Evaluate an R expression while collecting journals from completed futures

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
#> 1     min 0.10 secs           0.28 0.053 secs           0.15 0.37 secs
#> 2    mean 0.21 secs           0.56 0.132 secs           0.35 0.38 secs
#> 3  median 0.23 secs           0.60 0.078 secs           0.21 0.38 secs
#> 4     max 0.30 secs           0.78 0.264 secs           0.68 0.39 secs
#> 5   total 0.64 secs           0.56 0.396 secs           0.35 1.14 secs
#>    walltime
#> 1 0.37 secs
#> 2 0.38 secs
#> 3 0.38 secs
#> 4 0.39 secs
#> 5 1.14 secs

## Shut down parallel workers
plan(sequential)