Evaluate an expression asynchronously in a new background R process or persistent daemon (local or remote). This function will return immediately with a 'mirai', which will resolve to the evaluated result once complete.

eval_mirai(.expr, ..., .args = list(), .timeout = NULL)

mirai(.expr, ..., .args = list(), .timeout = NULL)

Arguments

.expr

an expression to evaluate asynchronously. This may be of arbitrary length, wrapped in {} if necessary.

...

(optional) named arguments specifying objects referenced in '.expr'.

.args

(optional) list supplying objects referenced in '.expr' (used in addition to or instead of named arguments specified as '...').

.timeout

(optional) integer value in milliseconds or NULL for no timeout. A mirai will resolve to an 'errorValue' 5 (timed out) if evaluation exceeds this limit.

Value

A 'mirai' object.

Details

This function will return a 'mirai' object immediately.

The value of a mirai may be accessed at any time at $data, and if yet to resolve, an 'unresolved' logical NA will be returned instead.

unresolved may be used on a mirai, returning TRUE if a 'mirai' has yet to resolve and FALSE otherwise. This is suitable for use in control flow statements such as while or if.

Alternatively, to call (and wait for) the result, use call_mirai on the returned mirai. This will block until the result is returned (although interruptible with e.g. ctrl+c).

The expression '.expr' will be evaluated in a separate R process in a clean environment consisting only of the named objects passed as '...' and/or the list supplied to '.args'.

If an error occurs in evaluation, the error message is returned as a character string of class 'miraiError' and 'errorValue'. is_mirai_error may be used to test for this.

is_error_value tests for all error conditions including 'mirai' errors, interrupts, and timeouts.

mirai is an alias for eval_mirai.

Examples

if (interactive()) {
# Only run examples in interactive R sessions

m <- mirai(x + y + 1, x = 2, y = 3)
m
m$data
Sys.sleep(0.2)
m$data

df1 <- data.frame(a = 1, b = 2)
df2 <- data.frame(a = 3, b = 1)
m <- mirai(as.matrix(rbind(df1, df2)), .args = list(df1, df2), .timeout = 1000)
call_mirai(m)$data

m <- mirai({
  res <- rnorm(n)
  res / rev(res)
}, n = 1e6)
while (unresolved(m)) {
  cat("unresolved\n")
  Sys.sleep(0.1)
}
str(m$data)

file <- tempfile()
cat("r <- rnorm(n)", file = file)
n <- 10L
m <- mirai({source(file, local = TRUE); r}, .args = list(file, n))
call_mirai(m)[["data"]]
unlink(file)

}