tracemem {base} | R Documentation |
This function marks an object so that a message is printed whenever the
internal function duplicate
is called. This happens when two
objects share the same memory and one of them is modified. It is a
major cause of hard-to-predict memory use in R.
tracemem(x) untracemem(x) retracemem(x, previous = NULL)
x |
An R object, not a function or environment or |
previous |
A value as returned by |
This functionality is optional, determined at compilation, because it
makes R run a little more slowly even when no objects are being
traced. tracemem
and untracemem
give errors when R is not
compiled with memory profiling; retracemem
does not (so it can be
left in code during development).
When an object is traced any copying of the object by the C function
duplicate
or by arithmetic or mathematical operations produces a
message to standard output. The message consists of the string
tracemem
, the identifying strings for the object being copied and
the new object being created, and a stack trace showing where the
duplication occurred. retracemem()
is used to indicate that a
variable should be considered a copy of a previous variable (e.g. after
subscripting).
The messages can be turned off with tracingState
.
It is not possible to trace functions, as this would conflict with
trace
and it is not useful to trace NULL
,
environments, promises, weak references, or external pointer objects, as
these are not duplicated.
These functions are primitive.
A character string for identifying the object in the trace output (an
address in hex enclosed in angle brackets), or NULL
(invisibly).
capabilities("profmem")
to see if this was enabled for
this build of R.
http://developer.r-project.org/memory-profiling.html
## Not run: a <- 1:10 tracemem(a) ## b and a share memory b <- a b[1] <- 1 untracemem(a) ## copying in lm d <- stats::rnorm(10) tracemem(d) lm(d ~ a+log(b)) ## f is not a copy and is not traced f <- d[-1] f+1 ## indicate that f should be traced as a copy of d retracemem(f, retracemem(d)) f+1 ## End(Not run)