Mechanisms of communication during future execution?

[tzakharko]

Is there a way for a future to communicate with the host before it completes? I am mostly interesting in receiving periodic progress reports. I have found mention of instant_relay_condition is some issues but this seems to be abandoned.

[HenrikBengtsson]

See the progressr package

[tzakharko]

Thanks, but can I use it with a regular future()? I tried signaling an immediateCondition but it doesn't seem to work. Neither does progressr. Here is my code for reference:

library(progressr)
library(future)
plan(multiprocess)
handlers("progress")

with_progress({
  p <- progressor(along = 1:3)

  task <- future({
    p(message="1")
    Sys.sleep(2)
    p(message="2")
    Sys.sleep(2)
    p(message="3")
  })

  value(task)
}) 

The out put is just NULL followed by 6 seconds pause and then nothing.

P.S. If I try to manually signal immediateCondition it is only raised once the future is completed.

[HenrikBengtsson]

Try it with multisession. That's the only parallel backend that support near-live updates. More backends might support it later but generic live communication is complicated.

[tzakharko]

Multisession works! There is some latency, but I can live with it.

Thanks!