Using exports from mlr3fselect during multisession execution fails due to non-loaded package

[skysyzygy]

mlr3fselect adds always_include to mlr_reflection$col_roles on package load.

This causes failures when training in with future::plan("multisession"), as the parallel workers don't seem to load mlr3fselect and complain about the existence of always_include in the col_roles for the task.

Error in .__Task__col_roles(self = self, private = private, super = super,  : 
  Assertion on 'names of col_roles' failed: Names must be a permutation of set {'feature','target','name','order','stratum','group','weight'}, but has extra elements {'always_included'}.
This happened PipeOp char_to_fct's $train()

Here is a working (sequential) MWE:

library(mlr3verse)
future::plan("sequential")

task <- tsk("zoo")
learner <- po("select") %>>% ppl("robustify") %>>% lrn("classif.rpart")
resample(task,learner,rsmp("cv"))

And a failing (multisession) MWE:

library(mlr3verse)
future::plan("multisession")

task <- tsk("zoo")
learner <- po("select") %>>% ppl("robustify") %>>% lrn("classif.rpart")
resample(task,learner,rsmp("cv"))

Here are the package versions I'm using

> mlr3verse::mlr3verse_info()
Key: <package>
             package version
              <char>  <char>
 1:            bbotk   1.0.1
 2:      mlr3cluster   0.1.9
 3:         mlr3data   0.7.0
 4:      mlr3filters   0.8.0
 5:      mlr3fselect   1.1.0
 6:    mlr3hyperband   0.6.0
 7:     mlr3learners   0.7.0
 8:          mlr3mbo   0.2.4
 9:         mlr3misc  0.15.1
10:    mlr3pipelines   0.7.0
11:       mlr3tuning   1.0.0
12: mlr3tuningspaces   0.5.1
13:          mlr3viz   0.9.0
14:          paradox   1.0.1

[be-marc]

Hey, sorry for the late reply. Our team was on vacation. Thanks for reporting this bug. A workaround should be to load only the required packages.

library(mlr3)
library(mlr3pipelines)

[skysyzygy]

Thanks for getting back! It's actually happening in a package, i.e. without explicit imports so not sure how to implement this workaround?

From what I can gather the issue is that po("select") causes an import from mlr3fselect, which has an .onLoad that modifies col_roles. For some reason this isn't happening in future workers though?

[be-marc]

Yes, it has something to do with it. When mlr3verse is loaded, mlr3fselect is also loaded which adds a new col_role. However, mlr3fselect does not appear in your workflow, which is why mlr3fselect is not loaded on the worker. There is then an error on the worker because the new col_role of the task is not known.

There is fix now. You can test the new versions with pak::pak(c("mlr-org/mlr3", "mlr-org/mlr3fselect")).

[skysyzygy]

😲 so fast and an elegant fix thank you!

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---

From: Marc Becker @.> Sent: Friday, October 18, 2024 1:13 AM To: mlr-org/mlr3 @.> Cc: Sky Syzygy @.>; Author @.> Subject: Re: [mlr-org/mlr3] Using exports from mlr3fselect during multisession execution fails due to non-loaded package (Issue #1183)

Yes, it has something to do with it. When mlr3verse is loaded, mlr3fselect is also loaded which adds a new col_role. However, mlr3fselect does not appear in your workflow, which is why mlr3fselect is not loaded on the worker. There is then an error on the worker because the new col_role of the task is not known.

There is fix now. You can test the new versions with pak::pak(c("mlr-org/mlr3, "mlr-org/mlr3fselect")).

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