1NRECV(3PVM)                     PVM Version 3.4                    NRECV(3PVM)
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NAME

6       pvm_nrecv - Non-blocking receive.
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SYNOPSIS

10       C    int bufid = pvm_nrecv( int tid, int msgtag )
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12       Fortran   call pvmfnrecv( tid, msgtag, bufid )
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PARAMETERS

16       tid     Integer  task  identifier  of  sending  process supplied by the
17               user.
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19       msgtag  Integer message tag supplied by the user.  msgtag should be  >=
20               0.
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22       bufid   Integer  returning  the  value of the new active receive buffer
23               identifier.  Values less than zero indicate an error.
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DESCRIPTION

27       The routine pvm_nrecv checks to see if a message with label msgtag  has
28       arrived  from  tid.  and also clears the current receive buffer if any,
29       If a matching message has arrived pvm_nrecv immediately places the mes‐
30       sage  in a new active receive buffer, and returns the buffer identifier
31       in bufid.
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33       If the requested message has not arrived,  then  pvm_nrecv  immediately
34       returns with a 0 in bufid.  If some error occurs bufid will be < 0.
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36       A  -1 in msgtag or tid matches anything.  This allows the user the fol‐
37       lowing options.  If tid = -1 and msgtag is defined by  the  user,  then
38       pvm_nrecv  will  accept a message from any process which has a matching
39       msgtag.  If msgtag = -1 and tid is defined by the user, then  pvm_nrecv
40       will accept any message that is sent from process tid.  If tid = -1 and
41       msgtag = -1, then pvm_nrecv will accept any message from any process.
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43       The PVM model guarantees the following about message order.  If task  1
44       sends  message A to task 2, then task 1 sends message B to task 2, mes‐
45       sage A will arrive at task 2 before message B.  Moreover, if both  mes‐
46       sages arrive before task 2 does a receive, then a wildcard receive will
47       always return message A.
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49       pvm_nrecv is non-blocking in the sense that the routine always  returns
50       immediately  either  with  the message or with the information that the
51       message has not arrived at the local pvmd yet.  pvm_nrecv can be called
52       multiple  times  to check if a given message has arrived yet.  In addi‐
53       tion the blocking receive pvm_recv can be called for the  same  message
54       if  the  application  runs  out  of  work  it  could do before the data
55       arrives.
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57       If pvm_nrecv returns with the message, then the data in the message can
58       be unpacked into the user's memory using the unpack routines.
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EXAMPLES

62       C:
63            tid = pvm_parent();
64            msgtag = 4 ;
65            arrived = pvm_nrecv( tid, msgtag );
66            if ( arrived > 0)
67                 info = pvm_upkint( tid_array, 10, 1 );
68            else
69                 /* go do other computing */
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71       Fortran:
72            CALL PVMFNRECV( -1, 4, ARRIVED )
73            IF ( ARRIVED .gt. 0 ) THEN
74               CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
75               CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
76            ELSE
77       *       GO DO USEFUL WORK
78            ENDIF
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ERRORS

82       These error conditions can be returned by pvm_nrecv.
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84       PvmBadParam
85              giving an invalid tid value or msgtag.
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87       PvmSysErr
88              pvmd not responding.
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SEE ALSO

91       pvm_bufinfo(3PVM),          pvm_getminfo(3PVM),         pvm_recv(3PVM),
92       pvm_unpack(3PVM), pvm_send(3PVM), pvm_mcast(3PVM)
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96                                30 August, 1993                    NRECV(3PVM)