方法为时间片时，R包插入符中的并行化

Question

当方法设置为timelice时，并行化是否可以在插入符号包中工作？

我使用doMC注册内核：

library(parallel)
library(doMC) 
numCores <- detectCores()
registerDoMC(numCores)

此示例按预期工作，所有内核均并行运行：

library(caret)
library(mlbench)
data(Sonar)

inTrain <- createDataPartition(y = Sonar$Class, p = .75, list = FALSE)
training <- Sonar[ inTrain,]
testing <- Sonar[-inTrain,]
grid_rf <- expand.grid(.mtry = c(2, 3, 4))

ctrl <- trainControl(method = "repeatedcv", number = 8, repeats = 2)
system.time({
   rf <- train(Class ~ ., data = training,  method = "rf", trControl = ctrl, ntree=50000,  tuneGrid = grid_rf)
})

此示例未按预期运行，在短暂使用所有内核之后，大部分时间仅使用一个内核：

ctrl <- trainControl(method = "timeslice", 
                  initialWindow = 10,
                  horizon = 1,
                  fixedWindow = TRUE,
                  allowParallel = TRUE)
system.time({
   rf <- train(Class ~ ., data = training,  method = "rf", trControl = ctrl, ntree=50000,  tuneGrid = grid_rf)
})

这是预期的行为吗？我错过了文档中显而易见的内容吗？