| tracemem {base} | R Documentation |
Trace Copying of Objects
Description
This function marks an object so that a message is printed whenever the internal code copies the object. It is a major cause of hard-to-predict memory use in R.
Usage
tracemem(x)
untracemem(x)
retracemem(x, previous = NULL)
Arguments
x |
An R object, not a function or environment or |
previous |
A value as returned by |
Details
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).
It is enabled in the CRAN macOS and Windows builds of R.
When an object is traced any copying of the object by the C function
duplicate produces a message to standard output, as does type
coercion and copying when passing arguments to .C or
.Fortran.
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.
Value
A character string for identifying the object in the trace output (an
address in hex enclosed in angle brackets), or NULL (invisibly).
See Also
capabilities("profmem") to see if this was enabled for
this build of R.
https://developer.r-project.org/memory-profiling.html
Examples
## Not run:
a <- 1:10
tracemem(a)
## b and a share memory
b <- a
b[1] <- 1
untracemem(a)
## copying in lm: less than R <= 2.15.0
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)