Optimize wk_coords() for sfc objects

[paleolimbot]

No description provided.

[paleolimbot]

This probably just applies to sfc_POINT, sfc_LINESTRING, and SFC_MULTIPOINT. For any greater level of nesting, the cost of sf's approach appears to be greater than the cost of wk's approach.

library(wk)

points <- xy(runif(1e5), runif(1e5))
points_sfc <- sf::st_as_sfc(points)

bench::mark(
  wk::wk_coords(points_sfc),
  sf::st_coordinates(points_sfc),
  check = F
)
#> # A tibble: 2 × 6
#>   expression                          min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr>                     <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 wk::wk_coords(points_sfc)        4.69ms   4.92ms      201.    4.26MB     26.4
#> 2 sf::st_coordinates(points_sfc)   1.07ms   1.22ms      819.    3.07MB     99.1

points2 <- xy(runif(1e6), runif(1e6))
linestrings_wkb <- wk_linestring(points2, rep(1:1e2, each = 1e3))
linestrings_sfc <- sf::st_as_sfc(linestrings_wkb)

bench::mark(
  wk::wk_coords(linestrings_sfc),
  sf::st_coordinates(linestrings_sfc),
  check = F
)
#> Warning: Some expressions had a GC in every iteration; so filtering is disabled.
#> # A tibble: 2 × 6
#>   expression                             min median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr>                          <bch:> <bch:>     <dbl> <bch:byt>    <dbl>
#> 1 wk::wk_coords(linestrings_sfc)      18.3ms 21.5ms      36.0     130MB     51.2
#> 2 sf::st_coordinates(linestrings_sfc) 10.3ms 11.2ms      83.0      42MB     31.6


points2 <- xy(runif(1e6), runif(1e6))
polygons_wkb <- wk_polygon(points2, rep(1:1e2, each = 1e3))
polygons_sfc <- sf::st_as_sfc(polygons_wkb)

bench::mark(
  wk::wk_coords(polygons_sfc),
  sf::st_coordinates(polygons_sfc),
  check = F
)
#> Warning: Some expressions had a GC in every iteration; so filtering is disabled.
#> # A tibble: 2 × 6
#>   expression                            min  median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr>                       <bch:tm> <bch:t>     <dbl> <bch:byt>    <dbl>
#> 1 wk::wk_coords(polygons_sfc)        18.3ms  20.8ms      32.1   130.1MB     51.0
#> 2 sf::st_coordinates(polygons_sfc)   24.8ms  29.8ms      28.6    99.4MB     22.9

^{Created on 2022-09-17 by the reprex package (v2.0.1)}