Dear Luke,
Thank you for the detailed explanation of the power of force()! It does
solve my problem in a much more reliable manner than setting function
environments manually.
On Fri, 8 Mar 2024 15:46:52 -0600 (CST)
luke-tier...@uiowa.edu wrote:
> Having a reference to a large environment is not much of an issue
> within a single process, but can be in a distributed memory parallel
> computing context. To avoid this you can force evaluation of the
> promises:
>
> mkLL1 <- function(m, s) {
> force(m)
> force(s)
> function(x) sum(dnorm(x, m, s, log = TRUE))
> }
> ll <- f(1e7)
> length(serialize(ll, NULL))
> ## [1] 2146
I think this also illustrates the danger of letting side effects come
near function arguments. A promise to read a file could survive on a
cluster node and result in a lot of head-scratching. A promise to write
to the connection number N, which coincides with a connection open on
the cluster node, could even do some damage. This is definitely
something to remember when creating closures.
> A very simple tool available in the snow package for snow clusters is
> snow.time(), which can produce some summary times and a Gantt chart
> (patterned after ones produced by xpvm and xmpi).
I can see the snow.time() plot being useful. Thank you for letting me
know about it!
--
Best regards,
Ivan
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