call_mirai {mirai}

mirai (Call Value)

Description

call_mirai waits for the ‘mirai’ to resolve if still in progress, storing the value at $data, and returns the ‘mirai’ object.

call_mirai_ is a variant of call_mirai that allows user interrupts, suitable for interactive use.

Usage

call_mirai(x)

call_mirai_(x)

Arguments

x

a ‘mirai’ object, or list of ‘mirai’ objects.

Details

Both functions accept a list of ‘mirai’ objects, such as that returned by mirai_map as well as individual ‘mirai’.

They will wait for the asynchronous operation(s) to complete if still in progress (blocking).

x[] may also be used to wait for and return the value of a mirai x, and is the equivalent of call_mirai_(x)$data.

Value

The passed object (invisibly). For a ‘mirai’, the retrieved value is stored at $data.

Alternatively

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.

Using unresolved on a ‘mirai’ returns TRUE only if it has yet to resolve and FALSE otherwise. This is suitable for use in control flow statements such as while or if.

Errors

If an error occurs in evaluation, the error message is returned as a character string of class ‘miraiError’ and ‘errorValue’ (the stack trace is available at $stack.trace on the error object). is_mirai_error may be used to test for this.

If a daemon crashes or terminates unexpectedly during evaluation, an ‘errorValue’ 19 (Connection reset) is returned (when not using dispatcher or using dispatcher with retry = FALSE). Otherwise, using dispatcher with retry = TRUE, the mirai will remain unresolved and is automatically re-tried on the next daemon to connect to the particular instance. To cancel the task instead, use saisei(force = TRUE) (see saisei).

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

Examples

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

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

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

}