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MPI provides a number of predefined attributes; these need to be supported by
the device. The support is through either global variables or defined
constants; the choice is left to the implementation.
-
MPID_TAG_UB
-
Maximum legal tag value
-
MPID_STDOUT
-
Nodes capable of writing to stdout. This
corresponds to the MPI attribute MPI_IO.
-
MPID_STDIN
-
The node capable of reading from stdin.
-
MPID_WTIME_IS_GLOBAL
-
Indicates whether MPID_Wtime provides a
globally synchronized time.
-
MPID_HOST
-
Rank of host, if any.
Note that MPID_STDIN has no corresponding value in the MPI
specification. Unfortunately, the MPI specification has no way to distinguish
between nodes capable of writing and nodes capable of reading; in addition,
the requirement that all non-MPI routines be ``local'' means that at most one
process can read from stdin at a time. While it is possible to
implement this feature in a demand mode (MPI_ANY_SOURCE) by modifying
the system read routine used by the application, it is often
simpler
to connect only a specific node (e.g., rank zero in MPI_COMM_WORLD) to stdin.
If these values are not defined, the implementation picks defaults (in
src/env/initutil.c.
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