PACK(3PVM)

PACK(3PVM) 💖

okay bestie, welcome to the PVM Version 3.4 girlies, this is PACK(3PVM) and it's literally the moment your message buffer gets ✨stuffed✨ with your data. we're packing. we're thriving. let's go 🎀

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🌸 NAME 🌸

pvm_pack — Pack the active message buffer with arrays of prescribed data type.

✨ 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 )

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🫶 PARAMETERS 🫶

• fmt — a printf-like format expression that says what to pack. (there's a whole discussion, scroll down babes ✨)
• nitem — the total number of items to be packed. NOT the number of bytes, okay?? items. we don't do bytes here 💀
• stride — the stride used when packing the items. like, if stride = 2 in pvm_pkcplx, then every other complex number gets packed. skipping through the array like it's a runway 💅
• xp — pointer to the beginning of a block of bytes. can be any data type, but it must match the corresponding unpack data type. no switching up mid-story 🔥
• 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 — integer specifying the type of data being packed. the options, bestie:
  • STRING — 0
  • REAL4 — 4
  • BYTE1 — 1
  • COMPLEX8 — 5
  • INTEGER2 — 2
  • REAL8 — 6
  • INTEGER4 — 3
  • COMPLEX16 — 7
• info — integer status code the routine hands back. values less than zero mean something went wrong 😭

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👑 DESCRIPTION 👑

Every single one of the pvm_pk* routines packs an array of the given data type into the active send buffer. the arguments for each routine 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. periodt ✨

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

A null string ("") can be packed — that's just a string with no characters before the terminating '\0'. However, packing a null string pointer, (char *)0, is not allowed. don't do it, bestie, it's giving chaos 🙈

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. iconic little one-item moment 💖

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. iykyk 🌟

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. 😭 mismatched energy = broken vibes, no cap.

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🍓 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 )

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⚠️ 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. so like, don't 💀

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💥 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. you forgot the setup step 🙈
• 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. doesn't fit. the math is not mathing 🔥

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🌈 SEE ALSO 🌈

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

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and that's the whole vibe check, bestie 🫶 this was PVM Version 3.4, dated 30 August, 1993 — yes she's a vintage icon and she ATE 👑💅 mwah, go pack something iconic ✨🎀🦋