Most of the time was being spent within the 'sapply' call. Here is a
list from Rprof:
0 18.4 root
1. 18.4 system.time
2. . 12.9 A1
3. . . 12.9 sapply
4. . . . 12.9 lapply
5. . . . | 12.9 FUN
6. . . . | . 12.9 sapply
7. . . . | . . 12.9 lapply
8. . . . | . . . 12.9 FUN
9. . . . | . . . . 12.9 sapply
10. . . . | . . . . | 12.8 lapply
11. . . . | . . . . | . 12.8 FUN
12. . . . | . . . . | . . 12.8 sapply
13. . . . | . . . . | . . . 12.8 lapply
14. . . . | . . . . | . . . . 12.8 FUN
15. . . . | . . . . | . . . . | 12.7 sapply
16. . . . | . . . . | . . . . | . 12.5 lapply
17. . . . | . . . . | . . . . | . . 12.5 FUN
18. . . . | . . . . | . . . . | . . . 12.4 sapply
19. . . . | . . . . | . . . . | . . . . 10.8 lapply
20. . . . | . . . . | . . . . | . . . . | 10.4 FUN
21. . . . | . . . . | . . . . | . . . . | . 9.8 sapply
22. . . . | . . . . | . . . . | . . . . | . . 4.3 unique
23. . . . | . . . . | . . . . | . . . . | . . . 1.6 unique.default
23. . . . | . . . . | . . . . | . . . . | . . . 1.5 unlist
24. . . . | . . . . | . . . . | . . . . | . . . . 1.3 lapply
22. . . . | . . . . | . . . . | . . . . | . . 4.0 lapply
23. . . . | . . . . | . . . . | . . . . | . . . 2.4 FUN
19. . . . | . . . . | . . . . | . . . . 1.1 unique
2. . 5.3 A0
3. . . 5.3 A0
4. . . . 5.3 A0
5. . . . | 5.3 A0
6. . . . | . 5.2 A0
7. . . . | . . 5.1 A0
8. . . . | . . . 4.6 A0
9. . . . | . . . . 3.3 A0
My guess is that you are at least 6 levels of calls down in the sapply
and within that, the 'unique' and 'lapply' split the time between
them. Notice that for A0, it is the only function being recorded.
On Thu, Sep 3, 2009 at 5:23 PM, Ben Bolker<bol...@ufl.edu> wrote:
>
>
>
> Bryan Keller wrote:
>>
>> The following recursion is about 120 times faster in C#. I know R is not
>> known for its speed with recursions but I'm wondering if anyone has a tip
>> about how to speed things up in R.
>>
>> #"T" is a vector and "m" is a number between 1 and sum(T)
>>
>> A <- function(T,m) {
>> lt <- length(T)
>>
>> if (lt == 1) {
>> if (0 <= m & m <= T[1]) {
>> return(1)
>> } else {
>> return(0)
>> }
>> }
>> R <- 0
>> for (u in 0:T[lt]) {
>> R <- (R+(A(T[1:(lt-1)],(m-u))))
>> }
>> return(R)
>> }
>>
>> -------------
>> Bryan Keller, Doctoral Student/Project Assistant
>> Educational Psychology - Quantitative Methods
>> The University of Wisconsin - Madison
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
> Can anyone tell me why my version takes TWICE AS LONG (to my surprise)?
>
>
> A0 <- function(T,m) {
> lt <- length(T)
>
> if (lt == 1) {
> if (0 <= m & m <= T[1]) {
> return(1)
> } else {
> return(0)
> }
> }
> R <- 0
> for (u in 0:T[lt]) {
> R <- (R+(A0(T[1:(lt-1)],(m-u))))
> }
> return(R)
> }
>
> A1 <- function(T,m) {
> lt <- length(T)
>
> if (lt == 1) {
> return(as.numeric(0 <= m & m <= T[1]))
> }
> sum(sapply(m-(0:T[lt]),A1,T=T[-lt]))
> }
>
> system.time(a0 <- A0(1:8,20)) ## about 5 secs
> system.time(a1 <- A1(1:8,20)) ## about 11 secs
>
> --
> View this message in context:
> http://www.nabble.com/Recursion-is-slow-tp25284189p25284359.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
