From ross at biostat.ucsf.edu  Thu Mar 20 03:22:23 2014
From: ross at biostat.ucsf.edu (Ross Boylan)
Date: Wed, 19 Mar 2014 19:22:23 -0700
Subject: [Rd] modifying data in a package
Message-ID: <1395282143.1752.111.camel@localhost>

I've tweaked Rmpi and want to have some variables that hold data in the
package.  One of the R files starts
mpi.isend.obj <- vector("list", 500) #mpi.request.maxsize())                                                                          
mpi.isend.inuse <- rep(FALSE, 500) #mpi.request.maxsize())    

and then functions update those variables with <<-.  When run:
  Error in mpi.isend.obj[[i]] <<- .force.type(x, type) :                                                                                
  cannot change value of locked binding for 'mpi.isend.obj'

I'm writing to ask the proper way to accomplish this objective (getting
a variable I can update in package namespace--or at least somewhere
useful and hidden from the outside).

I think the problem is that the package namespace is locked.  So how do
I achieve the same effect?
http://www.r-bloggers.com/package-wide-variablescache-in-r-packages/
recommends creating an environment and then updating it.  Is that the
preferred route?  (It seems odd that the list should be locked but the
environment would be manipulable.  I know environments are special.)

The comments indicate that 500 "should" be mpi.request.maxsize().  That
doesn't work because mpi.request.maxsize calls a C function, and there
is an error that the function isn't loaded.  I guess the R code is
evaluated before the C libraries are loaded. The packages zzz.R starts
.onLoad <- function (lib, pkg) {
    library.dynam("Rmpi", pkg, lib)

So would moving the code into .onLoad after that work?  In that case,
how do I get the environment into the  proper scope?  Would
 .onLoad <- function (lib, pkg) {
    library.dynam("Rmpi", pkg, lib)
    assign("mpi.globals", new.env(), environment(mpi.isend))
    assign("mpi.isend.obj", vector("list", mpi.request.maxsize(),
mpi.globals)
work?

mpi.isend is a function in Rmpi.  But I'd guess the first assign will
fail because the environment is locked.

Thanks.
Ross Boylan



[Rd] modifying data in a package
Ross Boylan