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Additional Message Passing Features

PVMFTRECV()

PVMFTRECV(TID, MSGTAG, SEC, USEC,BUFID)

• tid - task identifier (sending process)

• msgtag - message tag

• sec, usec - integers defining the time to wait before returning without a message
  • set both to 0 and it acts as a non-blocking receive

• bufid - returns the value of the new active receive buffer identifier ie <0 => error

PVMFPSEND()

PVMFPSEND(TID, MSGTAG, BUF, LEN,

DATATYPE, INFO)

• tid - task identifier of destination process

• msgtag - message tag supplied by the user, should be >= 1

• buf - pointer to a buffer to send

• len - length of buffer (in multiple of data type size)

• datatype - type of data to which buf points

• info - status code returned where <0 indicates an error

• pvmfpsend is asynchronous ie computation on the sending processor resumes as soon as the message is safely on its way to the receiving process

CALL PVMFPSEND(TID, MSGTAG, BUF, CNT,

REAL4, INFO)

• Creates and sends a single contiguous message (no stride argument)

• Data is not copied into a buffer (faster on MPP machines where latency is low)

• error conditions returned by pvmfpsend are
  • PvmBadParam - invalid tid or msgtag

  • PvmSysErr - pvmd not responding

PVMFSETRBUF()

PVMFSETRBUF(BUFID, OLDBUF)

• bufid - buffer identifier for the new active receive buffer eg 0 indicates the present active receive is saved and no active receive buffer exists

• oldbuf - buffer identifier for the previous active send buffer

• This routine is required when handling multiple message buffers for example switching back and forth between 2 buffers where one communicates with a graphical interface and the other is used to send data to the other tasks in the application.

• PVMFSETSBUF - send buffers

Error Handling

• All PVM routines return an error condition if they detect an error during execution

• PVM prints error conditions detected
  • pvmfsetopt() turns automatic reporting off

• Diagnostic prints can be viewed using
  • PVM console redirection or

  • calling pvmfcatchout() - this causes the standard output of all subsequently spawned tasks to appear on the standard output of the spawner

• The write statement - test the value of the status/return code in the PVM calls and write an appropriate message

PVMFPERROR()

PVMFPERROR (MSG, INFO)

• msg - character string supplied by the user and is prepended to the error message of the last PVM call

• info - status code returned by the routine where <0 indicates an error

CALL PVMFSEND(TID, MSGTAG)

IF (INFO .LT. 0) THEN

CALL PVMFPERROR(`Step 1', INFO)

ENDIF

Setting and Getting Options

• options may be set

• or got

• where
  • what is an integer defining what is being set

  • val is an integer specifying the new setting

  • oldval is an integer specifying the previous setting

• includes automatic error message printing, debugging level, and communication routing method etc