pvm_precv(3)

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

6       pvm_precv - Receive a message directly into a buffer.
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SYNOPSIS

10       C    int info = pvm_precv( int tid, int msgtag, char *buf,
11                                  int len, int datatype, int *atid,
12                                  int *atag, int *alen )
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14       Fortran   call pvmfprecv( tid, msgtag, buf, len, datatype,
15                               atid, atag, alen, info )
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PARAMETERS

19       tid     Integer task identifier of sending process (to match).
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21       msgtag  Integer message tag (to match).  msgtag should be >= 0.
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23       buf     Pointer to a buffer to receive into.
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25       len     Length of buffer (in multiple of data type size).
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27       datatype
28               Type of data to which buf points (see below).
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30       atid    Returns actual TID of sender.
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32       atag    Returns actual message tag.
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34       alen    Returns actual message length.
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36       info    Returns  PvmOk  on  success.  Values less than zero indicate an
37               error.
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DESCRIPTION

41       The routine pvm_precv blocks the process until  a  message  with  label
42       msgtag has arrived from tid.  pvm_precv then places the contents of the
43       message in the supplied buffer, buf, up to a maximum length  of  len  *
44       (size of data type).
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46       pvm_precv  can receive messages sent by pvm_psend, pvm_send, pvm_mcast,
47       or pvm_bcast.
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49       A -1 in msgtag or tid matches anything.  This allows the user the  fol‐
50       lowing  options.   If  tid = -1 and msgtag is defined by the user, then
51       pvm_precv will accept a message from any process which has  a  matching
52       msgtag.   If msgtag = -1 and tid is defined by the user, then pvm_precv
53       will accept any message that is sent from process tid.  If tid = -1 and
54       msgtag = -1, then pvm_precv will accept any message from any process.
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56       In  C the datatype parameter must be one of the following, depending on
57       the type of data to be unpacked: [Version 3.3.0 - This  parameter  only
58       determines  message  length,  not data conversion.  It only unpacks raw
59       bytes]
60           datatype    Data Type
61           PVM_STR     string
62           PVM_BYTE    byte
63           PVM_SHORT   short
64           PVM_INT     int
65           PVM_FLOAT   real
66           PVM_CPLX    complex
67           PVM_DOUBLE  double
68           PVM_DCPLX   double complex
69           PVM_LONG    long integer
70           PVM_USHORT  unsigned short int
71           PVM_UINT    unsigned int
72           PVM_ULONG   unsigned long int
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74       In Fortran the same data types specified for unpack should be used.
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76       The PVM model guarantees the following about message order.  If task  1
77       sends  message A to task 2, then task 1 sends message B to task 2, mes‐
78       sage A will arrive at task 2 before message B.  Moreover, if both  mes‐
79       sages arrive before task 2 does a receive, then a wildcard receive will
80       always return message A.
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82       If pvm_precv is successful, info will be = 0.   If  some  error  occurs
83       then info will be < 0.
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85       pvm_precv  is  blocking  which  means the routine waits until a message
86       matching the user specified tid and msgtag arrives at the  local  pvmd.
87       If  the  message has already arrived then pvm_precv returns immediately
88       with the message.
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90       pvm_precv does not affect the state of the current receive message buf‐
91       fer (created by the other receive functions).
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WARNINGS

94       In  some  versions  of  PVM  (CM5,  I860 and PGON), messages sent using
95       pvm_psend must be received only by pvm_precv, likewise those sent  with
96       pvm_send   must  be  received  by  pvm_recv,  pvm_nrecv  or  pvm_trecv.
97       pvm_psend  is  not  compatible  with  pvm_recv   (nor   pvm_send   with
98       pvm_precv).    In   addition,   pvm_probe  is  not  interoperable  with
99       pvm_psend.
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101       This problem occurs because nonstandard message headers  are  used  for
102       efficiency  in  the pvm_psend function.  In the generic Unix version of
103       PVM, the calls are fully interoperable.
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105       The message tag space is shared between pvm_send and pvm_psend, so  you
106       must  be  careful  to avoid selecting the wrong message (for example by
107       using a wildcard to match the message).
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EXAMPLES

110       C:
111           info = pvm_precv( tid, msgtag, array, cnt, PVM_FLOAT,
112                             &src, &rtag, &rlen );
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114       Fortran:
115           CALL PVMFPRECV( -1, 4, BUF, CNT, REAL4,
116          >                SRC, RTAG, RCNT, INFO )
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ERRORS

121       These error conditions can be returned by pvm_precv
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123       PvmBadParam
124              giving an invalid tid, msgtag, or datatype.
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126       PvmSysErr
127              pvmd not responding.
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