Checks whether two booster objects refer to the same underlying C object.
Details
As booster objects (as returned by e.g. xgb.train()) contain an R 'externalptr'
object, they don't follow typical copy-on-write semantics of other R objects - that is, if
one assigns a booster to a different variable and modifies that new variable through in-place
methods like xgb.attr<-(), the modification will be applied to both the old and the new
variable, unlike typical R assignments which would only modify the latter.
This function allows checking whether two booster objects share the same 'externalptr', regardless of the R attributes that they might have.
In order to duplicate a booster in such a way that the copy wouldn't share the same
'externalptr', one can use function xgb.copy.Booster().
Examples
library(xgboost)
data(mtcars)
y <- mtcars$mpg
x <- as.matrix(mtcars[, -1])
model <- xgb.train(
params = xgb.params(nthread = 1),
data = xgb.DMatrix(x, label = y, nthread = 1),
nrounds = 3
)
model_shallow_copy <- model
xgb.is.same.Booster(model, model_shallow_copy) # same C object
model_deep_copy <- xgb.copy.Booster(model)
xgb.is.same.Booster(model, model_deep_copy) # different C objects
# In-place assignments modify all references,
# but not full/deep copies of the booster
xgb.attr(model_shallow_copy, "my_attr") <- 111
xgb.attr(model, "my_attr") # gets modified
xgb.attr(model_deep_copy, "my_attr") # doesn't get modified