herr_t H5Pset_all_coll_metadata_ops(
hid_t accpl_id,
hbool_t is_collective
)
H5Pset_all_coll_metadata_ops
sets the metadata I/O mode
for read operations in the access property list accpl
.
When engaging in parallel I/O, all metadata write operations
must be collective.
If is_collective
is TRUE
, this property
specifies that the HDF5 Library will perform all metadata read
operations collectively;
if is_collective
is FALSE
, such operations
may be performed independently.
Users must be aware that several HDF5 operations can potentially issue
metadata reads. These include opening a dataset, datatype, or group;
reading an attribute; or issuing a get info call such as
getting information for a group with H5Gget_info
.
Collective I/O requirements must be kept in mind when issuing such calls
in the context of parallel I/O.
If this property is set to true on a file access property list that is used in creating or opening a file, then the HDF5 Library will assume that all metadata read operations issued on that file identifier will be issued collectively from all ranks irrespective of the individual setting of a particular operation. If this assumption is not adhered to, corruption will be introduced in the metadata cache and HDF5’s behavior will be undefined.
Alternatively, a user may wish to avoid setting this property globally on the file access property list, and individually set it on particular object access property lists (dataset, group, link, datatype, attribute access property lists) for certain operations. This will indicate that only the operations issued with such an access property list will be called collectively and other operations may potentially be called independently. There are, however, several HDF5 operations that can issue metadata reads but have no property list in their function signatures to allow passing the collective requirement property. For those operations, the only option is to set the global collective requirement property on the file access property list; otherwise the metadata reads that can be triggered from those operations will be done independently by each process.
Functions that do not accommodate an access property list but that might issue metadata reads are listed in “Functions with No Access Property List Parameter that May Generate Metadata Reads.”
TRUE
.
An approach that avoids this corruption risk is described above.
hid_t accpl_id |
|
IN: File, group, dataset, datatype, link, or attribute access property list identifier |
hbool_t is_collective |
|
IN: Boolean value indicating whether
metadata reads are collective (TRUE )
or independent (FALSE )
Default mode: Independent ( FALSE )
|
Release | Change |
1.10.0 | C function and Fortran wrapper introduced with this release. |