API

RCOMPSs provides an API for data synchronization and barrier.

Synchronization

The main program of the application is a sequential code that contains calls to the selected tasks. In addition, when synchronizing for task data from the main program, there exist six API functions that can be invoked:

compss_barrier(no_more_tasks=False): Performs a explicit synchronization, but does not return any object. The use of compss_barrier() forces to wait for all tasks that have been submitted before the compss_barrier() is called. When all tasks submitted before the compss_barrier() have finished, the execution continues. The no_more_tasks is used to specify if no more tasks are going to be submitted after the compss_barrier().
compss_wait_on(obj): Synchronizes for the last version of object specified by obj and returns the synchronized object.

To illustrate the use of the aforementioned API functions, the following example (Code 154).

Code 154 RCOMPSs Synchronization API functions usage

library(RCOMPSs)
source("file_with_functions.R")
compss_start()

add.t <- task(add, "add.R", return_value = TRUE)

a <- 1; b <- 2;
result <- add.t(a, b)

compss_barrier()

...

result <- compss_wait_on(result)

cat("The result is:", result, "\n")
compss_stop()

API Summary

Finally, Table 18 summarizes the API functions to be used in the main program of a COMPSs R application.

Table 18 COMPSs R API functions
Type	API Function	Description
Synchronization	`compss_barrier()`	Wait for all tasks submitted before the barrier.
Synchronization	`compss_wait_on(obj)`	Synchronizes for the last version of an object and returns it.