[R] line profiling

[Duncan Murdoch]

On 13-04-05 6:39 AM, Florent D. wrote:
> Hello,
>
> This is about the new "line profiling" feature in R 3.0.0. As I was
> testing it, I find the results somewhat disappointing so I'd like to
> get your opinion.
>
> I put some poorly written code in a test.R file, here are the contents:
>
> double <- function(x) {
>    out <- c()
>    for (i in x) {
>      out <- c(out, 2*i)   # line 4
>    }
>    return(out)
> }
>
> Then this how I source the file and run a profile:
>
> source("test.R", keep.source = TRUE)
> Rprof("test.profile", line.profiling=TRUE)
> y <- double(1:20000)
> Rprof(NULL)
> summaryRprof("test.profile", lines = "both")
>
> The relevant part of the output is:
>
> $by.total
>           total.time total.pct self.time self.pct
> "double"       0.98    100.00      0.00     0.00
> "c"            0.92     93.88      0.92    93.88
> test.R#4       0.06      6.12      0.06     6.12
>
> My problem is I was expecting test.R#4 (line 4 of my file) to show up
> somewhere between "c" and "double", because "c" is called on line #4
> of my file, and line #4 is inside the body of the "double" function.
> If I look at the "test.profile" where I told Rprof() to record, there
> are a lot of
>
> "c" "double"
>
> records while I was hoping to find
>
> "c" 1#4 "double"
>
> Can someone please explain why, when the profiler records "c", it does
> not record the extra information that "c" was called on line 4? Is it
> not possible to know? Is it a choice the developers made? An
> oversight?

Some function calls don't create stack frame records, so that may be 
your problem, but then I wouldn't have expected to see "c" there.  This 
may be a bug.

Duncan Murdoch