_RANK(file));
@@ -3209,11 +3137,7 @@ H5FD__mpio_read_selection(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED d
         /* Only retrieve bytes read if this rank _actually_ participated in I/O */
         if (!rank0_bcast || (rank0_bcast && file->mpi_rank == 0)) {
             /* How many bytes were actually read? */
-#if H5_CHECK_MPI_VERSION(3, 0)
             if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&mpi_stat, final_mtype, &bytes_read))) {
-#else
-            if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_read))) {
-#endif
                 if (rank0_bcast && file->mpi_rank == 0) {
                     /* If MPI_Get_elements(_x) fails for a rank 0 bcast strategy,
                      * push an error, but continue to participate in the following
@@ -3234,19 +3158,11 @@ H5FD__mpio_read_selection(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED d
          *          of the data.  (QAK - 2019/1/2)
          */
         if (rank0_bcast)
-#if H5_CHECK_MPI_VERSION(3, 0)
             if (MPI_SUCCESS != MPI_Bcast(&bytes_read, 1, MPI_COUNT, 0, file->comm))
-#else
-            if (MPI_SUCCESS != MPI_Bcast(&bytes_read, 1, MPI_INT, 0, file->comm))
-#endif
                 HMPI_GOTO_ERROR(FAIL, "MPI_Bcast failed", 0);
 
-                /* Get the type's size */
-#if H5_CHECK_MPI_VERSION(3, 0)
+        /* Get the type's size */
         if (MPI_SUCCESS != (mpi_code = MPI_Type_size_x(final_mtype, &type_size)))
-#else
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_size(final_mtype, &type_size)))
-#endif
             HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code);
 
         /* Compute the actual number of bytes requested */
@@ -3382,15 +3298,9 @@ H5FD__mpio_write_selection(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED
     char                    unused        = 0; /* Unused, except for non-NULL pointer value */
     H5_flexible_const_ptr_t mbb;
 
-#if H5_CHECK_MPI_VERSION(3, 0)
     MPI_Count bytes_written;
     MPI_Count type_size; /* MPI datatype used for I/O's size */
     MPI_Count io_size;   /* Actual number of bytes requested */
-#else
-    int bytes_written;
-    int type_size; /* MPI datatype used for I/O's size */
-    int io_size;   /* Actual number of bytes requested */
-#endif
 
 #ifdef H5FDmpio_DEBUG
     bool H5FD_mpio_debug_t_flag = (H5FD_mpio_debug_flags_s[(int)'t'] && H5FD_MPIO_TRACE_THIS_RANK(file));
@@ -3559,20 +3469,12 @@ H5FD__mpio_write_selection(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED
                                                          H5FD_mpi_native_g, file->info)))
             HMPI_GOTO_ERROR(FAIL, "MPI_File_set_view failed", mpi_code);
 
-            /* How many bytes were actually written */
-#if H5_CHECK_MPI_VERSION(3, 0)
+        /* How many bytes were actually written */
         if (MPI_SUCCESS != (mpi_code = MPI_Get_elements_x(&mpi_stat, final_mtype, &bytes_written)))
-#else
-        if (MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_written)))
-#endif
             HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code);
 
-            /* Get the type's size */
-#if H5_CHECK_MPI_VERSION(3, 0)
+        /* Get the type's size */
         if (MPI_SUCCESS != (mpi_code = MPI_Type_size_x(final_mtype, &type_size)))
-#else
-        if (MPI_SUCCESS != (mpi_code = MPI_Type_size(final_mtype, &type_size)))
-#endif
             HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code);
 
         /* Compute the actual number of bytes requested */
diff --git a/src/H5FDmpio.h b/src/H5FDmpio.h
index 96a9366..60deec2 100644
--- a/src/H5FDmpio.h
+++ b/src/H5FDmpio.h
@@ -48,8 +48,8 @@ H5_DLL hid_t H5FD_mpio_init(void);
  * \brief Stores MPI IO communicator information to the file access property list
  *
  * \fapl_id
- * \param[in] comm MPI-2 communicator
- * \param[in] info MPI-2 info object
+ * \param[in] comm MPI communicator
+ * \param[in] info MPI info object
  * \returns \herr_t
  *
  * \details H5Pset_fapl_mpio() stores the user-supplied MPI IO parameters \p
@@ -61,12 +61,12 @@ H5_DLL hid_t H5FD_mpio_init(void);
  *          and is not a collective function.
  *
  *          \p comm is the MPI communicator to be used for file open, as defined
- *          in \c MPI_File_open of MPI-2. This function makes a duplicate of the
+ *          in \c MPI_File_open of MPI. This function makes a duplicate of the
  *          communicator, so modifications to \p comm after this function call
  *          returns have no effect on the file access property list.
  *
  *          \p info is the MPI Info object to be used for file open, as defined
- *          in MPI_File_open() of MPI-2. This function makes a duplicate copy of
+ *          in MPI_File_open() of MPI. This function makes a duplicate copy of
  *          the Info object, so modifications to the Info object after this
  *          function call returns will have no effect on the file access
  *          property list.
@@ -96,8 +96,8 @@ H5_DLL herr_t H5Pset_fapl_mpio(hid_t fapl_id, MPI_Comm comm, MPI_Info info);
  * \brief Returns MPI IO communicator information
  *
  * \fapl_id
- * \param[out] comm MPI-2 communicator
- * \param[out] info MPI-2 info object
+ * \param[out] comm MPI communicator
+ * \param[out] info MPI info object
  * \returns \herr_t
  *
  * \details If the file access property list is set to the #H5FD_MPIO driver,
diff --git a/src/H5Fmodule.h b/src/H5Fmodule.h
index 8a3f8df..40ff6b4 100644
--- a/src/H5Fmodule.h
+++ b/src/H5Fmodule.h
@@ -1045,7 +1045,7 @@
  * The file access properties managed by #H5Pset_fapl_mpio and retrieved by
  * #H5Pget_fapl_mpio are the MPI communicator, comm, and the MPI info object, info. comm and
  * info are used for file open. info is an information object much like an HDF5 property list. Both
- * are defined in MPI_FILE_OPEN of MPI-2.
+ * are defined in MPI_FILE_OPEN of MPI.
  *
  * The communicator and the info object are saved in the file access property list fapl_id.
  * fapl_id can then be passed to MPI_FILE_OPEN to create and/or open the file.
diff --git a/src/H5Smpio.c b/src/H5Smpio.c
index 10a9cd5..1e0fef5 100644
--- a/src/H5Smpio.c
+++ b/src/H5Smpio.c
@@ -197,13 +197,9 @@ H5S__mpio_create_point_datatype(size_t elmt_size, hsize_t num_points, MPI_Aint *
     int          *inner_blocks      = NULL;  /* Arrays for MPI datatypes when "large" datatype needed */
     MPI_Aint     *inner_disps       = NULL;
     MPI_Datatype *inner_types       = NULL;
-#if MPI_VERSION < 3
-    int    *blocks = NULL; /* Array of block sizes for MPI hindexed create call */
-    hsize_t u;             /* Local index variable */
-#endif
-    hsize_t bigio_count;         /* Transition point to create derived type */
-    int     mpi_code;            /* MPI error code */
-    herr_t  ret_value = SUCCEED; /* Return value */
+    hsize_t       bigio_count;         /* Transition point to create derived type */
+    int           mpi_code;            /* MPI error code */
+    herr_t        ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_PACKAGE
 
@@ -216,24 +212,10 @@ H5S__mpio_create_point_datatype(size_t elmt_size, hsize_t num_points, MPI_Aint *
 
     /* Check whether standard or BIGIO processing will be employeed */
     if (bigio_count >= num_points) {
-#if H5_CHECK_MPI_VERSION(3, 0)
         /* Create an MPI datatype for the whole point selection */
         if (MPI_SUCCESS !=
             (mpi_code = MPI_Type_create_hindexed_block((int)num_points, 1, disp, elmt_type, new_type)))
             HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_indexed_block failed", mpi_code)
-#else
-        /* Allocate block sizes for MPI datatype call */
-        if (NULL == (blocks = (int *)H5MM_malloc(sizeof(int) * num_points)))
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTALLOC, FAIL, "can't allocate array of blocks");
-
-        for (u = 0; u < num_points; u++)
-            blocks[u] = 1;
-
-        /* Create an MPI datatype for the whole point selection */
-        if (MPI_SUCCESS !=
-            (mpi_code = MPI_Type_create_hindexed((int)num_points, blocks, disp, elmt_type, new_type)))
-            HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed failed", mpi_code)
-#endif
 
         /* Commit MPI datatype for later use */
         if (MPI_SUCCESS != (mpi_code = MPI_Type_commit(new_type)))
@@ -267,43 +249,20 @@ H5S__mpio_create_point_datatype(size_t elmt_size, hsize_t num_points, MPI_Aint *
         if (NULL == (inner_disps = (MPI_Aint *)H5MM_malloc(sizeof(MPI_Aint) * (size_t)total_types)))
             HGOTO_ERROR(H5E_DATASPACE, H5E_CANTALLOC, FAIL, "can't allocate array of blocks");
 
-#if MPI_VERSION < 3
-        /* Allocate block sizes for MPI datatype call */
-        if (NULL == (blocks = (int *)H5MM_malloc(sizeof(int) * bigio_count)))
-            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTALLOC, FAIL, "can't allocate array of blocks");
-
-        for (u = 0; u < bigio_count; u++)
-            blocks[u] = 1;
-#endif
-
         for (i = 0; i < num_big_types; i++) {
-#if H5_CHECK_MPI_VERSION(3, 0)
             if (MPI_SUCCESS != (mpi_code = MPI_Type_create_hindexed_block((int)bigio_count, 1,
                                                                           &disp[(hsize_t)i * bigio_count],
                                                                           elmt_type, &inner_types[i])))
                 HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed_block failed", mpi_code);
-#else
-            if (MPI_SUCCESS !=
-                (mpi_code = MPI_Type_create_hindexed((int)bigio_count, blocks, &disp[i * bigio_count],
-                                                     elmt_type, &inner_types[i])))
-                HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed failed", mpi_code)
-#endif
             inner_blocks[i] = 1;
             inner_disps[i]  = 0;
         } /* end for*/
 
         if (remaining_points) {
-#if H5_CHECK_MPI_VERSION(3, 0)
             if (MPI_SUCCESS != (mpi_code = MPI_Type_create_hindexed_block(
                                     remaining_points, 1, &disp[(hsize_t)num_big_types * bigio_count],
                                     elmt_type, &inner_types[num_big_types])))
                 HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed_block failed", mpi_code);
-#else
-            if (MPI_SUCCESS != (mpi_code = MPI_Type_create_hindexed((int)remaining_points, blocks,
-                                                                    &disp[num_big_types * bigio_count],
-                                                                    elmt_type, &inner_types[num_big_types])))
-                HMPI_GOTO_ERROR(FAIL, "MPI_Type_create_hindexed failed", mpi_code)
-#endif
             inner_blocks[num_big_types] = 1;
             inner_disps[num_big_types]  = 0;
         }
@@ -323,10 +282,6 @@ H5S__mpio_create_point_datatype(size_t elmt_size, hsize_t num_points, MPI_Aint *
 done:
     if (elmt_type_created)
         MPI_Type_free(&elmt_type);
-#if MPI_VERSION < 3
-    if (blocks)
-        H5MM_free(blocks);
-#endif
     if (inner_types)
         H5MM_free(inner_types);
     if (inner_blocks)
diff --git a/src/H5mpi.c b/src/H5mpi.c
index 005a99a..2725ec5 100644
--- a/src/H5mpi.c
+++ b/src/H5mpi.c
@@ -619,17 +619,12 @@ H5_mpio_gatherv_alloc(void *send_buf, int send_count, MPI_Datatype send_type, co
                       const int displacements[], MPI_Datatype recv_type, bool allgather, int root,
                       MPI_Comm comm, int mpi_rank, int mpi_size, void **out_buf, size_t *out_buf_num_entries)
 {
-    size_t recv_buf_num_entries = 0;
-    void  *recv_buf             = NULL;
-#if H5_CHECK_MPI_VERSION(3, 0)
+    size_t    recv_buf_num_entries = 0;
+    void     *recv_buf             = NULL;
     MPI_Count type_lb;
     MPI_Count type_extent;
-#else
-    MPI_Aint type_lb;
-    MPI_Aint type_extent;
-#endif
-    int    mpi_code;
-    herr_t ret_value = SUCCEED;
+    int       mpi_code;
+    herr_t    ret_value = SUCCEED;
 
     FUNC_ENTER_NOAPI(FAIL)
 
@@ -637,12 +632,8 @@ H5_mpio_gatherv_alloc(void *send_buf, int send_count, MPI_Datatype send_type, co
     if (allgather || (mpi_rank == root))
         assert(out_buf && out_buf_num_entries);
 
-        /* Retrieve the extent of the MPI Datatype being used */
-#if H5_CHECK_MPI_VERSION(3, 0)
+    /* Retrieve the extent of the MPI Datatype being used */
     if (MPI_SUCCESS != (mpi_code = MPI_Type_get_extent_x(recv_type, &type_lb, &type_extent)))
-#else
-    if (MPI_SUCCESS != (mpi_code = MPI_Type_get_extent(recv_type, &type_lb, &type_extent)))
-#endif
         HMPI_GOTO_ERROR(FAIL, "MPI_Type_get_extent(_x) failed", mpi_code)
 
     if (type_extent < 0)