callback_batch_tuning {mlr3tuning}

Create Batch Tuning Callback

Description

Function to create a CallbackBatchTuning. Predefined callbacks are stored in the dictionary mlr_callbacks and can be retrieved with clbk().

Tuning callbacks can be called from different stages of the tuning process. The stages are prefixed with ⁠on_*⁠.

Start Tuning
     - on_optimization_begin
    Start Tuner Batch
         - on_optimizer_before_eval
        Start Evaluation
             - on_eval_after_design
             - on_eval_after_benchmark
             - on_eval_before_archive
        End Evaluation
         - on_optimizer_after_eval
    End Tuner Batch
     - on_result
     - on_optimization_end
End Tuning

See also the section on parameters for more information on the stages. A tuning callback works with ContextBatchTuning.

Usage

callback_batch_tuning(
  id,
  label = NA_character_,
  man = NA_character_,
  on_optimization_begin = NULL,
  on_optimizer_before_eval = NULL,
  on_eval_after_design = NULL,
  on_eval_after_benchmark = NULL,
  on_eval_before_archive = NULL,
  on_optimizer_after_eval = NULL,
  on_result = NULL,
  on_optimization_end = NULL
)

Arguments

id

(character(1))
Identifier for the new instance.

label

(character(1))
Label for the new instance.

man

(character(1))
String in the format ⁠[pkg]::[topic]⁠ pointing to a manual page for this object. The referenced help package can be opened via method ⁠$help()⁠.

on_optimization_begin

(⁠function()⁠)
Stage called at the beginning of the optimization. Called in Optimizer$optimize().

on_optimizer_before_eval

(⁠function()⁠)
Stage called after the optimizer proposes points. Called in OptimInstance$eval_batch().

on_eval_after_design

(⁠function()⁠)
Stage called after the design is created. Called in ObjectiveTuning$eval_many(). The context available is ContextBatchTuning.

on_eval_after_benchmark

(⁠function()⁠)
Stage called after hyperparameter configurations are evaluated. Called in ObjectiveTuning$eval_many(). The context available is ContextBatchTuning.

on_eval_before_archive

(⁠function()⁠)
Stage called before performance values are written to the archive. Called in ObjectiveTuning$eval_many(). The context available is ContextBatchTuning.

on_optimizer_after_eval

(⁠function()⁠)
Stage called after points are evaluated. Called in OptimInstance$eval_batch().

on_result

(⁠function()⁠)
Stage called after the result is written. Called in OptimInstance$assign_result().

on_optimization_end

(⁠function()⁠)
Stage called at the end of the optimization. Called in Optimizer$optimize().

Details

When implementing a callback, each function must have two arguments named callback and context. A callback can write data to the state (⁠$state⁠), e.g. settings that affect the callback itself. Tuning callbacks access ContextBatchTuning.

Examples

# write archive to disk
callback_batch_tuning("mlr3tuning.backup",
  on_optimization_end = function(callback, context) {
    saveRDS(context$instance$archive, "archive.rds")
  }
)