Evaluate an R expression while collecting journals from completed futures

Usage

capture_journals(expr, substitute = TRUE, envir = parent.frame())

Arguments

expr: The R expression to evaluate
substitute: If TRUE, then expr is substituted, otherwise not.
envir: The environment where expr should be evaluated

Value

A list of FutureJournal:s.

Details

This function evaluates an R expression and capture the journals signaled by futures as they are completed. A future journal comprise a log of events appearing during the life-span of a future, e.g. the timestamps when the future was created, launched, queried, resolved, and its results are collected.

Examples

slow_fcn <- function(x) {
  Sys.sleep(x / 10)
  sqrt(x)
}

plan(multisession, workers = 2)
js <- capture_journals({
  fs <- lapply(3:1, FUN = function(x) future(slow_fcn(x)))
  value(fs)
})

## Summarize all journals
js_all <- Reduce(rbind, js)
print(summary(js_all), digits = 2L)
#> Number of futures: 3
#>   summary  evaluate evaluate_ratio  overhead overhead_ratio  duration  walltime
#> 1     min 0.10 secs           0.27 0.24 secs           0.61 0.39 secs 0.39 secs
#> 2    mean 0.27 secs           0.47 0.26 secs           0.44 0.58 secs 0.58 secs
#> 3  median 0.32 secs           0.51 0.26 secs           0.40 0.64 secs 0.64 secs
#> 4     max 0.39 secs           0.55 0.27 secs           0.38 0.70 secs 0.70 secs
#> 5   total 0.82 secs           0.47 0.77 secs           0.44 1.73 secs 1.73 secs

## Shut down parallel workers
plan(sequential)