bhost - LAM boot schema (host file) format


SYNTAX

       #
       # comments
       #
       <machine> [cpu=<cpucount>] [user=<userid>]
       <machine> [cpu=<cpucount>] [user=<userid>]
        ...


DESCRIPTION

       A  boot schema describes the machines that will combine to
       form a multicomputer running LAM.  It is used by  recon(1)
       to  verify  initial  conditions  for  running LAM, by lam­
       boot(1) to start LAM, and by lamhalt(1) to  terminate  LAM
       (note  that  wipe(1) has been deprecated by the lamhalt(1)
       command).

       The particular syntax of a LAM boot  schema  is  sometimes
       called  the "host file" syntax.  It is line oriented.  One
       line indicates the name of a machine, typically  the  full
       Internet domain name, an optional number of CPUs available
       on that machine, and optionally the userid with  which  to
       access it.

       Common boot schema for a particular site may be created by
       the system administrator and placed  in  the  installation
       directory  under etc/.  They typically start with the pre­
       fix bhost.  Individual users usually create their own boot
       schema, especially if the configurations are simple.


EXAMPLE

       Here is an example three node boot schema:

       #
       # example LAM host file
       #
       beowulf1.nd.edu cpu=2
       beowulf2.nd.edu
       beowulf2.nd.edu
       somewhere.else.college.edu user=guest

       Note  that  the  "guest" ID is significant, since the user
       has an alternate login ID  on  somewhere.else.college.edu.
       Additionally  note  that  beowulf1  has  a  CPU count of 2
       listed (a CPU count of 1 is assumed if it is  not  given).
       This  value  is  used by mpirun(1), MPI_Comm_spawn(2), and
       MPI_Comm_spawn_multiple(2) for the "C" (or  CPU)  notation
       that  specifies how many ranks to start.  This is particu­
       larly useful for running on SMP machines.

       beowulf2 is listed twice, but has no  specific  CPU  count
       listed.   In  this  case, LAM will keep a running tally of

       calculate  that  beowulf2  has two CPUs available for use.
       Calculating the number of CPUs by counting occurances of a
       hostname is useful in a batch environment where a hostfile
       may list the same hostname multiple times, indicating that
       the batch scheduler has allocated multiple CPUs for a sin­
       gle job (e.g., PBS operates this way).

       For the above-mentioned schema, the command "mpirun C foo"
       would  start  five  instances  of  the foo program; two on
       beowulf1, two on beowulf2, and one on somewhere.else.


FILES

       $LAMHOME/etc/bhost.def            default boot schema file


SEE ALSO

       lamboot(1),   lamhalt(1),   mpirun(1),  MPI_Comm_spawn(1),
       MPI_Comm_spawn_multiple(1), recon(1), wipe(1)


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