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.TH pvm_recv 1 "May 1998" "Scilab // Group" "Scilab function"
.so ../sci.an
.SH NAME
pvm_recv - receive a message.
.SH CALLING SEQUENCE
.nf
[buff, info, msgtid, tag] = pvm_recv(tid, msgtag)
.fi
.SH PARAMETERS
.TP 5
tid
: integer, task identifier of sending process supplied by the user.
.TP 5
msgtag : integer, message tag supplied by the user. msgtag should be
>= 0.
.TP 4
buff
: scilab variable, where the received message will be stored.
.TP 6
info
: integer, status code returned by the routine. Values less than zero indicate an error.
.TP 6
msgtid : integer, returning the source of the message. Useful when the
message was received with a wildcard tid.
.TP 6
tag
: integer, returning the message label. Useful when the message
was received with a wildcard msgtag.
.SH DESCRIPTION
\fVpvm_recv\fR
blocks the process until a message with label
.I msgtag
has arrived from
.I tid.
pvm_recv then places the message in \fIbuff\fR.
.PP
A -1 in
.I msgtag
or
.I tid
matches anything. This allows the user the following options. 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.
.PP
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.
.PP
.I info
will be the status code returned by the routine.
If some error occurs then
.I info
will be < 0.
.PP
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.
.PP
Once pvm_recv returns, the data in the message can be unpacked
into the user's memory using the unpack routines.
.SH EXAMPLE
.nf
[b, info, msgtid, tag] = pvm_recv(pvm_parent(),100)
g = pvm_recv(pvm_parent(),200)
.fi
.SH SEE ALSO
pvm_send, pvm_bcast
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