drake/future/multisession complains about unreliable random seed but values are ok

[kkmann]

Prework

• [x] Read and agree to the code of conduct and contributing guidelines.
• [x] If there is already a relevant issue, whether open or closed, comment on the existing thread instead of posting a new issue.
• [x] Post a minimal reproducible example so the maintainer can troubleshoot the problems you identify. A reproducible example is:
  • [x] Runnable: post enough R code and data so any onlooker can create the error on their own computer.
  • [x] Minimal: reduce runtime wherever possible and remove complicated details that are irrelevant to the issue at hand.
  • [x] Readable: format your code according to the tidyverse style guide.

Description

Evaluating drake plan using multisession futures on gives warning about random seed. The values seem to be ok though.

Reproducible example

> drake::clean()
> library(drake)
> 
> i <- 1:10
> plan <- drake::drake_plan(
+     test = target({
+         runif(1)
+     }, dynamic = map(i))
+ )
> 
> future::plan(future::multisession)
> drake::make(plan, seed = 42, parallelism = "future")
▶ dynamic test
> subtarget test_0b3474bd
> subtarget test_b2a5c9b8
> subtarget test_71f311ad
> subtarget test_98cf3c11
> subtarget test_0a86c9cb
> subtarget test_cb15b01f
> subtarget test_8531e6ff
> subtarget test_28b16d75
> subtarget test_4edaada2
> subtarget test_db4b2027
■ finalize test
Warning message:
UNRELIABLE VALUE: Future (‘test_0b3474bd’) unexpectedly generated random numbers without specifying argument '[future.]seed'. There is a risk that those random numbers are not statistically sound and the overall results might be invalid. To fix this, specify argument '[future.]seed', e.g. 'seed=TRUE'. This ensures that proper, parallel-safe random numbers are produced via the L'Ecuyer-CMRG method. To disable this check, use [future].seed=NULL, or set option 'future.rng.onMisuse' to "ignore". 
> tmp1 <- unlist(readd(test))
> drake::clean()
> drake::make(plan, seed = 42, parallelism = "future")
▶ dynamic test
> subtarget test_0b3474bd
> subtarget test_b2a5c9b8
> subtarget test_71f311ad
> subtarget test_98cf3c11
> subtarget test_0a86c9cb
> subtarget test_cb15b01f
> subtarget test_8531e6ff
> subtarget test_28b16d75
> subtarget test_4edaada2
> subtarget test_db4b2027
■ finalize test
> tmp2 <- unlist(readd(test))
> 
> tmp1 - tmp2
 [1] 0 0 0 0 0 0 0 0 0 0

Expected result

If this is no problem, the warning should be suppressed without user input.

Session info

End the reproducible example with a call to sessionInfo() in the same session (e.g. reprex(si = TRUE)) and include the output.

> sessionInfo()
R version 4.0.2 (2020-06-22)
Platform: x86_64-apple-darwin19.5.0 (64-bit)
Running under: macOS Catalina 10.15.6

Matrix products: default
BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: /usr/local/Cellar/openblas/0.3.10_1/lib/libopenblasp-r0.3.10.dylib

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] drake_7.12.5

loaded via a namespace (and not attached):
 [1] igraph_1.2.5      rstudioapi_0.11   magrittr_1.5      hms_0.5.3         progress_1.2.2    tidyselect_1.1.0 
 [7] R6_2.4.1          rlang_0.4.7       fansi_0.4.1       storr_1.2.1       globals_0.13.1    tools_4.0.2      
[13] parallel_4.0.2    cli_2.0.2         ellipsis_0.3.1    base64url_1.4     digest_0.6.25     assertthat_0.2.1 
[19] tibble_3.0.3      lifecycle_0.2.0   crayon_1.3.4      txtq_0.2.3        purrr_0.3.4       codetools_0.2-16 
[25] vctrs_0.3.2       glue_1.4.1        pillar_1.4.6      compiler_4.0.2    filelock_1.0.2    backports_1.1.10 
[31] prettyunits_1.1.1 future_1.19.1     listenv_0.8.0     pkgconfig_2.0.3  

[wlandau]

I see you are using drake 7.12.5. These warnings were fixed in https://github.com/ropensci/drake/commit/de861f86565faed70ba72cb487703eb662cb0e72 and the patch is in 7.12.6 (current CRAN).