% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/xgb.Booster.R
\name{xgb.is.same.Booster}
\alias{xgb.is.same.Booster}
\title{Check if two boosters share the same C object}
\usage{
xgb.is.same.Booster(obj1, obj2)
}
\arguments{
\item{obj1}{Booster model to compare with \code{obj2}.}

\item{obj2}{Booster model to compare with \code{obj1}.}
}
\value{
Either \code{TRUE} or \code{FALSE} according to whether the two boosters share the
underlying C object.
}
\description{
Checks whether two booster objects refer to the same underlying C object.
}
\details{
As booster objects (as returned by e.g. \code{\link[=xgb.train]{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 \code{\link[=xgb.attr<-]{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 \code{\link[=xgb.copy.Booster]{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
}
\seealso{
\code{\link[=xgb.copy.Booster]{xgb.copy.Booster()}}
}
