Merge pull request #1560 in HDFFV/hdf5 from hdf5-1-10-documentation-only to hdf5_1_10_5

* commit '5dd2fda18fbbeab95ba44200e48c8202dae65206':
  Modify RELEASE.txt in response to PR comments
  Updated RELEASE.txt with updates regarding HDFFV-10540

1 files changed, 19 insertions, 1 deletions

diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index b5ea8eb..353d63b 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -201,7 +201,7 @@ New Features
     -----------------
     - Changed the default behavior in parallel when reading the same dataset in its entirely
       (i.e. H5S_ALL dataset selection) which is being read by all the processes collectively.
-      The dataset mush be contiguous, less than 2GB, and of an atomic datatype.
+      The dataset must be contiguous, less than 2GB, and of an atomic datatype.
       The new behavior is the HDF5 library will use an MPI_Bcast to pass the data read from
       the disk by the root process to the remain processes in the MPI communicator associated
       with the HDF5 file.
@@ -695,6 +695,24 @@ Known Problems
     CPP ptable test fails on VS2017 with Intel compiler, JIRA issue: HDFFV-10628.
     This test will pass with VS2015 with Intel compiler.
 
+    Older MPI libraries such as OpenMPI 2.0.1 and MPICH 2.1.5 were tested
+    while attempting to resolve the Jira issue: HDFFV-10540.
+    The known problems of reading or writing > 2GBs when using MPI-2 was
+    partially resolved with the MPICH library. The proposed support recognizes
+    IO operations > 2GB and if the datatype is not a derived type, the library
+    breaks the IO into chunks which can be input or output with the existing
+    MPI 2 limitations, i.e. size reporting and function API size/count
+    arguments are restricted to be 32 bit integers.  For derived types larger
+    than 2GB, MPICH 2.1.5 fails while attempting to read or write data.
+    OpenMPI in contrast, implements MPI-3 APIs even in the older releases
+    and thus does not suffer from the 32 bit size limitation described here.
+    OpenMPI releases prior to v3.1.3 appear to have other datatype issues however,
+    e.g. within a single parallel test (testphdf5) the subtests (cdsetr, eidsetr)
+    report data verfication errors before eventually aborting.
+    The most recent versions of OpenMPI (v3.1.3 or newer) have evidently
+    resolved these isses and parallel HDF5 testing does not currently report
+    errors though occasional hangs have been observed.
+
     Known problems in previous releases can be found in the HISTORY*.txt files
     in the HDF5 source. Please report any new problems found to
     help@hdfgroup.org.