5.3.4 Reserved Keys
The following keys are reserved. An
implementation is not required to interpret these keys, but if it does
interpret the key, it must provide the functionality described.
- host
- Value is a hostname. The format of the hostname is determined by
the implementation.
- arch
- Value is an architecture name. Valid architecture names and
what they mean are determined by the implementation.
- wdir
- Value is the name of a directory on a machine on which
the spawned process(es) execute(s).
This directory is made the working directory of the executing process(es).
The format of the directory name is determined by the implementation.
- path
- Value is a directory or set of directories
where the implementation should look for the executable.
The format of path is determined by the implementation.
- file
- Value is the name of a file in which additional information
is specified. The format of the filename and internal format of the file
are determined by the implementation.
- soft
- Value specifies a set of numbers which are allowed values
for the number of processes that MPI_COMM_SPAWN (et al.) may create.
The format of the value is a comma-separated list of Fortran-90
triplets each of which specifies a set of integers and which together specify
the set formed by the union of these sets.
Negative values in this set and values greater than maxprocs are
ignored. MPI-/ will spawn the largest number of processes it can,
consistent with some number in the set. The order in which
triplets are given is not significant.
By Fortran-90 triplets, we mean:
- a means
- a:b means
- a:b:c means
,
where for
,
is the largest integer for which
and for
,
is the largest integer
for which
.
If
then
must be positive. If
then
must be negative.
Examples:
- a:b gives a range between
and
- 0:N gives full ``soft'' functionality
- 1,2,4,8,16,32,64,128,256,512,1024,2048,4096 allows
power-of-two number of processes.
- 2:10000:2 allows even number of processes.
- 2:10:2,7 allows 2, 4, 6, 7, 8, or 10 processes.
MPI-Standard for MARMOT