CODEWITHSUNDEEP
rprofiling
user12397
user12397

Reputation: 58

How to verify number of function evaluations when profiling R code

When profiling R code with Rprof-type functions we get the time spent in function alone and the time spent in function and callees. However, as far as I know we don't get the number of times a given function was evaluated.

For example, assume I wants to compare two integration functions:

integrate_1(myfunc, from = -Inf, to = Inf)
integrate_2(myfunc, from = -Inf, to Inf)

I could easily see how much time each function takes and where this time was spent, but I don't know how to check how many times myfunc had to be evaluated in each of the integrate functions.

Thanks,

Upvotes: 1

Views: 177

Answers (2)

Mike Dunlavey
Mike Dunlavey

Reputation: 40679

Rprof works by sampling the call stack on a timer. It does not count calls.

It records the sampled call stacks in a file, and though it does not record line numbers where calls occur, those samples are still useful for seeing what causes time to be spent.

For example, if you happen to look at M random samples, and you see a pattern like A calling B calling C on N of them, then you know the program spends roughly fraction N/M of its time doing that (assuming N > 1). If you see such a thing, and you can think of a way to avoid even part of it, you will save a substantial fraction of the total time.

Rprof comes with a summarization tool that gives you the kind of numbers you mentioned, but I don't find those numbers useful anyway. I would much rather get a real sense of what's happening.

Upvotes: 0

Richie Cotton
Richie Cotton

Reputation: 121127

One way of implementing Joran's counter method is to use the trace function.

For example, first we set the counter to zero. (Assigned in the global environment, for convenience.)

count <- 0

Then set up the trace. Here we set it on the identity function (that just returns the value that you input to it). 

trace("identity", quote(count <<- count + 1), print = FALSE)

Now whenever identity is called, the value of count is incremented. print = FALSE just stops a message being printed to the console when the function is called.

Let's call the function a few times and inspect the count:

for(i in seq_len(123)) identity(1)
count
## [1] 123

Upvotes: 1

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