Addition

The Addition application is a R application that performs several additions by means of a task. The initial values are 8 and they are accumulated two by two. Next, we provide the main code and the task declaration:

Code 170 add.R
add <- function(x, y) {
   return(x + y)
}
Code 171 addition.R
library(RCOMPSs)
source("add.R")
compss_start()

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

a <- 2; b <- 3;
c <- 4; d <- 5;
e <- 6; f <- 7;
g <- 8; h <- 9;

# Task (1) a + b
ab <- add.t(a, b)
# Task (2) c + d
cd <- add.t(c, d)
# Task (3) e + f
ef <- add.t(e, f)
# Task (4) g + h
gh <- add.t(g, h)

# Task (5) ab + cd
abcd <- add.t(ab, cd)
# Task (6) ef + gh
efgh <- add.t(ef, gh)

# Task (7) abcd + efgh
result <- add.t(abcd, efgh)

# Retrieve the result
result <- compss_wait_on(result)
cat("The result is:", result, "\n")

compss_stop()
This code uses the add function described in the add.R file to add:

  • a and b into ab

  • c and d into cd

  • e and f into ef

  • g and h into gh

Then adds these partial results:

  • ab and cd into abcd

  • ef and gh into efgh

And finally adds these partial results to achieve the final result:

  • abcd and efgh into result

On a normal R execution, each addition will be done after the other (sequentially), accumulating the computational time. RCOMPSs is able to parallelize this code thanks to its task decorator which wraps the add function instantiating the add.t function, and synchronize the results with the compss_wait_on API call.

The Addition application can be executed by invoking the runcompss command with the application file name and the --lang=r flag.

The following lines provide an example of its execution.

$ runcompss --lang=r addition.R
  [  INFO] Inferred PYTHON language
  [  INFO] Using default location for project file: /opt/COMPSs/Runtime/configuration/xml/projects/default_project.xml
  [  INFO] Using default location for resources file: /opt/COMPSs/Runtime/configuration/xml/resources/default_resources.xml
  [  INFO] Using default execution type: compss

  ----------------- Executing addition.R --------------------------

  WARNING: COMPSs Properties file is null. Setting default values
  [(763)    API]  -  Starting COMPSs Runtime v3.4 (build 20250513-0839.rfcc8f551ada00b095448810eee6b34a1baca40f8)
  The result is: 44
  [(9528)    API]  -  Execution Finished

  ------------------------------------------------------------

The task dependency graph is depicted in the next figure. It shows the parallelism that COMPSs has extracted and taken advantage of.

The dependency graph of the addition application

Figure 85 The dependency graph of the addition application

COMPSs has detected that the addition of a+b and c+d is independent, and consequently, that they can be done in parallel. While the addition of res1+res2 waits for the previous additions.