PACK(3PVM)

📦 version 3.4.6, in debian bookworm, ubuntu jammy

✨ PACK(3PVM) ✨

okay bestie, this is a PVM Version 3.4 page and it's literally all about shoving your data into the active message buffer 💖 no cap, it's giving "pack it up, pack it in" energy.

💫 NAME 💫

pvm_pack — pack the active message buffer with arrays of prescribed data type. that's it, that's the girl 🫶

🌸 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 — a printf-like format expression that says what to pack. (there's a whole discussion below, stay with me 💅)
  • nitem — the total number of items to be packed. and like, NOT the number of bytes, bestie, do not get it twisted 😭
  • stride — the stride used when packing the items. so for example, if stride = 2 in pvm_pkcplx, then every other complex number gets packed. skipping through the array, iconic behavior ✨
  • 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. no mix-and-matching, i don't make the rules 🙈
  • 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 that specifies the type of data being packed. the what options are:
    • STRING — 0
    • BYTE1 — 1
    • INTEGER2 — 2
    • INTEGER4 — 3
    • REAL4 — 4
    • COMPLEX8 — 5
    • REAL8 — 6
    • COMPLEX16 — 7
  • info — the integer status code the routine hands back to you. values less than zero mean something went wrong 😭

🦋 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. do not do it, i'm begging 🙈

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. yes bestie, one whole item, slay 💅

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. it's giving "read the receipt, match the receipt" 🧾✨

🌈 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.

like, it's just not happening. not a vibe, not a moment, not today 😭

🍓 ERRORS 🍓

  • PvmNoMem — Malloc has failed. Message buffer size has exceeded the available memory on this host. she's out of room, bestie, the closet is full 🫠
  • PvmNoBuf — There is no active send buffer to pack into. Try calling pvm_initsend before packing message. no buffer, no packing, no service 🙅
  • 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. it literally does not fit, and we are not going to make it fit 💀

👑 SEE ALSO 👑

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

okay and that's the whole page, you ate that fr fr 🫶 this was PVM Version 3.4, dated 30 August, 1993 — old money, vintage queen, still relevant, periodt 💖✨🎀

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