7.1.1 Environmental Inquiries

A set of attributes that describe the execution environment are attached to the communicator MPI_COMM_WORLD when MPI is initialized. The value of these attributes can be inquired by using the function MPI_ATTR_GET described in Chapter 5. It is erroneous to delete these attributes, free their keys, or change their values.

The list of predefined attribute keys include

MPI_TAG_UB
Upper bound for tag value.

MPI_HOST
Host process rank, if such exists, MPI_PROC_NULL, otherwise.
MPI_IO
rank of a node that has regular I/O facilities (possibly myrank). Nodes in the same communicator may return different values for this parameter.
MPI_WTIME_IS_GLOBAL
Boolean variable that indicates whether clocks are synchronized.

Vendors may add implementation specific parameters (such as node number, real memory size, virtual memory size, etc.)

These predefined attributes do not change value between MPI initialization (MPI_INIT and MPI completion (MPI_FINALIZE), and cannot be updated or deleted by users.

Advice to users. Note that in the C binding, the value returned by these attributes is a pointer to an int containing the requested value.(End of advice to users.)

The required parameter values are discussed in more detail below:



Subsections
MPI-Standard for MARMOT