[Rcpp-devel] RInside and MPI master slave model proper usage

[Dirk Eddelbuettel]

On 19 January 2013 at 17:44, Nicholas Pezolano wrote:
| Maybe I did not describe my question/problem clearly,
| 
| I've seen the examples and you would call 
| 
|  RInside R(int argc, int argv);  after int main and mpi_init, and all nodes
| should have an embedded R instance.

It works with MPI, and hence works the other way around.  

A controller/master node lauches all the worker nodes.  Then __each worker
node launches its own R instance via RInside__.  

How you get data and programs there is up for you. I like packages for many
reasons, they work here too.  

And sorry, I am in the middle of a few other things and cannot debug what you
have described in what is after all incomplete (or I missed it) and not
reproducible.

Dirk


| However the problem with using MPI and RInside in the above master slave model
| is the RInside objects/R instance will not be callable from the do_work
| function. 
| 
| for instance the following code snippet works in the examples with mpi but
| produces an error when used in a function or with the master slave model.
| 
| do_work(.......){
| 
| R["data"] = data;
| R.parseEvalQ();
| R.parseEvalQ(garch);
| 
| }
| 
| test.cpp: In function ‘void do_work(std::string, int&)’:
| test.cpp:278:4: error: expected primary-expression before ‘[’ token
| test.cpp:279:4: error: expected primary-expression before ‘.’ token
| test.cpp:280:4: error: expected primary-expression before ‘.’ token
| 
| The error is because the function doesn't have access to the the R object
| 
| 
| On Sat, Jan 19, 2013 at 5:14 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
| 
| 
|     On 19 January 2013 at 16:29, Nicholas Pezolano wrote:
|     | Hi I'm using Rinside with MPI and testing out a simple master slave
|     model.
|     |
|     | heres a basic example of what i'm trying to do.
|     | http://www.lam-mpi.org/tutorials/one-step/ezstart.php
|     |
|     | The function  do_work(unit_of_work_t work){ .....   gets run across all
|     the
|     |  N nodes until the M units of work are done. 
|     |     I am calling many R functions from C++, as well as loading R
|     libraries,
|     |  in the do_work function.
|     |
|     | Is there a way to load R once on each of the slaves and have the do_work
|     | function have access to RInside for every iteration of the master-slave
|     model?
|     |
|     | Do I have to run           RInside R(argc, argv);      for
|     every-time
|     | the function do_work is called by the master?
|     |
|     | Is there a way to free the R instance or is this handled automatically?
|     or is
|     | there a better approach?
| 
|     Do you know that there is a working example, contributed in the early days
|     by
|     Jianping Hua?
| 
|     All this assumes that you are a tad familiar with basic MPI. The model used
|     here uses straight MPI from C (or C++), and each (worker/slave) node just
|     happens to do its work with R.
| 
|     There are other models, notably Rmpi and you are not forced to use RInside
|     in
|     order to deploy MPI with R.  If you have basic questions, r-sig-hpc may be
|     a
|     better place.
|    
|     Dirk
| 
| 
| 
|     --
|     Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
| 
| 
| 
| 
| --
| Nicholas Pezolano
| Department of Applied Math & Statistics
| State University of New York at Stony Brook
| 

-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com