Hi Kylie,
For your question, I don't think a wrapper can completely solve your
problem. The duplication occurs since your variable y has more than 1
reference number( Please see highlighted), so even you have a wrapper, any
changes on the value of the wrapper still can trigger the duplication.
> .Internal(inspect(y))
> @7fb0ce78c0f0 13 INTSXP g0c0 *[NAM(7)]* matter vector (mode=3, len=3,
> mem=0)
My guess is that *matter:::as.altrep* function assigned the variable *y* to
a local variable so that it increases the reference number. For example:
*This would not cause a duplication*
> > a=c(1,2,3)
> > .Internal(inspect(a))
> @0x000000002384f530 14 REALSXP g0c3 [NAM(1)] (len=3, tl=0) 1,2,3
> > attr(a,"dim")=c(1,3)
> > .Internal(inspect(a))
> @0x000000002384f530 14 REALSXP g0c3 [NAM(1),ATT] (len=3, tl=0) 1,2,3
> ATTRIB:
> @0x0000000023864b58 02 LISTSXP g0c0 []
> TAG: @0x00000000044b1a90 01 SYMSXP g1c0 [MARK,LCK,gp=0x4000] "dim"
> (has value)
> @0x000000002384cb48 13 INTSXP g0c1 [NAM(7)] (len=2, tl=0) 1,3
>
*This would cause a duplication, even though the function test does
nothing.*
> > test<-function(x) x1=x
> > a=c(1,2,3)
> > .Internal(inspect(a))
> @0x000000002384f260 14 REALSXP g0c3 [NAM(1)] (len=3, tl=0) 1,2,3
> > test(a)
> > .Internal(inspect(a))
> @0x000000002384f260 14 REALSXP g0c3 [NAM(7)] (len=3, tl=0) 1,2,3
> > attr(a,"dim")=c(1,3)
> > .Internal(inspect(a))
> @0x000000002384f0d0 14 REALSXP g0c3 [NAM(1),ATT] (len=3, tl=0) 1,2,3
> ATTRIB:
> @0x00000000238666c0 02 LISTSXP g0c0 []
> TAG: @0x00000000044b1a90 01 SYMSXP g1c0 [MARK,LCK,gp=0x4000] "dim"
> (has value)
> @0x000000002384c6e8 13 INTSXP g0c1 [NAM(7)] (len=2, tl=0) 1,3
>
If that is the case and you are 100% sure the reference number should be 1
for your variable *y*, my solution is to call *SET_NAMED *in C++ to reset
the reference number. Note that you need to unbind your local variable
before you reset the number. To return an unbound SEXP, the C++ function
should be placed at the end of your *matter:::as.altrep *function. I don't
know if there is any simpler way to do that and I'll be happy to see any
opinion.
Also, I notice that you are using ALTREP to create a wrapper for your
*matter_vec *class. I'm an author of AltWrapper package and the package is
able to define an ALTREP in pure R level, it is capable to add an attribute
to ALTREP object when creating the object and has a correct reference
number. The simplest example would be
*CODE*
```
library(AltWrapper)
inspectFunc <- function(x) cat("Altrep object\n")
lengthFunc <- function(x) return(length(x))
getPtrFunc <- function(x, writeable) return(x)
setAltClass(className = "test", classType = "real")
setAltMethod(className = "test", inspect = inspectFunc)
setAltMethod(className = "test", getLength = lengthFunc)
setAltMethod(className = "test", getDataptr = getPtrFunc)
A = runif(6)
A_alt = makeAltrep(className = "test", x = A, *attributes = list(dim = c(2,
3))*)
```
*RESULT*
```
> .Internal(inspect(A_alt))
@0x000000002385ac00 14 REALSXP g0c0 [NAM(1),ATT] Altrep object
ATTRIB:
@0x000000002385a8b8 02 LISTSXP g0c0 []
TAG: @0x00000000044b1a90 01 SYMSXP g1c0 [MARK,LCK,gp=0x4000] "dim" (has
value)
@0x000000002384d590 13 INTSXP g0c1 [NAM(7)] (len=2, tl=0) 2,3
> A_alt
[,1] [,2] [,3]
[1,] 0.9430458 0.548670 0.4148741
[2,] 0.9550899 0.251857 0.6077540
```
I will be happy to talk more about it if you are interested in the package,
it is available at
https://github.com/Jiefei-Wang/AltWrapper
Best,
Jiefei
On Thu, Jul 18, 2019 at 3:28 AM Bemis, Kylie <k.be...@northeastern.edu>
wrote:
> Hello,
>
> I’m experimenting with ALTREP and was wondering if there is a preferred
> way to create an ALTREP wrapper vector without using
> .Internal(wrap_meta(…)), which R CMD check doesn’t like since it uses an
> .Internal() function.
>
> I was trying to create a factor that used an ALTREP integer, but
> attempting to set the class and levels attributes always ended up
> duplicating and materializing the integer vector. Using the wrapper avoided
> this issue.
>
> Here is my initial ALTREP integer vector:
>
> > fc0 <- factor(c("a", "a", "b"))
> >
> > y <- matter::as.matter(as.integer(fc0))
> > y <- matter:::as.altrep(y)
> >
> > .Internal(inspect(y))
> @7fb0ce78c0f0 13 INTSXP g0c0 [NAM(7)] matter vector (mode=3, len=3, mem=0)
>
> Here is what I get without a wrapper:
>
> > fc1 <- structure(y, class="factor", levels=levels(x))
> > .Internal(inspect(fc1))
> @7fb0cae66408 13 INTSXP g0c2 [OBJ,NAM(2),ATT] (len=3, tl=0) 1,1,2
> ATTRIB:
> @7fb0ce771868 02 LISTSXP g0c0 []
> TAG: @7fb0c80043d0 01 SYMSXP g1c0 [MARK,LCK,gp=0x4000] "class" (has
> value)
> @7fb0c9fcbe90 16 STRSXP g0c1 [NAM(7)] (len=1, tl=0)
> @7fb0c80841a0 09 CHARSXP g1c1 [MARK,gp=0x61] [ASCII] [cached]
> "factor"
> TAG: @7fb0c8004050 01 SYMSXP g1c0 [MARK,NAM(7),LCK,gp=0x4000] "levels"
> (has value)
> @7fb0d1dd58c8 16 STRSXP g0c2 [MARK,NAM(7)] (len=2, tl=0)
> @7fb0c81bf4c0 09 CHARSXP g1c1 [MARK,gp=0x61] [ASCII] [cached] "a"
> @7fb0c90ba728 09 CHARSXP g1c1 [MARK,gp=0x61] [ASCII] [cached] "b"
>
> Here is what I get with a wrapper:
>
> > fc2 <- structure(.Internal(wrap_meta(y, 0, 0)), class="factor",
> levels=levels(x))
> > .Internal(inspect(fc2))
> @7fb0ce764630 13 INTSXP g0c0 [OBJ,NAM(2),ATT] wrapper [srt=0,no_na=0]
> @7fb0ce78c0f0 13 INTSXP g0c0 [NAM(7)] matter vector (mode=3, len=3,
> mem=0)
> ATTRIB:
> @7fb0ce764668 02 LISTSXP g0c0 []
> TAG: @7fb0c80043d0 01 SYMSXP g1c0 [MARK,LCK,gp=0x4000] "class" (has
> value)
> @7fb0c9fcb010 16 STRSXP g0c1 [NAM(7)] (len=1, tl=0)
> @7fb0c80841a0 09 CHARSXP g1c1 [MARK,gp=0x61] [ASCII] [cached]
> "factor"
> TAG: @7fb0c8004050 01 SYMSXP g1c0 [MARK,NAM(7),LCK,gp=0x4000] "levels"
> (has value)
> @7fb0d1dd58c8 16 STRSXP g0c2 [MARK,NAM(7)] (len=2, tl=0)
> @7fb0c81bf4c0 09 CHARSXP g1c1 [MARK,gp=0x61] [ASCII] [cached] "a"
> @7fb0c90ba728 09 CHARSXP g1c1 [MARK,gp=0x61] [ASCII] [cached] "b"
>
> Is there a way to do this that doesn’t rely on .Internal() and won’t
> produce R CMD check warnings?
>
> ~~~
> Kylie Ariel Bemis
> Khoury College of Computer Sciences
> Northeastern University
> kuwisdelu.github.io<https://kuwisdelu.github.io>
>
>
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