[R] getTimeLimit?

[Henrik Bengtsson]

On Tue, Jan 3, 2017 at 2:43 PM, William Dunlap via R-help
<r-help at r-project.org> wrote:
> I am interested in measuring the time it takes to run an expression.
>  system.time(expr) does this but I would like to have it report just 'more
> than xxx seconds', where xxx is a argument to the timing function, when it
> takes a long time.  This is useful automating the process of seeing how
> processing time grows with the size of a dataset.
>
> My latest attempt is the following function, which adds a 'censored=TRUE'
> attribute when the cpu or elapsed time exceeds some limit:
>
> system.time2 <- function (expr, gcFirst = TRUE, cpu = Inf, elapsed = Inf)
> {
>     setTimeLimit(cpu = cpu, elapsed = elapsed, transient = TRUE)
>     censored <- NULL
>     time <- system.time(gcFirst = gcFirst, tryCatch(expr, error =
> function(e) if (grepl("reached (CPU|elapsed) time limit",
>         conditionMessage(e)))
>         censored <<- conditionMessage(e)
>     else stop(e)))
>     attr(time, "censored") <- censored
>     time
> }
>
> It would be used as
>
>> system.time(times <- lapply(10^(1:7), function(n)system.time2(for(i in
> 1:n)lgamma(1:i), elapsed=10) ))
>    user  system elapsed
>   33.55    0.25   33.82
>> vapply(times, function(t)t[["elapsed"]], 0)
> [1]  0.02  0.00  0.03  3.08 10.02 10.14 10.18
>> # following gives which times are valid
>> vapply(times, function(t)is.null(attr(t,"censored")), NA)
> [1]  TRUE  TRUE  TRUE  TRUE FALSE FALSE FALSE
>
> I have two questions.
> * Is this a reasonable way to compute such a censored time?
> * Is there a getTimeLimit()-like function?

I also wanted such a function, but I don't think it exists.
Internally in R the timeout is set in global variables 'cpuLimitValue'
and 'elapsedLimitValue'.  Grepping the source for it doesn't reveal
any external access to it, e.g.

$ grep -F "cpuLimitValue" -r --include="*.h" src/
src/include/Defn.h:extern0 double cpuLimitValue INI_as(-1.0);

$ grep -F "cpuLimitValue" -r --include="*.c" src/
src/main/sysutils.c:    cpuLimit = (cpuLimitValue > 0) ? data[0] +
data[1] + cpuLimitValue : -1.0;
src/main/sysutils.c:    cpuLimit = (cpuLimitValue > 0) ? data[0] +
data[1] + data[3] + data[4] + cpuLimitValue : -1.0;
src/main/sysutils.c:    double cpu, elapsed, old_cpu = cpuLimitValue,
src/main/sysutils.c:    if (R_FINITE(cpu) && cpu > 0) cpuLimitValue =
cpu; else cpuLimitValue = -1;
src/main/sysutils.c: cpuLimitValue = old_cpu;

Similar for 'elapsedLimitValue'.

>
> Also, I think it would be nice if the error thrown when timing out had a
> special class so I didn't have to rely on grepping the error message, but
> that is true of lots of errors.

FYI, R.utils::withTimeout() greps the error message (for any language;
https://github.com/HenrikBengtsson/R.utils/blob/2.5.0/R/withTimeout.R#L113-L114)
this way and returns an error of class TimeoutException.

FYI 2, there is as 'Working group for standard error (condition)
classes' proposal to the RConsortium "wishlist", cf.
https://github.com/RConsortium/wishlist/issues/6.

/Henrik

>
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
>         [[alternative HTML version deleted]]
>
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