The code in this vignette provides a basic introduction to parallel routing. Routing is something that is highly parallelisable because each route can be calculated independently of the others. The code should be fairly self-explanatory. No results are shown and the code is not run to reduce package build times.

library(stplanr)
library(sf)
library(dplyr)
library(tmap)
library(parallel)
library(cyclestreets)

With old route_cyclestreets function

# ?route
l = flowlines_sf %>%
  dplyr::filter()
t1 = Sys.time()
routes_route_cyclestreet = line2route(l)
Sys.time() - t1
ncol(routes_route_cyclestreet)
nrow(routes_route_cyclestreet)
names(routes_route_cyclestreet)
routes_route_cyclestreet_joined = dplyr::inner_join(routes_route_cyclestreet, sf::st_drop_geometry(l))
Sys.time() - t1
rnet_go_dutch = overline(routes_route_cyclestreet_joined, "All")
Sys.time() - t1
tm_shape(rnet_go_dutch) +
  tm_lines(lwd = 5, col = "All", breaks = c(0, 10, 100, 500, 1000), palette = "viridis")

With new route function

# ?route
t1 = Sys.time()
routes_journey = route(l = l, route_fun = cyclestreets::journey)
ncol(routes_journey)
nrow(routes_journey)

Sys.time() - t1
names(routes_journey)
rnet_go_dutch_journey = overline(routes_journey, "All")
Sys.time() - t1
rnet_go_dutch_agg = overline(routes_journey, "All")
Sys.time() - t1
tm_shape(rnet_go_dutch_agg) +
  tm_lines(lwd = 5, col = "All", breaks = c(0, 10, 100, 500, 1000), palette = "viridis")

With new route function in parallel

# ?route
t1 = Sys.time()


# load parallel stuff
cl <- makeCluster(detectCores())
clusterExport(cl, c("journey"))
Sys.time() - t1
routes_journey_par = route(l = l, route_fun = cyclestreets::journey, cl = cl) # multi-core
stopCluster(cl) # kill cluster

Sys.time() - t1
Sys.time() - t1
names(routes_journey_par)
rnet_go_dutch_journey = overline(routes_journey_par, "All")
Sys.time() - t1
rnet_go_dutch_agg = overline(routes_journey_par, "All")
Sys.time() - t1
tm_shape(rnet_go_dutch_agg) +
  tm_lines(lwd = 5, col = "All", breaks = c(0, 10, 100, 500, 1000), palette = "viridis")

In parallel with quietness plan

# ?route
t1 = Sys.time()


# load parallel stuff
library(parallel)
library(cyclestreets)
cl <- makeCluster(detectCores())
clusterExport(cl, c("journey"))
Sys.time() - t1
routes_journey_par = route(l = l, route_fun = cyclestreets::journey, cl = cl, plan = "quietest") # multi-core
stopCluster(cl) # kill cluster

Sys.time() - t1
Sys.time() - t1
names(routes_journey_par)
rnet_go_dutch_journey = overline(routes_journey_par, "All")
Sys.time() - t1
rnet_go_dutch_agg = overline(routes_journey_par, "All")
Sys.time() - t1
tm_shape(rnet_go_dutch_agg) +
  tm_lines(lwd = 5, col = "All", breaks = c(0, 10, 100, 500, 1000), palette = "viridis")

Tests

routes_journey_aggregated = routes_journey %>% # already has data from data frame in there!
  group_by(id) %>%
  summarise(All = median(All)) %>%
  sf::st_cast("LINESTRING")


rnet_journey_dplyr = routes_journey %>% # already has data from data frame in there!
  group_by(name, distances) %>%
  summarise(All = sum(All))
Sys.time() - t1
tm_shape(rnet_journey_dplyr) +
  tm_lines(lwd = 5, col = "All", breaks = c(0, 10, 100, 500, 1000), palette = "viridis") # quite different...


rnet_journey_go_dutch = routes_journey %>%
  group_by(start_longitude, start_latitude, finish_longitude, finish_latitude) %>%
  summarise(All = sum(All))