Benchmarking slopes calculation

library(slopes)
library(bench)

Performance

A benchmark can reveal how many route gradients can be calculated per second using different interpolation methods:

e = dem_lisbon()
r = lisbon_road_network
res = bench::mark(check = FALSE,
  bilinear = slope_raster(r, e),
  simple   = slope_raster(r, e, method = "simple")
)

res
#> # A tibble: 2 × 6
#>   expression      min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr> <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 bilinear     47.6ms   48.2ms      20.7   18.16MB     25.9
#> 2 simple       41.4ms   41.9ms      23.9    1.88MB     23.9

That is approximately

round(res$`itr/sec` * nrow(r))
#> [1] 5623 6473

routes per second using bilinear and simple interpolation methods, respectively.

To go faster, you can chose the simple method to gain some speed at the expense of accuracy:

res2 = bench::mark(check = FALSE,
  bilinear = slope_raster(r, e, method = "bilinear"),
  simple   = slope_raster(r, e, method = "simple")
)

res2
#> # A tibble: 2 × 6
#>   expression      min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr> <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 bilinear     48.7ms   48.8ms      20.3    1.73MB     25.4
#> 2 simple       42.7ms   43.2ms      23.2    1.81MB     19.3

round(res2$`itr/sec` * nrow(r))
#> [1] 5499 6289