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Aide Scilab >> Calculs Parallèles avec PVM > pvm_send

pvm_send

immediately sends (or multicast) data.

Calling Sequence

[info] = pvm_send(tids,buff,msgtag)

Arguments

tids

row of integers, contains the task IDs of the tasks to be sent to.

buff

scilab variable.

msgtag : integer, message tag supplied by the user. msgtag should be

>= 0. It allows the user's program to distinguish between different kinds of messages .

info

integer, status code returned by the routine. Values less than zero indicate an error.

Description

pvm_send sends (or multicasts) a message to the PVM process identified in the tids array. Note that the message is not sent to the caller even if listed in the array of tids. msgtag is used to label the content of the message.

The returned value will be >= 0 if the call is successful and will be will be < 0 if some error occurs.

The pvm_send routine is asynchronous. Computation on the sending processor resumes as soon as the message is safely on its way to the receiving processor. This is in contrast to synchronous communication, during which computation on the sending processor halts until the matching receive is executed by the receiving processor.

If a multicast is performed, pvm_send first determines which other pvmds contain the specified tasks. Then passes the message to these pvmds which in turn distribute the message to their local tasks without further network traffic.

The PVM model guarantees the following about message order. If task 1 sends message A to task 2, then task 1 sends message B to task 2, message A will arrive at task 2 before message B. Moreover, if both messages arrive before task 2 does a receive, then a wildcard receive will always return message A.

Terminating a PVM task immediately after sending a message or messages from it may result in those messages being lost. To be sure, always call pvm_exit() before stopping.

See Also

  • pvm_recv — receive a message.
  • pvm_bcast — broacasts a message to all members of a group
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Last updated:
Wed Oct 05 12:11:04 CEST 2011