NRECV(3PVM)

💖 NRECV — the pvm_nrecv page (3PVM) 💖

okay bestie, so you're in the PVM section of the manual (that's the 3PVM part, in case anyone asks) and you wanna know if a message showed up yet, without, like, standing at the door forever waiting. Say less. PVM Version 3.4 has you. 🦋

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✨ NAME ✨

pvm_nrecv — non-blocking receive. she checks, she does NOT wait around. main character energy only. 💅

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✨ SYNOPSIS ✨

C:

int bufid = pvm_nrecv( int tid, int msgtag )

Fortran:

call pvmfnrecv( tid, msgtag, bufid )

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🎀 PARAMETERS 🎀

• tid — integer task identifier of the sending process, supplied by you, bestie. 👑
• msgtag — integer message tag supplied by you. and like, msgtag should be >= 0. respectfully. 🌸
• bufid — integer that returns the value of the new active receive buffer identifier. values less than zero mean something went wrong. 💀

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🌈 DESCRIPTION 🌈

pvm_nrecv peeks to see if a message with label msgtag has arrived from tid, and it also clears the current receive buffer if there is one. if a matching message has already arrived, pvm_nrecv immediately drops that message into a brand-new active receive buffer and hands you back the buffer identifier in bufid. iconic behavior. ✨

if the message you asked for hasn't arrived yet, pvm_nrecv returns immediately with a 0 in bufid. no waiting, no drama. and if some error happens, bufid will be < 0. 😭

a -1 in msgtag or tid matches anything. this is the wildcard, and it gives you these options:

• if tid = -1 and msgtag is defined by you, then pvm_nrecv will accept a message from any process that has a matching msgtag. 🫶
• if msgtag = -1 and tid is defined by you, then pvm_nrecv will accept any message that is sent from process tid. 💜
• if tid = -1 and msgtag = -1, then pvm_nrecv will accept any message from any process. literally anything. wild. 🌈

okay and now the part that's giving ✨guaranteed✨ — the PVM model promises this 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. and on top of that, if both messages arrive before task 2 does a receive, then a wildcard receive will always return message A. no cap. 🔥

pvm_nrecv is non-blocking in the sense that the routine always returns immediately — either with the message, or with the info that the message hasn't arrived at the local pvmd yet. you can call pvm_nrecv multiple times to check if a given message has arrived yet. and also, the blocking receive pvm_recv can be called for the same message if your app runs out of work it could do before the data arrives. so like, you're never stuck. 😌

and if pvm_nrecv does return with the message, then the data in that message can be unpacked into your memory using the unpack routines. slay. 💖

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🌸 EXAMPLES 🌸

C:

tid = pvm_parent();
msgtag = 4 ;
arrived = pvm_nrecv( tid, msgtag );
if ( arrived > 0)
     info = pvm_upkint( tid_array, 10, 1 );
else
     /* go do other computing */

Fortran:

CALL PVMFNRECV( -1, 4, ARRIVED )
IF ( ARRIVED .gt. 0 ) THEN
   CALL PVMFUNPACK( INTEGER4, TIDS, 25, 1, INFO )
   CALL PVMFUNPACK( REAL8, MATRIX, 100, 100, INFO )
ELSE
*       GO DO USEFUL WORK
ENDIF

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😭 ERRORS 😭

these error conditions can be returned by pvm_nrecv. take notes bestie:

• PvmBadParam — you gave an invalid tid value or msgtag. 🙈
• PvmSysErr — pvmd not responding. she's ghosting you. 💀

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🦋 SEE ALSO 🦋

pvm_bufinfo(3PVM), pvm_getminfo(3PVM), pvm_recv(3PVM), pvm_unpack(3PVM), pvm_send(3PVM), pvm_mcast(3PVM)

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k bye ily, go forth and receive non-blockingly 💜 this whole thing is from PVM Version 3.4, dated 30 August, 1993 — yeah she's vintage, but vintage is just iconic with a timestamp. periodt. 👑✨