Re: [Rd] Result of 'seq' doesn't use compact internal representation
This is now resolved in R-devel and R_patched. Best, luke On Sun, 29 Apr 2018, Luke Tierney wrote: Thanks -- I'll commit a fix after some testing. Best, luke On 04/29/2018 06:22 AM, Duncan Murdoch wrote: On 28/04/2018 11:11 PM, Suharto Anggono Suharto Anggono via R-devel wrote: .Internal(inspect(1:10)) @300e4e8 13 INTSXP g0c0 [NAM(3)] 1 : 10 (compact) .Internal(inspect(seq(1,10))) @3b6e1f8 13 INTSXP g0c4 [] (len=10, tl=0) 1,2,3,4,5,... system.time(1:1e7) user system elapsed 0 0 0 system.time(seq(1,1e7)) user system elapsed 0.05 0.00 0.04 It seems that result of function 'seq' doesn't use compact internal representation. However, looking at the code of function 'seq.default', seq(1,n) produces 1:n. What is going on? It looks like it is related to using compiled or interpreted code: > library(gtools) > seq2 <- unByteCode(seq.default) > .Internal(inspect(seq.default(1,10))) @7fa53847dcd8 13 INTSXP g0c4 [] (len=10, tl=0) 1,2,3,4,5,... > .Internal(inspect(seq2(1,10))) @7fa537fa0bf0 13 INTSXP g0c0 [NAM(3)] 1 : 10 (compact) Duncan Murdoch h <- seq.default environment(h) <- .GlobalEnv library(compiler) enableJIT(0) [1] 3 .Internal(inspect(h(1,10))) @375ade8 13 INTSXP g0c0 [NAM(3)] 1 : 10 (compact) A non-byte-compiled version of function 'seq.default' can produce object that uses compact internal representation. sessionInfo() R version 3.5.0 (2018-04-23) Platform: i386-w64-mingw32/i386 (32-bit) Running under: Windows XP (build 2600) Service Pack 3 Matrix products: default locale: [1] LC_COLLATE=English_United States.1252 [2] LC_CTYPE=English_United States.1252 [3] LC_MONETARY=English_United States.1252 [4] LC_NUMERIC=C [5] LC_TIME=English_United States.1252 attached base packages: [1] compiler stats graphics grDevices utils datasets methods [8] base __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel -- Luke Tierney Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics andFax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: luke-tier...@uiowa.edu Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] Understanding the sequence of events when calling the R dpois function
Hello all, I am trying to get a better understanding of the underlying code for the stats::dpois function in R and, specifically, what happens under the hood when it is called. I finally managed to track down the C course at: https://github.com/wch/r-source/blob/trunk/src/nmath/dpois.c. It would seem that the dpois C function is taking a double for each of the x and lambda arguments so I am a bit confused why I can provide a vector and matrix to dpois in R, e.g. dpois(1:5, matrix(runif(2*5, 1, 10), nrow = 5))) and get a matrix back with the results. Due to this, I was expecting to see a loop, or similar, in the underlying C source but… to no avail. So I have to conclude that either a) there is a step between when I call dpois in R and the C code getting executed that loops over the inputs or b) that there is a construct in the C code (my proficiency here is limited) that is called per input. Any help in enlightening me on what code is responsible for iterating over the multiple inputs (or if someone is feeling energetic, the exact stepwise code that is executed when calling dpois) would be greatly appreciated!! Kind Regards, Jason Serviss [[alternative HTML version deleted]] __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] Understanding the sequence of events when calling the R dpois function
> On May 31, 2018, at 8:25 AM, Jason Serviss wrote:
>
> Hello all,
>
> I am trying to get a better understanding of the underlying code for the
> stats::dpois function in R and, specifically, what happens under the hood
> when it is called. I finally managed to track down the C course at:
> https://github.com/wch/r-source/blob/trunk/src/nmath/dpois.c. It would seem
> that the dpois C function is taking a double for each of the x and lambda
> arguments so I am a bit confused why I can provide a vector and matrix to
> dpois in R, e.g.
>
> dpois(1:5, matrix(runif(2*5, 1, 10), nrow = 5)))
>
> and get a matrix back with the results. Due to this, I was expecting to see a
> loop, or similar, in the underlying C source but… to no avail. So I have to
> conclude that either a) there is a step between when I call dpois in R and
> the C code getting executed that loops over the inputs or b) that there is a
> construct in the C code (my proficiency here is limited) that is called per
> input. Any help in enlightening me on what code is responsible for iterating
> over the multiple inputs (or if someone is feeling energetic, the exact
> stepwise code that is executed when calling dpois) would be greatly
> appreciated!!
Have a look at arithmetic.c. The math2 function handles calling dpois in a
vectorized fashion.
You need to trace how it is that the compiler knows to use dpois.c in
constructing `C_dpois' which is what the R function dpois is calling.
If you know how to grep the sources for dpois, that will get you started. You
will need to look over a bunch of #define's and a few C utilities to see how it
all fits together.
If you dig in and find the `do { ... } while(0)' construct confusing you might
look at
https://stackoverflow.com/questions/257418/do-while-0-what-is-it-good-for
HTH,
Chuck
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Re: [Rd] Understanding the sequence of events when calling the R dpois function
Jason,
as Chuck Berry (to whom, *thanks* for 'do {...} while(0)'!) suggested,
using grep, or even grep executed from find, such as
find . -type f -exec grep -H "dpois" \{\} \; | less
(executed from the root of an R source tree), is your friend.
cheers, Greg
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