PACK(3PVM)

📦 version 3.4.6, in debian bookworm, ubuntu jammy

💖 PACK(3PVM) 💖

okay bestie, gather round, because this is the page for pvm_pack — that's the PVM Version 3.4 family of routines that packs the active message buffer with arrays of prescribed data type. PACK(3PVM), she's iconic, she's the moment. ✨

🌸 NAME 🌸

pvm_pack — pack the active message buffer with arrays of prescribed data type. literally her whole job. no cap. 💅

✨ SYNOPSIS ✨

🩷 C

int info = pvm_packf( const char *fmt, ... )
int info = pvm_pkbyte( char *xp, int nitem, int stride )
int info = pvm_pkcplx( float *cp, int nitem, int stride )
int info = pvm_pkdcplx( double *zp, int nitem, int stride )
int info = pvm_pkdouble( double *dp, int nitem, int stride )
int info = pvm_pkfloat( float *fp, int nitem, int stride )
int info = pvm_pkint( int *ip, int nitem, int stride )
int info = pvm_pkuint( unsigned int *ip, int nitem, int stride )
int info = pvm_pkushort( unsigned short *ip, int nitem, int stride )
int info = pvm_pkulong( unsigned long *ip, int nitem, int stride )
int info = pvm_pklong( long *ip, int nitem, int stride )
int info = pvm_pkshort( short *jp, int nitem, int stride )
int info = pvm_pkstr( char *sp )

🩵 Fortran

     call pvmfpack( what, xp, nitem, stride, info )

🎀 PARAMETERS 🎀

  • fmt — the printf-like format expression that says what to pack. (there's a whole discussion down below, keep scrolling babe 🫶)
  • nitem — the total number of items to be packed. that's items, bestie, NOT bytes. do not get it twisted. 💀
  • stride — the stride used when packing the items. so like, if stride = 2 in pvm_pkcplx, then every other complex number gets packed. every. other. one.
  • xp — pointer to the beginning of a block of bytes. can be any data type, but it has to match the corresponding unpack data type. that's the rule. 👑
  • cp — complex array at least nitem*stride items long.
  • zp — double precision complex array at least nitem*stride items long.
  • dp — double precision real array at least nitem*stride items long.
  • fp — real array at least nitem*stride items long.
  • ip — integer array at least nitem*stride items long.
  • jp — Integer*2 array at least nitem*stride items long.
  • sp — pointer to a null terminated character string.
  • what — an integer specifying the type of data being packed. the what options, served fresh:
    • STRING — 0
    • BYTE1 — 1
    • INTEGER2 — 2
    • INTEGER4 — 3
    • REAL4 — 4
    • COMPLEX8 — 5
    • REAL8 — 6
    • COMPLEX16 — 7
  • info — integer status code returned by the routine. anything less than zero means an error happened. 😭

🦋 DESCRIPTION 🦋

Each of the pvm_pk* routines packs an array of the given data type into the active send buffer. The arguments for each of the routines are a pointer to the first item to be packed, nitem which is the total number of items to pack from this array, and stride which is the stride to use when packing.

An exception is pvm_pkstr() which by definition packs a NULL terminated character string and thus does not need nitem or stride arguments. The Fortran routine pvmfpack( STRING, ... ) expects nitem to be the number of characters in the string and stride to be 1.

A null string ("") can be packed; this is just a string with no characters before the terminating '\0'. However, packing a null string pointer, (char *)0, is not allowed. 🚫

If the packing is successful, info will be 0. If some error occurs then info will be < 0.

A single variable (not an array) can be packed by setting nitem = 1 and stride = 1. one item, one stride, main character energy. ✨

The routine pvm_packf() uses a printf-like format expression to specify what and how to pack data into the send buffer. All variables are passed as addresses if count and stride are specified otherwise, variables are assumed to be values. A BNF-like description of the format syntax is:

format : null | init | format fmt
init : null | '%' '+'
fmt : '%' count stride modifiers fchar
fchar : 'c' | 'd' | 'f' | 'x' | 's'
count : null | [0-9]+ | '*'
stride : null | '.' ( [0-9]+ | '*' )
modifiers : null | modifiers mchar
mchar : 'h' | 'l' | 'u'

Formats:

  • + — means initsend — must match an int (how) in the param list.
  • c — pack/unpack bytes
  • d — integers
  • f — float
  • x — complex float
  • s — string

Modifiers:

  • h — short (int)
  • l — long (int, float, complex float)
  • u — unsigned (int)

’*' count or stride must match an int in the param list.

Future extensions to the what argument in pvmfpack will include 64 bit types when XDR encoding of these types is available. Meanwhile users should be aware that precision can be lost when passing data from a 64 bit machine like a Cray to a 32 bit machine like a SPARCstation. As a mnemonic the what argument name includes the number of bytes of precision to expect. By setting encoding to PVMRAW (see pvmfinitsend) data can be transferred between two 64 bit machines with full precision even if the PVM configuration is heterogeneous.

⚠️ Messages should be unpacked exactly like they were packed to insure data integrity. Packing integers and unpacking them as floats will often fail because a type encoding will have occurred transferring the data between heterogeneous hosts. Packing 10 integers and 100 floats then trying to unpack only 3 integers and the 100 floats will also fail. so like, match your vibes on both ends, fr fr. 😭

🌈 EXAMPLES 🌈

C:

info = pvm_initsend( PvmDataDefault );
info = pvm_pkstr( "initial data" );
info = pvm_pkint( &size, 1, 1 );
info = pvm_pkint( array, size, 1 );
info = pvm_pkdouble( matrix, size*size, 1 );
msgtag = 3 ;
info = pvm_send( tid, msgtag );

int count, *iarry;
double darry[4];
pvm_packf("%+ %d %*d %4lf", PvmDataRaw, count, count, iarry, darry);

Fortran:

CALL PVMFINITSEND(PVMRAW, INFO)
CALL PVMFPACK( INTEGER4, NSIZE, 1, 1, INFO )
CALL PVMFPACK( STRING, 'row 5 of NXN matrix', 19, 1, INFO )
CALL PVMFPACK( REAL8, A(5,1), NSIZE, NSIZE , INFO )
CALL PVMFSEND( TID, MSGTAG, INFO )

💀 WARNINGS 💀

Strings cannot be packed when using the PvmDataInPlace encoding, due to limitations in the implementation. Attempting to pack a string using pvm_pkstr or pvm_packf will cause error code PvmNotImpl to be returned. not a vibe. 🙈

🔥 ERRORS 🔥

  • PvmNoMem — Malloc has failed. Message buffer size has exceeded the available memory on this host. she's full, bestie. 🫠
  • PvmNoBuf — There is no active send buffer to pack into. Try calling pvm_initsend before packing message.
  • PvmOverflow — Attempt to pack a value too large. E.g. packing an 8-byte long with XDR encoding if the value won't fit into 4 bytes. too big, didn't fit, so sorry. 💅

👑 SEE ALSO 👑

  • pvm_initsend(3PVM)
  • pvm_unpack(3PVM)
  • pvm_send(3PVM)
  • pvm_recv(3PVM)
  • pvm_pkmesg(3PVM)

and that's the whole page, angel! 🧚 this one's from PVM Version 3.4 and she's dated 30 August, 1993 — so yes, this manual page is older than everyone in the group chat, and she still ate. periodt. 💖✨🎀🦋🌸

📦 where this page comes from