Hi,
there was a memory improvement done in R going from R 3.3.3 to R 3.4.0
when it comes to comparing an integer 'x' an double 'y' (either may be
scalar or vector).
For example, in R 3.3.3, I get:
> getRversion()
[1] '3.3.3'
> x <- integer(1000)
> y <- double(1000)
> profmem::profmem(z <- (x < y))
Rprofmem memory profiling of:
z <- (x < y)
Memory allocations:
bytes calls
1 8040 <internal>
2 4040 <internal>
total 12080
>
and in R 3.4.0, I get:
> getRversion()
[1] '3.4.0'
> x <- integer(1000)
> y <- double(1000)
> profmem::profmem(z <- (x < y))
Rprofmem memory profiling of:
z <- (x < y)
Memory allocations:
bytes calls
1 4040 <internal>
total 4040
Note how in R (<= 3.3.3), the (x < y) comparison will cause an
internal coercion of integer vector 'x' into a double, which then can
be compared to double 'y'. In R (>= 3.4.0), it appears that this
coercion is done per element and will therefore avoid introducing a
new, temporary copy internally. The same is observed with when
comparing with (x == y).
This is a great improvement that I think deserves more credit. I
couldn't find any mentioning of it in the R 3.4.0 NEWS
(https://cran.r-project.org/doc/manuals/r-release/NEWS.html). Does
anyone know whether this was a specific improvement for such
comparison, or a side effect of something else, e.g. an improved byte
compiler?
Thanks,
Henrik
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