[R-package] Disabled early stopping when using 'dart' boosting strategy (#2443)

R-package/R/aliases.R

+# Central location for parameter aliases.
+# See https://lightgbm.readthedocs.io/en/latest/Parameters.html#core-parameters
+
+# [description] List of respected parameter aliases. Wrapped in a function to take advantage of
+#               lazy evaluation (so it doesn't matter what order R sources files during installation).
+# [return] A named list, where each key is a main LightGBM parameter and each value is a character
+#          vector of corresponding aliases.
+.PARAMETER_ALIASES <- function(){
+    return(list(
+        "boosting" = c(
+            "boosting"
+            , "boost"
+            , "boosting_type"
+        )
+        , "early_stopping_round" = c(
+            "early_stopping_round"
+            , "early_stopping_rounds"
+            , "early_stopping"
+            , "n_iter_no_change"
+        )
+        , "metric" = c(
+            "metric"
+            , "metrics"
+            , "metric_types"
+        )
+        , "num_class" = c(
+            "num_class"
+            , "num_classes"
+        )
+        , "num_iterations" = c(
+            "num_iterations"
+            , "num_iteration"
+            , "n_iter"
+            , "num_tree"
+            , "num_trees"
+            , "num_round"
+            , "num_rounds"
+            , "num_boost_round"
+            , "n_estimators"
+        )
+    ))
+}

R-package/R/callback.R

@@ -37,7 +37,11 @@ cb.reset.parameters <- function(new_params) {
 
     # Some parameters are not allowed to be changed,
     # since changing them would simply wreck some chaos
-    not_allowed <- c("num_class", "metric", "boosting_type")
+    not_allowed <- c(
+      .PARAMETER_ALIASES()[["num_class"]]
+      , .PARAMETER_ALIASES()[["metric"]]
+      , .PARAMETER_ALIASES()[["boosting"]]
+    )
     if (any(pnames %in% not_allowed)) {
       stop(
         "Parameters "

R-package/R/lgb.cv.R

@@ -136,17 +136,7 @@ lgb.cv <- function(params = list(),
     begin_iteration <- predictor$current_iter() + 1
   }
   # Check for number of rounds passed as parameter - in case there are multiple ones, take only the first one
-  n_trees <- c(
-    "num_iterations"
-    , "num_iteration"
-    , "n_iter"
-    , "num_tree"
-    , "num_trees"
-    , "num_round"
-    , "num_rounds"
-    , "num_boost_round"
-    , "n_estimators"
-  )
+  n_trees <- .PARAMETER_ALIASES()[["num_iterations"]]
   if (any(names(params) %in% n_trees)) {
     end_iteration <- begin_iteration + params[[which(names(params) %in% n_trees)[1]]] - 1
   } else {
@@ -225,30 +215,52 @@ lgb.cv <- function(params = list(),
     callbacks <- add.cb(callbacks, cb.record.evaluation())
   }
 
-  # Check for early stopping passed as parameter when adding early stopping callback
-  early_stop <- c("early_stopping_round", "early_stopping_rounds", "early_stopping", "n_iter_no_change")
-  if (any(names(params) %in% early_stop)) {
-    if (params[[which(names(params) %in% early_stop)[1]]] > 0) {
-      callbacks <- add.cb(
-        callbacks
-        , cb.early.stop(
-          params[[which(names(params) %in% early_stop)[1]]]
-          , verbose = verbose
-        )
-      )
-    }
-  } else {
-    if (!is.null(early_stopping_rounds)) {
-      if (early_stopping_rounds > 0) {
-        callbacks <- add.cb(
-          callbacks
-          , cb.early.stop(
-            early_stopping_rounds
-            , verbose = verbose
-          )
-        )
+  # If early stopping was passed as a parameter in params(), prefer that to keyword argument
+  # early_stopping_rounds by overwriting the value in 'early_stopping_rounds'
+  early_stop <- .PARAMETER_ALIASES()[["early_stopping_round"]]
+  early_stop_param_indx <- names(params) %in% early_stop
+  if (any(early_stop_param_indx)) {
+    first_early_stop_param <- which(early_stop_param_indx)[[1]]
+    first_early_stop_param_name <- names(params)[[first_early_stop_param]]
+    early_stopping_rounds <- params[[first_early_stop_param_name]]
+  }
+
+  # Did user pass parameters that indicate they want to use early stopping?
+  using_early_stopping_via_args <- !is.null(early_stopping_rounds)
+
+  boosting_param_names <- .PARAMETER_ALIASES()[["boosting"]]
+  using_dart <- any(
+    sapply(
+      X = boosting_param_names
+      , FUN = function(param){
+        identical(params[[param]], 'dart')
       }
-    }
+    )
+  )
+
+  # Cannot use early stopping with 'dart' boosting
+  if (using_dart){
+    warning("Early stopping is not available in 'dart' mode.")
+    using_early_stopping_via_args <- FALSE
+
+    # Remove the cb.early.stop() function if it was passed in to callbacks
+    callbacks <- Filter(
+      f = function(cb_func){
+        !identical(attr(cb_func, "name"), "cb.early.stop")
+      }
+      , x = callbacks
+    )
+  }
+
+  # If user supplied early_stopping_rounds, add the early stopping callback
+  if (using_early_stopping_via_args){
+    callbacks <- add.cb(
+      callbacks
+      , cb.early.stop(
+        stopping_rounds = early_stopping_rounds
+        , verbose = verbose
+      )
+    )
   }
 
   # Categorize callbacks

R-package/R/lgb.train.R

@@ -108,24 +108,13 @@ lgb.train <- function(params = list(),
     begin_iteration <- predictor$current_iter() + 1
   }
   # Check for number of rounds passed as parameter - in case there are multiple ones, take only the first one
-  n_rounds <- c(
-    "num_iterations"
-    , "num_iteration"
-    , "n_iter"
-    , "num_tree"
-    , "num_trees"
-    , "num_round"
-    , "num_rounds"
-    , "num_boost_round"
-    , "n_estimators"
-  )
-  if (any(names(params) %in% n_rounds)) {
-    end_iteration <- begin_iteration + params[[which(names(params) %in% n_rounds)[1]]] - 1
+  n_trees <- .PARAMETER_ALIASES()[["num_iterations"]]
+  if (any(names(params) %in% n_trees)) {
+    end_iteration <- begin_iteration + params[[which(names(params) %in% n_trees)[1]]] - 1
   } else {
     end_iteration <- begin_iteration + nrounds - 1
   }
 
-
   # Check for training dataset type correctness
   if (!lgb.is.Dataset(data)) {
     stop("lgb.train: data only accepts lgb.Dataset object")
@@ -207,30 +196,52 @@ lgb.train <- function(params = list(),
     callbacks <- add.cb(callbacks, cb.record.evaluation())
   }
 
-  # Check for early stopping passed as parameter when adding early stopping callback
-  early_stop <- c("early_stopping_round", "early_stopping_rounds", "early_stopping", "n_iter_no_change")
-  if (any(names(params) %in% early_stop)) {
-    if (params[[which(names(params) %in% early_stop)[1]]] > 0) {
-      callbacks <- add.cb(
-        callbacks
-        , cb.early.stop(
-          params[[which(names(params) %in% early_stop)[1]]]
-          , verbose = verbose
-        )
-      )
-    }
-  } else {
-    if (!is.null(early_stopping_rounds)) {
-      if (early_stopping_rounds > 0) {
-        callbacks <- add.cb(
-          callbacks
-          , cb.early.stop(
-            early_stopping_rounds
-            , verbose = verbose
-          )
-        )
+  # If early stopping was passed as a parameter in params(), prefer that to keyword argument
+  # early_stopping_rounds by overwriting the value in 'early_stopping_rounds'
+  early_stop <- .PARAMETER_ALIASES()[["early_stopping_round"]]
+  early_stop_param_indx <- names(params) %in% early_stop
+  if (any(early_stop_param_indx)) {
+    first_early_stop_param <- which(early_stop_param_indx)[[1]]
+    first_early_stop_param_name <- names(params)[[first_early_stop_param]]
+    early_stopping_rounds <- params[[first_early_stop_param_name]]
+  }
+
+  # Did user pass parameters that indicate they want to use early stopping?
+  using_early_stopping_via_args <- !is.null(early_stopping_rounds)
+
+  boosting_param_names <- .PARAMETER_ALIASES()[["boosting"]]
+  using_dart <- any(
+    sapply(
+      X = boosting_param_names
+      , FUN = function(param){
+        identical(params[[param]], 'dart')
       }
-    }
+    )
+  )
+
+  # Cannot use early stopping with 'dart' boosting
+  if (using_dart){
+    warning("Early stopping is not available in 'dart' mode.")
+    using_early_stopping_via_args <- FALSE
+
+    # Remove the cb.early.stop() function if it was passed in to callbacks
+    callbacks <- Filter(
+      f = function(cb_func){
+        !identical(attr(cb_func, "name"), "cb.early.stop")
+      }
+      , x = callbacks
+    )
+  }
+
+  # If user supplied early_stopping_rounds, add the early stopping callback
+  if (using_early_stopping_via_args){
+    callbacks <- add.cb(
+      callbacks
+      , cb.early.stop(
+        stopping_rounds = early_stopping_rounds
+        , verbose = verbose
+      )
+    )
   }
 
   # "Categorize" callbacks

R-package/tests/testthat/test_parameters.R

@@ -43,3 +43,35 @@ test_that("Feature penalties work properly", {
   # Ensure that feature is not used when feature_penalty = 0
   expect_length(var_gain[[length(var_gain)]], 0)
 })
+
+expect_true(".PARAMETER_ALIASES() returns a named list", {
+  param_aliases <- .PARAMETER_ALIASES()
+  expect_true(is.list(param_aliases))
+  expect_true(is.character(names(param_aliases)))
+  expect_true(is.character(param_aliases[["boosting"]]))
+  expect_true(is.character(param_aliases[["early_stopping_round"]]))
+  expect_true(is.character(param_aliases[["metric"]]))
+  expect_true(is.character(param_aliases[["num_class"]]))
+  expect_true(is.character(param_aliases[["num_iterations"]]))
+})
+
+expect_true("training should warn if you use 'dart' boosting, specified with 'boosting' or aliases", {
+  for (boosting_param in .PARAMETER_ALIASES()[["boosting"]]){
+    expect_warning({
+      result <- lightgbm(
+        data = train$data
+        , label = train$label
+        , num_leaves = 5
+        , learning_rate = 0.05
+        , nrounds = 5
+        , objective = "binary"
+        , metric = "binary_error"
+        , verbose = -1
+        , params = stats::setNames(
+          object = "dart"
+          , nm = boosting_param
+        )
+      )
+    }, regexp = "Early stopping is not available in 'dart' mode")
+  }
+})