sendrecv.replace-method: Send and Receive an Object to and from Other Ranks

Description

This method lets a rank send an object to the other rank and receive an object from another rank in the same communicator. The default return is x.

Usage

sendrecv.replace(x,
  rank.dest = (comm.rank(.pbd_env$SPMD.CT$comm) + 1) %%
              comm.size(.pbd_env$SPMD.CT$comm),
  send.tag = .pbd_env$SPMD.CT$tag,
  rank.source = (comm.rank(.pbd_env$SPMD.CT$comm) - 1) %%
                comm.size(.pbd_env$SPMD.CT$comm),
  recv.tag = .pbd_env$SPMD.CT$tag,
  comm = .pbd_env$SPMD.CT$comm, status = .pbd_env$SPMD.CT$status)

Value

A x is returned by default.

Arguments

x: an object to be sent from a rank.
rank.dest: a rank of destination where x send to.
send.tag: a send tag number.
rank.source: a source rank where x sent from.
recv.tag: a receive tag number.
comm: a communicator number.
status: a status number.

Methods

For calling spmd.sendrecv.replace.*():

signature(x = "ANY")
signature(x = "integer")
signature(x = "numeric")
signature(x = "raw")

Author

Wei-Chen Chen wccsnow@gmail.com, George Ostrouchov, Drew Schmidt, Pragneshkumar Patel, and Hao Yu.

Details

A corresponding sendrecv.replace() should be evoked at the corresponding ranks rank.dest and rank.source.

rank.dest and rank.source can be as.integer(NULL) to create a silent sendrecv operation which is more efficient than setting rank.dest and rank.source to be equal.

Warning: sendrecv.replace() is not safe for R since R is not a thread safe package that a dynamic returning object requires certain blocking or barrier at some where. The replaced object or memory address `MUST' return correctly. This is almost equivalent to sendrecv().

References

Programming with Big Data in R Website: https://pbdr.org/

Examples

Run this code

if (FALSE) {
### Save code in a file "demo.r" and run with 2 processors by
### SHELL> mpiexec -np 2 Rscript demo.r

spmd.code <- "
### Initialize
suppressMessages(library(pbdMPI, quietly = TRUE))
.comm.size <- comm.size()
.comm.rank <- comm.rank()

### Examples.
N <- 5
x <- (1:N) + N * .comm.size
x <- sendrecv.replace(matrix(x, nrow = 1))
comm.print(x, rank.print = 1)

### Finish.
finalize()
"
# execmpi(spmd.code, nranks = 2L)
}

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