[R-sig-hpc] Rmpi: What tag gets assigned to mpi.bcast.cmd?

[Till Francke]

Dear list,
when passing messages with Rmpi using mpi.send.Robj(), it is possible to  
supply argument "tag" to tag the message. mpi.bcast.cmd() does not have  
this option.
However, messages issued by mpi.bcast.cmd() still get a value for tag (see  
example below), which in my case makes the slaves misinterpret the meaning  
of the message.
Is there any way of providing a tag to mpi.bcast.cmd() or prevent its  
tranfer altogether?

Thanks for your advice,

Till

<code>
library(Rmpi)

slave_func=function() #does nothing but print the received messages into  
files
{
     sink(paste("slave",mpi.comm.rank(),sep="")) #create logfiles for  
slaves to see their output

     tag <- 1
     while(tag!=7)   #
     {
         slave_message <- mpi.recv.Robj(mpi.any.source(),mpi.any.tag())
         slave_message_info <- mpi.get.sourcetag()
         slave_id <- slave_message_info[1]
         tag      <- slave_message_info[2]
         print(paste("tag:",tag,"message:",slave_message))
     }
     sink()
}

   mpi.spawn.Rslaves(nslaves=2)

   mpi.bcast.Robj2slave(slave_func)               #send  function to slaves
   mpi.bcast.cmd(slave_func())

	mpi.send.Robj(obj=1, dest=1, tag=1)      #yields "tag: 1 message: 1"  
-correct
	mpi.send.Robj(obj=2, dest=2, tag=2)      #yields "tag: 2 message: 2"  
-correct
   mpi.bcast.cmd(slave_func())              #yields "tag: 1 message:  
slave_func()" on slave 1
                                            #       "tag: 2 message:  
slave_func()" on slave 2
                                            #where does the value for "tag"  
come from?

	mpi.send.Robj(obj=11, dest=1, tag=11)     #correct
	mpi.send.Robj(obj=22, dest=2, tag=22)     #correct
   mpi.bcast.cmd(slave_func())              #yields "tag: 1 message:  
slave_func()" on slave 1
                                            #       "tag: 2 message:  
slave_func()" on slave 2
                                            #Is the first-ever used tag  
always used by mpi.bcast.cmd()?
                                            #I don't think so, but I cannot  
reproduce an example.

   mpi.send.Robj(obj=1, dest=1, tag=7)      #finish
   mpi.send.Robj(obj=1, dest=2, tag=7)      #finish

   mpi.close.Rslaves()
</code>


> sessionInfo()

R version 2.15.0 (2012-03-30)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252
LC_MONETARY=German_Germany.1252
[4] LC_NUMERIC=C                    LC_TIME=German_Germany.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] Rmpi_0.6-2