[Rd] mclapply returns NULLs on MacOS when running GAM

[Shian Su]

Dear R-devel,

I am experiencing issues with running GAM models using mclapply, it fails to return any values if the data input becomes large. For example here the code runs fine with a df of 100 rows, but fails at 1000.

library(mgcv)
library(parallel)

> df <- data.frame(
+     x = 1:100,
+     y = 1:100
+ )
>
> mclapply(1:2, function(i, df) {
+         fit <- gam(y ~ s(x, bs = "cs"), data = df)
+     },
+     df = df,
+     mc.cores = 2L
+ )
[[1]]

Family: gaussian
Link function: identity

Formula:
y ~ s(x, bs = "cs")

Estimated degrees of freedom:
9  total = 10

GCV score: 0

[[2]]

Family: gaussian
Link function: identity

Formula:
y ~ s(x, bs = "cs")

Estimated degrees of freedom:
9  total = 10

GCV score: 0

>
>
> df <- data.frame(
+     x = 1:1000,
+     y = 1:1000
+ )
>
> mclapply(1:2, function(i, df) {
+         fit <- gam(y ~ s(x, bs = "cs"), data = df)
+     },
+     df = df,
+     mc.cores = 2L
+ )
[[1]]
NULL

[[2]]
NULL

There is no error message returned, and the code runs perfectly fine in lapply.

I am on a MacBook 15 (2016) running MacOS 10.14.6 (Mojave) and R version 3.6.2. This bug could not be reproduced on my Ubuntu 19.10 running R 3.6.1.

Kind regards,
Shian Su
----
Shian Su
PhD Student, Ritchie Lab 6W, Epigenetics and Development
Walter & Eliza Hall Institute of Medical Research
1G Royal Parade, Parkville VIC 3052, Australia


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