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PACK(3PVM)			PVM Version 3.4			    PACK(3PVM)

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 )

PARAMETERS
       fmt     Printf-like format expression specifying	 what  to  pack.  (See
	       discussion).

       nitem   The  total  number  of  items  to  be packed (not the number of
	       bytes).

       stride  The stride to be	used when packing the items.  For example,  if
	       stride  = 2 in pvm_pkcplx, then every other complex number will
	       be packed.

       xp      Pointer to the beginning	of a block of bytes. Can be  any  data
	       type, but must match the	corresponding unpack data type.

       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.
		    what options
		    STRING	   0	REAL4	       4
		    BYTE1	   1	COMPLEX8       5
		    INTEGER2	   2	REAL8	       6
		    INTEGER4	   3	COMPLEX16      7

       info    Integer status code returned by the routine.  Values less  than
	       zero indicate an	error.

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 charac-
       ters  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.

       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,	 vari-
       ables  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)

       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	preci-
       sion  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 of-
       ten  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.

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.

ERRORS
       PvmNoMem
	      Malloc has failed. Message buffer	size has exceeded  the	avail-
	      able memory on this host.

       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.

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

				30 August, 1993			    PACK(3PVM)

NAME | SYNOPSIS | PARAMETERS | DESCRIPTION | EXAMPLES | WARNINGS | ERRORS | SEE ALSO

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