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Aide Scilab >> Calculs Parallèles avec PVM > pvm_recv

pvm_recv

receive a message.

Calling Sequence

[buff, info, msgtid, tag] = pvm_recv(tid, msgtag)

Arguments

tid

integer, task identifier of sending process supplied by the user.

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

>= 0.

buff

scilab variable, where the received message will be stored.

info

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

msgtid : integer, returning the source of the message. Useful when the

message was received with a wildcard tid.

tag

integer, returning the message label. Useful when the message was received with a wildcard msgtag.

Description

pvm_recv blocks the process until a message with label msgtag (-1 can be used to match all message tags) has arrived from tid (-1 can be used to match all tids). pvm_recv returns the message in buff.

If tid=-1 and msgtag is defined by the user, then pvm_recv will accept a message from any process which has a matching msgtag.

If msgtag = -1 and tid is defined by the user, then pvm_recv will accept any message that is sent from process tid . If tid=-1 and msgtag = -1 then pvm_recv will accept any message from any process.

When wildcard are used, the application is able to receive any incoming message. If the action taken depends on the source tid and the msgtag associated with the message that comes in first, the information given by msgtid and tag can be very usefull.

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.

info will be the status code returned by the routine. If some error occurs then it will be < 0.

pvm_recv is blocking which means the routine waits until a message matching the user specified tid and msgtag values arrives at the local pvmd. If the message has already arrived then pvm_recv returns immediately with the message.

Once pvm_recv returns, the data in the message can be unpacked into the user's memory using the unpack routines.

See Also

  • pvm_send — immediately sends (or multicast) data.
  • 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