C int bufid = pvm_mkbuf( int encoding )
Fortran call pvmfmkbuf( encoding, bufid )
Options in C are: Encoding value MEANING PvmDataDefault 0 XDR PvmDataRaw 1 no encoding PvmDataInPlace 2 data left in place Option names in Fortran are: Encoding value MEANING PVMDEFAULT 0 XDR PVMRAW 1 no encoding PVMINPLACE 2 data left in place
With the default setting XDR encoding is used when packing the message because PVM can not know if the user is going to add a heterogeneous machine before this message is sent. The other options to encoding allow the user to take advantage of knowledge about his virtual machine even when it is heterogeneous. For example, if the user knows that the next message will only be sent to a machine that understands the native format, then he can use PvmDataRaw encoding and save on encoding costs.
PvmDataInPlace encoding specifies that data be left in place during packing. The message buffer only contains the sizes and pointers to the items to be sent. When pvm_send is called the items are copied directly out of the user's memory. This option decreases the number of times a message is copied at the expense of requiring the user to not modify the items between the time they are packed and the time they are sent.
pvm_mkbuf is required if the user wishes to manage multiple message buffers and should be used in conjunction with pvm_freebuf. pvm_freebuf should be called for a send buffer after a message has been sent and is no longer needed.
Receive buffers are created automatically by the pvm_recv and pvm_nrecv routines and do not have to be freed unless they have been explicitly saved with pvm_setrbuf.
Typically multiple send and receive buffers are not needed and the user can simply use the pvm_initsend routine to reset the default send buffer.
There are several cases where multiple buffers are useful. One example where multiple message buffers are needed involves libraries or graphical interfaces that use PVM and interact with a running PVM application but do not want to interfere with the application's own communication.
When multiple buffers are used they generally are made and freed for each message that is packed.
C: bufid = pvm_mkbuf( PvmDataRaw ); /* send message */ info = pvm_freebuf( bufid ); Fortran: CALL PVMFMKBUF(PVMDEFAULT, MBUF) * SEND MESSAGE HERE CALL PVMFFREEBUF( MBUF, INFO )
PvmBadParam giving an invalid encoding value. PvmNoMem Malloc has failed. There is not enough memory to create the buffer